WO2005103078A1 - Avian gm-csf - Google Patents

Abstract

The current invention relates to the field of veterinary immunology, namely to avian cytokines, more specifically to avian granulocyte-macrophage colony-stimulating factor (GM­CSF). In particular the invention relates to a protein, or functional fragment thereof, having at least one of the biological activities of avian GM-CSF, as well as to a nucleic acid encoding such protein or fragment. Also the invention relates to a recombinant DNA molecule, a live recombinant carrier, or a host cell. Further the inventon relates to the use as a medicament, and to compositions comprising such a protein or functional fragment thereof, or a nucleic acid encoding such protein or fragment.

Description

AVIAN GM-CSF

The current invention relates to the field of veterinary immunology, namely to avian cytokines, more specifically to avian granulocyte-macrophage colony-stimulating factor (GM- CSF). In particular the invention relates to a protein, or functional fragment thereof, having at least one of the biological activities of avian GM-CSF, as well as to a nucleic acid encoding such protein or fragment. Also the invention relates to a recombinant DNA molecule, a live recombinant carrier, or a host cell. Further the invention relates to the use as a medicament, and to compositions comprising such a protein or functional fragment thereof, or a nucleic acid encoding such protein or fragment.

Cytokines are proteins present in the serum of most vertebrate organisms that regulate proliferation, differentiation, and activation of blood cells. Cytokines play essential roles in e.g. haemopoiesis and immunological responses. Grouped under the general name of cytokines are families of proteins arranged by origin, function or structure: Interleukins, Lymphokines, Interferons, Chemokines, tumour necrosis factors, and growth factors. Most cytokines are both produced by, and have effects on, blood cells that span the range from undifferentiated pluripotent stem cells up to differentiated activated effector cells. These effects are mostly reached in combination with other (cytokine) factors, thereby forming a complex balance of both stimulatory and inhibitory signals. The respective signals are detected by the various target cells through specific receptors on the cell surface

Well-known in the art is the T1-T2 paradigm, representing the central role of cytokines in coordinating the immune response to pathogens in mammalian species: Th1 cells produce a distinct panel of cytokines (in particular IFN-γ and TNF-β) that drive strong inflammatory reactions (classically defined as cell-mediated immunity) and promote antibody isotype switching to certain isotypes. Th2 cells (classically defined as driving humeral immunity) produce a second distinct panel of cytokines (in particular IL-4, IL-5 and IL-13) that drive anti- helminthic worm reactions and allergic reactions, and promote antibody isofype switching to other, distinct isotypes, including IgE. The paradigm has now been extended to CD8⁺ cytotoxic T cells, dendritic cells and to include the Th3/Tr1 regulatory subset of Th cells, but essentially stands: T1 cytokines drive inflammatory reactions; T2 cytokines drive anti- helminth reactions and allergy. See for a review: Asnagli H. & Murphy K. (2001, Curr. Opin. Immunol., vol. 13, p. 242-247). Because of these crucial roles and potent effects, cytokines have been employed in many different (veterinary) medical uses, for instance for influencing an organisms' immunological response to infection or vaccination. Such (immuno)therapeutic use is known for granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF is also known as granulocyte-monocyte colony-stimulating factor, and its encoding gene is also named the colony stimulating factor 2 (CSF-2) gene. GM-CSF is a cytokine from the growth factor family. It is categorised as a colony stimulating-, and a haematopoietic growth factor. GM-CSF is not the same as related cytokines: myelomonocytic growth factor (MGF), macrophage colony-stimulating factor (M- CSF), stem cell factor (SCF), or granulocyte colony-stimulating factor (G-CSF), which is also known as CSF-1. GM-CSF is produced by activated T-lymphocytes, macrophages, endothelial cells, and fibroblasts, and has potent stimulatory and/or modulatory effects via multiple pathways on myeloid cells such as neutrophils, eosinophils, and various antigen presenting cells; see for a review Baldwin, G.C. (1992, Dev. Biol., vol. 151, p. 352-367). The normal biological activity of GM-CSF in the stimulation of proliferation and response to infection or vaccination is caused by its induction of proliferation of macrophages and granulocytes from precursor cells; the stimulation of differentiation of dendritic cells; the stimulation of antigen- presentation; the expression of molecules from the major histocompatibility complex (MHC); and activation of both CD4+ Th1 and Th2, as well as CD8+ cytotoxic T lymphocytes.

The genes encoding GM-CSF of human and mouse were described already in 1984 (Metcalf, D., 1985, Science, vol. 225, p. 16-22), and since then genes encoding the GM-CSF of several other mammalian species have been described, such as: cat, dog, cow, sheep and pig. In all species for which the GM-CSF gene has been described so far, the gene consists of 4 exons, and encodes a protein of approximately 144 amino acids. GM-CSF has an N-terminal signal sequence for secretion from the cell. It shares with other members of the cytokine growth factor family a secondary structure comprising four alpha-helices.

The availability of the genes for mammalian GM-CSF enabled the production of GM-CSF by recombinant expression technology, thereby providing unlimited amounts of protein of desired purity. This in turn made (immuno)therapeutic use of GM-CSF possible. For instance, rec. human GM-CSF is sold commercially amongst other names as Sargramostim®, and has been used for the treatment of neutropenia, allergy, cancer, and infections. Alternative therapeutic applications have used the cDNA for human GM-CSF as a nucleic acid construct or in a live recombinant carrier. In human therapy, administration of rec human GM-CSF to premature babies helped overcome infections (Carr, R. etal., 2003, Cochrane database Syst. Rev.: CD003066). Also, stimulation of dendritic cells by GM-CSF was reported by Yebenes, V. et al. (2002, Immunobiology, vol. 99, p. 2948-2955), and by Gajewska B. et al. (2003, Curr. Drug Targets Inflamm. Allergy, vol. 2, p. 279-292). The effect of GM-CSF as an adjuvant has been described: for HIV vaccines by Ahlers, J. etal. (2003, Curr. Mol. Med., vol. 3, p. 285-301); for Hepatitis-B by: das Gracas, M. etal. (2003, Vaccine, vol. 21, p. 4545-4549), and was reviewed in: Villinger, F. (2003, Expert Rev. Vaccines, vol . 2, p. 317-326). Specific constructs and uses of mammalian GM-CSF are also described in WO 85/04188, WO 86/03225, WO 00/77210, and WO 01/95919. In addition, Kass etal. (2001, Cancer Res., vol. 61 , p. 206-214) describe the use of an avian poxvirus for the expression of mouse GM-CSF in mice. Wessely etal. (1998, J. of Cell Biol., vol. 141, p. 1041-1051) describe the use of human GM-CSF on chicken embryo fibroblasts transfected with a viral vector carrying the human GM-CSF receptor.

There is a general need in human and veterinary medicine to influence immune responses to prevent or cure diseases and infections. Additionally, in veterinary medicine, reaching and maintaining an effective immune status is one of the crucial factors to make modern ways of intensive animal farming possible in the first place. Consequently, it is a common goal in the art to search for ways to make an organisms' immune response more effective, to make it start earlier after infection or vaccination, and to maintain an immune response for a longer duration.

This also applies to modern ways of rearing poultry. Chickens, ducks, turkeys etc. are being kept in- or outdoors in flocks of many thousand animals. A crucial aspect of their management is the prevention of diseases caused by the combination of environmental stress factors and exposure to pathogens, through efficient immune protection methods. To that purpose, poultry produced in developed countries, both for consumption and egg-laying, are routinely vaccinated against a variety of viral, bacterial, and parasitic antigens. A continued need exists to improve and prolong the immuneresponses from these vaccinations. For avian organisms such vaccinations can be performed either before or after hatching from the egg. Vaccination before hatching, usually at a few days before hatch, has as major advantage that the chick at hatch already has some immunity against pathogenic agents that would otherwise put it at risk already at that stage. However, as the immune systems of embryos and newly hatched birds is not yet fully developed, it cannot give rise to an immune response that is as effective as when vaccinated at 1 - 3 weeks after hatching. For the development of vaccines used pre-hatching or at-hatching, therefore a need exists for agents that promote immunomaturation, i.e. that stimulate or enhance the development of the birds' immune response.

In the search for immunomodulators, avian cytokines have been used for improving immune protection with varying levels of success. Avian cytokines have been administered as therapeutic protein, as vaccine adjuvant, and as insert in viral vectors. General reviews on avian cytokines and their uses were given by Hilton, L.S., et al. (2002, Vet. Immunol. Immunopathol., vol. 85, p. 119-128), Staeheli, P. etal. (2001, J.

Interferon Cytokine Res., vol. 21, p. 993-1010) and Lowenthal, J. et al. (2000, Dev. Comp. Immunol, vol. 24, p. 355-365). Specific constructs of avian cytokines other than GM-CSF, and their uses in poultry medicine are described in e.g. WO 97/028816 and WO 02/102404. In a recent publication (P. Kaiser et al., 2004, Dev. and Comp. Immunol., vol. 28, p.

375-394) a cluster of cytokine genes on chicken chromosome 13 was described, comprising the chicken orthologs of IL-4, IL-13 and IL-5. However, the Ch GM-CSF could not be identified in these studies.

Therefore, neither a protein nor a gene for a GM-CSF of an avian species has so far been described. Whether an avian equivalent to the mammalian GM-CSF even exists is so far unknown, as attempts for the identification of a gene or a protein of GM-CSF of an avian species using common techniques have not been successful. These included the use of (degenerated) probes or primers based on conserved regions in mammalian GM-CSF encoding nucleic acids (e.g. as employed in WO 00/77210), or use of multivalent polyclonal antibodies. Also the use of genetic markers known from mammalian cytokine genetics (e.g. as employed in P. Kaiser, 2004, supra) has not been successful. Apparently there is a lack of significant homology between mammalian and avian GM-CSF genes and proteins, causing the failure of these approaches. Additionally, mammalian GM-CSF is generally considered not to be effective in avian organisms.

For the purpose of inducing immunomaturation and immunomodulation in avian species it would be highly advantageous to have a biologically active avian GM-CSF protein or its encoding gene available. It is therefore an object of the invention to provide a protein, or a nucleic acid encoding such protein, that has at least one of the biological activities of an avian GM-CSF. It was surprisingly found now that the amino acid sequence of SEQ ID NO: 2, and the nucleotide sequence of SEQ ID NO: 1, constitute respectively a protein and a cDNA encoding such a protein, which protein is shown to have the biological activities of an avian GM-CSF.

Herewith the first avian GM-CSF protein and encoding nucleic acid are disclosed. The GMCSF protein and the encoding nucleic acid can now be employed as described above for mammalian GM-CSF, e.g. by expression and purification from recombinant expression systems, by synthesis of nucleic acid constructs, and by incorporation into live recombinant carriers. Additionally, this first avian GM-CSF nucleic acid and protein now allows the generation of primers, probes and antibodies for the identification of homologous GM-CSF molecules in other avian species. Consequently it is now possible for the first time to use an avian GM-CSF for the purpose of immunomaturation and/or immunomodulation in avian organisms, by efficient stimulation of avian blood cell proliferation and differentiation, and by enhancing, increasing, or otherwise facilitating the quantity and/or quality of an immune response in an avian organism. Advantageous effects of such uses of avian GM-CSF are e.g. stronger, earlier, and longer lasting vaccine efficacies, resulting in the possibility to reduce the number and the dose of vaccinations, as well as the possibility to immunize effectively at an earlier age, even before hatching.

Therefore, the invention relates to an isolated protein or a functional fragment thereof, characterised in that the protein comprises an amino acid sequence having at least 70 % amino acid similarity to the amino acid sequence of SEQ ID NO: 2, whereby the protein or the fragment has at least one of the biological activities of avian GM-CSF.

In an embodiment, the protein of the invention comprises an amino acid sequence having 75 %, preferably 80, 85, 90, 92, 94, 95, 96, 97, 98 or 99 % amino acid similarity to the amino acid sequence of SEQ ID NO: 2, whereby the protein has at least one of the biological activities of avian GM-CSF.

In a more preferred embodiment, the amino acid sequence of the protein of the invention is SEQ ID NO: 2. SEQ ID NO: 2 represents the amino acid sequence of protein forming chicken GM-CSF, predicted by computer translation from the nucleotide sequence of SEQ ID NO: 1.

With "isolated" is meant that the protein is isolated from the natural state, i.e. it has been changed or moved from its natural environment or both. The molecule is separate and discrete from the whole organism with which the molecule is found in nature.

The term "protein" is meant to incorporate a molecular chain of amino acids. A protein is not of a specific length, structure or shape and can, if required, be modified in vivo or in vitro, by, e.g. glycosylation, amidation, carboxylation, phosphorylation, or changes in spatial folding. Also, protein-salts, -amides, and -esters (especially C-terminal esters), and N-acyl derivatives are within the scope of the invention. Inter alia, peptides, oligopeptides and polypeptides are included within the definition of protein, as well as precursor-, pre-pro- and mature forms of the protein. A protein can be of biologic and/or of synthetic origin. A protein may be a chimeric or fusion protein, created from fusion by biologic or chemical processes, of two or more protein fragments.

The term "similarity" refers to a degree of similarity between proteins in view of differences in amino acids, wherein the differing amino acids are functionally similar e.g. in view of almost equal size, polarity or hydrophobicity. The "% amino acid similarity" of a proteins' amino acid sequence with a protein according to the invention can be determined by amino acid alignment to the full-length amino acid sequence of SEQ ID NO: 2. The percentage of similarity with a protein according to the invention can be determined with the computer program "BLAST 2 SEQUENCES" by selecting sub-program: "BlastP" (T. Tatusova & T. Madden, 1999, FEMS Microbiol. Letters, vol. 174, p. 247-250), that can be used via the internet address www.ncbi.nlm.nih.gov/blast/bl2seq/bl2.html. The comparison-matrix to be used is: "Blosum62"₁ with the default parameters: open gap penalty: 11; extension gap penalty: 1, and gap x_dropoff: 50. This computer program reports the percentage of amino acids that are identical as

"Identities", and the percentage of amino acids that are similar as "Positives". "Positive" amino acids are those amino acids that are identical plus those that are equivalent; "equivalent" are amino acids that are related and commonly substituted, as described below.

The skilled person appreciates that for avian GM-CSF proteins natural variations exist between such proteins present in various individuals, races and species of avians. Such variant, homologous, or polymorphic forms of the protein may take the form of (an) amino acid difference(s) in the overall sequence or by deletions, substitutions, insertions, inversions or additions of (an) amino acid(s) in said sequence. For example, amino acid substitutions, which do not essentially alter biological activities have been described, e.g. by Neurath et al. (1979, in: "The Proteins", Academic Press New York). Amino acid replacements between related amino acids or replacements which have occurred frequently in evolution are, i.a. Ser/Ala, Ser/Gly, Asp/Gly, Asp/Asn, and lle/Val (see Dayhof, M.D., 1978, "Atlas of protein sequence and structure", Nat. Biomed. Res. Found., Washington D.C., vol. 5, suppl. 3). Other common amino acid substitutions include Asp/Glu, Thr/Ser, Ala/Gly, Ala Thr, Ser/Asn, Ala/Val, Thr/Phe, Ala Pro, Lys/Arg, Leu/He, Leu/Val and Ala/Glu. Such related and commonly substituted amino acids are termed "equivalenf , for the purpose of calculation of the percentage similarity by the BlastP program. Based on this information, Lipman and Pearson developed a method for rapid and sensitive protein comparison (1985, Science, vol. 227, p. 1435-1441) and determination of the functional similarity between proteins. Such amino acid substitutions of a protein according to the invention or a functional fragment thereof, as well as variations having deletions and/or insertions are considered as biological- or functional homologs, and are within the scope of the invention as long as the resulting protein retains at least one of the biological activities of an avian GM-CSF. This explains why a protein according to the invention or a functional fragment thereof, when isolated from different avian organisms, may have an amino acid similarity down to 70. % when compared to the amino acid sequence depicted in SEQ ID NO: 2, while still representing the same protein with the same biological activities.

A comparison of the amino acid sequences of GM-CSF proteins known to date with that of SEQ ID NO: 2 (derived from a chicken), is presented in Figures 1-3. In Figure 2 pair wise amino acid alignments using the BlastP program were performed, and the resulting percentages of similar amino acids (% Positives) are indicated. This shows that similarities amongst mammalian GM-CSF proteins, can be as high as 98 % (Baboon -vs- Macaque) or as low as 60 % (Gerbil -vs- Guinea Pig). However, the similarity of mammalian GM-CSF proteins with the amino acid sequence of chicken GM-CSF as in SEQ ID NO: 2 is maximally 45 % (Baboon or Macaque -vs- Chicken). This illustrates the low level of homology between mammalian and avian GM-CSF molecules that prevented identification of an avian GM-CSF protein based on homology or conservation of sequence, before the invention. From Figure 2 also follows the extent of the amino acid similarity of GM-CSF proteins between related species. For instance: mouse - rat - gerbil: 69-72 %, horse - cow - red deer - sheep: 86 - 90 %; dog - cat: 86 %; and human - baboon - macaque: 88-98 %. Therefore, a level of at least 70 % amino acid similarity can be expected between the amino acid sequence of GM-CSF proteins obtained from related avian species.

The term "avian" is meant to incorporate all species and organisms of the class Aves. Preferred organisms are selected from the group consisting of chicken, turkey, duck, goose, quail, partridge, pheasant, guinea fowl, ostrich, pigeon, canary, budgerigar, and parrot. More preferred organisms are selected from the group consisting of chicken, turkey, duck and goose. Most preferred is chicken.

The "biological activities" of avian GM-CSF comprise the ability of avian GM-CSF on avian cells to function as a colony stimulating- or haematopoietic growth factor, similar to the activities of mammalian GM-CSF on mammalian cells, as outlined above. Preferred biological activities are the proliferation and differentiation of granulocyte and macrophage precursors, and the ability to induce differentiation of dendritic cells from monocytes, for instance when applied together with IL-4. Such activities are normally detected in colony formation assays, e.g. using bone marrow cells; or in assays measuring activation of cells, e.g. through uptake of a marker compound, e.g. ³H-Thymidine, or through release of a detectable substance, e.g. NO. Such techniques are well-known in the art, e.g. from publications studying mammalian GM-CSF, whereby the interchange of avian cells for the mammalian cells is well with in the capacity of the skilled person; or from publications on the study of other avian cytokine growth factors, e.g. on bioactivity studies of chicken SCF, and Ch MGF. A well-known text book describing such methods is: Immunology Methods Manual, I. Lefkovits ed., Academic press San Diego, USA., ISBN: 0124427103. An assay for monitoring NO synthesis in HD11 cells is described in there: Siatskas, C. et al., 1997, p. 2255-2268, in: Immunology Methods Manual. Alternatively an NO assay is described by Ding, A, etal., (1988, J. Immunol., vol. 141, p. 2407-2412), and by Stuehr, D. J., & Nathan, C.F., (1989, J. Exp. Med., vol. 169, p. 1543-1555). A bioassay of rec expressed GM-CSF (mouse in E. coli) was described by: DeLamarter, J.F. et al. (1985, EMBO J., vol.4, p. 2575-2581), and proliferation of bone marrow cells by GM-CSF (human in E. coli) was described by Pullman W.E., etal. (1989, J. Immunol. Methods, vol. 24, p. 153-161). Finally, Nicolas-Bolnet, C. etal. (1995, Poultry Sci., vol. 74, p. 1970-1976) describe assays for induction of cell proliferation by other avian cytokines. Exemplary protocols of these techniques are also described in the examples to this invention. A "functional fragment" of a protein according to the invention is a protein fragment that has at least one of the biological activities of an avian GM-CSF outlined above, by retaining the part(s) of the protein which is/are essential for the proteins' biological activity. Such a functional fragment can fulfil this function, for example, when used alone or fused to heterologous sequences. Thus, such a functional fragment, may be a protein that is functional per se, or the fragment may be functional when linked to another protein, to obtain a chimeric protein.

The determination of a functional fragment of an avian GM-CSF can be based upon the results of studies of mammalian GM-CSF proteins, which have shown which regions are relevant for binding to the receptor and/or for biological activity. See for instance: Shanafelt A.B. et al. (1991, EMBO J., vol. 10, p. 4105-4112), Diederichs, K., etal. (1991, Science, vol. 254, p. 1779-1782), and Meropol, N.J. et al. (1992, J. Biol. Chem., vol. 267, p. 14266-14269). Although there is little amino acid sequence similarity between chicken and mammalian GM- CSF, it has been found now that there is conservation of the secondary structure between the proteins. This is depicted in Figure 4. As is well-known in the art, a proteins' primary structure (the amino acid sequence) determines its secondary structure, which is in turn the effector of its biological activity. Consequently, when the secondary structure is conserved, so are the functional regions, even if there are differences in the primary structure. The regions of secondary structure essential for the biological activity of GM-CSF, as for instance described for the mouse and human GM-CSF, are the same in the chicken counterpart.

Fragments can inter alia be produced by enzymatic cleavage of precursor molecules, using restriction endonucleases for the encoding nucleic acids, or proteases for the proteins. Other methods include chemical synthesis of the fragments or the expression of protein fragments from DNA fragments. Also fragments can be isolated from nature. For instance the signal sequence of GM-CSF is cut off upon passage of the native molecule through the cell on route to secretion. Therefore a mature secreted GM-CSF protein is a functional fragment within the scope of the invention.

In a preferred embodiment a functional fragment according to the invention has a length of at least 8 amino acids; more preferably 10, 15, 20, 25, 30, 40, 50, 75, 100, 125, or 144 amino acids.

The preferred way to produce a protein according to the invention or a functional fragment thereof is by using techniques of genetic engineering and recombinant expression. These may comprise using nucleic acids, cDNA fragments, recombinant DNA molecules, live recombinant carriers, and/or host cells.

It is well-known in the art, that many different nucleic acids can encode one and the same protein. This is a result of what is known in molecular biology as "wobble", or the

"degeneracy of the genetic code"; wherein several codons or triplets of mRNA will cause the same amino acid to be attached to the chain of amino acids growing in the ribosome during translation. It is most prevalent in the second and especially the third base of each triplet encoding an amino acid. This phenomenon can result in a heterology of about 30% for two different nucleic acids that still encode the same protein. Thus, two nucleic acids having a nucleotide sequence identity of about 70 % can still encode one and the same protein.

Therefore, another aspect of the invention relates to an isolated nucleic acid capable of encoding a protein according to the invention or a functional fragment thereof, characterised in that the nucleic acid has at least 70 % nucleotide sequence identity to the nucleotide sequence of SEQ ID NO: 1 , whereby the encoded protein or the functional fragment has at least one of the biological activities of avian GM-CSF.

In an embodiment, the nucleic acid of the invention is characterised in that the nucleic acid has at least 75 %, preferably 80, 85, 90, 92, 94, 95, 96, 97, 98 or 99 % nucleotide sequence identity to the nucleotide sequence of SEQ ID NO: 1 , whereby the encoded protein has at least one of the biological activities of avian GM-CSF.

In a more preferred embodiment, the nucleotide sequence of the nucleic acid of the invention is SEQ ID NO: 1.

SEQ ID NO: 1 represents the nucleotide sequence of cDNA of chicken GM-CSF obtained as outlined in Example 1.

The term "nucleic acid" is meant to incorporate a molecular chain of desoxy- or ribo-nucleic acids. A nucleic acid is not of a specific length, therefore polynucleotides, genes, open reading frames (ORF's), probes, primers, linkers, spacers and adaptors, consisting of DNA and/or RNA, are included within the definition of nucleic acid. A nucleic acid can be of biologic and/or synthetic origin. The nucleic acid may be in single stranded or double stranded form. The single strand may be in sense or anti-sense orientation. Also included within the definition are modified RNAs or DNAs. Modifications in the bases of the nucleic acid may be made, and bases such as Inosine may be incorporated. Other modifications may involve, for example, modifications of the backbone.

The term "encodes" is meant to incorporate: providing the possibility of protein expression, i.a. through transcription and/or translation when brought into the right context.

A nucleic acid according to the invention when brought into the right context, is capable of encoding a protein according to the invention, or a functional fragment thereof. For instance a nucleic acid according to the invention can be manipulated to encode a GM-CSF protein that lacks the N-terminal signal sequence, using techniques known in the art.

The "% nucleotide sequence identity" of a nucleic acids' nucleotide sequence with that of a nucleic acid according to the invention can be determined by nucleotide sequence alignment to the whole of, or to the relevant part of the nucleotide sequence of SEQ ID NO: 1.

The percentage of identity between a nucleic acid and a nucleic acid according to the invention can be determined with the computer program "BLAST 2 SEQUENCES" by selecting sub-program: "BlastN" (T. Tatusova & T. Madden, 1999, FEMS Microbiol. Letters, vol. 174, p. 247-250), that can be found at the internet address: www.ncbi.nlm.nih.gov/blast/bl2seq/bl2.html. Parameters that are to be used are the default parameters: reward for a match: +1 ; penalty for a mismatch: -2; open gap penalty: 5; extension gap penalty: 2; and gap x_dropoff: 50. Unlike the output of the BlastP program described above, the BlastN program does not list similarities, only identities: the percentage of nucleotides that are identical is indicated as "Identities".

Next to using computer algorithms for determining the level of identity/mismatch between a nucleic acid and a nucleic acid according to the invention, experimental techniques can also be used. Especially by hybridisation under conditions of controlled stringency.

The definition of stringent hybridisation conditions, as a function of the identity between two nucleotide sequences, follows from the formula for the melting temperature Tm of Meinkoth and Wahl (1984, Anal. Biochem., vol. 138, p. 267-284):

Tm = [81.5°C + 16.6(log M) + 0.41 (%GC) - 0.61 (%formamide) - 500/L] - 1 °C/1 % mismatch In this formula: M is the molarity of monovalent cations; %GC is the percentage of guanosine and cytosine nucleotides in the DNA; L is the length of the hybrid in base pairs; and "mismatch" is the lack of an identical match. Washing conditions subsequent to the hybridization can also be made more or less stringent, thereby selecting for higher or lower percentages of identity respectively. In general, higher stringency is obtained by reducing the salt concentration, and increasing the incubation temperature. It is well within the capacity of the skilled person to select hybridisation conditions that match a certain percentage-level of identity as determined by computer analysis.

"Stringent conditions" are those conditions under which a nucleic acid still hybridises if it has a mismatch of 30 %; i.e. if it is 70 % identical to the (relevant part of the) nucleotide sequence depicted in SEQ ID NO: 1. Therefore, if a nucleic acid hybridises under stringent conditions to the nucleotide sequence depicted in SEQ ID NO: 1 , it is considered a nucleic acid according to the invention.

The nucleotide sequence identity between chicken and mammalian cDNA coding for GMCSF is so low that a standard BlastN alignment of SEQ ID NO: 1 to e.g. the GenBank database does not report a significant match to any GM-CSF encoding sequence. From unrelated sequences no significant matches are detected of any sequence segment over 22 nucleotides. Sequences of such short length can only encode small peptides of some 7 amino acids. Such peptides are not able to induce one of the biological activities of a protein according to the invention. Therefore, peptides of 7 or less amino acids are not functional fragments of a protein according to the invention.

Therefore in a preferred embodiment a nucleic acid according to the invention is at least 25 nucleotides long, more preferably 50, 75, 10, 150, 200, 250, 300, 350, 400, or 435 nucleotides long.

Because the conservation of sequence identity among avian organisms is far greater than that between avian and mammalian organisms, it is now for the first time possible to use the sequence of an avian GM-CSF to obtain similar or homologous GM-CSF nucleotide sequences such as genes and mRNA's from other avian species. Such homologous genes can be called paralogs or orthologs. Methods to isolate a nucleic acid capable of encoding a GM-CSF from avian species are well-known in the art. For instance the chicken GM-CSF cDNA as depicted in SEQ ID NO: 1 can be used to make or isolate probes or primers. These can be used to screen libraries of genomic or mRNA sequences by PCR or hybridization selection. From a positive clone or colony, the GM-CSF insert can be obtained, subcloned and used e.g. in an expression system.

Alternatively, GM-CSF variants or homologues in other avian organisms can now conveniently be identified by computerised comparisons of SEQ ID NO:1 or a part thereof in silico to other avian sequences that may be comprised in a computer database. For that purpose many computer programs are publicly available. For instance the suite of BLAST programs (Altschul, S.F., et al, 1997, Nucleic Acids Res., vol. 25, p. 3389-3402) can be employed to compare SEQ ID NO: 1 to EST- and genomic sequence databases of avian organisms.

Therefore, in a preferred embodiment, the nucleic acid according to the invention is obtainable from an avian organism. More preferred, the nucleic acid is obtainable from an organism selected from the group consisting of chicken, turkey, duck, goose, quail, partridge, pheasant, guinea fowl, ostrich, pigeon, canary, budgerigar, and parrot. Even more preferred the nucleic acid is obtainable from an organism selected from the group consisting of chicken, turkey, duck and goose. In the most preferred embodiment, the nucleic acid according to the invention is obtainable from a chicken.

Nucleic acids according to the invention also include nucleic acids having variations in the nucleotide sequence when compared to SEQ ID NO: 1. "Variant" nucleic acids may be natural or non-natural variants. Natural variants include homologues, polymorphic forms and allelic variations between such nucleic acids obtainable from different individuals, races and species of avians. Non-naturally occurring variants may be introduced by mutagenesis. An allelic variant is one of several alternate forms of a gene occupying a locus on a chromosome of an organism. Sometimes, a gene is expressed in a certain tissue as a splicing variant, resulting in an altered 5' or 3' mRNA or the inclusion or exclusion of one or more exon sequences. These variant sequences, as well as the proteins encoded by these variant sequences, as far as these proteins have at least one of the biological activities of GM-CSF according to the invention, are within the scope of the invention.

Nucleic acids encoding a protein according to the invention or a functional fragment thereof, can be obtained, manipulated and expressed by standard techniques in molecular biology that are well-known to the skilled artisan, and are explained in great detail in standard textbooks like Sambrook & Russell: "Molecular cloning: a laboratory manual" (2001, Cold Spring Harbour Laboratory Press; ISBN: 0879695773). One such type of manipulation is the synthesis of a cDNA fragment from RNA, preferably from mRNA that is obtainable from an avian organism by techniques known in the art.

Therefore, in another aspect, the invention relates to a cDNA fragment according to the invention.

An isolated cDNA sequence may be incomplete due to incomplete transcription from the corresponding mRNA, or clones may be obtained containing fragments of the complete cDNA. Various techniques are known in the art to complete such partial cDNA sequences, such as RACE (rapid amplification of cDNA ends).

The preferred method of obtaining a cDNA fragment by reverse transcription is through a polymerase chain reaction (PCR) technique. Standard techniques and protocols for performing PCR are e.g. extensively described in C. Dieffenbach & G. Dveksler: "PCR primers: a laboratory manual" (1995, CSHL Press,

ISBN 879694473).

In yet another aspect, the invention relates to a recombinant DNA molecule comprising a nucleic acid, or a cDNA fragment according to the invention, the nucleic acid, or the cDNA fragment being functionally linked to a promoter.

To construct a recombinant DNA molecule according to the invention, preferably DNA plasmids are employed. Such plasmids are useful e.g. for enhancing the amount of DNA- insert, as a probe, and as tool for further manipulations. Examples of such plasmids for cloning are plasmids of the pBR, pUC, and pGEM series; all these are available from commercial suppliers. The nucleic acid or the cDNA fragment encoding a protein according to the invention or a functional fragment thereof, can be cloned into plasmids and be modified to obtain the desired conformation using techniques well-known in the art. Modifications to the coding sequences encoding a protein according to the invention or a functional fragment thereof may be performed e.g. by using restriction enzyme digestion, by site-directed mutations, or by polymerase chain reaction (PCR) techniques. For the purpose of purification, detection, or improvement of expression level of protein encoded by a recombinant DNA molecule according to the invention, additional nucleic acids may be added. This may result in the final nucleic acid or cDNA fragment comprised in the recombinant DNA molecule being larger than the sequences required for encoding a GM- CSF protein or a functional fragment thereof. When such additional elements are inserted in frame, a fusion protein is expressed, comprising a protein according to the invention or a functional fragment thereof. Such fusion proteins are also within the scope of the invention

An essential requirement for the expression of a nucleic acid, a cDNA fragment, or a recombinant DNA molecule is that these are operably linked to a transcriptional regulatory sequence such that this is capable of controlling the transcription of a nucleic acid, a cDNA fragment, or recombinant DNA molecule. Transcriptional regulatory sequences are well-known in the art and comprise i.a. promoters and enhancers. It is obvious to those skilled in the art that the choice of a promoter extends to any eukaryotic, prokaryotic or viral promoter capable of directing gene transcription, provided that the promoter is functional in the expression system used.

In again another aspect, the invention relates to a live recombinant carrier comprising a nucleic acid, a cDNA fragment, or a recombinant DNA molecule according to the invention.

A live recombinant carrier (LRC) is a micro-organism such as e.g. bacteria, parasites and viruses, in which additional genetic information has been cloned, in this case a nucleic acid, a cDNA fragment, or a recombinant DNA molecule, capable of encoding a protein according to the invention or a functional fragment thereof. Target organisms inoculated with such LRC's will produce an immunogenic response not only against the immunogens of the carrier, but also against the heterologous protein(s) or fragments) for which the genetic code is additionally cloned into the LRC, e.g. a nucleic acid encoding a GM-CSF protein or a functional fragment thereof. As an example of bacterial LRC's, attenuated Salmonella strains known in the art can attractively be used. Alternatively, live recombinant carrier parasites have i.a. been described by Vermeulen, A. N. (1998, Int. Journ. Parasitol., vol. 28, p. 1121-1130). LRC's may be used as a way of transporting a nucleic acid to or into a target cell, so only as a delivery vehicle relying on the cell itself to provide expression. Also an LRC may itself provide expression of the heterologous nucleic acid, in the target organisms, or inside a cell of the target organism. LRC's have several advantages over administration e.g. of a subunrt protein, among these: only small quantities of inoculum are required (when the carrier is able to replicate); and the immune response induced by the carrier micro-organism may boost the response to the heterologous protein. Also, an LRC with an insert may form a combination vaccine, providing multiple protection in one vaccination. When the LRC is a virus, such viruses are also called carrier- or vector viruses. Viruses used as vectors are for instance vaccinia-, herpes-, or retroviruses, as well as pox- and myxomaviruses. (For reviews, see theme issue of Meth. Mol. Biol, vol. 246, 2004.)

The technique of in vivo homologous recombination, well-known in the art, can be used to introduce a nucleic acid according to the invention into the genome of an LRC bacterium, parasite or virus of choice, capable of inducing expression of the inserted nucleic acid, cDNA fragment or recombinant DNA molecule according to the invention, in the target organism.

In an embodiment, the LRC according to the invention is itself an avian pathogen. Preferably the strain of the pathogen is one that has attenuated pathogenicity or virulence compared to wild type strains. This attenuated phenotype is present e.g. because the strain used is itself a vaccine strain, or because the insertion of the heterologous nucleic acid disrupts a virulence gene. Preferred pathogens for use as LRC are: Salmonella, Herpes Virus of Turkeys (HVT), Marek's disease virus, infectious laryngotracheitis virus, fowl adenovirus, Fowlpox virus, myxomavirus, or Newcastle disease virus. Each may.comprise a nucleic acid, a cDNA fragment, or a recombinant DNA molecule according to the invention. Most preferred LRC is an HVT viral vector. Methods of introducing a heterologous nucleic acid into a viral vector have e.g. been described for HVT by Sondermeijer, P. et al. (1993, Vaccine, vol. 11 , p. 349-358).

Therefore, in a preferred embodiment the invention relates to a live recombinant carrier according to the invention, comprising HVT.

The LRC may also comprise heterologous nucleic acid sequences in addition to those according to the invention, for instance coding for additional cytokines or for an antigen. Preferred additional cytokine-encoding nucleic acid is one encoding the chicken Interleukin 4, for instance as represented by SEQ ID NO: 15 and 16; preferred antigen-encoding nucleic acids are those encoding the nucleoprotein from Infectious bronchitis virus, and the fusion protein from Newcastle disease virus. Bacterial, yeast, fungal, insect, and vertebrate cells are commonly used as host cells for an expression system. Such expression systems are well-known in the art and generally available, e.g. commercially through Invitrogen (the Netherlands).

Therefore, in even another aspect, the invention relates to a host cell comprising a nucleic acid, a cDNA fragment, a recombinant DNA molecule, or a live recombinant carrier, all according to the invention.

A host cell according to the invention may comprise a nucleic acid, a cDNA fragment, a recombinant DNA molecule, or a live recombinant carrier according to the invention, stably integrated into its genome, or as an extrachromosomal body replicating autonomously.

A host cell to be used for expression of a protein according to the invention or a functional fragment thereof, may be a cell of bacterial origin, e.g. from Escherichia coli, Bacillus subtilis, Lactobacillus sp. or Caulobacter crescentus, in combination with the use of bacteria-derived plasmids or bacteriophages for expressing the sequence encoding a GM-CSF protein. The host cell may also be of eukaryotic origin, e.g. yeast-cells (e.g. Saccharomyces, Pichia) in combination with yeast-specific vector molecules; insect cells in combination with recombinant baculo-viral vectors e.g. Sf9 and pVL1393 (Luckow et a/.,1988, Bio-technology, vol. 6, p. 47-55); plant cells in combination with e.g. Ti-plasmid based vectors or plant viral vectors (Barton, K.A. et al., 1983, Cell, vol. 32, p. 1033-1043); or mammalian cells also with appropriate vectors or recombinant viruses, such as Hela cells, CHO, CRFK, or BHK cells, or avian cells such as chicken embryo fibroblasts (CEF), HD11 (a chicken macrophage cell line) or DT-40 (a chicken B-lymphocyte cell line).

Preferred host cell for the invention is an insect cell such as Sf9 or Sf158, comprising a recombinant baculovirus, which insect cell comprises a nucleic acid or cDNA fragment according to the invention inserted behind a baculoviral promoter, such as the polyhedrin or p10 promoter.

Next to cellular expression systems, whole organism expression systems are attractive expression systems. For instance, plant expression systems, as the proteins produced can be used as animal feed. Plant cell expression systems for polypeptides for biological application are e.g. discussed in R. Fischer etal. (Eur. J. of Biochem. 1999, vol. 262, p. 810- 816), and J. Larrick et al. (Biomol. Engin. 2001 , vol. 18, p. 87-94). Also, expression of a protein according to the invention or a functional fragment thereof, may be achieved by generation of a genetically modified avian organism. Techniques creating genetically engineered organisms are well-known in the art. For instance techniques of generating transgenic chickens have been reviewed in Ivarie, R. (2003, Trends Biotechnol., vol. 21, p. 14-19). In a transgenic avian organism a constant level of expression of an additional, a heterologous, or a modified GM-CSF would ensure the biological activity of GM-CSF is effectuated at a desired time and at a desired level. Careful selection of the level of GM-CSF expression must be made, in order not to disturb the organisms' homeostasis.

Expression may also be performed in so-called cell-free expression systems. Such systems comprise all essential factors for expression of an appropriate nucleic acid, operably linked to a promoter that will function in that particular system. Examples are the E. coli lysate system (Roche, Basel, Switzerland), or the rabbit reticulocyte lysate system (Promega corp., Madison, USA).

A protein according to the invention, or a functional fragment thereof, or a nucleic acid, cDNA fragment, recombinant DNA molecule, live recombinant carrier, and/or a host cell according to the invention for the first time allow the identification of molecules capable of specific binding to these compounds by well-known screening techniques. For instance an avian GMCSF protein or a functional fragment thereof can be used to identify the avian receptor for GM-CSF on target cells. Alternatively, specific antibodies can be generated against a protein according to the invention or a functional fragment thereof. Such antibodies can be used e.g. for therapy, for diagnostics, or for quality assurance purposes.

Therefore a further aspect of the invention relates to an antibody capable of specific binding to a protein according to the invention, or to a functional fragment thereof.

Methods of raising and producing antibodies, or antisera comprising antibodies, as well as the concept of "specific binding" by an antibody, are well-known in the art.

As outlined above, mammalian GM-CSF is known to be beneficial in treatment of neutropenia, allergy, cancer, and infections. Also described is the use of avian cytokines, other than GM-CSF, for influencing the immunological response of an avian organism. The medical uses of the protein of the invention or a functional fragment thereof have been outlined above: the immunomaturation and/or immunomodulation in avian organisms, by efficient stimulation of avian blood cell proliferation and differentiation, and/or by enhancing, increasing, or otherwise facilitating the quantity and/or quality of an immune response in an avian organism. These can be put to practice in avian veterinary medicine e.g. by administering to an avian organism a protein according to the invention or a functional fragment thereof.

Therefore, a further aspect of the invention relates to the protein according to the invention or a functional fragment thereof, for use as a medicament for an avian organism.

The invention also relates in a further aspect, to the use of a protein according to the invention or a functional fragment thereof, for the manufacture of a medicament for influencing the immunological response of an avian organism.

In a further aspect, the invention relates to a method of influencing the immunological response of an avian organism by administering to an avian organism a protein according to the invention or a functional fragment thereof in a pharmaceutically effective amount and in a pharmaceutically acceptable formulation.

A "pharmaceutically effective amount" will be outlined below.

A "pharmaceutically acceptable formulation" can e.g. be water, saline, or a buffer suitable for the purpose. In a more complex form the formulation may comprise an emulsion which itself comprises other compounds, such as a cytokine, an adjuvant, an antigen etc.

Preferred medical uses for a protein according to the invention or a functional fragment thereof, are the induction of immunomaturation and immunomodulation in an avian organism.

Immunomaturation can be achieved by administering to an avian organism a protein according to the invention or a functional fragment thereof, which results in efficient proliferation and differentiation of blood cells. This results in an earlier, stronger, more efficient immune response to infection or vaccination, which also is of longer duration. This is caused, besides other effects, by the proliferation of granulocytes, macrophages and dendritic cells, which cause the immune system of the target organism to mature at an enhanced rate compared to untreated organisms. This results in the treated targets to be susceptible to vaccination at an earlier age, or to be better able to cope with infections or disease at an earlier age.

In an embodiment immunomaturation by a protein according to the invention or a functional fragment thereof, is achieved by administration to chickens in ovo. Such administration can e.g. be in the form of injection in ovo of a composition comprising the protein of SEQ ID NO: 2 and a pharmaceutically acceptable additive.

Therefore, in a further aspect, the invention relates to a composition comprising a protein according to the invention or a functional fragment thereof, in a pharmaceutically acceptable formulation.

Immunostimulation is achieved by the immunomaturation above, but preferably by the use of a protein according to the invention or a functional fragment thereof, as an adjuvant.

An "adjuvant" is a substance that boosts the immune response of the target. The choice for a particular adjuvant determines the route of the immune response, and therefore its efficacy. For that purpose GM-CSF can be used as adjuvant or as additional adjuvant, to steer an immune response towards the Th1 or to the Th2 route. Additionally, an adjuvant, such as GM-CSF helps to strengthen the immune response upon vaccination, infection or disease.

Such use as an adjuvant can be implicit in the use for immunomaturation. However, as cytokines are known to resort their effects in combination with and depending from other factors, the application of a protein according to the invention or a functional fragment thereof, in a context that does not favour immunomaturation, may give rise only to the effect of immunostimulation. Such a context can exists for instance when organisms are treated at an older age, or when a protein according to the invention or a functional fragment thereof, is mixed with other immuno-active compounds that do not favour immunomaturation.

For use as an adjuvant, a protein according to the invention or a functional fragment thereof, can be administered to an avian organism as described above. Alternatively, the use as an adjuvant of a protein according to the invention or a functional fragment thereof, is achieved by admixture with an existing vaccine. The protein or the functional fragment can be added to the antigen or to the adjuvant when present; can be added to the water phase or can be emulsified into an oil phase when present. Alternatively, antigens and pharmaceutically acceptable additives can be admixed with the protein according to the invention or the functional fragment. In a preferred embodiment a protein according to the invention or a functional fragment thereof is admixed with a vaccine of a live, live attenuated, or killed avian pathogen. This way, at least one of the biological activities of avian GM-CSF is added to the effects of the receiving vaccine composition, causing additional or more desired immunostimulatory effects, for instance by modulating an immune response that would normally proceed via the Th2 route, to proceed along a Th1 route now. The avian pathogen can be of viral, bacterial or parasitic origin. The vaccine antigen can be a whole (killed) organism or an isolated part or fraction. The vaccine can itself be a combination vaccine. The vaccine can comprise an adjuvant. The adjuvant can comprise an additional cytokine.

Similar to the medical use of a protein according to the invention or a functional fragment thereof, such medical uses are now for the first time possible using a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell according to the invention, to induce immunomaturation and immunostimulation in an avian organism.

The concepts of immunomaturation and immunostimulation have been described above. Preferred use of a nucleic acid, a cDNA fragment, or a recombinant DNA molecule according to the invention for the purpose of immunomaturation and/or immunostimulation is through DNA vaccination. DNA plasmids carrying a nucleic acid, a cDNA fragment, a recombinant DNA molecule according to the invention can be administered to an avian organism as described above. Such methods are well-known in the art. Nucleic acid vaccines (or gene- or genetic-vaccines as they are called) may require a targetting- or a delivery vehicle other than an LRC to target or protect it, or to assist in its uptake by (the cells of) the host. Such vehicles may be biologic or synthetic, and are for instance virus-like particles, liposomes, or micro-, powder-, or nano particles delivered for instance via a GeneGun®. All these are well-known in the art. A targetting- or delivery vehicle comprising a nucleic acid, a cDNA fragment, or a recombinant DNA molecule according to the invention, is within the scope of the invention.

These uses will result in nucleic acid being delivered, or protein being expressed inside the target organism or its cells.

Therefore, the invention relates in a further aspect, to a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention, for use as a medicament for an avian organism.

In a further aspect, the invention relates to the use of a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention, for the manufacture of a medicament for influencing the immunological response of an avian organism. In a further aspect, the invention relates to a method of influencing the immunological response of an avian organism by administering to an avian organism a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention, in a pharmaceutically effective amount and in a pharmaceutically acceptable formulation.

A nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention, can advantageously be admixed with an existing vaccine, as described above for a protein according to the invention or a functional fragment thereof.

Also, the invention relates in a further aspect to a composition comprising a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention, in a pharmaceutically acceptable formulation.

Similar to what is described above for compositions comprising a protein according to the invention or a functional fragment thereof, in an embodiment, a composition comprising a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention, can be admixed with antigen, adjuvant, cytokine, vaccine, etc.

Therefore, in a preferred embodiment the invention relates to an adjuvant composition comprising a protein according to the invention or a functional fragment thereof, or a nucleic acid, a cDNA fragment, a recombinant DNA molecule, a live recombinant carrier, or a host cell, all according to the invention.

A composition according to the invention can advantageously be combined with a pharmaceutical component such as an antibiotic, a hormone, or an anti-inflammatory drug.

A composition according to the invention can equally be used as prophylactic and as therapeutic treatment, to achieve immunomaturation and/or immunostimulation. This way it interferes with establishment and/or with the progression of an infection, with the progression of clinical symptoms of a disease, or with the efficacy of a vaccination. A composition according to the invention can be administered to a target according to methods known in the art, depending on characteristics of the target species, characteristics of the composition itself, desired effects, and economy of application. Application methods comprise application e.g. parenterally, comprising all routes of injection into or through the skin: e.g. intramuscular, intravenous, intraperitoneal, intradermal, submucosal, or subcutaneous. Also, they may be applied by topical application as a drop, spray, gel or ointment to the mucosal epithelium of the eye, nose, mouth, anus, or vagina, or onto the epidermis of the outer skin at any part of the body. Other possible routes of application are by spray, aerosol, or powder application through inhalation via the respiratory tract. In this case the particle size that is used will determine how deep the particles will penetrate into the respiratory tract. Alternatively, application can be via the alimentary route, by combining with the feed or drinking water e.g. as a powder, a liquid, or tablet, or by administration directly into the mouth as a liquid, a gel, a tablet, or a capsule, or to the anus as a suppository.

A composition according to the invention may take any form that is suitable for veterinary administration, and that matches the desired route of application and desired effect. Preparation of a composition according to the invention is carried out by means conventional for the skilled person. Preferably the composition according to the invention is formulated in a form suitable for injection such as a suspension, solution, dispersion, emulsion, and the like. Commonly such compositions are prepared sterile.

The dosing scheme of the application of a composition according to the invention to the target organism can be in single or multiple doses, which may be given at the same time or sequentially, in a manner compatible with the dosage and formulation, and in such an amount as will be immunologically effective. It is well within the capacity of the skilled person to determine whether a treatment is

"immunologically effective", for instance by determining a targets' clinical signs of disease or serological parameters.

A target organism for the invention is an organism of the class Aves. Preferred target organisms are selected from the group consisting of chicken, turkey, duck, goose, quail, partridge, pheasant, guinea fowl, ostrich, pigeon, canary, budgerigar, and parrot. More preferred target organisms are selected from the group consisting of chicken, turkey, duck and goose. Most preferred target organism is chicken. The target organism may be healthy or diseased. The target may be of either sex, and of any age, even premature. Preferred target for administration of a composition according to the invention, is the fertilized avian egg. In ovo vaccinations are normally deposited into the amniotic cavity or into the embryo in the fertilized egg. For chickens a much used time of in ovo application is at about 18 days of age i.e. about 3 days before hatch.

A stabilizer can be added to a composition according to the invention e.g. to protect it from degradation, to enhance the shelf-life, or to improve freeze-drying efficiency. Useful stabilizers are i.a. SPGA (Bovarnik etal., 1950, J. Bacteriology, vol. 59, p. 509), skimmed milk, gelatine, bovine serum albumin, carbohydrates e.g. sorbitol, mannitol, trehalose, starch, sucrose, dextran or glucose, proteins such as albumin or casein or degradation products thereof, and buffers, such as alkali metal phosphates.

It goes without saying that admixing other stabilizers, carriers, diluents, emulsions, and the like to compositions according to the invention are also within the scope of the invention.

Such additives are for instance described in well-known handbooks such as: "Remington: the science and practice of pharmacy" (2000, Lippincot, USA, ISBN: 683306472), and: "Veterinary vaccinology" (P. Pastoret etal. ed., 1997, Elsevier, Amsterdam, ISBN: 0444819681).

For reasons of e.g. stability or economy a composition according to the invention may be freeze-dried. In general this will enable prolonged storage at temperatures above zero ° C, e.g. at 4°C. Procedures for freeze-drying are known to persons skilled in the art; equipment for freeze-drying at different scales is available commercially. Therefore, in a preferred embodiment, a composition according to the invention is characterised in that the composition is in a freeze-dried form.

To reconstitute a freeze-dried composition, it may be suspended in a physiologically acceptable diluent. Such a diluent can e.g. be as simple as sterile water, or a physiological salt solution. In a more complex form it may be suspended in an emulsion e.g. as outlined in PCT/EP99/10178.

What constitutes a "pharmaceutically effective amounf for a composition according to the invention, is dependent on the desired effect and on the target organism. Determination of the effective amount is well within the routine skills of the practitioner. A preferred amount of a protein according to the invention or a functional fragment thereof, comprised in a composition according to the invention, is between 1 ng and 1 mg. Preferably the amount is between 10 ng and 100 μg/dose, more preferably between 100 ng and 10 μg/dose. A preferred amount of a nucleic acid, a cDNA fragment, or a recombinant DNA molecule according to the invention, comprised in a composition according to the invention, is between 1 ng and 100 μg. Preferably the amount is between 10 ng and 10 μg/dose. A preferred amount of a live recombinant carrier according to the invention, comprised in a composition according to the invention, is dependent on the characteristics of the carrier microorganism used. Such an amount is expressed for instance as plaque forming units (pfu), colony forming units (cfu) or tissue culture infective dose 50% (TCID₅₀), depending on what is a convenient way of quantifying the LRC organism. For instance for a live viral vector a dose rate between 1 and 10¹⁰ plaque forming units (pfu) may advantageously be used; preferably a dose rate between 10 and 10⁵ pfu per animal. A preferred amount of a host cell according to the invention, comprised in a composition according to the invention, is between 1 and 10⁹ host cells per dose. Preferably between 10 and 10⁷ cells per dose are used.

The invention will now be further described with reference to the following, non-limiting, examples.

EXAMPLES

Example 1 : Isolation of Chicken GM-CSF cDNAfrom HD11 cells

The chicken macrophage-like cell-line HD11 (Beug, H. etal., Cell, vol. 18, p. 375-390) was cultured in RPM1 1640 (Sigma), containing 10 % v/v tryptose phosphate broth, 2.5 % v/v heat-inactivated foetal calf serum, 2.5 % v/v heat-inactivated chick serum (Invitrogen), 20 mM L-glutamine, 1U/ml penicillin and 1 μg/ml streptomycin, at 41 °C in a humidified incubator with 5% CO₂ environment. The cells were passaged every 3-4 days using trypsin.

HD11 cells were stimulated with lipopolysaccharide (LPS) as follows: at 75-80 % confluence,

HD11 cells in a T75 flask were incubated with LPS (serotype E. coli O55:B5, Sigma) for 3 hours. Thereafter cells were washed, trypsinised, centrifuged and used for RNA isolation, using an RNeasy® mini kit (Qiagen), following the manufacturer's instructions. Next, chicken GM-CSF cDNA was made by RT-PCR: 39 μl of DEPC treated water was added to Ready-To-Go® RT-beads (Amersham Biosciences) and incubated for 5 minutes on ice. Primers used were

GMC/1 : 5' - ATGCTGGCCCAGCTCACTATTC - 3' (SEQ ID NO: 3), and

GMC/4: 5' - CAGTTGCAGTAGAGTTATTTCCTG - 3' (SEQ ID NO: 4), Each primer was added at 5 μl of 4 pM/μl, to 1 μl of RNA (obtained as described above), and an RT-PCR program was run: 1 cycle of 42°C for 30 min, followed by 95°C for 5 min. Subsequently 30 cycles were run with 1 min 95°C; 2 min 55°C; and 2 min 72°Cper cycle. This was followed by a second round of PCR amplification, using 26 μl water, 5 μl RT PCR product, 5 μl of each primer GMC/1 and GMC/4 (4 pM/μl), 5 μl 10x PCR buffer (Invitrogen), 1.5 μl MgCI₂ (50 mM), 2.0 μl dNTPs (10 mM), and 0.5 μl Taq polymerase (Invitrogen). Again 30 cycles of 1 min 95°C; 2 min 55°C; and 2 min 72°C per cycle were run. A sample from the second round of amplification was tested via electrophoresis on an agarose gel using standard conditions. A band of approximately 435 bp was visible. Next, the entire PCR product from the second amplification was run on an agarose gel, and the 435 bp band was cut out from the gel. A QIAquick® gel extraction kit (Qiagen) was used to isolate and purify the cDNA. Then samples were made for sequence analysis; 2 μl of product from the second PCR, was mixed with 4 pmoles of each primer in separate reactions, and 4 μl of Quickstart® mix (Beckman Coulter) in a final reaction volume of 20 μl. PCR was performed using 30 x [20 sec. 96 °C; 20 sec. 50°C; 4 min 60 °C]. The sequencing reactions were precipitated using 0.3 M final concentration Sodium acetate and glycogen, and sequenced on a CEQ 8000 capillary sequencer (Beckman Coulter). The sequencing result revealed the sequence of chicken GM-CSF cDNA, as represented in SEQ ID NO:1.

The amino acid sequence of GM-CSF as represented in SEQ ID NO: 2 was obtained by translation of SEQ ID NO: 1 via 'Translate', a computer program from the GCG/Wisconsin suite of molecular biology analysis programs.

Example 2: Subcloning chicken GM-CSF cDNA

The PCR product from the second round of PCR as outlined in Example 1 was TA cloned into pGEM®-T easy vector (Promega), by following the manufacturer's protocol. Next 4 μl of ligation reaction were used to transform competent DH5-α E. coli bacterial cells by heat shock, the cells were plated out onto LB plates with 100 μg/ml Ampicillin (LB Amp-mo plates), and incubated overnight (o/n) at 37 °C. Resulting colonies were picked and plasmid DNA prepared using QIAprep® miniprep kit (Qiagen). Plasmid obtained was pGTChGMCSF. Isolated plasmids were digested with EcoRI to excise the insert, which was separated on an agarose gel, cut out and isolated using a QIAquick® gel extraction kit. The insert was ligated into shrimp-alkaline phosphatase-treated and EcoRI digested pClneo vector

(Promega) using T4 DNA ligase (Invitrogen). Two μl of the ligation reaction were used to transform competent DH5-alpha E. coli cells, by heat-shock treatment. Cells were again plated onto LB-Amp₁₀o plates, and incubated o/n. Resulting colonies were picked and plasmid DNA prepared using the miniprep kit. Miniprep plasmid samples were screened by restriction digest and analysis on agarose gel, to identify clones containing the GM-CSF cDNA insert. A positive plasmid was again sequenced to confirm the correctness of the insert. A large batch of endotoxin-free plasmid DNA was prepared from that positive plasmid sample by overnight culture in LB Ampioo medium and isolation using Endotoxin-free Plasmid Maxi® kit (Qiagen) according to the manufacturer's instructions. This resulted in a working batch of pClneoChGMCSF plasmid, which was quantified via GeneQuant® pro spectrophotometer (Amersham Biosciences). Example 3: Real-time quantitative RT-PCR analysis of GM-CSF expression in tissues and activated cells

GM-CSF mRNA expression in chicken cells and tissues was quantitated using a well described method of real-time quantitative RT-PCR analysis (see: Kaiser, P. et al., 2002, J. Immunol., vol. 168, p. 4216-4220; and Kaiser, P. et al., 2003, J. Virol., vol. 77, p. 762-768). Probes used for GM-CSF and 28S RNA-specific amplification are presented in Table 1. Real-time quantitative RT-PCR was performed using the Reverse Transcriptase qPCR Master Mix RT-PCR kit® (Eurogentec, Belgium). Amplification and detection of specific products were performed using the ABI PRISM 7700® Sequence Detection System (PE Applied Biosystems) with the following cycle profile: one cycle of [50°C for 2 min, 96°C for 5 min, 60°C for 30 min, and 95°C for 5 min], and 40 cycles of [94°C for 20 sec, 59°C for 1 min]. Quantification was based on the increased fluorescence detected due to hydrolysis of the target-specific probes by the 5'-exonuclease activity of the rTth DNA polymerase during PCR amplification. The passive reference dye 6-carboxy-χ-rhodamine, which is not involved in amplification, was used for normalization of the reporter signal. Results are expressed in terms of the threshold cycle value (C_t), the cycle at which the change in the reporter dye passes a significance threshold (ΔR„). To account for variation in sampling and RNA preparation, the values for cytokine- specific product for each sample were standardised using the C_t value of 28S rRNA product for the same sample from the reaction run simultaneously. To normalise RNA levels between samples within an experiment, the mean C_t value for 28S rRNA-specific product was calculated by pooling values from all samples in that experiment. Tube to tube variations in 28S rRNA C_t values about the experimental mean were calculated. The slope of the 28S rRNA logio dilution series regression line was used to calculate differences in input of total RNA. Using the slopes of the GM-CSF logio dilution series regression lines, the difference in input total RNA, as represented by the 28S rRNA, was then used to adjust GM-CSF C_t values. Results were expressed as 40- C_t values, and are represented in Figure 6. Tissues tested were: 1, spleen; 2, thymus; 3, bursa of Fabricius; 4, caecal tonsil; 5, bone marrow; 6, liver; 7, kidney; 8, lung; 9, brain; 10, heart; 11, muscle.

Stimulated lymphocytes tested were: 12, splenocytes stimulated with ConA; 13, thymocytes stimulated with PHA; 14, bursal cells stimulated with PMAand ionomycin; 15, LPS-stimulated monocyte/macrophages; 16, LPS-stimulated HD11 cells. Lymphocyte cells were stimulated as described herein. These results show Ch GM-CSF mRNA is expressed in mitogen-activated chicken splenocytes, bursal cells, and HD11 cells. The expression of Ch GM-CSF mRNA in non- lymphoid tissues was detected in lung and heart.

Table 1:

(1) Database accession nr. X59733

Example 4: COS cell transfection for GM-CSF expression

COS cells (african green monkey kidney cells) were routinely grown to 75 - 90% confluency in T75 (at 7.5 x 10⁵ cells/flask) or T175 (2.5 x 10⁶ cells/flask) culture flasks, passaged twice a week by trypsinisation, and incubated at 37 °C at 5% CO₂. Medium used was DMEM, with 2 mM L- Glutamine, 1 U/ml penicillin, 1 μg/ml streptomycin, and 1% v/v non-essential amino" acids (from 100 x stock, Invitrogen). The medium is normally supplemented with 10 % v/v foetal calf serum. For transfection, healthy COS cells were trypsinised and seeded in T25 flasks at 2 x 10⁶ cells/flask or T75 at 6 x 10⁶/flask. These were cultured for 18 - 24 hr. Next cell layers were washed two times with PBS prewarmed to 37 °C. The cell layers were incubated with a mixture in serum-free medium (5 ml/T25; 15 ml/T75), containing 37.5 μg plasmid DNA, 50 μl chloroquine (stock solution 5.16 mg/ml (10 M) - final concentration 0.1 mM), and 30 μl DEAE/dextran (stock solution100 mg/ml - final concentration 600 μg/ml). Plasmid DNA samples used were of pClneoChGMCSF and appropriate controls. The transfection mixture was incubated on the cells for 3 - 3.5 hours at 37°C/5% CO₂. Next the mixture was removed, the cell layers were washed once with PBS, and cells were shocked by incubation With 10 % v/v DMSO in PBS for 2 minutes at room temperature. This was again removed, and the cells were allowed to recover in serum containing medium, by incubation for 16-24 hours. Then the medium was again replaced by serum free medium, and cells were incubated for 3 days. After the 3 days, the supernatant now containing expressed GM-CSF was harvested, centrifuged and stored at 4 °C until use. From the transfected cell layers, total RNA was isolated for confirmation of GM-CSF expression by RT-PCR, by RNeasy® mini kit as described in Example 1.

Example 5: Isolation, subcloninq and expression of Ch IL-4:

Chicken splenocytes were isolated by teasing apart the spleen in DMEM (Sigma) to release a single cell suspension. The single cell suspension was layered over Ficoll Paque (density 1077) (Amersham Biosciences) and centrifuged at 1000 xg, for 20 min at room temperature. The lymphocytes were collected from the interface and were washed in DMEM supplemented with 2 mg/ml bovine serum albumin (BSA, Sigma), 20 mM L-glutamine, 1 U/ml pencillin and 1 μg/ml streptomycin in DMEM/BSA. Splenocytes were resuspended at 5x10⁶ cells/ml in DMEM/BSA and cultured (30 ml cell suspension per T75 flask), in the presence of 1 μg/ml ConA (Sigma) for 24 h at 41 °C, 5% CO₂. Cells were harvested from the flask and pelleted by centrifugation (450 xg for 10 min). RNA was isolated from the cells using an RNeasy mini kit ( QIAGEN) following the manufacturer's instructions.

Primers were used to obtain the chicken IL-4 cDNA by RT-PCR:

IL-4/5: 5'- ATCATTGGAAATATAGTGTCAATATAA - 3' SEQ ID NO: 11

IL-4/6: 5'- AGGTTGTGTCCCAGAGATATG -3" SEQ ID NO: 12

39 μl of DEPC-treated water was added to Ready-To-Go® RT-PCR beads (Amersham Biosciences) and incubated on ice for 5 mins, then 20 pmol of each primer and 1 μl ConA- stimulated spleen RNA was added. An RT -PCR programme was run: 1 cycle of 42°C for 30 min, 95°C for 5 min; followed by 40 cycles [94°C for 1 min, 50°C for 2 min, 72°C for 2 min]. A second round of PCR amplification was carried out using 23 μl water, 8 μl of RT-PCR product, 20 pmol of each primer (at 4 pmol/μl), 5μl of 10x PCR buffer (Invitrogen), 1.5 μl MgCI₂ (50 mM), 2 μl dNTPs (10 mM each) and 0.5 μl Taq polymerase (Invitrogen). Again 40 cycles of [94 °C for 1 min, 50°C for 2 min, 72°C for 2 min] per cycle were run. A sample from the second round of amplification was visualized after electrophoresis on an agarose gel under standard conditions. Amongst several other bands, a band of 470 bp was visible. The entire PCR product was then run on an agarose gel and the 470 bp band was excised and the cDNA extracted using a QIAquick® gel extraction kit (Qiagen). The IL-4 PCR product was TA-cloned into pGEM- T Easy® vector (Promega) and transformed into competent JM 109 E. coli cells (Promega) following the manufacturer's protocol. Cells were plated onto LB Amp ₁₀o plates and incubated overnight at 37°C. Resulting colonies were picked, and plasmid DNA prepared Using a QIAprep® Spin miniprep kit (Qiagen). Plasmids were digested with Notl and tested on agarose gels, to screen for presence of inserts. Those colonies containing an insert were then sequenced with vector specific commercial primers:

T7 : 5'- TAATACGACTCACTATAGGG -3' SEQ ID NO: 13

SP6 : 5'-TACTCAAGCTATGCATCC -3'. SEQ ID NO: 14.

The plasmid inserts were sequenced by each sequencing reaction contained 1 μl of plasmid DNA, 4 pmol of primer and 2 μl of Quickstart® mix (Beckman Coulter) in water to a 20 μl reaction volume. The cycle conditions were: 96°C for 2 min, followed by 30 cycles of [96°, 20 sec; 50°C, 20 sec; 60°C, 4 min]. The sequencing reaction was precipitated and sequenced as described herein. The results obtained revealed the sequence of cDNA of chicken IL-4 cDNA, which is disclosed herein as SEQ ID NO: 15. The encoded Ch IL-4 protein, disclosed as SEQ ID NO: 16, was predicted by computer translation.

Next the Ch IL-4 cDNA was sub-cloned into pClneo plasmid (Promega) by releasing the insert from the pGEM-T Easy vector with a Notl digest under standard conditions and separating the insert on an agarose gel. It was then purified from the agarose using a QIAquick gel extraction kit (Qiagen). The insert was ligated into Notl digested, shrimp- alkaline phosphatase-treated pClneo vector using T4 DNA ligase (Invitrogen). Two μl of the ligation reaction were used to transform competent DH5-alpha E. coli cells by heat shock treatment. Cells were plated onto LB Amp₁₀o plates and incubated o/n at 37°C. Resulting colonies were picked and plasmid DNA prepared using a QIAprep Spin miniprep kit (Qiagen) and screened by restriction digest and analysis on agarose gel to identify clones containing the IL-4 cDNA insert. A positive clone was sequenced to confirm the insert and its orientation. An endotoxin-free plasmid prep was prepared, resulting in pure plasmid DNA with a concentration of 4.6 μg/ml, carried out as described herein

Recombinant Ch IL-4 was produced by transfecting COS cells with this plasmid DNA, following the procedure as outlined in Example 4 exactly. Example 6: Differentiation of chicken monocvtes to dendritic cells with Ch GM-CSF and Ch lL-4

From a healthy chicken 20 ml of blood was collected into a vacutainer® with EDTA (0.5 M, pH 8.0), to isolate the periferal blood mononuclear cells (PBMC). The blood was mixed at a 1:1 ratio with ice cold 1 % methylcellulose (Sigma) to sediment red blood cells, centrifuged 55 xg for 30 min at 4°C, and serum supernatant was collected. Serum was diluted with ice- cold Hank's balanced salt solution (HBSS) w/o calcium or magnesium, in a 1:1 ratio. 20 ml samples of serum/HBSS were centrifuged in 50 ml conical tubes underlayed with 20 ml of Histopaque 1.077 (Sigma). These were centrifuged at 225 xg for 1 hour at 4°C, after which the interface was collected to obtain the white blood cells. Isolated white blood cells were washed twice in ice-cold HBSS w/o Ca or Mg at 1000 rpm for 10 min in ice-cold R5 medium (RPMI medium with 5% FCS, 1 U/ml penicillin, 1 μg/ml streptomycin and 25 U/ml nystatin. Next B- and T-lymphocytes were depleted from the mononuclear white blood cell population by incubating with a B-lymphocyte specific monoclonal antibody (moab): mouse-anti chicken Bu1 (Southern Biotech), and a T- lymphocyte specific moab: mouse anti-chicken CD3 (Southern Biotech). Both incubations were done sequentially, with the cells at 2x10⁷/ml in ice-cold PBS/BSAfor 30 min. In between cells were washed twice in PBS/BSA. Finally, the cells were resuspended in 90 μl of PBS/BSA with 10 μl of goat anti-mouse IgG coated on magnetic microbeads® (Miltenyi Biotec) per 10⁷ cells. This mixture was incubated for 30 min on ice, washed twice in ice-cold PBS/BSA, and cells were resuspended to 10⁶ cells/ml in cold R5 medium (supra). Three ml of cell suspension was aliquotted into each well of a 6-well plate. A sample containing different dilutions of supernatant containing chicken GM-CSF or IL-4 from transfected COS cells (Experiments 4 and 5 respectively) was added to the wells, or appropriate control samples. This was incubated for 3 days at 41 °C, after which the adherent and non-adherent cells were collected by scraping with cell disassociation medium (Sigma) and washing in PBS.

Resulting differentiated dendritic cell were visualized and photographed unstained, using a digital camera (Nikon E4500) attached to an inverted light microscope, and photographed with a digital camera. Results are presented in Figure 5; dilutions refer to the final dilution of each cytokine (expressed from COS cells) as used on the PBMC culture. From these results it is clear PBMC's differentiate into dendritic cells upon incubation with GM-CSF and IL-4. Example 7: Cloning of GM-CSF cDNA into a baculovirus vector

Starting material was plasmid pGTChGMCSF (Example 2). This was modified by PCR cloning, so that the GM-CSF cDNA contained at its 5' end a Notl restriction site and a Kozak sequence preceding the startcodon, and at its 3' end instead of the stopcodon a 6x Histidine tag fused to the reading frame of GM-CSF, followed by a stopcodon and an Xbal restriction site. Primers used were: GM-CSF Notl/Kozak: 5'- TGCGGCCGCCACCATGCTGGCCCAGCTCACTAT -3' (SEQ ID NO: 17), and GM-CSF His/Xbal: 5'- GTCTAGATTAGTGATGGTGATGGTGATGGATGCAGTCTTTCTCCTCT -3' (SEQ ID NO: 18)

For both primers, the sequence similar to GM-CSF cDNA is underlined. The primers used created sticky ends. 20 ng plasmid pGTChGMCSF template was mixed with 0.5 μl of 1 unit/μl Supertaq®

(HT Biotechnology Ltd.), 1 μl of 10 ng/μl each of primers GM-CSF Notl/Kozak and GM-CSF His/Xbal, 1.6 μl of 2 mM dNTPs, and 2 μl of 10x ST PCR buffer (HT Biotechnology Ltd.) in a final volume of 20 μl. The reaction cycling conditions were: 2 min 94°C, followed by 30 cycles [30 s 94°C; 1 min 55°C; 1 min 72°C], and 5 min 72°C for a final extension. Next the PCR products were gel-purified using the Qiaquick GelExtraction kit (Qiagen) and ligated into the pCR2.1-TOPO® vector (TA Cloning kit, Invitrogen). Plasmid DNA was purified using the Plasmid Midi kit (Qiagen). All clones were sequenced from both 5' and 3' directions using a DNA sequencing kit(BigDye® Terminator V3.0 Cycle Sequencing Ready Reaction, Applied Biosystems) and suitable sequencing primers, according to the manufacturers' instructions. Sequences were analyzed with Sequencher® 4.0 software (Gene Codes Corporation). Sequence analysis confirmed a 471 nt fragment comprising a Not-GM-CSF-His-Xba insert of the correct sequence had been inserted into plasmid vector, named pNGHX. Subsequently, the Not-GM-CSF-His-Xba insert was subcloned from pNGHX into pFastbad® (Invitrogen). For this purpose, the 471 nt insert was excised using Notl and Xbal restriction enzymes, purified using Qiaquick GelExtraction kit and ligated into pFastBacl vector that had been digested with Notl and Xbal. Vector and insert boundaries were confirmed by sequencing as described herein, using suitable sequencing primers, and proved to be as expected. A large batch of endotoxin-free plasmid DNA was prepared from that positive plasmid sample by transformation into DH5α cells, o/n culture, and isolation using QIAquick® maxiprep kit according to the manufacturers' instructions. This resulted in a working batch of plasmid pFBNGHX.

Example 8: Expression of Ch GM-CSF in the baculovirus expression vector system

Using plasmid pFBNGHX, recombinant baculovirus was constructed using the Bac-to-bac system (Invitrogen) according to the manufacturers' instructions. Briefly: plasmid pFBNGHX was transfected into DHIOBac® E. coli cells by heatshock, and plated in several dilutions on LB agar plates containing 3 antibiotics, Bluo-gal and IPTG. These plates were incubated at 37 °C for 48 hrs. White colonies were picked and replated and re-incubated for 48 hours. 6 white colonies were picked, and bacmid DNA was isolated by miniprep isolation. These constructs were checked by PCR using recommended primers. All 6 turned out to be correct. Purified bacmid DNA of two correct clones was transfected into Sf9 cells, using Cellfectin® (Invitrogen) according to the manufacterers' instructions. Sf9 insect cell culture was performed in SF900 II® medium (Invitrogen) with pimafucine and gentamycin, at 27 °C for 5 days. The supernatant of these cultures contained recombinant baculovirus vBacChGM-CSF-His, which was stored at 4°C until further use. The cells from this transfection were used to detect expression of the GM-CSF-His insert, by immuno- fluorescence staining with a monoclonal mouse antibody directed against penta-His tag (Qiagen) as recommended. Positive fluorescence was detected in a majority of the cells of both bacmid transfections.

Example 9: Western blot of insect-cell expressed GM-CSF Sf9 cells in two T175 flasks were infected each with an individual clone of recombinant baculovirus vBacChGM-CSF-His comprising the His-tagged chicken GM-CSF cDNA (as obtained in Experiment 7), at an moi of 0.1 , and cultured for 3-5 days. Cells were pipetted off the flask, and pelleted by centrifugation. Pelleted cells were resuspended in 1/10 of the original cell culture volume. Samples of 9 μl of the cell suspension of each of the two rec virus cultures were size fractionated by elecfrophoresis on 4-12% Nu-PAGE (Invitrogen). As controls were used: a cell suspension of Sf9 cells that had been infected with an empty pFastBacl vector; and 10 μl of purified His-tagged chicken IL-6 (ChlL-6-His) were used. His- tagged Ch-IL6 was expressed in E. coli, and purified over Ni-agarose, as outlined by Schneider etal. (2001, Eur. J. Biochem., vol. 268, p. 4200-4206). The protein marker was the Kaleidoscope® Prestained Standard (Biorad) at 10 μl/lane. After SDS-PAGE, the proteins were blotted from the gel onto a nitrocellulose filter (Schleicher & Schuell) using a semi-dry blotting apparatus (BioRad). The blotted membrane was blocked in 3% skimmed milk in PBS (MPBS) and subsequently incubated with a monoclonal mouse anti-penta-His antibody (Qiagen) diluted 1:500 in MPBS. After extensive washing, the blot was incubated with alkaline phosphatase (AP)-conjugated goat anti-mouse IgG (H+L) antibodies (KPL) diluted 1:500 in MPBS. After washing, bound AP-labelled secondary antibodies were visualized via staining with BCIP/NBT. The blocking- and antibody incubations were performed for 1 h at room temperature. A digital scan was made of the stained membrane, the result of which is presented as Figure 7: in lanes 3 and 4 a sample of cells infected with either of the two clones of recombinant baculovirus vBacChGM-CSF-His was loaded. This shows a prominent band at 17 kDa and some larger bands; 17 kDa is the calculated size of unglycosylated GM-CSF with a His tag.

Example 10: Cloning of GM-CSF cDNA into HVT vector

Plasmid transfer vectors comprising GM-CSF were constructed from plasmid pNGHX, which comprised a 471 nt Not-GM-CSF-His-Xba insert in a pCR2.1-TOPO® vector. For this purpose two specific primers with integrated Bglll endonuclease restriction sites (underlined) were used:

HVT-fwd: 5'- GATCAGATCTATGCTGGCCCAGCTCACTAT -3' SEQ ID NO: 19

HVT-rev: 5'- GATCAGATCTTTAGATGCAGTCTTTCTCCTC -3' SEQ ID NO: 20

and subsequently ligated into standard HVT transfer vectors as described (Sondermeijer, P. et al., 1993, Vaccine, vol. 11, p. 349-358). The resulting plasmids each contain a different promoter to control expression of GM-CSF: the gB-promoter of pseudorabies virus and the LTR-promoter of Rous Sarcoma virus (RSV), respectively for pVEC165 and pVEC166. The pVEC165 and pVEC166 transfer vectors were used to recombine the promoter- GM-CSF inserts into the genome of HVT. Plasmids were linearised with an appropriate restriction enzyme and then co-transfected with HVT viral DNA to CEF cells, by calcium- phosphate precipitation transfection, as described. After DNA had entered the cells, recombination occurred between sequences in the US10 region of the HVT genome and homologous flanking regions in the transfer vector, thereby integrating the promoter-GM-CSF insert into the viral genome. Supernatant from CEF cell-cultures transfected rec HVT obtained from pVEC165 (gB promoter-GM-CSF ), was used to induce proliferation of chicken bone marrow cells, see Example 11 and Figure 8. Recombinant viral plaques that have developed after transfection will be amplified once on CEF and checked for the presence and percentage of recombinant HVT in an immunofluorescence assay and by hybridizing filter-lifts of infected monolayers with labelled DNA probes hybridizing to the promoter region. The recombinant virus will be purified by plaque isolation. Dishes with infected CEF will be overlaid with agarose in culture medium once plaques have developed. Several plaques will be picked randomly and passaged three times in CEF before harvesting and storage as cell associated preparations. Plaques transferred from infected CEF monolayers to nitrocellulose membranes will be hybridized with ³ P-labeled DNA probes

Example 11 : Assay for bone marrow cell proliferation by GM-CSF

Tibias and femurs from an SPF chicken (White leghorn, layer) were flushed with ice-cold HBSS+ medium (Hank's Balanced Salt Solution, pH 7.2 supplemented with 100 μg/ml streptomycin, 100 U/ml penicillin and 20 mM HEPES to collect the bone marrow (BM). BM cell clumps were brought into a single cell suspension using an 100 μm mesh nylon gauze cell harvester (Falcon) and a 5 ml syringe with a 21 GA needle. The BM cell suspension was centrifuged at room temperature for 10 min at 323 xg, washed with HBSS+ medium, centrifuged again and finally resuspended at a concentration of 5x10⁶ cells/ml in RPMI-10 medium (RPMI-1640 medium supplemented with 5% FCS, 5% chicken serum (Gibco), 100 μg/ml streptomycin, 100 U/ml penicillin, 2 mM L-glutamine, 1 mM pyruvate in 20 mM HEPES buffer containing as mitogen LPS (Sigma) in a concentration range 30 μg/ml - 1 ng/ml. BM cells were seeded in triplicate in a 96-well plate at a density of 0.5 x 10⁶ cells/well (in 100 μl). To each well containing BM cells was added 25 μl of serial dilutions of culture supernatant either obtained from:

- COS cell culture, either untransfected or transfected with Ch GM-CSF containing plasmid or with a plasmid without insert (Mock), see Example 2, or from

- culture of CEF cells, transfected or not with HVT comprising the Ch GM-CSF construct behind the gB promoter, or no insert at all; see Example 10. Plates were incubated at 41 °C with 5% CO₂. After 48 h. 18.5 kBq ³H-Thymidine in 25 μl medium was added per well and the BM cells were incubated for an additional 18-20 h. After incubation the BM cell cultures were harvested onto glass-fibre filters using a Skatron micro cell harvester®. The radioactivity incorporated in the cells was counted using a scintillation fluid in an LKB Betaplate® β-counter. The results are presented in Figure 8; the induction of proliferation of BM cells by GM-CSF is evident from the increased uptake of tritiated thymidine. GM-CSF obtained by expression from the baculovirus insect cell system (Example 8) will be tested on Ch BM cells in a similar way.

Example 12: Assay for induction of colony formation by GM-CSF

Chicken BM cells will be obtained as described in Example 11, and added in a density of 7.5x10⁴/ml to warm RPMI-10/0.5% agarose (41 °C). Other suitable solidifiers may be used, for instance Na-methylcellulose. The medium will also contain a mitogen, for instance: LPS, PMA, PHA, ConA or any other suitable mitogen, in a concentration range between 0.1 μg/ml and 50 μg/ml. All these are available commercially. One millilitre aliquots will then quickly be pipetted into six-well plates already containing 150 μl of undiluted cell culture supernatant from GM-CSF transfected COS-7 cells (Example 2). The medium will be left at room temperature for 10 - 20 min. to solidify, after which the plates will be incubated at 37°C/5% CO₂ for 10-14 days. Using a dissecting microscope, colonies of cells that have formed in the agarose will be studied. This will demonstrate the capacity of GM-CSF to induce proliferation. Optionally, the plates will be stained to increase the visibility by incubation with 0.5 ml of 0.005% Crystal Violet in culture medium for ≥1 h.

Example 3: Nitric oxide (NO)- assay for demonstration of induction of IFN-y by GM-CSF Chicken primary spleen cells (splenocytes) can be isolated by methods well-known in the art. Splenocytes will be seeded in triplicate in a 96-well plate at a density of 0.5 x 10⁶ cells/well in 100 μl and incubated with 50 μl of serial dilutions of cell culture supernatants from COS-7 cells transfected with GM-CSF (Example 2). After incubation with the COS cell supernatant, splenocyte supernatants (75 μl) will be collected and analyzed for the presence of biologically active Ch IFN^y, via the NO assay. For this purpose, 100 μl of 1.5 x 10⁶/ml HD11 cells will be incubated with 75 μl splenocyte supernatant for 24 h at 37°C/5% CO₂ in 96-well plates. Activation of HD11 cells by Ch IFN^y will than be measured spectrophoto-metrically as a function of nitric oxide accumulation in the culture supernatants using the Griess assay. See for references: Ding, A, etal., (1988, J. Immunol., vol. 141, p. 2407-2412), and Stuehr, D. J., & Nathan, C.F. (1989, J. Exp. Med., vol. 169, p. 1543-1555). Example 14: Vaccination with recHVT carrying GM-CSF

To test the effect of Ch GM-CSF on immunomaturation and immunostimulation, vaccination trials in chickens will be performed. Either in SPF white leghorn chickens, or in commercial broiler chickens that have maternally derived antibodies. The chickens will be immunised, either at 1 day old, or in ovo, at 18 days embryonic age. Either of the HVT-constructs VEC165, or VEC166 will be used. The dose of the HVT virus will be adapted to fit the general protocol. In ovo vaccination will be by inoculation of approximately 50 μl into the amniotic cavity or the embryo, and day-old vaccination will be by i.m. or s.c. inoculation of approximately 0.2 ml. To assess the effect of GM-CSF on the humeral immunoresponse, the HVT inoculation in some groups of vaccinated chicks, or chicks from vaccinated eggs, will be combined with an antigen inducing a detectable serologic response, such as Clostridium perfringens α-toxoid, or an inactivated poultry vaccine, such as a vaccine against NDV, IBDV, or avian Influenza. The effect of GM-CSF on the cellular immune response will be assessed by challenge-protection trial, wherein some groups of HVT-GM-CSF inoculated chicks/eggs, will also receive a live vaccine against for instance ILT, or avipox. This additional vaccination is applied either simultaneous or shortly after the HVT inoculation, to be determined by the characteristics of the vaccine. Subsequently, subgroups of vaccinated chicks will be challenged at various times post vaccination, e.g. after 1 -4 weeks.

The results of these trials will be monitored by determining the level and kinetics of the development of specific antibodies, and the clinical symptoms and virus re-isolations after challenge. The outcome will show an earlier, stronger, and longer lasting immune response induced by GM-CSF, when compared to chickens not receiving GM-CSF.

Example 15: Use of Ch GM-CSF in an HVT vector as an immune enhancer in ovo:

Recombinant HVT vector constructs carrying the Ch GM-CSF gene were obtained as outlined in Example 10; in one viral vector construct the Ch GM-CSF gene was inserted behind the PRV gB promoter (HVT-ChGMCSF165), in the other it was behind the RSV LTR promoter (HVT-ChGMCSF166). The gB promoter is somewhat weaker relative to the LTR promoter. These constructs were used in vaccination-challenge experiments as generally outlined in Example 14, to assess the immune enhancing capacity of Ch GM-CSF when administered in ovo, by improving the resistance of the vaccinated embryo against a bacterial infection by aerosol challenge.

Experimental design:

Six groups of fifteen fertilised SPF broiler chicken eggs, at an embryonal age of 18 days old, were placed per group in isolators under negative pressure. Within the different groups, each egg was inoculated in ovo with 100 μl containing

3000 pfu HVT using the stock solutions: either HVTChGMCSF165-R5, at 0.34 x 10⁶ pfu/ml; or HVTChGMCSF166-T19, at 0.9 x 10⁶ pfu/ml. One group received a control HVT inoculation in ovo, also 3000 pfu, from a stock at 0.8 x 10⁶. The HVT-PB1 virus used was the vaccine strain of HVT from which the two recombinant constructs had been derived. This PB1 strain does not carry any recombinant insert. After hatch, all chickens were individually marked. At the age of 7 days post hatch the chickens were challenged by aerosol inoculation. For each isolator, 100 ml of a culture of E. coli strain APEC-1, mixed with Newcastle disease virus (NDV) strain C2 was sprayed with the use of a paint sprayer and the birds remained in the spray for 10 minutes with the air circulation closed. NB: sensibilisation in the context of NDV was applied to mimic field conditions, wherein replication of NDV may aggravate the symptoms of an E. coli infection. The E. coli inoculum was prepared fresh, in standard bacterial culture medium, using avian pathogenic E. coli of strain APEC-1 , at 10⁸ - 10⁹ CFU/ml. These were mixed with a standard vaccine dose of NDV strain C2 prior to use at challenge.

One group received in ovo inoculation only with saline, and was only challenged with NDV strain C2 alone, serving as NDV challenge control. During 1 week after challenge the birds were observed daily for abnormalities in general health and/or behaviour. Clinical signs of disease, and mortality were recorded. All dead and euthanized birds (in case of severe clinical signs), as well as all survivors that were subsequently killed at 7 days post challenge, were subjected to post-mortem examination. Symptoms of E. coli infection were monitored as clinical signs at life, and as lesion scores at post-mortem, according to a numerical scoring system. Special interest was in air- sacculitis, and pneumonia. Results of the affection rate per group, presented as percentage of the maximal possible pathology score of the group, were as follows:

Y = Yes

Results: As is clear from these results, providing Ch GM-CSF to a chicken in ovo is effective in enhancing resistance of the newborn chick to a pathogenic infection. Chicken GM-CSF administration in ovo reduces the signs of pathology and disease relative to groups receiving sham in ovo inoculation. The construct wherein Ch GM-CSF was inserted behind the stronger LTR promoter was even more effective than the construct comprising the relatively weaker gB promoter. The pathology observed was caused by E. coli APEC-1 infection, not by NDV infection alone.

Conclusion: Ch GM-CSF is effective in enhancing an avian's immune response. This can advantageously be applied at very young age, even prematurely. LEGEND TO THE FIGURES

Figure 1 : Multiple alignment of known GM-CSF amino acid sequences to that of Chicken GM-CSF. Programs used: GCG - Pileup and ClustalX, all using standard parameters. Database accession numbers of the amino acid sequences used are: Human: P04141; Baboon: AAO85329; Macaque: AAG16626; Gerbil: AAN16349; Mouse: P01587; Rat: P48750; Dog: P48749; Cat: 062757; Guinea pig: Q60481; Pig: Q29118; Horse: AAL41017; Cow: P11052; Red deer: P51748; Sheep: P28773; Chicken: SEQ ID NO: 2. n.s. = no significant similarity was found.

Figure 2: Table of pair-wise alignment results of known GM-CSF amino acid sequences and Chicken GM-CSF. Amino acid sequences were the same as those used for Figure 1. Alignment program used was BlastP, using standard parameters. Percentages indicated are the % positives.

Figure 3: Phylogenetic tree representing the level of similarity between all known GM-CSF amino acid sequences and Chicken GM-CSF. Program used was Phylip, on the data from the ClustalX analysis performed for Figure 1. The distance of the scale bar represents 0.1 amino acid substitution per site.

Figure 4: Comparative representation of the secondary structure of GM-CSF protein from human, mouse and chicken. - Amino acid sequences used are the same as those used for Figure 1 - h = human, m=mouse, ch=chicken - Shaded areas represent conservation of aa similarity, the darker the shading the more conserved the residue across species. - the multiple alignment was made using program Clustal X - The down arrow represents the cleavage site for the signal peptide in human and mouse GM-CSF - Asterisks indicate Cysteine residues in the chicken GM-CSF - Alpha helixes are overlined, and indicated with Helix A, A', B, C, or D - Beta sheets are overlined and indicated with β1 and β2 - "h" under the sequence represents the hydrophobic amino acids in positions 1 and 4 of the heptad repeats in the α-helices of chicken GM-CSF - Potential N-linked glycosylation sites in chicken GM-CSF protein are underlined.

Figure 5: In vitro differentiation of chicken monocytes to dendritic cells by GM-CSF and IL-4. Chicken PBMC were incubated with Ch IL-4 and Ch GM-CSF expressed in supernatant of transfected cell cultures. Scanned photographs from 6 well plates are presented. A: no IL-4, no GM-CSF; B 1:25 IL-4; C: 1:25 GM-CSF; D: 1:25 IL-4 and 1:25 GM-CSF; E: 1:25 IL-4 and 1:500 GM-CSF; F: 1:100 IL-4 and 1:25 GM-CSF; G: 1:100 IL-4 and 1:100 GM-CSF; H: detail of G; 1: 1:500 IL-4 and 1:25 GM-CSF; J: duplo of D.

Figure 6: Expression patterns determined by quantitative RT-PCR of GM-CSF mRNA in various chicken tissues and stimulated lymphoid cells. Measurement results of real-time quantitative RT-PCR, are expressed as 40-Ct values. Significance intervals are indicated. Tissues: 1, spleen; 2, thymus; 3, bursa of Fabricius; 4, caecal tonsil; 5, bone marrow; 6, liver; 7, kidney; 8, lung; 9, brain; 10, heart; 11, muscle. Stimulated lymphocytes: 12, splenocytes stimulated with ConA; 13, thymocytes stimulated with PHA; 14, bursal cells stimulated with PMA and ionomycin; 15, LPS-stimulated monocyte/macrophages; 16, LPS-stimulated HD11 cells.

Figure 7: Western blot of chicken GM-CSF expressed in the baculovirus expression vector system. Lanes: 1. purified ChlL6-His 2. lysate of insect cells infected with empty recombinant expression vector 3. lysate of insect cells transfected with recombinant expression vector BacChGM- CSF-His clonel 4. similar to lane 3, but BacChGM-CSF-His clone2 Staining was performed with anti-His antibody. Molecular weights are indicated from a weight marker lane which is not shown. Figure 8: Bone marrow proliferation assay Chicken bone marrow cells were induced to proliferate by Ch GM-CSF expressed into the supernatant of transfected COS cells and into supernatant from rec HVT infected CEF cells. Horizontal axis: supernatant sample dilutions; Vertical axis: cpm incorporated ³H- Thymidine. For panels A and C the standard deviation is indicated.

Panels: A: Supernatant from plasmid transfected COS cell culture on BM cells; BM cells stimulated with LPS at 10 μg/ml . B: idem; BM cells stimulated with LPS at 10 ng/ml. C: Supernatant from HVT transfected CEF culture on BM cells; BM cells stimulated with LPS at 10 μg/ml. D: idem; BM cells stimulated with LPS at 10 ng/ml.

Columns: samples added to the BM cell + LPS cultures: GM-CSF = supernatant sample comprising GM-CSF, either from COS cells transfected with pClneo plasmid carrying GM-CSF insert (panels A, B), or from CEF transfected with HVT-carrying GM-CSF insert (panels C, D). mock = supernatant sample of COS cells transfected with a pClneo plasmid without insert (panels A, B), or from CEF transfected with rec HVT without insert (panel C, D). medium = plain BM cell culture medium.

Claims

1. Isolated protein or a functional fragment thereof, characterised in that the protein comprises an amino acid sequence having at least 70 % amino acid similarity to the amino acid sequence of SEQ ID NO: 2, whereby the protein or the fragment has at least one of the biological activities of avian GM-CSF.

2. Protein according to claim 1, wherein the amino acid sequence is SEQ ID NO: 2.

3. Isolated nucleic acid capable of encoding a protein or a functional fragment thereof according to claim 1 , or a protein according to claim 2, characterised in that the nucleic acid has at least 70 % nucleotide sequence identity to the nucleotide sequence of SEQ ID NO: 1 , whereby the encoded protein or functional fragment has at least one of the biological activities of avian GM-CSF.

4. Nucleic acid according to claim 3, wherein the nucleic acid is SEQ ID NO: 1.

5. Recombinant DNA molecule comprising a nucleic acid according to any one of claims 3 or 4, the nucleic acid being functionally linked to a promoter.

6. Live recombinant carrier comprising a nucleic acid according to any one of claims 3 or 4, or a recombinant DNA molecule according to claim 5.

7. Live recombinant earner according to claim 6, comprising Herpes Virus of Turkeys.

8. Host cell comprising a nucleic acid according to any one of claims 3 or 4, a recombinant DNA molecule according to claim 5, or a live recombinant carrier according to any one of claims 6 or 7.

9. Protein or functional fragment thereof according to claim 1 , or a protein according to claim 2, for use as a medicament for an avian organism.

10. Composition comprising a protein or a functional fragment thereof according to claim 1, or a protein according to claim 2, in a pharmaceutically acceptable formulation.

11. Nucleic acid according to any one of claims 3 or 4, for use as a medicament for an avian organism.

12. Composition comprising a nucleic acid according to any one of claims 3 or 4, a recombinant DNA molecule according to claim 5, a live recombinant carrier according to any one of claims 6 or 7, or a host cell according to claim 8, in a pharmaceutically acceptable formulation.