WO2012141989A2

WO2012141989A2 - Immunogens

Info

Publication number: WO2012141989A2
Application number: PCT/US2012/032720
Authority: WO
Inventors: Barton F. Haynes; Guido FERRARI; Jerome Kim; Nelson MICHAEL
Original assignee: Duke University; The Government Of The United States, As Represented By The Secretary Of The Army, On Behalf Of Walter Reed Army Institute Of Research
Priority date: 2011-04-09
Filing date: 2012-04-09
Publication date: 2012-10-18
Also published as: WO2012141989A3

Abstract

The present invention relates, in general, to HIV and, in particular, to novel immunogens suitable for use in inducing an immune response to HIV.

Description

1MMUNOGENS

This application claims priority from U.S. Provisional Application

No. 61 /473 ,748, filed April 9, 201 1 , the entire content of which is incorporated herein by reference.

This invention was made with government support under Grant No, CHAVI U 19 A1067854 awarded by the National Institutes of Health. The government has certain rights in the invention,

TECHNICAL FIELD

The present invention relates, in genera!, to HIV and, in particular, to novel immunogens suitable for use in inducing an immune response to HIV.

BACKGROUND

Antibodies that bind to the Fey-Receptor (FcR) ili a on the surface of natural killer (NK) cells can mediate antibody dependent cytotoxic activity (ADCC) or antibody dependent cellular viral inhibition (ADCVI) (4). In addition, binding of immunoglobulin (lg) Fc to FcR can induce anti-HlV- 1 chemokine release (5, 29), These types of effector functions have been implicated in protective immune responses against HIV- 1 (3, 12, 20). Several studies have reported active and passive immunization that protected from S1V or SHIV infection in non-human primates. The mechanism of protection was related at least in part, to ADCC- and ADCVI-mediating antibodies ( 1 1 , 13, 16, 17, 35). Antibodies that mediate FcR-dependent anti-HlV-1 activities that are non- neutralizing in conventional HlV- l neutralizing assays have been postulated to be a coirelate of protection in the Thai RV1 144 gpl 20 vaccine efficacy trial ( 1 5, 26).

FcR-mediated antibody activity is dependent on both the state of glycosylation of the Fc region (2, 23, 25), as well as on the specificity of the Fab region (i.e. the antibody must target epitopes on the surface of virus-infected cells). While the epitopes involved in mediating virus neutralization have been comprehensibly profiled, HIV- 1 epitopes that are capable of mediating ADCC and ADCVI in HIV- 1 infection have not been adequately studied. Thus, an analysis has been undertaken of existing non-neutralizing anti-Env human monoclonal antibodies (mAbs) for their ability to bind to HIV- 1 infected cells and to sensitize target CD4+ T cells for ADCC,

A human mAb (A32) recognizes a conformational epitope involving the C I and C4 gp l20 regions following Env binding to CD4 (22), The present invention results, least in part, from a study demonstrating that the A32 epitope is expressed on the surface of transmitted/founder virus -infected CD4 T cells beginning at day 3 of in vitro infection, and can mediate potent ADCC activity with both virus-infected and g l 20-coated CD4 T cells, Moreover, mAb A32 Fab blocks the majority of ADCC antibody activity m HIV- 1 chronically infected sera,

SUMMARY OF THE INVENTION

Objects and advantages of the present invention will be clear from the description that follows,

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 . Detection of Env expression on the cellular membrane of the

A 1953_SupTl cell line, A 1953-SupTl cells (0. 1 -0.2x l 0⁶) were stained with five different concentrations of primary Ab as indicated in the figure (range 20- 0.5μ§/ι^η1). The primary Ab preparations were: 1 ) mAb A32 and Synagis®

9 (negative control); 2) IgG preparations HIV1G and IVIG as positive and negative controls, respectively. The results are reported overlaying histogi'ams representing the cells after incubation with no Ab (unstained; gray area), with the secondary Ab alone ( Secondary Ab Alone; black curve), and with primary and secoiidary Ab (primary Ab + secondary Ab: green curve). Where positive staining was detected, the Median Fluorescence Intensity (MFI) of the positive population is reported.

Figure 2. Detection of Env expression on the cellular membrane of HIV-infected CD4⁺ T cells, Activated CD4⁺ T cells were infected with two HIV- 1 strains, the laboratory adapted NL4-3 and transmitted/founder primary CH077.t infectious molecular clones, as described in Example 1 below. Replicate cultures of mock and HIV-infected cells were plated in a 96 well/plate, Each cell condition was harvested starting 3 days post-infection and every 24 hours thereafter to detect the expression of Env proteins on the cellular membrane, One-two hundred thousand cells were stained with 10ng/ml of the mAb A32, 17b, and 2G 12 as well as with the IgG preparation HIVIG as primary Ab source. The Synagis® and IVIG were used as negative controls for the mAb and IgG preparation, respectively, The results are reported overlaying histograms representing the cells a ter incubation with no Ab (unstained; gray area), with the secondary Ab alone (Secondary Ab Alone; black curve), and with primary and secondary Ab (primary Ab+ secondary Ab; green curve).

Figures 3A-3C. Antibody Dependent Cellular Cytotoxicity (ADCC) activity, The ability of mAbs A32 (red line), 1 7b (green line), and 2G 12 (blue line) to mediate ADCC activity was tested using g l 20wn o-coated (Fig. 3 A), gp l 40cno40

(Fig. 3B), and A 1953-chronically infected (Fig. 3C) CEM.NKR_CCR5 cell line. The Synagis® was used as negative control (black line). The mAb were tested starting at a concentration of 40ng/ml using 4-fold dilutions. The results are reported as %GzB activity after background was subtracted, The results represent the average of triplicate experiments ± standard deviation. The black dotted line represents the cut-off (8%GzB activity). PBMC from a healthy HlV- 1 seronegative donor were used as source of effector cells and for an effector to target cell ratio of 30: 1 in all experiments.

Figure 4. Antibody Dependent Cellular Cytotoxicity (ADCC) activity. The ability of mAbs A32, HIV1G (positive control) and Synagis® (negative control) to mediate ADCC activity was tested at the concentration indicated on the axis. Activated PB CD4+ T cells from a healthy HIV- seronegative donor after 3 -day infection with the IMC, NL-LucR.T2A- BaL.ecto, were used as target cells, NK cells obtained by negative selection from autologous PBMC were used as source of effector cells, The effector to target cell ratios of 40 (red bars) and 10 (blue bar) to 1 were used. The results are reported as %GzB activity after background was subtracted.

Figures 5A and 5B. Inhibition of ADCC activity by A32 Fab fragment. The

A 1953_CEM.N RCCR5 cell line as used as target cells and PBMC from a healthy HIV- l seronegative donor as source of effector cells, The effector to target cell ratio was 30: 1 in all experiments. The results are reported as %GzB activity after background was subtracted. The values above the bars represent the percentage of inhibition when the A32 Fab fragment was used in the pre-incubation. Fig. 5A. The target cells were pre-incubated with medium only (pre-treatment, red bars), with 10 pg/ml of the A32 Fab fragment (blue bars), or with 10 g/ml of the Synagis® (black bars). The results represent the average of results from triplicate experiments, After washing, the cells were incubated with the mAb A32 at 10 μ^ηιΐ. Fig. 5B. The target cells were pre-incubated as previously described with medium only, Λ32 Fab or Synagis®. After washing, the plasma collected from each donor were subsequently added at the dilutions indicated in parenthesis. The mAb A32 and HIVIG preparation were used as positive controls. Figure 6. Shown is the sequence of the HlV-1 glycoprotein 120 (gp l 20). The binding site for the monoclonal antibodies (mAb) A32 is highlighted, The monoclonal antibodies are capable of binding a conformational site on the g l 20 that includes C' l and C2 regions.

Figure 7. As shown in Fig. 5A, if the target cells used in the assay were pre- incubated treated with the A32-Fab, the A32 mAb could not bind to the gp 120 and mediate ADCC. The same applies to the ADCC activity mediated by the Ab present in the plasma collected from HIV- 1 infected individuals. The HIV- 1 A 1953 chronically infected cell line was used as target cells without preincubation (red dots) or incubated with the A32-Fab (blue dots) or the control Ab (black dot). Pre-incubation with A32-Fab but not with control Ab was able to reduce the ADCC activity mediated by Ab present in the plasma of different groups of HIV- 1 infected individuals. Each dot represents one individual and the lines connect the dots representing the same individual in each of the

experimental conditions. The results are reported as percentage of Granzyme B (%GzB) activity after background was subtracted.

Figure 8. The same methodology was applied to evaluate the presence of A32- like Ab responses capable of mediating ADCC activity in RV 144 vaccine recipients. The effect of pre-incubation with the A32-Fab was even more dramatic in this group with a significant decrease in the %GzB activity when the plasma was added to target cells pre-incubated with A32-Fab compared to that observed when no pre-incubation was performed.

Figure 9. Specificity of RV 144 induced antibodies.

Figure 10. RV144 induced antibody responses. Figure 1 1 . Quaternary mAb CHO I binding to A244 gp l 20 is abrogated by N160K mutation.

Figure 12, Differential binding of RV 144 vaccince purified IgG to A244WT versus A244 N1 60K g l 20.

DETAILED DESCRIPTION OF THE INVENTION Among non-neutralizing HIV- 1 envelope antibodies, those capable of mediating antibody dependent cellular cytoxicity ( ADCC) activity have been postulated to be important for control of HIV- 1 infection, ADCC-mediating Ab must recognize HIV- 1 antigens expressed on the membrane of infected cells and bind the Fcy-receptor (Fcy-R) of the effector cell population, However, the precise targets of serum ADCC antibody are poorly characterized, The human mAb A32 is a non-neutralizing antibody isolated from a HIV- 1 chronically infected person. An investigation was made of the ability of mAb A32 to recognize HIV- 1 envelope expressed on the surface of CD4+ T cells infected with primary and laboratory adapted strains of HIV- 1 , as well as of its ability to mediate ADCC activity. Mab A32 epitope was expressed on the surface of H IV- 1 infected CD4r T cells earlier than the CD4-inducible (CD4i) epitope bound by mAb 1 7b and the gp l 20 carbohydrate epitope bound by mAb 2G 1 2. Importantly, mAb A32 was a potent mediator of ADCC, Finally, an A32 Fab blocked the maj ority of ADCC- mediated Ab activity in chronic HIV- 1 infection serum, These data demonstrate that the epitope defined by mAb A32 is a major target on gp l 20 for plasma ADCC activity.

Previous studies have demonstrated the frequent induction of CD4i antibody responses in acute (27) and chronic (7) HIV- 1 subtype B infection and that they contribute to the neutralizing activity in acute subtype C infection ( 14), These data, together with the observations of the ability of mAb A32 to recognize Env expression on the surface of H IV- 1 -infected cells earlier than 17b and 2G 1 2, emphasizes the importance of the A32 epitope as a candidate for the target of non- neutralizing gpl 20 antibodies that may participate in protection for H IV- 1 acquisition, The present studies also demonstrate the importance of understanding what role A32-like antibodies may have in preventing H IV- 1 acquisition in vaccine trials such as RV 144 (26).

The present invention relates to HIV envelope imm unogens that induce the production in a subj ect (e. g. , a human) of A32-like antibodies, that is, antibodies that are blocked by A32 Fab binding. The invention further relates to nucleic acids encoding such antigens and to vectors comprising same. The invention also relates to methods of inducing an immune response against HIY in a subject(e. g. , a human) by administering an effective amount of such

imrnunogens/encoding nucleic acids,

Certain aspects of the invention can be described in greater detail in the non-limiting Example that follows. (See also U . S . Provisional Application No. 61 /407,299, filed October 27, 201 0.)

EXAMPLE 1

Experimental Details Monoclonal antibodies and IVIG preparation. The A32 and 17b monoclonal antibodies (mAb) utilized in this study were originally isolated by James Robinson (Tulane University, New Orleans, LA). The 2G 12 mAb was purchased from Polymun (POLYMUN Scientific Immunobiologische Forschung GmbH, Vienna, Austria). The humanized monoclonal antibody (IgG l _k) directed to an epitope in the A antigenic site of the F protein of respiratory syncytial virus, Synagis® (palivizumab; Medlmmune, LLC; Gaithersburg, MD) was purchased from the manufacturer and used as a control . Human polyclonal anti-HIV- 1 IgG preparation was used as a positive control from NIH AIDS Research & Reference Reagent Repository (HIVIG lot#l 14; (6)).

Target cells. CEM,NKRCCR5 cell line (3 1 ), chronically infected SupTl CD4+ T cells, and activated peripheral blood (PB) CD4+ T cells were used as target cells. PB CD4+ T cells were generated from cryopreserved PB

Mononuclear Cells (PBMC) as follows. PBMC samples obtained from an HIV- seronegative donor were thawed and activated by 72-hour culture at 37°C and 5% CO? in RPMI 1640 medium (Invitrogen, Carlsbad, CA), supplemented with 20% Fetal Bovine Serum (FBS) (Gemini Bio-Products, West Sacramento, CA) (R20) in presence of 20 U/ml rhlL-2 (Peprotech, Rocky Hill, J) (R20-IL2), and containing anti-CD3 (clone OKT3, eBioscience, San Diego, CA) and anli-CD28 (clone CD28.2, BD Biosciences, San Jose, CA) at 1 50 ng/ml. After activation, the CD4⁺ enriched population was obtained by removing CD8⁺ T cells by magnetic bead separation (Miltenyi Biotec). All the samples from the seronegative donors were obtained according to institutional IRB protocol .

Recombinant gp 120 HIV -I proteins. The recombinant gp l 20 HIV- l protein from the YVTTO early-infection env-clone (Genebank No. AY83545 1 ; Immune Technology Corp, New York) and the recombinant gp l 40 cleavage-site deficient (C) oligomer from the transmitted/ founder recombinant Env from subject CH040 ( 1 8). For each recombinant gp l 20 or gp l 40, the optimum amount to coat target cells was determined as that amount able to compete >50% the binding of the anti-CD4 Leu3 A mAb antibody (BD Bioscience. San Jose, CA, USA), This competition was determined as reduction of the mean fluorescence intensity of Leu 3A reactivity in gp l 20-coated CEM .NKRcc_R.^ells compared to control cells.

Virus, infectious molecular clones (IMC), chronically infected cells, The following three replication-competent infectious molecular clones (IMC) of clade B HIV- l starins were used: X4-tropic pNL4-3 (Genebank No. M l 9921 & AF324493.2)( 1 ); R5-tropic NL-LucR.T2A-BaL.ecto which expresses BaL env sequence (Genebank No. AY4261 10) in cis in an isogenic, pNL4-3 based reporter virus backbone that preserves all viral orfs as described by Edmonds et al. (8); and recently generated full-length IMC, pCH077.t (Ochsenbauer et al. , manuscript in preparation), representing the transmitted / founder virus strain from subject CH077 (28). Virus stocks were generated by transfection of 293T cells with proviral DNA, and titered on TZMbl cells. The A1953 vims was derived from the HXB2 isolate selected for the inability to clownregulate CD4 from the surface of chronically infected T-cell lines. It was subsequently shown to be defective in Nef expression. SupTl and CEM.NKRCCRS cells that are chronically infected with A1953 characteristically express high levels of surface CD4 bound to gp 120 (i.e., detectable with OKT4, which does not compete with gpl 20 for binding to CD4; and not detectable by anti-CD4 antibodies known to compete with gp l 20). These A 1953-infected cells express high levels of CD4 complexed with envelope glycoprotein on the cell surface (J. Hoxie, unpublished data). Chronically infected A 1 953_SupTl _CCR5 and A 1 53_CEM.NICR_CCR5 cell lines were used to evaluate the binding capacity and ADCC activity of A32 mAb to the env protein expressed on the surface of HIV-1 infected cells, respectively,

Effector cells, PBMC obtained by leukopheresis from a seronegative donor were cryopreserved and subsequently used as effector cell population or as the source of purified natural killer (N ) cells. Cryopreserved PBMC were thawed, and then rested overnight at 2x l 0⁶ cell in in RPMI 1640 medium

(Invitrogen) supplemented with 10% FBS (RI O), Cells were counted for viability and adjusted to the proper concentration to obtain an effector to target (E:T) ratio of 30: 1 , In experiments where infected CD4⁺-enriched cells were used as targets, NK cell populations were isolated from cryopreserved PBMCs by negative selection with magnetic beads (Miltenyi Biotec), In these experiments, N K effector cells were used at an E:T ratio of 10: 1 .

Indirect surface immunofluorescence analysis of HIV- 1 -infected CD4+ T cells. Activated CD4⁺-enrichcd T cells and A1953 _SupTl cells were obtained as described above. CD4^'1' T cells were infected by spinoculation ( 1200 x g for 2 hours; (24)) with 0.33 TCID₅o cell of HIV- 1 vims stock derived from the IMCs, pNL4-3 (accession number M 19921 & AF324493.2)( 1 ) and pCH077.t

(Ochsenbauer et al,, manuscript in preparation), respectively, representing a X4- tropic reference strain of HIV- 1 , and the transmitted/ founder virus from subject CH077 (28), Cells spinoculated in the absence of virus (mock-infected) were used as a negative infection control. Following 72 hours of infection in R20-1L-2, CD4 '^'-enriched T cells were washed in PBS, dispensed in 96-well V-bottom plates at l x l O⁵ viable cells/well, and stained with a vital dye (LIVE/DEAD Fixable Aqua Dead Cell Stain, Invitrogen) to exclude non-viable cells from subsequent analyses. The cells were then washed twice with

of washing buffer (WB; PBS+ 1 FBS), and incubated at 4°C for 25 minutes with the primary Ab or IgG preparation. After two washes, cells were stained with Phycoerythrin (PE)- conjugated goat anti-human IgG secondary (2ary) Ab (Southern Biotech, Binningham, AL) for 25 minutes at 4°C. Cells were subsequently washed 3 times and fixed with 1 % formaldehyde PBS , The samples were acquired on a LS RIl (BD Biosciences) within 24 hours. A minimum of 1 0,000 total singlet events was acquired for each test to identity live events, Data analysis was performed using FlowJ o 8.8 ,4 software (TreeStar Inc. , Ashland, OR),

Longitudinal Env Expression Assay. To assess the time course of env antigen expression on the membrane of CD4⁺-enriched T cells, PBMC were stimulated and cultured at a concentration of 1 ] 0⁶ cells/mL in RPMI +20% FBS supplemented with 0.05mg/mL Gentamicin (Sigma), 20U/mL recombinant human IL-2 (Peprotech) (R20-IL2), 50ng/mL O -T3 (R&D Systems), and l OOng/^'mL a-CD28 (BD Biosciences). These cultures were incubated at 37°C and 5% CO2 for 72 hours. CD8+ T-cells were depleted from 1 .5x 1 0 stimulated hPBMCs via Mi ltenyi separation (Miltenyi Human Microbead Kit) using the AUTOMacs Deplete/Rinse program. CD4⁺-enriched T cells were then resuspended at l O l O⁶ cells/mL in R20-1L2 and bulk infected with 0,977 TCID Q/CCII of CH077,t virus stock via spin-inoculation at 1200 RCF for 2 hours. Vitus infected cel ls were then split into the appropriate number of flasks for culture and incubated at 37°C and 5% C0o for 3-7 days, Days 3-7 post-infection, viral envelope expression was analyzed by indirect immunofluoresence staining of virus infected CD4 ' -enriched T cells ( l x l O⁶ cells) with the appropriate antibodies at a final concentration of l Oug/'mL, Additionally, culture supernatants were col lected and virus infectivity was analyzed via TZM-bl assay.

ADCC assay. Antibody Dependent Cellular Cytotox ic (ADCC) activity was detected according to modifications of the previously described GranToxiLux (GTL) procedure ( 1 9). Infected and uninfected target cells in 96 well plates were counted, washed, resuspended in RPMI 1640 medium (Invitrogen) supplemented with 1 0% FBS (R 10) at l x l O⁶ cell/ml, and labeled with a fluorescent target-cell marker (TFL4; Oncolmmunin, Inc., Gaithersburg, MD) and a viability marker

(NFL l ; Oncolmmunin. Inc. ) for 1 5 minutes in a 37°C water bath, fol lowed by two washes. Both effector and target populations were counted and concentrations were adjusted to reach a final effector to target ratio of 30: 1 and 10: 1 when PBMC and NK. cells were used respectively. For the A32-Fab blocking assay, the A 1953_CEN.^'NKRccR5 target cells were plated, incubated for 1 5 min at 37°C and washed once before the effector cells were added to the wells. GzB substrate (Oncolmmunin, Inc.) was dispensed into each well of a 96-well V-bottom plate to reach a final GzB substrate concentration of 0,25x. After incubation for 5 minutes at room temperature (RT), 25μ1 of the appropriate antibody and IgG dilutions were added to the target/effector cell suspension and then incubated for 15 minutes at RT. The plates were centrifuged for 1 minute at 300xg, and incubated for 1 hour at 37°C and 5% CO?. After two washes with VVB, cells were resuspended in 225μ1 of WB, placed at 4°C, and acquired with the LSRll within 5 hours, A minimum of 5 and 10x 10^" events representing viable gp l 20-coated and infected target cells, respectively, was acquired for each well. Data analysis was performed using FlowJo 8.8.4 software. The results are expressed as %GzB activity, defined as the percentage of cells positive for proteolytically active GzB out of the total viable target cell population. The final results are expressed after subtracting the background represented by the %GzB activity observed in wells containing effector and target cell populations in absence of mAb, IgG preparation, or plasma. The results were considered positive if %GzB activity after background subtraction was >8% for the gp 120- coated and A1953 target cells. For the IMC-infected target cells, the results were considered positive if % GzB activity after background subtraction was > 1 5%.

Results

Binding of mAb A32 to the surface of HIV- J A 1953-chronically infected SupTl cell line. The first question asked was whether the A32 epitope was expressed on the surface of HIV- 1 infected CD4¹ T cells. Observed were saturation binding levels of A32 mAb between 5-20 μ^πιΐ and peak of mean fluorescence intensity at ^ig/ml on the A 1953 -infeeted SupTl CD4⁺ T cell line. Most of the A1953-mfected SupT l CD4+ T cells were positive for A32 mAb reactivity (Figure 1 ).

Expression of Ail binding site on the surface of HIV- 1 infected PB CD4⁺ T cells. CD8-depleted PBMCs obtained from HIV- 1 seronegative healthy subjects were activated for three days using the anti-CD3/CD28 Ab combination (9) and infected with either an infectious molecular clone (IMC) of the

transmitted/founder virus CH077.t or the laboratory-adapted HIV- 1 strain, NL4-3 at a multiplicity of infection of 0.33 TCID₅₀/cell. Mock-infected CD8-depleted cells from the same donor were used as uninfected cell controls. Cells were harvested and mAb surface reactivity determined at 24 hours intervals starting 72 hours post-infection and continuing through day 7, The A32, 17b, 2G 1 2 mAbs and controls were used at 10^ig/ml saturating concentration (Figure 2), Neither the three mAbs nor the HIVIG preparation nor the negative controls (Synagis© and IVIG) bound to mock-infected cells, In contrast, the expression of Env antigens on HIV-1 -infected cells was always detected with A32 mAb on day 3 of infection before expression of both CCR5 binding site ( 1 7b mAb) and the gp l 20 carbohydrate epitope defined by 2G 12 mAb, and also before epitopes recogni ed by HIVIG. MAbA32-reactive CD4+ T cells infected with the R5 transmitted/ founder IMC. CH077.t appeared on day 3 of in vitro infection whereas PB CD4+ T cells infected with NL4-3 X4 HIV-1 appeared on day 5. HIV- 1 infected cells positive for staining with the 2G 12, 17b, and HIVIG Ab were not detected at any time point from day 3 through 7 among the CH077-infected cells but were seen at days 6 and 7 in NL4-3 infected CD4+ T cell cultures. These data suggested that HIV- 1 envelope glycoproteins expressed on the surface of H IV- 1 infected cells could be recognized by mAb A32 earlier than by either 1 7b or 2G 1 2 mAbs or by Env-specific Abs present in HIVIG. Moreover, these data suggest that expression of the HIV- 1 -derived surface epitopes on R5 transmitted/founder virus infected CD4 T cells may differ from those expressed on X4 chronic vims infected CD4 T cells,

Monoclonal Antibody A32 can mediate ADCC, It was originally reported that A32 mAb does not mediate HIV- 1 neutralizing activity (22, 34). Similarly, in our neutralization assays in both TZM-bl cells and in PBMC cultures, it has also been found that A32 mAb did not neutralize HIV- 1 (data not shown), The next question asked was whether mAb A32 could mediate ADCC activity. The CEM.NKRccR5 cell line was first utilized as a source of target cells upon their coating with recombinant Env proteins or as a chronically infected cell line, The recombinant Env proteins utilized to coat the CENINKRCCRS cell represented the g l 20 and gp 140 sequence, respectively, of the transmitted/founder HIV env from subjects W1TO4160 ("WITO") and CH040. A32 mAb was able to recognize both the gp l 20\viTO and to mediate ADCC activity expressed as % GzB activity (Fig. 3 A). The maximum %GzB activity detectable with A32 was 52±8% at

0.1 56pg/ml of A32 mAb, At this concentration, its activity was almost 6 fold higher than that observed with mAb 2G 12 (8±5.8%) and 17b (9±2%). Similar results were observed when the gp MOcHMO-coated target cells were used (Fig. 3B). A32 was able to mediate a maximum of 40% GzB ADCC activity at the concentration of 0, 1 56^ig/ml that was 2,6-fold higher than that observed with mAb 17b at 40μ ε/ιη1 ( 1 5% GzB), In contrast to W1TO g l 20 coated targets, no

ADCC activity against the gp l 40cH04 -coated target cells was detected using mAb 2G 1 2. Tt should be noted that in both settings the A32 ADCC activity displayed the previously described prozone phenomena with high concentrations of antibody inhibiting ADCC (21 , 33),

A32 mAb is capable of mediating ADCC responses against HIV- 1 infected targe! ceils, Using the A 1953_CEM,N R_CCR5 target cells the peak of the ADCC activity mediated by A32 mAb was 42%GzB at 0.625μ&^<Ίη1 (Fig. 3 C). This was a 4-fold higher activity than what observed with 1 7b mAb at the concentration of 40pg/ml . Moreover, ADCC activity mediated by A32 mAb was detected at concentrations of 50 and 5 ^tg/ml when NL-LucR.T2A-BaL.ecto infected PB CD4⁺ T cells obtained from a healthy HIV- 1 seronegative were used to generate target cells as described in the method section. (Fig. 4). The M to target cell ratio of 40: 1 was required to detect an activity comparable to what observed when the HIVIG preparation was tested at 50μg/ml, These levels of granzyme B release compared to those obtained using recombinant envelope protein-coated and chronically infected target cells indicate that higher concentrations of A32 and effector cells are required to eliminate H IV- 1 -infected CD4⁺ T cells.

Inhibition of ADCC-mediating Ab activity in plasma from infected individuals by the Fab of A32 antibody. To determine whether the epitope recognized by A32 mAb was also targeted by ADCC responses in chronically infected individuals, a strategy was devised where target cells were preincubated with an A32 Fab fragment to prevent the subsequent binding and ADCC activity of Ab present in the plasma of HIV- 1 -infected subjects (Fig. 5), The preincubation of the target cells with 1 and O. ^g/ml of the A32 Fab blocked 92 and 80% of the A32 mAb ADCC activity when 10Mg/ml of the A32 were used, respectively (Fig. 5A). Based on this experiment, the ability of the A32 Fab to inhibit ADCC activity of Ab present in the plasma of HIV- 1 infected individuals was determined. A test was made of plasma samples from donors recruited in the cohort of chronically infected individuals representing a range of ADCC- mediating Ab responses (Fig. 5B), A 10^ig/ml concentration of A32 Fab was used to pre-incubate target cells in order block the A32 binding on the

A1953 _CEM.N RccR5 cells. The plasma samples from HIV- 1 infected individuals were added to the target cells after this initial incubation at two dilutions representing the peak and subsequent ADCC reactivity for each sample, Observed was a range of inhibitory activity for the peak of the response due to the A32 Fab from 19% to 90% in the lower dilution (average ± standard deviation 56±24), In each individual , a higher level of inhibition of the ADCC activity was at the higher dilution ranging from 48 to 96% (75± 1 6); the majority of ADCC activity (>50%GzB activity) was also inhibited in 12 out of 14 patients (86%) at the lowest dilution . In both instances, the ADCC activity in the plasma samples was significantly lower when the target cells were pre-incubated with the A32- Fab ( Wilcoxon matched-pairs signed rank test p= <0.0001 ), whereas preincubation with control Ab did not inhibit the observed level of ADCC activity (Wilcoxon matched-pairs signed rank test p= <0.4556), (See also Figs. 6-8. ) In summary, in this study, it was demonstrated that the HIV- 1 Env gp l 20 mAb A32 binds to the surface of transmitted/founder H IV- 1 -infected CD4+ T cells earlier in the course of in vitro infection than the gpl 20 Env mAbs 1 7b and 2G 12. Moreover, A32 mAb was able to mediate ADCC activity that was 4-6-fold higher than the other two anti-g l 20 mAbs when either gp l 20-coated or HIV- 1 - infected target CD4⁺ cells were used. Finally, it was demonstrated that antibodies that are blocked by A32 Fab comprise a majority of ADCC-mediating Ab responses elicited during the course of HIV- 1 infection.

It has been previously reported that mAb A32 can be expressed on the surface of H IV- 1 infected cells during the latter stages of HIV- 1 mediated CD4+ T cell line fusion ( 10), MAbs directed toward the C-termimis, V3 loop and CD4 binding domain of the gp l 20 display a broad spcctram of binding capacity to the HIV- 1 envelope glycoproteins expressed on the surface of infected cells ( 36). 1 7b and 2G 1 2 mAbs were previously shown to stain the surface of a HeLa cell line that produced replication-defective HXB2 virions and inhibit cell-to-cell fusion ( 1 0). In this current study, activated peripheral blood CD4⁺ T lymphocytes were used in the experiments to more closely replicate what may occur in vivo. It was observed that A32 mAb was capable of binding to CD4 i^~ T cells infected with both primary (transmitted/founder) and laboratory adapted HIV- 1 isolates before potent neutralizing 17b and 2G12 mAb could bind. This was somewhat surprising and suggested that in vitro cell surface expression of gp l 20 Env epitopes may be differentially regulated. It was important to determine that A32 provided the earliest positive signal to identify envelope expression on the surface of H IV- 1 5 infected cells. A32 mAb binds to a conformation gp l 20 determinant that involves the CI region (34), A32 is non-neutralizing and the reason for this lias been attributed to the inability of A32 to bind to virions, i.e. the antibody has been suggested to not bind to the native trimer (34). The work on PB CD4+ T cells and the previous work of Finnegan et al. clearly demonstrate that mAb A32 does i o bind to the surface of the native trimer on the surface of HIV- 1 -infected cells.

Moreover, these data suggest that the conformation of the Env trimer with regard to the conformational C I region is dramatically different on virions compared to virus-infected cells.

The ability of mAb A32 to mediate ADCC was further explored using a

15 variety of target cell populations including gp l 20-coated CD4+ T cell line cells, chronically infected CD4+ T cells using the A 1953 isolate and PB CD4+ T cells infected with transmitted/founder HIV- 1 infectious molecular clones. The ADCC- mediating activity observed for 2G 12 using the gp l 20-coated target cells was comparable to that previously reported (32) and the paucity of ADCC reactivity

2 0 observed for 17b confirms previous observations indicating the need for sCD4 triggering of some Envs for exposure of the 17b CCR5-binding site epitope (30), The ability of A32 to mediate ADCC activity has also been confirmed in recent studies exploring the role of CD4i mAbs in ADCC responses, The ability of A32 to mediate ADCC activity has also been confirmed by recent studies performed

2 5 by George Lewis and Anthony DeVico while exploring the role of CD4i mAbs in ADCC responses. Importantly, observed was a 4-6 fold higher ADCC activity of A32 mAb to mediate ADCC .activity compared to 17b and 2G 12 mAbs and was comparable to ADCC mediated by HIV+ immunoglobulin (HIVIG®). Most importantly, the presence ot^' A32-!ike Ab responses was observed in the serum of subjects with chronic HlV- 1 infection. It was observed that A32-like Ab mediated the majority of the total ADCC activity in S6⁰ o of the chronically infected subjects when the highest dilution was tested.

It will be appreciated from a reading of this disclosure that if mAb A32 is shown to mediate a component of prevention of acquisition in passive protection trials in non-human primates, then it will be important to design immiinogens that could enhance the antigenicity of the gpl 20 region for mAb A32 binding in order to improve HIV- 1 vaccine candidates,

EXAMPLE 2

Specificity of RV 144 induced antibodies is shown in Fig. 9 by measuring the blocking of RV 144 vaccinee purified plasma IgG binding to Immunogen (A244) Env gp l 20 protein by g l 20 mAbs in a SPR assay. The binding of RV 144 IgG to A244 gpl 20 was blocked by A32 C I mAb (66%), the neutralizing V2 conformational mAb 697-30D ( 19%), the broadly neutralizing quaternary mAb CHO I (24%), and the Tier 1 restricted V3 neutralizing antibody 19b (42%). n= number of vaccinee IgG studied.

RV144 induced antibody responses on C I (A32), V2 (697-30D), V3 ( 19b) and at or near the conformational-Quatemary V2-V3 epitope (CHO I ) are shown in Fig. 10.

Quaternary Abs require a V2 N-linked glycosylation site at V2 loop aa 160 (N 160) for binding and for neutralization. Therefore, a search was made in serum for Abs that bound better to N 160 than to N 160 A244 gp l 20.

Quaternary mAb CHO I binding to A244 gp l 20 is abrogated by 160 mutation, as shown in Fig. 1 1 . Differential binding of RV 144 vaccinee purified IgG to A244 WT versus A244g N 160 gpl 20 (see Fig, 12), SPR binding responses of RV 144 plasma IgG to A244-N 160 WT versus A244-N 160 mutant were measured on a BIAcore 4000. IgG samples that gave higher sensitivity (>25% reduction) to N 160K mutation are circled in red. About 20% of the RV 144 vaccinee IgG showed N 160 sensitivity, which is compatible to specificities of neutralizing conformational-quatemary gp l 20 antibodies.

Summary of Results

• The binding specificities of RV 144 IgGs map to epitopes within CI , V2, and V3 domains of g l 20

^• C I (A32 blocking), V3 ( 19b blocking) and V2 (697D) specificities were predominant

^• About 20% of RV 144 IgG samples showed sensitivity to N 160K mutation

^• Blocking with CHOI mAb and sensitivity to V2-N 160K mutation

suggested that V2-V3 quaternary antibodies may have been induced in select RV 144 vaccinees

* * *

All documents and other information sources cited above are hereby incorporated in their entirety by reference.

References.

1 , Adachi, A., H. E. Gendelnian, S. Koenig, T. Folks, R, Willey, A.

Rabson, and M. A, Martin.1986. Production of acquired

immunodeficiency syndrome-associated retrovirus in human and nonhuman cells transfected with an infectious molecular clone. J Virol

59:284-291.

2. AUhorn, M., A. I. Olin, F. Nimmerjahn, and M. Collin.2008. Human IgG/Fc gamma R interactions are modulated by streptococcal IgG glycan hydrolysis. PLoS ONE 3:el413.

3. Ban in, L. L., K. J. Cassutt, K. Knigge, R, Khattri, J. Margolick, C.

Rinaldo, C. A. KJeeberger, P. Nishanian, D. R. Henrard, and J. Phair, 1996. HIV-1 gp 120- specific antibody-dependent cell-mediated cytotoxicity correlates with rate of disease progression. J Immunol

157:2168-2173,

4, Chung, A., E. Rollman, S. Johansson, S. J. Kent, and I. Stratov.2008.

The utility of ADCC responses in HIV infection. CUIT HIV Res 6:515- 519.

5. Chung, A. W., E. Rollman, R. J. Center, S. J. Kent, and I. Stratov.

2009. Rapid degranulation of NK cells following activation by HIV- specific antibodies. J Immunol 182:1202-1210.

6. Cummins, L. M., K. J. Weinhold, T. J. Matthews, A. J, Langlois, C. F.

Perno, R. M. Condic, and J. P. Allain.1991. Preparation and characterization of an intravenous solution of IgG from human

immunodeficiency virus-seropositive donors. Blood 77:1111-1117.

7. Decker, J. M., F. Bibollet-R che, X. Wei, S. Wang, D. N. Levy, W.

Wang, E. Delaporte, M. Peeters, C. A. Derdeyn, S. Allen, E. Hunter, M. S, Saag, J. A. Hoxie, B. H. Hahn, P. D, Kn ong, J. E. Robinson, and G. M. Shaw. 2005. Antigenic conservation and immunogenicity of the HIV coreeeptor binding site. J Exp Med 201 : 1407- 1 419.

Edmonds, T. G., H. Ding, X. Yuan, Q. Wei, K. S. Smith, J. A.

Conway, L. Wieczorek, B. Brown, V. Polonis, J, T. West, D. C.

Montefiori, J. C. Kappes, and C. Ochsenbaucr. 2010. Replication competent molecular clones of HIV- 1 expressing Renilla luciferase facilitate the analysis of antibody inliibition in PBMC. Virology 408: 1 -13. Ferrari, G., \Y. Humphrey, M. J. McElrath, J.-L. Excler, A.-M.

Duliege, M. L. Clements, L. C, Corey, D. P, Bolognesi, and K. J, Weinhold. 1997. Clade B-based HIV- 1 vaccines elicit cross-clade cytotoxic T lymphocyte reactivities in uninfected volunteers. Proc, Natl. Acad. Sci. USA 94: 1396-1401 .

Finnegan, C. M., W, Berg, G. K. Lewis, and A. L. DcVico. 2001 .

Antigenic properties of the human immunodeficiency virus envelope during cell-cell fusion, J Virol 75: 1 1096- 1 1 105.

Florese, R. H., T. Demberg, P, Xiao, L, Kuller, . Larsen, L, E.

Summers, D. Venzon, A, Cafaro, B, Ensoli, and M. Robert-Guroff. 2009. Contribution of nonneutralizing vaccine-elicited antibody activities to improved protective efficacy in rhesus macaques immunized with Tat/Env compared with multigenic vaccines. J Immunol 182:371 8-3727. Forthal, D. IN., G, Landucci, R. Haubrich, B. Keenan, B. D.

Kuppermann, J. G. Tilles, and J. Kaplan. 1 99. Antibody-dependent cellular cytotoxicity independently predicts survival in severely immunocompromised human immunodeficiency virus-infected patients. J Infect Dis 180: 1338- 1341.

Gomez- oman, V. R., L. J. Patterson, D. Venzon, D, Liewehr, K, Aldrich, R. Florese, and M. Robert-Guroff. 2005. Vaccine-elicited antibodies mediate antibody-dependent cellular cytotoxicity con-elated with significantly reduced acute viremia in rhesus macaques challenged with SIVmac251 . J Immunol 174:2185-2189.

14. Gray, E. S., P. L. Moore, I. A. Choge, J. M. Decker, F. Bibollet-Ruche, H. Li, N. Leseka, F. Treurnicht, K. MJisana, G, M. Shaw, S. S. A.

5 Karim, C. Williamson, L. Morris, and C. S. Team. 2007. Neutralizing antibody responses in acute human immunodeficiency virus type 1 subtype C infection. J Virol 81 :6187-6196.

1 5. Haynes, B. F., H.-X. Liao, and G, D. Tomaras. 2010. Is developing an HIV-1 vaccine possible? Curr Opin HIV AIDS 5:362-367. i o 16. Hessell, A. J., L. Hangartner, M. Hunter, C. E. G. Havenith, F. J.

Bcurskens, J. M. Bakker, C. M. S. Lanigan, G. Landucci, D. N.

Forthal, P. W. H. I. Parren, P. A. Marx, and D. R. Burton. 2007. Fc receptor but not complement binding is important in antibody protection against HIV. Nature 449: 101 - 104,

1 5 17. Hidajat, R., P. Xiao, Q. Zhou, D. Vcnzon, L. E. Summers, V. S.

Kalyanaraman, D. C. Montefiori, and M. Robert-Guroff. 2009.

CoiTelation of vaccine-elicited systemic and mucosal nonneutralizing antibody activities with reduced acute viremia following intrarectal simian immunodeficiency vims SIVmac251 challenge of rhesus macaques. J 2 0 Virol 83 :791 -801 .

1 8. Keele, B. F., E. E. Giorgi, J. F. Salazar-Gonzalez, J. M. Decker, K. T.

Pham, M. G. Salazar, C. Sun, T. Grayson, S. Wang, H. Li, X. Wei, C.

Jiang, J. L. irchherr, F. Gao, J. A. Anderson, L.-H. Ping, R.

Swanstrom, G. D. Tomaras, W. A. Blattner, P. A. Goepfert, J. M. 25 Kilby, M. S. Saag, E. L. Delwart, M. P. Busch, M. S. Cohen, D. C.

Montefiori, B, F. Haynes, B. Gaschen, G. S. Athreya, H. Y. Lee, N.

Wood, C. Seoighe, A. S. Perelson, T. Bhattacharv a. B. T. Korber, B.

H. Hahn, and G. M. Shaw. 2008. Identification and characterization of transmitted and early founder virus envelopes in primary HiV- 1 infection. Proc Natl Acad Sci USA 105:7552-7557.

Liu, L., A. Chahroudi, G. Silvestri, M. E. Wernett, W. J. Kaiser, J. T. Safrit, A. Komoriya, J. D, Altman, B, Z, Packard, and M. B. Feinberg.

2002. Visualization and quantification of T cell-mediated cytotoxicity using cell-permeable fluorogenic casp_tase substrates. Nat Med 8: 1 85- 1 89. Ljunggren, K., V. Moschese, P. A. Broliden, C. Giaquinto, I. Quinti, E. M, Fenyo, B. Wahren, P. Rossi, and M, Jondal. 1990, Antibodies mediating cellular cytotoxicity and neutralization correlate with a better clinical stage in children bom to human immunodeficiency vims-infected mothers. J Infect Dis 161 : 198-202.

Lyerly, H. K., T, J, Matthews, A. J. LangloLs, D, P, Bolognesi, and K. J. Weinhold. 1987. Human T-cell lymphotropic virus II1B glycoprotein (gp l 20) bound to determinants on normal lymphocytes and expressed by infected cells serves as targets for immune attack, Proc. Natl. Acad. Sci. U.S.A. 84:3797-3801 .

Moore, J. P., and J. Sodroski. 1996, Antibody cross-competition analysis of the human immunodeficiency virus type 1 gp l 20 exterior envelope glycoprotein, J Virol 70: 1 863- 1 872.

Ninimerjahn, F., and J, V. Ravetch. 2008. Analyzing antibody-Fc- receptor interactions. Methods Mol Biol 415: 1 51 - 162.

O'Doherty, U., W. J. Swiggard, and M. H. Malim. 2000. Human immunodeficiency vims type 1 spinoculation enhances infection through virus binding. J Virol 74: 10074- 10080.

Presta, L, G, 2008, Molecular engineering and design of therapeutic antibodies. Curr Opin Immunol 20:460-470.

Rerks-Ngarni, S,, P. Pitisuttithum, S. Nitayaphan, J. Kaevvkungvs al, J. Chiu, R. Paris, N. Premsri, C. Namwat, M. de Souza, E. Adams, M. Benenson, S. Curunathan, J. Tartaglia, J. G. McNeil, D. P. Francis, D. Stablein, D. L. Birx, S. Chunsuttiwat, C. Khaniboonruang, P.

Thongcharoen, M, L. Robb, N. L. Michael, P. Kunasol, J. H. Kim, and M.-T. Investigators. 2009. Vaccination with ALVAC and AIDS VAX to prevent HIV- 1 infection in Thailand. N Engl J Med 361 :2209-2220.

Robinson, J. E., D. H. Elliott, E. A. Martin, K. Micken, and E. S. Rosenberg. 2005. High frequencies of antibody responses to CD4 induced epitopes in HIV infected patients started on HAART during acute infection. Hum Antibodies 14: 1 15- 121 .

Salazai -Gonzalez, J. F., M. G. Salazar, B. F. Keele, G. H. Learn, E. E. Giorgi, H. Li, J. M. Decker, S. Wang, J. Baalwa, M. H. Kraus, N. F. Parrish, K. S. Shaw, M. B. Guffey, K. J. Bar, K. L. Davis, C.

Ochsenbauer-Jambor, J. C. Kappes, M. S. Saag, M. S. Cohen, J.

Mulenga, C. A. Derdeyn, S. Allen, E. Hunter, M. Markovvitz, P.

Hraber, A. S. Perelson, T. Bhattacharya, B. F. Haynes, B. T. Korber, B. H. Hahn, and G, M. Shaw. 2009, Genetic identity, biological phenotype, and evolutionary pathways of transmitted/founder viruses in acute and early HIV- 1 infection. J Exp Med 206: 1273-1289.

Stratov, I., A. Chung, and S. J. Kent. 2008. Robust NK cell-mediated human immunodeficiency virus (HTV)-specific antibody-dependent responses in HIV-infected subjects. J Virol 82 :5450-5459.

Thali, M., J. P. Moore, C. Furman, M. Charles, D. D. Ho, j. Robinson, and J. Sodroski. 1993. Characterization of conserved human

immunodeficiency virus type 1 gp l 20 neutralization epitopes exposed upon gp l 20-CD4 binding. J Virol 67:3978-3988.

Trkola, A., J. Matthews, C. Gordon, T. Ketas, and J. P. Moore. 1 99. A cell line-based neutralization assay for primary human immunodeficiency virus type 1 isolates that use either the CCR5 or the CXCR4 coreceptor. J Virol 73 : 8966-8974,

Trkola, A., M. Purtscher, T. Muster, C. Ballaun. A. Buchacher, N. Sullivan, K. Srinivasan, J. Sodroski, J, P. Moore, and H. Katinger.

1996. Human monoclonal antibody 2G 12 defines a distinctive

neutralization epitope on the gp l 20 glycoprotein of human

immunodeficiency virus type 1 . J Virol 70: 1 100- 1 108.

Tyler, D. S., S. D. Stanley, S. Zolla-Pazner, M. K. Gorny, P. P.

Shadduck, A. J. Langlois, T. J. Matthews, D. P. Bolognesi, T. J.

Palker, and K. J. Weinhold. 1990. Identification of sites within gp41 that serve as targets for antibody-dependent cellular cytotoxicity by using human monoclonal antibodies. J , Immunol. 145 :3276-3282.

Wyatt, R., J. Moore, M. Accola, E. Desjardin, J. Robinson, and J. Sodroski. 1995. Involvement of the V1/V2 variable loop structure in the exposure of human immunodeficiency virus type 1 gpl 20 epitopes induced by receptor binding. J Virol 69:5723-33.

Xiao, P., J. Zhao, L. J. Patterson, E. Brocca-Cofano, D, Venzon, P. A. Kozlowski, R. Hidajat, T. Demberg, and M. Robert-Guroff. 2010. Multiple vaccine-elicited non-neutralizing anti-envelope antibody activities contribute to protective efficacy by reducing both acute and chronic viremia following SHIV89.6P challenge in rhesus macaques. J Virol. 84:7161 -7173

Zolla-Pazner, S., J. O'Leary, S. Burda, M. K. Gorny, M. Kim, J.

Mascola, and F. McCutchan. 1995. Serotyping of primary human immunodeficiency virus type 1 isolates fi-om diverse geographic locations by flow cytometry. J Virol 69:3807-38 1 5.

Claims

WHAT IS CLAIMED IS :

1 . An isolated human immunodeficiency virus type 1 (HIV- 1 ) envelope immunogen that induces the production in a subject of antibodies the binding of which to said immunogen is blocked by monoclonal antibody A32 or binding fragment thereof.

2. The immunogen according to claim 1 wherein said binding fragment is a Fab fragment.

3. A composition comprising the immunogen according to claim 1 and a carrier.

4. An isolated nucleic acid encoding said immunogen according to claim 1 .

5. The nucleic acid according to claim 4, wherein said nucleic acid is present in a vector.

6. A composition comprising the nucleic acid according to claim 1 and a earner.

7. A method of inducing an immune response against HIV- 1 comprising administering a subject in need thereof an amount of said immunogen according to claim 1 sufficient to effect said induction.

8. The method according to claim 7 wherein said subject is a human

9. The method according to claim 7 wherein a nucleic acid encoding said immunogen is administered to said subject under conditions such that said nucleic acid is expressed and said immunogen is thereby produced.