CN115975023B

CN115975023B - Preparation method of recombinant TP antigen and antibody detection reagent prepared by preparation method

Info

Publication number: CN115975023B
Application number: CN202211622174.2A
Authority: CN
Inventors: 詹先发; 柳静
Original assignee: Beijing Key Biotechnology Co ltd
Current assignee: Beijing Key Biotechnology Co ltd
Priority date: 2022-12-16
Filing date: 2022-12-16
Publication date: 2023-06-13
Anticipated expiration: 2042-12-16
Also published as: CN115975023A

Abstract

The invention provides a preparation method of recombinant TP antigen and an antibody detection reagent prepared by the preparation method, which are used for modifying a natural TPN47 antigen, deleting a sequence structural region with high consistency with human related proteins so as to improve the subsequent detection specificity; the recombinant TP antigen also comprises an epitope with high specificity, and part of epitopes are repeatedly arranged, so that the screening success probability of the high-specificity antibody is improved; the preparation process of the recombinant TP antigen is optimized, comprising the steps of designing the nucleotide sequence of the recombinant protein by using the preferential codons of escherichia coli, and improving the production capacity; optimizing the process steps and operating parameters in the preparation process, and providing a fermentation medium with good production performance, thereby obtaining high-purity recombinant protein; screening and obtaining monoclonal antibodies with high affinity with target antigens, and effectively recognizing TP; the antibody and the related kit can effectively detect TP infection, and provide a detection means with high specificity, high sensitivity and good stability.

Description

Preparation method of recombinant TP antigen and antibody detection reagent prepared by preparation method

Technical field:

the invention belongs to the field of disease diagnosis, and particularly provides a preparation method of a recombinant TP antigen and an antibody detection reagent prepared by the preparation method.

The background technology is as follows:

syphilis is a disease of multiple systems in humans caused by a pathogenic microorganism called treponema pallidum (Treponema pallidum, TP). Most cases of syphilis are due to sexual contact, so the infection is considered a sexually transmitted infectious disease, congenital syphilis occurs when pregnant women are infected, and is still common in many parts of the world; cases of syphilis infection are also reported to be obtained by blood transfusion, common needles, contact open lesions, organ transplantation or occupations and other contacts. Despite the existence of effective antibiotic therapies, the burden of global syphilis infection has increased dramatically over the past few decades, with an estimated 1060-thousand cases each year becoming a global health problem.

The development cycle of syphilis is long and can be divided into several stages according to its clinical manifestations, and after initial contact with the skin or mucosa, the spirochete replicates locally, triggering inflammatory reactions and transmission through blood and lymphatic vessels, and then a unique painless, normally isolated, induration ulcer appears three weeks after contact. In penicillin treated individuals, ulcers began to resolve within a few days, whereas in untreated individuals, primary lesions spontaneously resolved without scarring within 3-6 weeks. At this point, spirochetes spread from the main site of infection to multiple organ tissues, mainly the skin, developing a new stage called secondary syphilis, which occurs within 4-10 weeks after the initial contact, with extensive skin mucosal lesions and systemic symptoms and signs. Patients with secondary syphilis have a strong cellular and humoral immune response, and about one third of untreated patients develop potentially damaging recurrent disease, termed tertiary syphilis, characterized by neurosyphilis, cardiovascular syphilis, or gelatinous skin syphilis.

Treatment of syphilis depends on the stage of the disease. Primary, secondary or early latent syphilis is treated with 240 ten thousand units of single-dose intramuscular injection of benzathine, and its alternative therapy comprises oral doxycycline 100mg 2 times daily for 14 days; oral ceftriaxone 1 to 2gm daily for 10 to 14 days; the tetracycline was administered 100mg 4 times daily for 14 days. The late-stage latent syphilis is treated with 240 ten thousand units of benzathine by intramuscular injection once a week for 3 weeks, and the replacement therapy comprises oral doxycycline 100mg, 2 times a day for 28 days; tetracycline 100mg was administered orally 4 times daily for 28 days (see Maria e.Tudor et al, syphilis, 2022.01).

Although researchers have developed effective drugs for treating syphilis, the trend of syphilis infection has not been effectively suppressed in recent years, and it is counted that the incidence of congenital syphilis has decreased from 2008 to 2012, but increased by 38% in 2012. If early diagnosis of syphilis and subsequent medical delays occur, serious complications can result. Thus, there is a need for a highly sensitive and specific syphilis screening test that can be performed quickly and reduces labor costs.

Methods for diagnosing syphilis include non-spirochete tests and spirochete tests. Non-spirochete tests, such as venereal disease laboratory studies (venereal disease research laboratory, VDRL) and rapid plasma reactions (rapid plasma reagin, RPR), are easy to use, inexpensive and widely available, but often require the combination of other test results for final confirmation. Spirochete assays include chemiluminescence, treponema pallidum particle agglutination assays (t.pallidum particle agglutination, TPPA), treponema pallidum hemagglutination assays (t.pallidum hemagglutination, TPHA), treponema fluorescin antibody absorption assays (fluorescent treponemal antibody absorption test, FTA-ABS), enzyme-linked immunosorbent assays (enzyme-linked immunosorbent assay, ELISA), immunochromatography, and the like, which are more expensive and require complex manual manipulations than non-spirochete assays. In treponema pallidum detection, ELISA is the most commonly used method in treponema pallidum diagnosis due to its simplicity, low cost and ease of automation.

Among treponema pallidum polypeptides, at least five (TPN 15, TPN17, TPN37, tmpA and TPN 47) have been shown to have diagnostic relevance, wherein TPN15, TPN17 are common diagnostic antigens in early stages, and recent studies have shown that TPN47 antigen has better immunoreactivity and can be used as an important marker for early diagnosis of syphilis (see Jianbo Liang et al, comparison of "lumipuls anti-Treponema pallidum" and "Architect Syphilis TP" and further examination, comparative Study J Clin Lab Anal,2020.03,34 (5): e 23194), and applications such as CN105542014A, CN104080801a have proposed a preparation method of TPN47 antigen and use for syphilis testing. However, structural studies on the TPN47 antigen show that a sequence in the TPN47 antigen has high homology with human fibronectin, so that false positive detection results may be caused, and misleading of clinical treatment is caused, therefore, in CN101293919a, it is proposed to use truncated TPN47 as an antigen, so as to reduce the false positive rate.

Although the prior art has disclosed using TPN47 antigen for syphilis detection, the prior art still faces the technical problems of low detection accuracy, poor sensitivity and the like, and limits the application of the method in syphilis detection and subsequent treatment. Therefore, the application provides a preparation method of a recombinant TP antigen, wherein an epitope with high immunogenicity is selected from amino acid sequences of a natural TPN47 antigen, and a repeated sequence is arranged for part of high-activity epitopes, so that the success probability of subsequent screening of high-specificity antibodies is improved, and all epitopes are connected by using flexible connectors; the recombinant TP antigen is used for screening monoclonal antibodies and preparing a syphilis diagnosis kit, so that the sensitivity and the specificity of detection can be improved.

Disclosure of Invention

In order to solve the technical problems, the invention provides a preparation method of a recombinant TP antigen, which is characterized in that the amino acid sequence of the recombinant TP antigen is shown as SEQ ID NO.1, and the preparation method comprises the following steps: constructing an expression vector carrying the recombinant TP antigen gene; causing the expression vector to be in an E.coli expression system; culturing Escherichia coli by high-density fermentation; and (3) collecting escherichia coli thalli, and separating and purifying to obtain the soluble recombinant TP antigen.

The recombinant TP antigen provided by the invention removes sequence sections with high similarity with related genes in human bodies, thereby ensuring the specificity and the effectiveness of detection and identification; based on the existing research results, the antigen epitope with high specificity is screened out through bioinformatics analysis, the recombinant antigen comprises the antigen epitope with high specificity, partial epitope repetition areas are also arranged, and flexible connectors are adopted to connect all the areas so as to more effectively excite immune response in vivo, thereby providing favorable conditions for developing related vaccines and screening detection antibodies.

Furthermore, the nucleotide sequence of the recombinant TP antigen is shown as SEQ ID NO. 2. The nucleotide sequence is designed according to the preferential codons of the escherichia coli, so that the expression efficiency in an escherichia coli expression system can be improved, and the preparation and purification processes of recombinant proteins are facilitated.

Further, the preparation method further comprises the following steps: amplifying the recombinant protein gene by PCR, introducing XhoI and EcoRI enzyme cutting sites at two ends of a nucleotide sequence of the recombinant protein gene, connecting the recombinant protein gene to a pET28a vector after enzyme cutting, and electrically transforming the recombinant protein gene into DH5 alpha competent cells; screening positive clones, and performing enzyme digestion and sequencing to identify correct clones; connecting the recombinant protein gene to a prokaryotic expression vector pGEX6P-1, introducing the prokaryotic expression vector into escherichia coli BL21, performing amplification culture, inoculating to a bioreactor, adding a fermentation medium, culturing at 37 ℃, and stirring at a speed of 350-450r/min, wherein the ventilation rate is 0.8-1.5L/L.min; adding IPTG to induce for 16 hours, and centrifugally collecting thalli; the thallus is crushed by ultrasonic wave, protein is purified by a ProteinA method, and the soluble recombinant TP antigen is obtained.

Further, the fermentation medium comprises 10g/L of tryptone, 5g/L of yeast extract, 2.34g/L of monopotassium phosphate, 3.58g/L of monopotassium phosphate, 10g/L of sodium chloride, 0.64g/L of magnesium sulfate heptahydrate, 0.56g/L of ferric chloride hexahydrate, 10g/L of glycerol and 5g/L of glucose.

The preparation method of the recombinant antigen is optimized in the invention, and comprises the detailed steps, operation parameters, the composition of the used culture medium and the like, the preparation means of the existing recombinant protein are comprehensively and systematically improved, the synergistic effect is obtained, the product yield is greatly improved, and meanwhile, the high-purity protein can be obtained.

A monoclonal antibody specifically recognizing TP is provided, wherein the heavy chain variable region of the antibody comprises CDR-H1-3 with an amino acid sequence shown as SEQ ID No. 3-5; the light chain variable region of the antibody comprises CDR-L1-3 with an amino acid sequence shown as SEQ ID No. 6-8.

Further, the amino acid sequence of the heavy chain variable region of the antibody is shown as SEQ ID No. 9.

Further, the amino acid sequence of the light chain variable region of the antibody is shown as SEQ ID No. 10.

Further, the preparation method of the antibody comprises the following steps: immunizing a mouse with the recombinant TP antigen of any one of claims 1-3, collecting, purifying, and screening from ascites in the mouse to obtain the antibody.

The monoclonal antibody can recognize TP with high specificity, improves sensitivity and specificity of syphilis diagnosis, provides diagnosis basis for early detection and treatment of syphilis, and further reduces treatment period and economic burden of patients.

A kit for detecting treponema pallidum is provided, which is characterized by comprising the monoclonal antibody.

Provides an application of the monoclonal antibody in preparing a kit for detecting treponema pallidum.

Advantageous effects

The application provides a preparation method of recombinant TP antigen and an antibody detection reagent prepared by the preparation method, which have the following advantages:

(1) The natural TPN47 antigen is modified, and a sequence structural region with high consistency with human related proteins is deleted so as to improve the specificity of subsequent detection; the recombinant TP antigen also comprises an epitope with high specificity, and part of epitopes are repeatedly arranged, so that the screening success probability of the high-specificity antibody is improved.

(2) The preparation process of the recombinant TP antigen is optimized, comprising the steps of designing the nucleotide sequence of the recombinant protein by using the preferential codons of escherichia coli, and improving the production capacity; optimizing the process steps and operating parameters in the preparation process and providing a fermentation medium with good productivity, thereby obtaining recombinant proteins with high purity.

(3) Screening and obtaining monoclonal antibodies with high affinity with target antigens, and can effectively recognize TP.

(4) The antibody and the related kit can effectively detect TP infection, and provide a detection means with high specificity, high sensitivity and good stability.

Drawings

Fig. 1: carrying out enzyme digestion and identification on TP recombinant antigen genes to obtain an electrophoresis chart;

fig. 2: SDS-PAGE electrophoresis of recombinant antigen;

Detailed Description

The following non-limiting examples will enable those of ordinary skill in the art to more fully understand the invention and are not intended to limit the invention in any way. All techniques implemented based on the above description of the invention should be within the scope of the protection claimed in this application.

The experimental methods described in the following examples, unless otherwise specified, are all conventional; the reagent biological material and the detection kit can be obtained from commercial sources unless otherwise specified.

EXAMPLE 1 design and preparation of recombinant TP antigen

1.1 design of recombinant TP antigen

According to TPN47 gene sequences published by NCBI database, high-activity antigen binding epitope in TPN47 region is obtained by screening respectively through sequence comparison, analysis and simulation calculation and referring to published syphilis antibody epitope, and repeated sequences are arranged for part of high-activity epitopes to improve success probability of subsequent screening of high-specificity antibodies, and flexible linkers (GGGGS) are used between each epitope ₃ And (3) connecting to obtain the recombinant TP antigen, wherein the amino acid sequence of the antigen is shown as SEQ ID NO. 1. According to the preference of the escherichia coli codon, the nucleotide sequence of the TP antigen is designed and synthesized as shown in SEQ ID NO. 2, and the gene sequence is obtained by an artificial synthesis method.

1.2 preparation of recombinant TP antigen

Amplifying a recombinant protein gene sequence by PCR, introducing XhoI and EcoRI enzyme cutting sites at two ends of a nucleotide sequence, purifying, and connecting to a vector pET28a at 4 ℃ overnight under the action of T4 ligase, and naming the vector pET28 a-HCV; then the carrier is subjected to electric shock under the conditions of 7.5kV/cm of electric field intensity, 200 omega of resistance and 25 mu F of capacitance to be transformed into DH5 alpha competent cells; coating the DH5 alpha competent cells on an LB solid medium containing ampicillin, picking positive clones, inoculating the positive clones into an LB liquid medium, and culturing at 37 ℃ under shaking at 250rpm for overnight; the cells were collected by centrifugation at 3000rpm, and positive clones were identified by double digestion with XhoI and EcoRI using a plasmid extraction kit (purchased from Beijing full gold Bio Inc.); the positive clone was sent to Shanghai bioengineering company for sequence identification, and the result showed that the sequence was correct.

The pET28a-HCV plasmid was digested with XhoI and EcoRI, purified and ligated overnight at 4℃under the action of T4 ligase to the vector prokaryotic expression vector pGEX6P-1, which was transferred into E.coli BL 21. Inoculating the escherichia coli into an LB liquid culture medium, and performing shaking culture at 37 ℃ and 250rpm overnight to obtain seed liquid; inoculating 5% of seed solution into a 5L small-sized bioreactor, wherein the fermentation medium comprises 10g/L of tryptone, 5g/L of yeast extract, 2.34g/L of monopotassium phosphate, 3.58g/L of monopotassium phosphate, 10g/L of sodium chloride, 0.64g/L of magnesium sulfate heptahydrate, 0.56g/L of ferric chloride hexahydrate, 10g/L of glycerol and 5g/L of glucose (the balance is purified water); culturing at 37deg.C, introducing air at 0.8-1.5L/L.min, stirring at 350-450r/min until OD600nm reaches above 10, adding 0.2mM IPTG, inducing for 16 hr, and centrifuging to collect thallus.

Adding cell lysate (50 mmol/L sodium phosphate, 300mmol/L sodium chloride, 20mmol/L imidazole, pH 7.4) and 2mg/mL lysozyme, oscillating at 4deg.C for 30min, and performing ultrasonic treatment to fully break cells; then adding a cell lysate containing 6mol/L urea, carrying out ultrasonic dissolution of inclusion bodies in an ice bath, and carrying out oscillation action for 2 hours at 4 ℃; centrifugation was performed at 15000rpm for 30min at 4℃and the supernatant was collected. Protein was purified by the ProteinA method, the column was equilibrated with equilibration buffer (1 XPBS, 2mmol/L dithiothreitol, 0.1% sarcosyl, pH 7.4), the protein solution was eluted at a flow rate of 1mL/min, and the target protein was collected. The renaturated sample was then collected by ultrafiltration with a 10kD retention, concentrated, sterilized by filtration through a 0.2 μm microporous membrane, and then subjected to SDS-PAGE electrophoresis (as shown in FIG. 2), and the gray scale value of the electrophoretic protein band was analyzed by imageJ software to calculate the protein purity. Through detection, the protein purity reaches more than 98%, and meets the requirement of subsequent experiments.

EXAMPLE 2 screening and preparation of Targeted TP monoclonal antibodies

BALB/c female mice were selected 5, 6-8 weeks old. Female BALB/C mice were immunized with 50. Mu.g each, 3 times each at two week intervals, using the recombinant protein obtained in example 1. Serum from 20. Mu.L mouse tail venous blood was collected, serum titers of immunized mice were measured by indirect ELISA, and mice with higher relative titers were boosted by adjuvant-free intraperitoneal injection (50. Mu.g/mouse). After 1 week of the last immunization, when the number of B lymphoblastic cells was maximized, mouse spleen cells were taken for fusion.

Separating spleen cells into single cell suspension, mixing with mouse myeloma cells SP2/0 in logarithmic phase according to the ratio of 1:5, slowly dripping PEG, and performing cell fusion by using a cell fusion instrument; after fusion, cells were plated into 96-well cell culture plates, HAT screening reagent was added, and after 5 days of culture, a full change of fluid was performed. About 10 days of fusion, the 96-well culture supernatant is subjected to primary screening by adopting an indirect ELISA method, and ELISA positive hybridoma maternal clone cells are transferred into a 24-well cell culture plate for expansion culture.

BALB/C mice of 10-20 weeks of age were selected, and Freund's incomplete adjuvant (0.5 mL/mouse) was injected intraperitoneally in advance, 2X 10 mice each after 5-10 days ⁶ The individual cells can be collected after the abdominal cavity of the mouse is full of ascites, the ascites is purified by a ProteinA method, and the antibody is quantitatively purified by SDS-PAGE detection (for specific methods, refer to section 1.2).

In this example, 10 monoclonal antibodies meeting the requirements were obtained by a total screening, and the affinity of the monoclonal antibodies to the target antigen was measured using a Fortebio biomacromolecule interactometer (available from eremoto corporation, usa) and the results are shown in table 1:

TABLE 1 affinity detection of individual antibodies to target antigens

Single domain antibodies	Affinity (nM)	Single domain antibodies	Affinity (nM)
				01	7.06E-07	07	5.02E-08
02	2.87E-08	08	8.30E-07
				03	9.26E-07	09	6.13E-07
04	4.85E-07	10	1.53E-09
				05	6.11E-09	11	5.83E-08
06	1.20E-07	12	2.05E-07

In the invention, the No.10 antibody with higher affinity with the target antigen is selected for subsequent research so as to obtain the monoclonal antibody capable of efficiently recognizing TP, and a corresponding detection reagent is prepared. Through sequence analysis, the heavy chain variable region of the antibody No.10 comprises CDR-H1-3 with the amino acid sequence shown as SEQ ID No. 3-5; the light chain variable region comprises CDR-L1-3 with the amino acid sequence shown as SEQ ID No. 6-8. Further, the amino acid sequence of the heavy chain variable region of the antibody is shown as SEQ ID No. 9; the amino acid sequence of the light chain variable region of the antibody is shown as SEQ ID No. 10.

Example 3 preparation and testing of TP detection kit

3.1 Preparation of TP detection kit

The syphilis detection kit prepared by the embodiment comprises the following components:

(1) Coating plate coated with TP antibody: 10mg of the monoclonal antibody provided in the present invention was coated in a 96-well plate;

(2) Chemiluminescent substrate: comprises a solution A and a solution B, wherein the solution A is 10mmol/L citric acid-sodium acetate buffer solution containing 0.6g/L carbamide peroxide; the substrate B solution is a 10mmol/L citric acid solution of 0.5g/L TMB (tetramethyl benzidine) and 0.6g/L EDTA-Na 2;

(3) Enzyme conjugate: the horseradish peroxidase is selected to mark the anti-human IgG monoclonal antibody;

(4) Positive control solution: is a diluted TP antigen standard substance;

(5) Negative control solution: is a dilution without TP antigen;

(6) Dilution liquid: 1.0mmol/L citric acid-sodium acetate buffer.

3.2 specificity experiments

In order to detect the detection specificity of the kit provided by the invention, ELISA is used for detection in the embodiment, the samples are blood samples respectively containing TP (treponema pallidum), HAV (hepatitis A Virus), HBV (hepatitis B Virus), HCV (hepatitis C Virus), CMV (cytomegalovirus) and EBV (Epstein Barr Virus) infection, and the detection rate is calculated according to the positive result of detection, as shown in Table 2.

Table 2 test kit specificity test results

Virus species	Number of samples	Number of positives	Detection rate of
				TP	76	73	96.05％
HAV	58	1	1.72％
				HBV	62	0	0.00％
HCV	55	0	0.00％
				CMV	72	3	4.17％
EBV	67	2	2.99％

The results show that the detection kit provided by the invention has high specificity to TP, and can effectively distinguish viruses such as TP and HAV, HBV, HCV, CMV, EBV.

3.3 sensitivity experiment

The test results of the test using the kit for ELISA were shown in Table 3, after the serum was collected by centrifugation using TP positive clinical serum samples and diluted 10-fold, 100-fold, 1000-fold, 10000-fold and 100000-fold.

TABLE 3 sensitivity test results for detection kits

Sample of	1X 10 fold dilution	1×10 ² Dilution by multiple	1×10 ³ Dilution by multiple	1×10 ⁴ Dilution by multiple	1×10 ⁵ Dilution by multiple
						Detection result	Positive and negative	Positive and negative	Positive and negative	Negative of	Negative of

The experimental results show that the detection kit provided by the invention has higher sensitivity and can still effectively detect TP positive blood samples when diluted by 1000 times.

3.4 stability test

The test kit was set at room temperature and tested for stability of positive or negative samples, and the results are shown in Table 4.

Table 4 test results of stability test kit

Room temperature standing time	For 1 week	For 2 weeks	4 weeks of	8 weeks of	For 12 weeks
						Positive sample	Positive and negative	Positive and negative	Positive and negative	Positive and negative	Positive and negative
Negative sample	Negative of	Negative of	Negative of	Negative of	Negative of

The results show that the kit provided by the invention has good detection stability, can still effectively detect the target sample after being placed at room temperature for 12 weeks, and can be stored for a longer time if being placed in an environment of 4 ℃.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

1. A monoclonal antibody specifically recognizing TP, wherein the heavy chain variable region of the antibody comprises CDR-H1-3 having the amino acid sequence shown in SEQ ID No. 3-5; the light chain variable region of the antibody comprises CDR-L1-3 with an amino acid sequence shown as SEQ ID No. 6-8.

2. The monoclonal antibody of claim 1, wherein the amino acid sequence of the heavy chain variable region of the antibody is set forth in SEQ ID No. 9.

3. The monoclonal antibody of claim 1, wherein the amino acid sequence of the light chain variable region of the antibody is set forth in SEQ ID No. 10.

4. A kit for detecting treponema pallidum comprising the monoclonal antibody of any one of claims 1-3.

5. Use of a monoclonal antibody according to any one of claims 1-3 for the preparation of a kit for detecting treponema pallidum.

6. A preparation method of a recombinant TP antigen is characterized in that the amino acid sequence of the recombinant TP antigen is shown as SEQ ID NO.1, and the preparation method comprises the following steps: constructing an expression vector carrying the recombinant TP antigen gene; causing the expression vector to be in an E.coli expression system; culturing Escherichia coli by high-density fermentation; and (3) collecting escherichia coli thalli, and separating and purifying to obtain the soluble recombinant TP antigen.

7. The method of claim 6, wherein the nucleotide sequence of the recombinant TP antigen is shown in SEQ ID NO. 2.

8. The method of preparing a soluble recombinant TP antigen of claim 7, further comprising: amplifying the recombinant protein gene by PCR, introducing Xho I and EcoR I enzyme cutting sites at two ends of a nucleotide sequence of the recombinant protein gene, connecting the recombinant protein gene to a pET28a vector after enzyme cutting, and electrically transforming the recombinant protein gene into DH5 alpha competent cells; screening positive clones, and performing enzyme digestion and sequencing to identify correct clones; connecting the recombinant protein gene to a prokaryotic expression vector pGEX6P-1, introducing the prokaryotic expression vector into escherichia coli BL21, performing amplification culture, inoculating to a bioreactor, adding a fermentation medium, culturing at 37 ℃, and stirring at a speed of 350-450r/min, wherein the ventilation rate is 0.8-1.5L/L.min; adding IPTG to induce for 16 hours, and centrifugally collecting thalli; the thallus is crushed by ultrasonic wave, protein is purified by Protein A method, and the soluble recombinant TP antigen is obtained.

9. The method for preparing a soluble recombinant TP antigen according to claim 8, wherein the fermentation medium comprises 10g/L of tryptone, 5g/L of yeast extract, 2.34g/L of potassium monohydrogen phosphate, 3.58g/L of potassium dihydrogen phosphate, 10g/L of sodium chloride, 0.64g/L of magnesium sulfate heptahydrate, 0.56g/L of ferric chloride hexahydrate, 10g/L of glycerol, and 5g/L of glucose.