1. An isolated nucleotide is encoding gene Rv2706(- |3020323-3020511|) of Mycobacterium tuberculosis H37Rv, and the nucleotide sequence of the encoding gene is shown as SEQ ID NO. 1.

2. An Rv2706 encoded protein encoded by the gene Rv2706(- | 3020323-.

3. A polypeptide contained in the Rv2706 encoded protein of claim 2, the amino acid sequence of which is set forth in SEQ ID No. 3.

4. An IgG antibody detection antigen for Mycobacterium tuberculosis, comprising all or part of the amino acids of the protein encoded by the Rv2706 of claim 2, or a combination of all or part of the amino acids of the protein encoded by the Rv2706 and a known antigen protein of Mycobacterium tuberculosis.

5. A reagent for detecting Mycobacterium tuberculosis, comprising at least one of:

1) PCR primers for amplifying a part or the whole of the DNA sequence of the gene Rv2706(- |3020323-3020511|) encoded by Mycobacterium tuberculosis H37Rv according to claim 1 or a part or the whole of the template sequence obtained by reverse transcription of the RNA obtained by transcription of the DNA sequence;

2) the detection antigen of claim 4;

3) the Mycobacterium tuberculosis H37 Rv-encoding gene Rv2706 (-3020323-3020511. mu.l) partially or wholly DNA thereof or RNA obtained by transcription thereof as claimed in claim 1.

6. The detection reagent of claim 5, wherein the PCR primer sequence is:

F1:5’-GGCGGTTGCAGACCGAAATTCGGGA-3’(SEQ ID NO.5)；

R1:5’-AAACTGCGCGCGCTACCGGCATTGT-3’(SEQ ID NO.6)。

7. the detection reagent of claim 5, wherein the PCR primer sequence is:

F2:5’-CCGGAATTCATGAACGCAACTCTGA-3’(SEQ ID NO.7)；

R2:5’-CAAGCTTCTATTCGCTCCCGCTGAC-3’(SEQ ID NO.8)。

8. a mycobacterium tuberculosis antigen comprising a substance selected from one of the following groups:

a) the mycobacterium tuberculosis H37Rv gene, Rv2706 (-3020323-3020511 |) of claim 1 encodes all or part of the amino acids of the protein;

b) all or part of the amino acids of the Rv2706 encoded protein of claim 2.

9. The use of the gene Rv2706(- |3020323-3020511|) encoded by mycobacterium tuberculosis H37Rv as claimed in claim 1 or the Rv2706 encoded protein as claimed in claim 2 in epidemiological investigation of tuberculosis and/or rapid differential diagnosis of tuberculosis patients in clinic.

10. Use of a mycobacterium tuberculosis antigen as defined in claim 8 in the preparation of a tuberculosis vaccine.

Background

Tuberculosis is a major public health problem worldwide, and Mycobacterium Tuberculosis (MTB) is the causative pathogen of tuberculosis in humans. According to the worldwide tuberculosis report data published by the WHO newly in 2019, about 1000 million new active tuberculosis patients are newly added in 2018, and tuberculosis is still the head killer in infectious diseases. In addition to active tuberculosis patients, about 1/4 people in the world are infected with MTB and are at risk of further progression to active tuberculosis. Therefore, the establishment of a quick, accurate, specific, sensitive and cheap tuberculosis detection method is a necessary prerequisite for effectively treating and controlling tuberculosis spreading.

At present, the diagnosis of tuberculosis mainly depends on 1) sputum bacteriological examination and chest radiography examination, but has the defects of low sensitivity or long time consumption; 2) immunological diagnosis, but cross immune reaction with BCG vaccine or other environmental mycobacteria, which results in high false positive, especially BCG vaccine inoculation area. At home and abroad, a plurality of kits similar to T-SPOT.TB or kits relying on protein chip immunodiagnosis auxiliary technology exist so far, but the core problem that effective specific new antigens of mycobacterium tuberculosis can be identified is lacked, and the problems that the positive can not be confirmed and the negative can not be eliminated are difficult to solve. Therefore, the development of the specific high-efficiency antigen of the mycobacterium tuberculosis is a core problem to be solved urgently in the industry, and any progress provides original innovative achievements and technical support for the development of clinical diagnosis technology of tuberculosis and the development of a kit.

Disclosure of Invention

The invention aims to provide a mycobacterium tuberculosis H37Rv missed-release gene Rv2706(- | 3020323-.

The second object of the present invention is to provide a protein product encoded by the above gene.

The third purpose of the invention is to provide a mycobacterium tuberculosis IgG antibody detection antigen.

The fourth purpose of the invention is to provide a mycobacterium tuberculosis detection reagent.

The fifth object of the present invention is to provide a Mycobacterium tuberculosis antigen.

The sixth purpose of the invention is to provide the application of the mycobacterium tuberculosis IgG antibody detection antigen and the mycobacterium tuberculosis antigen.

According to one aspect of the invention, the isolated nucleotide is a gene Rv2706(- |3020323-3020511|) encoded by mycobacterium tuberculosis H37Rv, and the nucleotide sequence of the encoded gene is shown in SEQ ID NO. 1.

We identified a high quality peptide segment "AKLPSGAELLFCQHHANEHEAK" encoding the gene expression product by accurate proteomic techniques (FIG. 1). The original spectrogram and the spectrogram of the synthesized peptide fragment are basically consistent by artificially synthesizing the peptide fragment and analyzing by liquid chromatography-mass spectrometry (figure 2). After NCBI-BLASTP is carried out on the encoded protein of the new gene Rv2706 (-3020323-3020511 |), no sequence is aligned in a database, and the encoded protein belongs to a protein with unknown function. The Bepipred line Epitope Prediction (v2.0) and BioSun predicted 1 and 3 high score B cell epitopes, respectively, covering 85.48% of the entire protein sequence (Table 1), suggesting that it may have B cell antigenicity and be useful in the humoral immunoassay of Mycobacterium tuberculosis, with the protein sequence shown in SEQ ID No. 2.

TABLE 1 high confidence epitope theoretically predicted by Rv2706

According to another aspect of the invention, the Rv2706 encoded protein is encoded by the gene Rv2706(- | 3020323-.

According to still another aspect of the present invention, an IgG antibody detection antigen for Mycobacterium tuberculosis comprises all or part of the amino acids of the protein encoded by the said Rv2706, or comprises all or part of the amino acids of the protein encoded by the Rv2706 in combination with a known antigen protein of Mycobacterium tuberculosis.

According to still another aspect of the present invention, a reagent for detecting Mycobacterium tuberculosis, comprising at least one of:

1) PCR primers for amplifying partial or whole DNA sequence of the encoding gene Rv2706(- |3020323-3020511|) of the mycobacterium tuberculosis H37Rv or partial or whole template sequence obtained by reverse transcription of RNA obtained by transcription of the DNA sequence;

2) the amino acid sequence of the peptide segment is shown as SEQ ID NO. 3;

3) the antigen for detecting the mycobacterium tuberculosis IgG antibody is obtained;

4) the DNA of a part or the whole of the gene Rv2706(- |3020323-3020511|) encoded by the above-mentioned Mycobacterium tuberculosis H37Rv or the RNA obtained by transcription thereof.

In a preferred embodiment, the PCR primer sequence used in the detection reagent can be, but is not limited to, the following sequence:

F1:5’-GGCGGTTGCAGACCGAAATTCGGGA-3’(SEQ ID NO.5)；

R1:5’-AAACTGCGCGCGCTACCGGCATTGT-3’(SEQ ID NO.6)。

in another preferred embodiment, the PCR primer sequence used in the detection reagent can be, but is not limited to, the following sequence:

F2:5’-CCGGAATTCATGAACGCAACTCTGA-3’(SEQ ID NO.7)；

R2:5’-CAAGCTTCTATTCGCTCCCGCTGAC-3’(SEQ ID NO.8)。

it will be appreciated by those skilled in the art that the detection antigen of the present invention can be prepared as various detection reagents as desired, for example, by nucleic acid hybridization (e.g., gene chip hybridization assay, northern blot, dot blot, etc.) and/or by nucleic acid amplification (e.g., PCR, qPCR, RT-PCR, qRT-PCR, mass spectrometry, etc.), and the detection reagents can also be antibodies, and detection can be by immunochemical assays (e.g., ELISA, chemiluminescence, immunofluorescence assay, etc.).

In a specific embodiment of the present invention, the detection method for detecting mycobacterium tuberculosis using the above-described detection reagent may comprise: (a) isolating and/or amplifying DNA or RNA from a biological sample obtained from a subject; (b) contacting the isolated and/or amplified DNA or RNA with the detection reagent; (c) detecting the level of the H37Rv encoding gene Rv2706(- |3020323-3020511|) and/or the protein encoded by the Rv 2706; and (d) optionally in combination with a reference detection reagent.

According to still another aspect of the present invention, a mycobacterium tuberculosis antigen comprises a substance selected from one of the following groups:

a) the gene Rv2706(- |3020323-3020511|) of the mycobacterium tuberculosis H37Rv codes all or part of amino acids of protein;

b) all or part of the amino acids of the protein encoded by Rv 2706;

c) the peptide fragment.

The mycobacterium tuberculosis antigen can be used for preparing tuberculosis vaccines by means of animal immunization or genetic engineering.

Has the advantages that: the present invention provides a novel antigen useful as a diagnosis of tuberculosis that can effectively distinguish tuberculosis patients from healthy persons. The diagnosis method using the antigen overcomes the defects of long strain culture time, limited sputum sample and the like in the existing tuberculosis diagnosis process. The new antigen Rv2706 has the characteristics of rapidness, accuracy, specificity, sensitivity and low price, and can be used for auxiliary diagnosis of clinical tuberculosis patients infected by mycobacterium tuberculosis and large-scale tuberculosis epidemiological investigation.

The invention provides a preparation process of an Rv2706 antigen, and whether a patient to be detected is a tuberculosis patient or not is judged by comparing the levels of IgG antibodies in serum of the tuberculosis patient and normal human through detection of immunoblotting (Western Blot), enzyme-linked immunosorbent assay (ELISA), chemiluminescence and the like. The detection result shows that the sensitivity of the new antigen for auxiliary diagnosis of tuberculosis infection patients is 66.25%, and the specificity is 62.50%, which shows that the new antigen based on the Rv2706 has antigenicity, can be used for screening tuberculosis patients, and has application value in tuberculosis diagnosis and prevention.

Drawings

FIG. 1: detecting a secondary spectrogram of the peptide fragment by mass spectrometry;

FIG. 2: comparing the mass spectrogram of the synthesized peptide fragment with the image spectrogram of the original identified peptide fragment;

FIG. 3: designing a sequence of a specific primer sequence of a new gene Rv2706(- |3020323-3020511 |);

FIG. 4: a new gene Rv2706(- |3020323-3020511|) specific amplification agarose gel electrophoresis picture;

the specific information of each lane sample is shown in Table 2.

FIG. 5: an Rv2706(- |3020323-3020511|) target gene PCR amplification nucleic acid electrophoresis chart;

FIG. 6: an Rv2706 (-3020323-3020511) target gene double enzyme digestion nucleic acid electrophoresis picture;

FIG. 7: the result of PCR amplification of a new gene Rv2706 (-3020323 | -3020511|) of the H37Rv strain is compared with the result of standard sequence BLASTN;

FIG. 8: 10% SDS-PAGE gel picture of induced expression of Rv2706(- |3020323-3020511 |);

FIG. 9: 10% SDS-PAGE gel map of Rv2706(- |3020323-3020511 |);

FIG. 10: detecting the coverage of the peptide segment by an Rv2706 (-3020323-3020511) purified protein mass spectrum;

FIG. 11: ROC curve for ELISA detection of Rv2706 antigen in serum samples.

Detailed Description

The invention is further described with reference to specific embodiments, but the scope of the claims is not limited thereto. The reagents used in the present invention are all commercially available.

Example 1: discovery and verification of new gene Rv2706 (-3020323-3020511 |)

We performed high-coverage proteomic studies on mycobacterium tuberculosis H37Rv strain using deep-coverage proteomic techniques. The whole genome (NC _000962.3) file published by NCBI at H37Rv using pAnno software developed by the institute of computational technology of the chinese academy of sciences translates one amino acid according to the rule of 3 contiguous nucleotides on the plus and complementary strands, co-translates into 141,851 Open Reading Frames (ORFs) using the terminator-to-terminator translation pattern, using the 3 specific initiation codons ATG, GTG and TTG of MTB. This database was used to search H37Rv high coverage proteome data. In order to reduce the false positive rate, strict quality control is carried out on two levels of the annotated peptide segment and the new peptide segment respectively in the data filtering process. 1 high-quality peptide segment AKLPSGAELLFCQHHANEHEAK generated by encoding is identified at H37Rv minus chain 3020293-3020509, as shown in figure 1, the spectrogram quality is good, b/y ions are continuously matched, the signal of a peak is low, and the result is reliable.

To further distinguish the authenticity of the peptide fragment, we artificially synthesized the peptide fragment "AKLPSGAELLFCQHHANEHEAK" of the amino acid sequence. The mass spectrum of the synthesized peptide fragment is produced by the liquid chromatography-mass spectrometry combined analysis, and the secondary Mass Spectrum (MS) of the synthesized peptide fragment is manually compared₂) (FIG. 2) and mass spectrum of mass spectrum for large scale identification of new peptide fragment, the two are basically consistent, the similarity of the spectra (Cosin value) is 0.89, which shows that we utilize proteomics to identify peptide fragment generated by digesting protein encoded by a missed-release gene corresponding to a DNA sequence from Mycobacterium tuberculosis.

After confirming the sequence of the peptide fragment to be released, according to the gene position of the peptide fragment, taking the region included by the initiation codon ATG and the termination codon TGA as a boundary, and obtaining the DNA sequence of the Open Reading Frame (ORF) containing the new peptide fragment to be released, wherein the DNA sequence is shown as SEQ ID NO. 1. The gene sequence starts from ATG, is 189bp in total, encodes 62 amino acids, has the theoretical molecular weight of 6.68kDa, and is named as the Rv2706 gene according to the position of the gene on a chromosome and the tubercle bacillus gene naming rule.

ATGAACGCAACTCTGACCAGTCCTGAGCTGACTAGAGCAGACCGCTGCGACCGCTGTGGCGCTGCAGCTCGGGTGCGCGCCAAGCTGCCCTCCGGAGCCGAGCTTCTTTTCTGCCAGCATCACGCCAACGAGCACGAGGCGAAACTGACCGAGATGTCCGCCGTGCTGGAGGTCAGCGGGAGCGAATAG(SEQ ID NO.1)

The theoretical coding product amino acid sequence of the gene is shown as SEQ ID NO. 2:

MNATLTSPELTRADRCDRCGAAARVRAKLPSGAELLFCQHHANEHEAKLTEMSAVLEVSGSE(SEQ ID NO.2)

the peptide fragment sequence identified by the proteomics technology is shown as SEQ ID NO. 3:

AKLPSGAELLFCQHHANEHEAK(SEQ ID NO.3)

example 2: method for establishing and identifying target gene specificity verification

(1) Designing a primer:

the Mycobacterium sequence (nearly 200 species, 8,046 strains) that had been subjected to whole genome sequencing was downloaded from the NCBI database, and a Mycobacterium database was constructed. After the target genes were aligned to have local homology, a region having homology but a sequence having a difference was subjected to primer design (FIG. 3).

PCR specific primers are designed by comparing the difference regions of the front and back extension 600bp sequences (SEQ ID NO.4) of the target gene by using Primer Premier 5, and the Primer sequences are as follows:

F1:5’-GGCGGTTGCAGACCGAAATTCGGGA-3’(SEQ ID NO.5)；

R1:5’-AAACTGCGCGCGCTACCGGCATTGT-3’(SEQ ID NO.6)。

the position relationship of the above primers in the vicinity of the Rv2706(- | 3020323-.

(2) Extracting total DNA including M.tuberculosis H37Rv, near-source mycobacteria and other infectious strains, wherein 6 mycobacterium standard strains are preserved by China medical bacterial strain preservation management center (CMCC), the other 6 non-tuberculosis mycobacteria are clinical isolates of 309 hospital of China people' S liberation force, the work of sequencing and comparing strains 16S RNA genes and submitting NCBI sequences is completed, and the specific amplification to-be-detected strains are shown in Table 2:

TABLE 2 related strains selected

(3) The DNA fragment was amplified and subjected to Polymerase Chain Reaction (PCR) using the F1/R1 primer designed as described above.

PCR System (25. mu.L) as dd H₂O (9.5. mu.L), 2XTaq PCR MasterMix (TIANGEN, 12.5. mu.L), primer F (10. mu.M, 1. mu.L), primer R (10. mu.M, 1. mu.L), DNA template (1. mu.L);

and (3) amplification procedure: pre-denaturation at 94 deg.C for 3min, denaturation at 94 deg.C for 1min, annealing at 58 deg.C for 1min, extension at 72 deg.C for 2min, 35 cycles, and extension at 72 deg.C for 5 min.

(4) And (4) detecting the amplified product by electrophoresis in agarose gel and 1 xTBE electrophoresis solution. As a result, as shown in FIG. 4, a specific amplification band appeared only at 728bp of the H37Rv strain, and the amplification result was consistent with the expectation, meaning that the specific primer can effectively distinguish Mycobacterium tuberculosis from other mycobacteria and pathogenic bacteria.

Example 3: prokaryotic cloning, expression, purification and mass spectrum identification of Rv2706(- |3020323-3020511|)

Cloning of 3.1Rv2706(- | 3020323-plus 3020511|)

(1) Designing a primer:

PCR primers are designed by using Primer Premier 5, and EcoR I and Hind III restriction enzyme sites are respectively added to the upstream Primer and the downstream Primer, so that the subsequent cloning construction is facilitated. The primer sequences are as follows:

F2:5’-CCGGAATTCATGAACGCAACTCTGA-3’(SEQ ID NO.7)；

R2:5’-CAAGCTTCTATTCGCTCCCGCTGAC-3’(SEQ ID NO.8)。

(2) total DNA of the cyberculosis H37Rv strain was provided by the infectious disease institute tuberculosis ward of chinese center for disease prevention and control.

(3) The DNA fragment was amplified and subjected to Polymerase Chain Reaction (PCR) using the F2/R2 primer described above.

PCR System (25. mu.L) as dd H₂O (9.5. mu.L), 2XTaq PCR MasterMix (TIANGEN, 12.5. mu.L), primer F (10. mu.M, 1. mu.L), primer R (10. mu.M, 1. mu.L), DNA template (1. mu.L);

and (3) amplification procedure: pre-denaturation at 94 deg.C for 3min, denaturation at 94 deg.C for 1min, annealing at 60 deg.C for 1min, extension at 72 deg.C for 2min, 35 cycles, and extension at 72 deg.C for 5 min.

(4) The amplified product was detected by electrophoresis of 5. mu.L in agarose gel, 1 XTBE. As a result, as shown in FIG. 5, a DNA band corresponding to the expected target band was amplified at 205 bp.

(5) Separating the remaining 20. mu.L × 4 sample by 50mL of 1.8% agarose gel electrophoresis to obtain a target band, cutting the gel for recovery, and recovering the target band by using Takara DNA gel recovery kit (adding 50. mu.L of dd H₂O), and freezing and storing the recovered product in a refrigerator at the temperature of-80 ℃ for later use.

(6) The pMD18-T vector is ligated to the amplified gene of interest.

The connection system (10 mu L) is Solution I (5 mu L), PMD-18-T carrier (Takara, 0.5 mu L) and DNA gel cutting recovery products in the step (5); the ligation was carried out at 16-18 ℃ for 12 h.

(7) E.coli DH5 alpha transformation

Placing escherichia coli DH5 alpha competent cells (Beijing kang, century Biotechnology Co., Ltd.) in ice bath, adding the ligation product of (6) into the competent cell suspension after the competent cells are melted, blowing and uniformly mixing, and carrying out ice bath for 20-30 min;

heating at 42 deg.C for 90s, rapidly transferring into ice bath, and standing for 1 min;

heating at 42 deg.C for 1min, and cooling in ice bath for 2 min;

to a 1.5mL EP centrifuge tube containing DH 5. alpha. competent cells was added 800. mu.L of LB liquid medium (tryptone, 10g, yeast extract 5g, sodium chloride 10g, dd H)₂Supplementing O to 1 liter), mixing uniformly, placing on a shaking table at 37 ℃, and carrying out shaking culture at 200rpm for 1 h;

taking out the EP tube, centrifuging at 4000rpm for 5min, reserving 100 μ L of supernatant, resuspending the thallus and coating the thallus on LA solid culture medium (preparing LB solid culture medium, sterilizing at high temperature and condensing to 50-60 ℃, adding ampicillin (Amp) with final concentration of 100 μ g/mL), culturing for 1h in an upright way, then inverting, and culturing for 12-16h at 37 ℃.

(8) Extracting a PMD18-T target gene plasmid.

5mL of LA liquid medium (LB liquid medium was prepared, and ampicillin (Amp) was added to a final concentration of 100. mu.g/mL after cooling to room temperature) was added to a sterile test tube, and a single clone was inoculated thereto, followed by shaking at 37 ℃ in a 200rp shakerm after 12H of culture, collecting the cells, extracting the plasmid with a plasmid DNA miniprep kit (Takara), and finally adding 50. mu.L dd H₂And O, freezing and storing the plasmids in a refrigerator at the temperature of-80 ℃ for later use.

(9) Obtaining target gene fragment by double enzyme digestion

The double digestion system (50. mu.L) is the plasmid (44. mu.L) and NEBuffer in (8)^TM 2.1(5μL)、EcoR I(0.5μL)、Hind III(0.5μL)；

The enzyme is cut for 5h at 37 ℃, and the cut target fragment is detected by 1 percent agarose gel electrophoresis. As shown in FIG. 6, the band of interest was observed at the size of the object, and gel recovery was carried out using Takara DNA gel recovery kit, and 50. mu.Ldd H was added₂And O, recovering the product, and freezing the product in a refrigerator at the temperature of 80 ℃ below zero for later use.

(10) pMAL-c2X vector ligation fragment of interest

The ligation system (10. mu.L) is the pMAL-c2X vector (1. mu.L) double digested with DNA fragment (4. mu.L), Solution I (5. mu.L), EcoR I and Hind III in (9); the ligation was carried out at 16-18 ℃ for 12 h.

(11) E.coli DH5 alpha transformation

Placing escherichia coli DH5 alpha competent cells in an ice bath, adding the ligation product of the step (10) into competent cell suspension after the competent cells are melted, uniformly mixing, and carrying out ice bath for 20-30 min;

heat shock at 42 deg.C for 90s, ice bath for 1 min;

heating at 42 deg.C for 1min, and cooling in ice bath for 2 min;

adding 800 microliter LB liquid culture medium into an EP centrifuge tube containing competent cells of Escherichia coli DH5 alpha, uniformly mixing, placing in a 37 ℃ shaking table, and carrying out shake culture at 200rpm for 1 h;

taking out the EP tube, centrifuging at 4000rpm for 5min, retaining 100 μ L of supernatant, resuspending thallus and coating on LA solid culture medium, culturing for 1h at normal position, then inverting, and culturing at 37 deg.C for 12-16 h.

(12) Extracting pMAL-c 2X-target gene plasmid.

Adding 5mL LA liquid culture medium into sterile test tube, inoculating monoclonal antibody, culturing at 37 deg.C with shaking table at 200rpm for 12H, collecting thallus, extracting plasmid with plasmid DNA small amount purification kit (Takara), and adding 50 μ L dd H₂Cooling the plasmid in a refrigerator at-80 deg.CFreezing for later use.

(13) The plasmid (12) was sequenced (Biotech, Oncorks, Beijing), and the sequencing results were aligned by BLAST as shown in FIG. 7

3.2 induced expression of the encoded protein of Rv2706(- |3760359-3761516|) gene

(1) Coli BL21(DE3) expression recombinant plasmid

Putting the host cell into an ice bath, adding 0.5 mu L of recombinant plasmid into the host cell suspension after the host cell is melted, uniformly mixing, and carrying out ice bath for 20-30 min;

heat shock at 42 deg.C for 90s, ice bath for 1 min;

heat shock at 42 deg.C for 1min, ice bath for 2 min;

adding 800 μ L LB liquid culture medium, mixing, placing in 37 deg.C shaking table, and performing shaking culture at 200rpm for 1 h;

taking out the EP tube, centrifuging at 4000rpm for 5min, retaining 100 μ L of supernatant, resuspending thallus and coating on LA solid culture medium, culturing for 1h at normal position, then inverting, and culturing at 37 deg.C for 12-16 h.

(2) The Rv2706(- |3760359-3761516|) gene coding protein IPTG induced expression

Transferring the monoclonal antibody in the step (1) into a 250mL triangular flask filled with 50mL LA medium, and culturing at 37 ℃ overnight;

transferring into a triangular flask containing 500mL LA medium in an amount of initial OD 0.1, shake-culturing at 37 deg.C and 200rpm until OD 0.6, and collecting 14OD bacteria and storing at-80 deg.C as pre-induction bacteria;

adding IPTG into the rest bacterial liquid for induction (final concentration is 1mmol/L), carrying out induction culture at 28 ℃ for 6h, diluting by 20 times to measure OD value, taking out 14OD bacteria, and storing at-80 ℃ as induced bacteria;

collecting other induced thallus together, and storing at-80 deg.C;

carrying out ultrasonication on thalli for 5min (30% power, ultrasonic for 2s and ice bath for 4s) before and after induction, centrifuging for 5min at 13000rpm, and transferring supernatant to a new 1.5mLEP tube;

precipitation treatment before and after induction: adding 400 μ L of 1XSDS Loading buffer to resuspend the thallus, adding DTT with final concentration of 5mmol/L, boiling at 95 deg.C for 10min, centrifuging at 13000rpm for 5min, collecting supernatant, and storing at-80 deg.C;

protein detection was performed on protein samples before and after induction by 10% SDS-PAGE, and the gel image is shown in FIG. 8.

3.3 purification of Rv2706 protein an appropriate amount of lysate was added to the cells, sonicated for 5min, centrifuged at 13000rpm for 10min, and the supernatant was retained;

adding 100 mu L of Amylose beads into the purification column, adding 500 mu L of Washing solution (Washing buffer) into the purification column, and balancing the purification column;

adding 200 mu L of the cell lysate after ultrasonic treatment into a well-balanced purification column, quickly sleeving a yellow interception tube, and incubating for 1h in a refrigerator at 4 ℃ so as to be fully combined;

after incubation at 4 ℃, removing the lower yellow retention tube, allowing the liquid to slowly flow out, adding 1ml of the shaking buffer solution into the purification column, allowing the liquid to slowly flow out, and repeating the steps for three times;

adding 50 μ L of eluent (Elution buffer) solution into the purification column, allowing the liquid to slowly flow into a 1.5mL centrifuge tube, repeating twice, and collecting the obtained target protein;

all the above steps were performed in an ice bath. mu.L of the collected eluate was added to 5. mu.L of 2XSDS Loading buffer, freshly prepared DTT was added to a final concentration of 5mmol/L, denatured at 95 ℃ for 10min, detected by 10% SDS-PAGE, stained with Coomassie Brilliant blue, and the results are shown in FIG. 9.

The compositions of the buffers used in the above purification processes are shown in tables 3 to 5.

TABLE 3 protein lysate Components

TABLE 4 cleaning solution composition

TABLE 5 eluent composition

3.4 Mass Spectrometry detection of Rv2706 purified protein

Cutting the purified target strip to 1mm³Colloidal particles, dehydrating, evaporating to dryness, digesting with acetylated trypsin (10 ng/. mu.L) overnight at 37 deg.C, extracting peptide, and evaporating to dryness.

The peptide fragments evaporated to dryness were loaded with buffer (1% acetonitrile + 1% formic acid + 98% ddH)₂O) was sufficiently dissolved. Separating by ultra-high pressure liquid chromatography, wherein the separation column adopts C with inner diameter of 75 μm and length of 15cm₁₈Reverse phase chromatography column, internal C₁₈The inner diameter of the filler was 3 μm. And (4) spraying the elution component through a nano-upgrading electrospray ion source interface to enter LTQ Orbitrap Velos for analysis.

The ion transmission temperature of the capillary tube is 250 ℃, and the electrospray voltage is 1.8 kV. The mass spectrum adopts a primary mass spectrum Data dependent secondary mass spectrum scanning mode (Data dependent MS/MS scan) to crack primary ions in a collision-induced dissociation (CID) mode. The range of the first-order mass spectrum scanning mass-nuclear ratio is 300-1600(m/z), and the resolution is set to 30000; automatic Gain Control (AGC) is 10⁶. Sequentially selecting 20 ions with the highest primary signal intensity to perform secondary fragmentation analysis, wherein the collision normalized energy is 35%; AGC is 10⁴(ii) a The maximum ion implantation time is 30 ms; the dynamic exclusion was 40 s.

MaxQuant performed a protein database search on the mass spectrometry generated data file (. raw), consisting of the download of the target e.coli complete proteome sequence from UniProt (Version: 2016-01), omission of the annotated protein Rv2706 sequence from mycobacterium tuberculosis H37Rv, the pMAL-c2X vector tag MBP protein sequence and common contaminations, with peptide segment coverage as in fig. 10.

Example 4: diagnosis and screening of tuberculosis infection assisted by Rv2706 antigen

4.1 Collection and screening of serum samples to be tested

Clinical peripheral blood samples of tuberculosis and healthy volunteers were collected according to WHO guidelines (table 6), and the specific information is shown in tables 7-9.

TABLE 6 clinical serum sample information

^*Tuberculin: the thallus components of tubercle bacillus including Pure Protein Derivative (PPD) and Old Tuberculin (OT); and (4) judging the standard: PPD (p-phenylene diamine)>10mm；

^#Interferon assay: tuberculosis specific antigens ESAT-6 and CFP-10 are utilized, and whether tuberculosis effector T lymphocytes exist in a test subject is detected through an enzyme-linked immunosorbent assay (ELISPOT) technology, so that whether the test subject is infected with tubercle bacillus at present is judged. And (4) judging the standard: number of monoclonal antibody primary spots>6。

80 sera of tuberculosis patients were collected according to the above criteria, wherein 40 of the samples were collected from the positive, 40 of the samples were collected from the negative, and 40 of the samples were collected from the healthy patients.

And (4) judging the standard:

tuberculosis patients: 1) chest radiograph (CXR) is abnormal, has clinical symptoms and is effective in anti-tuberculosis treatment; 2) positive in T-SPOT test; 3) the fast culture result of tubercle bacillus is positive/negative;

healthy volunteers: 1) no abnormality in chest radiographs (CXR); 2) negative in T-SPOT test; 3) tuberculin negative.

All the above samples excluded Human Immunodeficiency Virus (HIV) positive and immunosuppressed drug-administered volunteers.

TABLE 7 Mycobacterium tuberculosis culture Positive patient information

TABLE 8 Mycobacterium tuberculosis culture negative patient information

TABLE 9 healthy volunteer information

4.2 serum IgG antibody detection

The commercial mycobacterium tuberculosis IgG detection kit with better domestic application comprises a seven-antigen combined positive antigen control (such as a Shanghai Rongsheng mycobacterium tuberculosis IgG detection kit) and an internationally recognized 38kD antigen as positive controls, the Rv2706 encoding protein expressed by fusion is coated, and the reagents and the process of the Shanghai Rongsheng mycobacterium tuberculosis IgG detection kit are uniformly used for operation and screening.

The detection result shows that the sensitivity of the Shanghai nabobism kit to the clinical serum samples of 120 different people collected by the inventor is 75% (60/80) and the specificity is 62.5% (25/40), and the sensitivity and the specificity ratio are not much different from those reported by the kit, which means that the kit and the detection system thereof can be used as a positive reference and a detection scheme for the subsequent screening of the target antigen.

In order to further detect the coating condition and the detection system of the target protein, the fusion expression system which is the same as the Rv2706 target protein is used for expressing the internationally known positive antigen 38kD protein of the mycobacterium tuberculosis, the coating and the antigenicity detection are carried out after the purification, and the detection reagent is the reagent in the Shanghai Pengsheng mycobacterium tuberculosis IgG detection kit, and the specific operation method is as follows:

coating: use coating buffer (weigh 2.93g NaHCO)₃、1.59g Na₂CO₃Add dd H₂Diluting Rv2706 protein to 1000mL (pH is about 9.6) by constant volume O (constant volume), carrying out autoclaving), obtaining a final concentration of 30 mug/mL, coating an enzyme label plate (corning) by 100 mug L per hole, and coating overnight at 4 ℃;

washing the plate: 1 XPBST (kit) 300 uL per well, wash plate 5 times, pat dry;

and (3) sealing: adding blocking solution (3% BSA in PBS) into each well, and blocking for 2h at 37 ℃;

washing the plate: washing the plate for 5 times by 300 mu L of washing liquid in each hole, and drying by beating;

primary antibody (serum): adding 100 μ L of negative and positive control serum for each protein, and repeating the steps once; setting a hole blank control, adding 100 mu L of sample diluent and 10 mu L of serum to be detected into each other hole, and incubating for 30min at 37 ℃; washing the plate: washing the plate for 5 times by 300 mu L of washing liquid in each hole, and drying by beating;

secondary antibody (enzyme conjugate): add 100. mu.L per well (except for blank control well) and incubate 20min at 37 ℃;

washing the plate: washing the plate for 5 times by 300 mu L of washing liquid in each hole, and drying by beating;

color development: adding 50 μ L of each of color development liquid A and B into each well, shaking gently, and developing at 37 deg.C in dark for 10 min;

and (3) terminating the reaction: adding 50 mu L of stop solution into each hole to stop the reaction;

reading: the microplate reader reads the absorbance value (OD) at a wavelength of 450 nm.

The detection result shows that the sensitivity and specificity of the positive antigen 38kD are 65.83% and 55% respectively, which means that the fusion expression protein is coated, and the detection system and the reagent in the Shanghai Pengsheng Mycobacterium tuberculosis are feasible, so that the detection method can be used for detecting the antigenicity of the Rv2706 target protein. In view of the results of the preliminary experiments, the serum IgG antibody detection of the new coating protein of the Rv2706 is carried out, and the specific detection values are shown in the table 10.

TABLE 10 OD measurement values of 120 serum samples for Rv2706 neo-antigen measurement

The shaded portion is the patient's data

And (3) detection and classification: the Yu-den index was calculated from each tangent point given in the ROC curve (FIG. 11), the highest value of the Yu-den index was defined as the Cut-off value, the Cut-off value of the protein was 0.128, the protein was judged to be positive (patient) and negative (healthy) at values of 0.128 or more.

As a result, 53 positive sera were correctly judged in 80 patients, the sensitivity was 66.25%, and 25 negative sera were correctly judged in 40 healthy patients, with a specificity of 62.50%. This shows that the method for screening tuberculosis patients based on the new antigen Rv2706 is real and reliable.

SEQUENCE LISTING

<110> Peking proteome research center

<120> Mycobacterium tuberculosis H37Rv new gene Rv2706 and coding protein and application thereof

<130> BJ1936-20P150031

<160> 8

<170> PatentIn version 3.5

<210> 1

<211> 189

<212> DNA

<213> Mycobacterium tuberculosis H37Rv

<400> 1

atgaacgcaa ctctgaccag tcctgagctg actagagcag accgctgcga ccgctgtggc 60

gctgcagctc gggtgcgcgc caagctgccc tccggagccg agcttctttt ctgccagcat 120

cacgccaacg agcacgaggc gaaactgacc gagatgtccg ccgtgctgga ggtcagcggg 180

agcgaatag 189

<210> 2

<211> 62

<212> PRT

<213> Mycobacterium tuberculosis H37Rv

<400> 2

Met Asn Ala Thr Leu Thr Ser Pro Glu Leu Thr Arg Ala Asp Arg Cys

1 5 10 15

Asp Arg Cys Gly Ala Ala Ala Arg Val Arg Ala Lys Leu Pro Ser Gly

20 25 30

Ala Glu Leu Leu Phe Cys Gln His His Ala Asn Glu His Glu Ala Lys

35 40 45

Leu Thr Glu Met Ser Ala Val Leu Glu Val Ser Gly Ser Glu

50 55 60

<210> 3

<211> 22

<212> PRT

<213> Mycobacterium tuberculosis H37Rv

<400> 3

Ala Lys Leu Pro Ser Gly Ala Glu Leu Leu Phe Cys Gln His His Ala

1 5 10 15

Asn Glu His Glu Ala Lys

20

<210> 4

<211> 1389

<212> DNA

<213> Mycobacterium tuberculosis

<400> 4

aggctttcgg caagatccgt ccggtgacga gcatggtcga ggttaccgcg ctgattgcgc 60

ccggcctgct ggtagagatc gaggccgacg cctacgtagg gtcggcggtt gcagaccgaa 120

attcgggagc cggcccgaag gacccgtcac cagccggtgg gtaggcggcg gccccaatca 180

cagcgcgcac cggcagtggg ccgtagagat gcgggaaaag catcgaccgc ggatcagtag 240

gcacgcccgg ctcccaacgc acgggtgagt cgagcgccgc cgggtcgatg tacagcagca 300

ccaggtcagc acggccacgg taaaggcggt tggcgggcag gtgaacctgc tcgagtgtcg 360

acaggtggat ataccccgtc ttgtcggact cgggatagat cccaccgcgt tctcgggcat 420

gcgaccactc ctgcaccccg cataggtgca ccagcatggc aggatcgggc gtcattctca 480

ccaccctgcc cgattggcgg gggcgaaagt cgtgagaaat gacacacccg acagcggccg 540

gggaacacgg cgagaacccc gaacgtctga gaaggtgaag atacccgaga acggagagcc 600

atgaacgcaa ctctgaccag tcctgagctg actagagcag accgctgcga ccgctgtggc 660

gctgcagctc gggtgcgcgc caagctgccc tccggagccg agcttctttt ctgccagcat 720

cacgccaacg agcacgaggc gaaactgacc gagatgtccg ccgtgctgga ggtcagcggg 780

agcgaataga ccgaactcac ccgtccacaa tgccggtagc gcgcgcagtt ttcggtaatg 840

ctggactggt atgagcgacc aggtccccaa gccacaccgc caccacatct ggcgaatcac 900

ccgtaggact ttgtccaaaa gctgggacga ctcgatcttc tcggagtcag cgcaagcggc 960

tttttggtcg gccttgtctt tgccgccgct actgctggga atgctgggca gtctggccta 1020

cgttgctccg ctattcggcc cggacacctt gcccgcgatt gaaaagagcg cgctttcgac 1080

ggcccacagc tttttctccc ccagtgtggt caacgagatc atcgagccca ccatcggcga 1140

tatcaccaac aacgcccgcg gtgaggtggc gtcgctgggc ttcttgatct cgctgtgggc 1200

aggatcgtcg gcaatctcgg cgttcgtcga tgcagtggtg gaagcgcacg accagacacc 1260

gctacgccac ccggtccggc aacgcttctt tgcgctcttc ctctacgtgg tgatgttggt 1320

gttcctagta gcgaccgcac cggtaatggt ggtgggtcca cgcaaggtaa gcgagcacat 1380

cccggagag 1389

<210> 5

<211> 25

<212> DNA

<213> Synthetic

<400> 5

ggcggttgca gaccgaaatt cggga 25

<210> 6

<211> 25

<212> DNA

<213> Synthetic

<400> 6

aaactgcgcg cgctaccggc attgt 25

<210> 7

<211> 25

<212> DNA

<213> Synthetic

<400> 7

ccggaattca tgaacgcaac tctga 25

<210> 8

<211> 25

<212> DNA

<213> Synthetic

<400> 8

caagcttcta ttcgctcccg ctgac 25