CN116769022A - Antibody and application thereof in protein A detection - Google Patents

Abstract

The application relates to the technical field of biological detection, in particular to an antibody and application thereof in protein A detection. The coated antibody and the labeled antibody provided by the application have high affinity with SPA protein, and are used for detecting SPA residues. The coating antibody coats the magnetic particles, the labeled antibody is labeled by horseradish peroxidase, and the SPA is accurately and rapidly detected by a one-step sandwich detection method.

Description

Antibody and application thereof in protein A detection

The application discloses a divisional application with the name of antibody and application thereof in protein A detection, wherein the application date is 2021, 12 and 06, the application number is 202111478482.8.

Technical Field

The application relates to the technical field of biological detection, in particular to an antibody and application thereof in protein A detection.

Background

Staphylococcus aureus (Staphylococcus aureus) is an extremely common class of gram-positive bacteria belonging to the genus staphylococcus (staphylococcus). Staphylococcus aureus protein A (Staphylococcus aureus, protein A, SPA) is a protein on the surface of a staphylococcus aureus membrane, and accounts for about 6.7% of the protein component of the whole cell wall, and is covalently connected with the cell wall peptidoglycan through the COOH end, and the molecular mass is 42Kda, so that almost 90% of the surface of the cell wall of staphylococcus aureus contains SPA.

Therefore, the detection of SPA can reflect the existence of staphylococcus aureus, and commercial kits are mostly adopted for monitoring SPA residues in the pharmaceutical industry at present. Currently, commercial SPA detection kits mostly adopt a double-antibody sandwich method, and the antibody used is an antibody aiming at SPA.

SPA is a highly stable type I membrane cell surface receptor capable of specifically binding to the Fc fragment of a monoclonal antibody. The SPA polypeptide chain consists of five homologous regions E, D, A, B, C, each of which can bind to the Fc fragment of IgG in human and some mammalian serum without affecting the activity of the Fab fragment of the antibody molecule with the antigen binding site.

Aiming at the characteristics of SPA, a novel detection method is developed, so that the detection efficiency is further improved, and the method has important significance.

Disclosure of Invention

In view of the above, the technical problem to be solved by the present application is to provide a pair of antibodies having high affinity with SPA protein and their use in SPA protein detection.

The antibody provided by the application comprises a coated antibody and a labeled antibody.

The coated antibody provided by the present application,

the amino acid sequences of the three CDR regions of the heavy chain have the amino acid sequences shown in SEQ ID NO. 1, 2 and 3 respectively;

the amino acid sequences of the three CDR regions of the light chain have the amino acid sequences shown in SEQ ID NOs 4, 5 and 6, respectively.

In some embodiments, the amino acid sequence of the heavy chain of the coated antibody is shown in SEQ ID NO. 7.

In some embodiments, the coated antibody light chain has an amino acid sequence as set forth in SEQ ID NO. 8.

The application also provides a conjugate prepared by coupling the coated antibody with a medium.

In the present application, the medium coupled to the coated antibody is solid or non-solid. In a specific embodiment, the medium is a magnetic bead.

The present application provides a labeled antibody which,

the amino acid sequences of the three CDR regions of the heavy chain have the amino acid sequences shown in SEQ ID NO. 9, 10 and 11 respectively;

the amino acid sequences of the three CDR regions of the light chain have the amino acid sequences shown in SEQ ID NOS 12, 13 and 14, respectively.

In some embodiments, the amino acid sequence of the heavy chain of the marker antibody is shown in SEQ ID NO. 15;

in some embodiments, the amino acid sequence of the light chain of the labeled antibody is shown in SEQ ID NO. 16.

The application also provides a conjugate prepared by modifying the labeled antibody by a marker.

In the present application, the label is a chemical label or a biomarker, and in some embodiments, the label is horseradish peroxidase.

The application relates to a coated antibody, a conjugate, a labeled antibody and an application of the conjugate in preparation of a reagent for detecting SPA protein.

The application provides a reagent for detecting SPA protein, which comprises the conjugate and the conjugate.

The reagent also comprises a washing liquid, a substrate A and a substrate B;

the washing liquid is PBST buffer solution;

the substrate a comprises luminol;

the substrate B comprises hydrogen peroxide.

The application also provides a method for detecting SPA protein, which uses the reagent of the application to detect samples.

In vitro diagnostic tests, particularly for the double antibody sandwich test mode, if SPA remains in both the coated and labeled antibodies, high background or false positive results will occur in both sandwiches. Thus, one of the functions of the reagents of the application is to detect samples that require SPA residue detection of antibodies. In some embodiments, the sample to be tested is an antibody obtained by purification by SPA affinity chromatography.

In the application, the detection adopts a one-step sandwich method.

The coated antibody and the labeled antibody provided by the application have high affinity with SPA protein, and are used for detecting SPA residues. The coating antibody coats the magnetic particles, the labeled antibody is labeled by horseradish peroxidase, and the SPA is accurately and rapidly detected by a one-step sandwich detection method.

Detailed Description

The application provides antibodies and their use in protein a detection, and those skilled in the art can, in light of the disclosure herein, suitably modify the process parameters. It is expressly noted that all such similar substitutions and modifications will be apparent to those skilled in the art, and are deemed to be included in the present application. While the methods and applications of this application have been described in terms of preferred embodiments, it will be apparent to those skilled in the relevant art that the application can be practiced and practiced with modification and alteration and combination of the methods and applications herein without departing from the spirit and scope of the application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. For definitions and terms in the art, the expert may refer specifically to Current Protocols in Molecular Biology (Ausubel). The abbreviations for amino acid residues are standard 3-letter and/or 1-letter codes used in the art to refer to one of the 20 commonly used L-amino acids.

An "antibody" refers to a protein composed of one or more polypeptides capable of specifically binding an antigen. One form of antibody constitutes the basic structural unit of an antibody. This form is a tetramer that is composed of two identical pairs of antibody chains, each pair having one light chain and one heavy chain. In each pair of antibody chains, the variable regions of the light and heavy chains are taken together to be responsible for binding to the antigen, while the constant regions are responsible for the effector functions of the antibody.

The "variable region" of an antibody heavy or light chain is the N-terminal mature region of that chain. Currently known antibody types include kappa and lambda light chains, as well as alpha, gamma (IgG 1, igG2, igG3, igG 4), delta, epsilon and mu heavy chains or other types of equivalents thereof. The full-length immunoglobulin "light chain" (about 25kDa or about 214 amino acids) comprises a sequence consisting of NH ₂ A variable region of about 110 amino acids at the end, and a kappa or lambda constant region at the COOH-end. The full length immunoglobulin "heavy chain" (about 50kDa or about 446 amino acids) also comprises a variable region (about 116 amino acids), and one of the heavy chain constant regions, e.g., gamma (about 330 amino acids).

"CDR regions" or "CDRs" as used herein refer to the hypervariable regions of the heavy and light chains of immunoglobulins, as defined by Kabat et al (Kabat et al Sequences ofproteins of immunological interest,5th Ed., U.S. device of Health and Human Services, NIH,1991, and later versions). There are three heavy chain CDRs and three light chain CDRs. The term CDR or CDRs as used herein is intended to indicate one of these regions, or several or even all of these regions, as the case may be, comprising the majority of amino acid residues responsible for binding by the affinity of the antibody for the antigen or its recognition epitope.

Antibodies provided herein include labeled antibodies and coated antibodies, which are antibodies to SPA proteins that are not specific for antibodies, but which have a high affinity for the Fc region of antibodies to SPA proteins.

The three CDR regions of the light chain of the coated antibody are sequentially as follows: KSLLHSNGFTY, QMS, QHHFGTPWT. The specific amino acid sequence of the light chain of the coated antibody is as follows: DIVMTQAAFS NPVTLGTSASISCRSSKSLLHSNGFTYLNWYLQKPGQSPQLLIYQMSNLAS GVPDRFSSSGSGTDFTLRISRVEAEDVGVYYCQHHFGTPWTFGGGTKLEI K。

The three CDR regions coating the heavy chain of the antibody are in sequence: GYSFTNYW, IDPANDNA, ALYYYGPTY, the amino acid sequence of the coated antibody heavy chain is: EVQLQQSGTVLARPGASVKISCKASGYSFTNYWMNWIEQRPGQGLEWIGTIDPANDNANF NQNFKGKAKLTAVTSTSTAYMELSSLTNEDSAVYYCALYYYGPTYWGQGT LVTVSA。

The three CDR regions of the labeled antibody heavy chain are in sequence: ENIYSY, NAI, AQNLELPWT. The amino acid sequence of the light chain of the labeled antibody is as follows: DIQMTQSPASLSASVGKSVTITCRASENIYSYLAWYQQKQGESPHLLVYNAITLAEGVPSRFRGSGSGTQFSLRINSL QPEDLGSYYCAQNLELPWTFGGGTKLEIK。

The three CDR regions of the labeled antibody heavy chain are in sequence: GFNIIDTY, IYPGNQNA, STYYRYDVGWFAS. The heavy chain amino acid sequence of the labeled antibody is: EVQLKQSGAELVKP GASVKLSCTASGFNIIDTYIHWVKQRPEQGLEWIGKIYPGNQ NAEYDPKF RGKATVTSDTSSNTAFLQLSSLTSEDTAVYYCSTYYRYDVGWFASWGQGT LVTVSA。

"antibody" includes antibodies or immunoglobulins of any isotype, or antibody fragments that remain specifically bound to an antigen, including but not limited to Fab, fv, scFv, and Fd fragments, chimeric antibodies, humanized antibodies, single chain antibodies, and fusion proteins comprising an antigen-binding portion of an antibody and a non-antibody protein.

Antibodies can be labeled and detected, and in the present application, the label includes a chemical label or a biological label. The labeled antibody can be detected by labeling with a radioisotope, an enzyme capable of producing a detectable substance, a fluorescent protein, or biotin. The chemical label is an isotope, an immunotoxin and/or a chemical drug; in some embodiments, the biomarker is biotin, avidin, or an enzyme label. The enzyme label is preferably horseradish peroxidase or alkaline phosphatase. The immunotoxin is preferably aflatoxin, diphtheria toxin, pseudomonas aeruginosa exotoxin, ricin, abrin, mistletoe lectin, podophyllotoxin, PAP, sequoyins, gelonin or luffa toxin. In an embodiment of the present application, the labeled antibody is labeled with a biological enzyme. In some embodiments, the labeled antibody is horseradish peroxidase.

Antibodies may also be coated on solid or non-solid supports. The solid medium or non-solid medium is selected from colloidal gold, polystyrene plates or beads. In the present application, the coated antibody is coated on the magnetic particles.

The coated antibody and the labeled antibody provided by the application have high affinity with SPA protein, and are used for detecting SPA residues. The coating antibody coats the magnetic particles, the labeled antibody is labeled by horseradish peroxidase, and the SPA is accurately and rapidly detected by a one-step sandwich detection method. The SPA is detected by the same method, and the result shows that the accuracy and the sensitivity are not as good as those of the kit prepared by the application.

The screening method of the two antibodies comprises the following steps: coating SPA protein, adding an antibody, comparing with a non-dissociating agent, detecting the dissociating agent (6M urea, 1M guanidine hydrochloride or 1.5M NaSCN) added to the antibody, dissociating, washing the plate, and adding the HRP-marked goat anti-mouse secondary antibody. OD450 was detected, dissociating wells/no dissociating agent added. The higher the value, the higher the affinity. Screening to an affinity of > 60%, and then carrying out pairing screening. Screening the paired antibodies capable of sandwich detection of SPA protein.

In the application, the preparation method of the coated antibody coated on the magnetic particles comprises the following steps: the magnetic particles and the coated antibody are coupled by adopting a carboxyl two-step method, and the EDC concentration is 10mg/ml in the preparation process; NHS concentration 10mg/ml (molar ratio EDC: NHS: antibody=50:50:1), magnetic particle coating concentration 0.2-0.5. Mu.g/T.

The step of labeling the labeled antibody by horseradish peroxidase comprises the following steps: the enzyme-labeled antibody is prepared by adopting a sodium periodate method. The enzyme-labeled antibody has a working concentration of 1/4K-1/5K.

In the application, the SPA protein is prepared by adopting a recombinant escherichia coli expression method, and the expressed crude protein is obtained by combining metal chelate chromatography with ion exchange chromatography.

In the detection method, recombinant SPA protein is used as a standard substance. The concentration of the standard is 0, 10pg/ml, 40pg/ml, 100pg/ml, 200pg/ml, 400pg/ml.

The one-step sandwich method detection method is characterized by comprising the following reaction principle:

(1) adding 20 μl of the magnetic particles coated with the antibody, and adding 50 μl of the sample to be detected; adding 50 μl of enzyme-labeled antibody, and reacting for 15min; (2) washing solution was added thereto for 6 times, 50. Mu.l of each of the luminescent substrates A and B was added thereto, and detection was carried out.

The lotion comprises the following components: PBST (pbs+tween 20); substrate A component: luminol; substrate B component: hydrogen peroxide.

The test materials adopted by the application are all common commercial products and can be purchased in the market. The application is further illustrated by the following examples:

example 1 high affinity antibody screening

1. SPA protein coating:

1) SPA protein was diluted with pH 9.6.01M carbonate buffer to 5. Mu.g/ml, 50 ul/well, and added to 96-well enzyme-free plates at 37℃for 12h.

2) The wells were dried by washing with PBST buffer 5 times, and 50. Mu.l of blocking solution (5% Casein buffer) was added thereto at 37℃for 2 hours.

3) The residual liquid in the dry hole is taken on the absorbent paper, and the absorbent paper is dried and sealed and stored in a vacuum packaging bag for standby.

2. Antibody screening:

1) The antibodies to be screened are diluted to 5 mug/ml by using 0.01M phosphate buffer solution;

2) Taking out the coated enzyme-free plate, adding 100 mu l of diluted antibody to be tested into each of the holes A1 and B1, and carrying out multi-hole sample adding on other samples to be tested in the same way;

3) Shaking on a micro-oscillator for 30 seconds to uniformly mix the liquid in the hole, and incubating for 30 minutes at 37 ℃;

4) Washing the plate for 5 times, and beating the residual liquid in the dry holes on the absorbent paper;

5) One well was added with 100. Mu.l of control buffer (pH 9.6.01M Tris buffer) (e.g.A1, C1, E1, G1) and the other well was added with 100. Mu.l of dissociation solution (pH 9.6.01M Tris buffer+6M urea) (e.g.B1, D1, F1, H1);

6) Repeating the operation step 3, and incubating for 10min at 37 ℃;

7) Repeating the operation step 4;

8) Mu.l of enzyme conjugate (HRP-labeled goat anti-mouse secondary antibody, 1/3K dilution) was added to each well;

9) Repeating the operation steps 3 and 4;

10 Adding 50 μl of each of the substrate solution and the color-developing agent into each of the wells, and reacting at 37deg.C in dark for 10min;

11 Adding 50 μl of stop solution into each hole, shaking, and testing immediately;

12 Absorbance (OD) of each well was measured with a microplate reader at a wavelength of 450 nm.

13 Result calculation:

IgG antibody affinity = dissociation buffer well OD/control buffer well OD x 100%.

3. Antibody pairing establishment:

1) Antibodies with affinity > 60% were screened and then paired screened.

2) The high affinity antibodies are screened, and HRP labeling is carried out by adopting a sodium periodate method.

3) The cross pairing of the coating and the enzyme-labeled antibody is screened by adopting an enzyme-linked immunosorbent assay, the coating concentration is 5 mug/ml, and the enzyme label is 1/4K-1/5K.

4) E.coli recombinant SPA protein dilution gradient, sandwich detection.

5) Finally, a pair of antibodies is selected and used as a pairing antibody for detecting the SPA protein, and the affinity of the pairing antibody to the SPA protein is obviously superior to other antibodies through ELISA detection.

Through the sequence-finding process,

the amino acid sequence of the light chain of the coated antibody is as follows:

DIVMTQAAFSNPVTLGTSASISCRSSKSLLHSNGFTYLNWYLQKPGQSPQLLIYQMSNLASGVPDRFSSSGSGTDFTLRISRVEAEDVGVYYCQHHFGTPWTFGGGTKLEIK

the amino acid sequence of the heavy chain of the coated antibody is as follows:

EVQLQQSGTVLARPGASVKISCKASGYSFTNYWMNWIEQRPGQGLEWIGTIDPANDNANFNQNFKGKAKLTAVTSTSTAYMELSSLTNEDSAVYYCALYYYGPTYWGQGTLVTVSA

the amino acid sequence of the light chain of the labeled antibody is as follows:

DIQMTQSPASLSASVGKSVTITCRASENIYSYLAWYQQKQGESPHLLVYNAITLAEGVPSRFRGSGSGTQFSLRINSLQPEDLGSYYCAQNLELPWTFGGGTKLEIK

the heavy chain amino acid sequence of the labeled antibody is:

EVQLKQSGAELVKPGASVKLSCTASGFNIIDTYIHWVKQRPEQGLEWIGKIYPGNQNAEYDPKFRGKATVTSDTSSNTAFLQLSSLTSEDTAVYYCSTYYRYDVGWFASWGQGTLVTVSA

example 2 preparation of the kit

1. Antibody coated magnetic particles:

1) Coating the magnetic particles and the coated antibody by adopting a carboxyl two-step method, wherein the coating concentration of the magnetic particles is 0.2 mug/T;

2) Mixing the magnetic bead stock solution uniformly, taking 30 mu l of magnetic bead stock solution plus 300 mu l of pH 7.4.01M phosphate buffer solution, washing for 5 times, adding 10mg/ml EDC 50 mu l (prepared by pH 4.7.01M acetate buffer solution) +10mg/ml NHS 50 mu l (prepared by pH 4.7.01M acetate buffer solution), mixing uniformly, and then vibrating and reacting for 1h;

3) Washing with 300 mu.l B solution for 2 times, diluting 100 mu.l (quantitative antibody with pH 4.7.01M acetate buffer\diluting), mixing well, and shaking for 2h; (wherein molar ratio EDC: NHS: antibody=50:50:1)

4) Adding 300 mu L of ethanolamine with the concentration of 1mol/L to terminate the reaction for 30min;

5) Removing the supernatant, adding 300 μl of blocking solution, and blocking for 4 times by washing method;

6) 3ml of a protective solution (blocking solution) was added thereto and the mixture was stored at 2 to 8 ℃.

The sealing liquid comprises: 0.01M PBS pH7.4 (1% BSA+10% glycerol).

2. HRP modified labeled antibody

The preparation of the enzyme-labeled antibody adopts a sodium periodate method for labeling, and comprises the following steps: activation of HRP, reaction of the activated HRP with the antibody, termination of the reaction, dialysis, and addition of 50% glycerol to obtain an HRP-labeled antibody.

3. Washing liquid: preparing a PBST buffer comprising: mu.l of Tween-20 was added to 100ml of PBS and the mixture was ready for use.

4. Substrate a: luminol solution.

5. Substrate B: hydrogen peroxide solution.

6. Standard substance: the escherichia coli expresses recombinant SPA protein (GI: 1442983453), and is obtained by combining metal chelating chromatography with ion exchange chromatography, and the concentration is 0pg/mL, 10pg/mL, 40pg/mL, 100pg/mL, 200pg/mL and 400pg/mL in sequence by gradient dilution.

Example 3 one-step sandwich assay for detecting SPA residue

1. The sample to be measured is:

2. detection reagent: example 2 preparation:

3. the detection step comprises the following steps:

3.1 adding a standard substance and a sample to be detected in sequence into a reaction container, wherein the adding amount is 50 mu l/hole

3.2 adding 20. Mu.l of the antibody-coated magnetic particle suspension per well;

3.3 adding 50 μl (working concentration 1/5K) of enzyme-labeled antibody;

3.4, after mixing evenly, incubating for 15min at 37 ℃;

3.5 adding washing liquid, and washing for 6 times;

3.6 adding 50 μl of each of the luminescent substrate A solution and the luminescent substrate B solution into each well;

3.7, uniformly mixing for 1-5min, and detecting the luminous intensity.

4. Analysis of results:

standard detection results:

detection results of the to-be-detected product:

as shown in the table above, when the SPA content in the sample is greater than 0.2ng/ml, the consistency of the results of the kit and the commercial SPA detection kit is higher, which indicates that the kit has good accuracy. The commercial kit cannot effectively detect and obtain a result when the content is lower than 0.2ng/ml, which indicates that the sensitivity of the kit is higher than that of the commercial kit.

The foregoing is merely a preferred embodiment of the present application and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present application, which are intended to be comprehended within the scope of the present application.

Claims (5)

1. A labeled antibody, characterized in that,

the amino acid sequences of the three CDR regions of the heavy chain have the amino acid sequences shown in SEQ ID NO. 9, 10 and 11 respectively;

the amino acid sequences of the three CDR regions of the light chain have the amino acid sequences shown in SEQ ID NOS 12, 13 and 14, respectively.

2. The labeled antibody according to claim 1, wherein,

the amino acid sequence of the heavy chain is shown as SEQ ID NO. 15;

the amino acid sequence of the light chain is shown as SEQ ID NO. 16.

3. The conjugate of claim 1 or 2, wherein the conjugate is modified with a label.

4. A conjugate according to claim 3, wherein the label is horseradish peroxidase.

5. Use of the labeled antibody of claim 1 or 2, the conjugate of claim 3 or 4, for the preparation of a reagent for SPA protein detection.