Nucleic acid fragment, recombinant vector, recombinant cell, recombinant procalcitonin antigen and preparation method and application thereof

Abstract

The invention discloses a nucleic acid fragment, a recombinant vector, a recombinant cell and a recombinant procalcitonin antigen as well as a preparation method and application thereof, and relates to the field of procalcitonin preparation. The amino acid sequence of the recombinant procalcitonin antigen is as shown in SEQ ID NO: 1, or the amino acid sequence of the recombinant procalcitonin antigen is an amino acid sequence obtained by connecting a protein purification tag to the C terminal or N terminal of the amino acid sequence as shown in SEQ ID NO: 1. The recombinant procalcitonin antigen provided by the invention has higher expression quantity and purity.

Description

Technical Field

[0001] The present invention relates to the field of procalcitonin preparation, and in particular to a nucleic acid fragment, a recombinant vector, a recombinant cell and a recombinant procalcitonin antigen, and a preparation method and application thereof. Background Art

[0002] Procalcitonin (PCT) is a calcitonin propeptide glycoprotein without hormone activity. It is the precursor peptide of calcitonin (CT). It comes from a single copy gene located on chromosome 11 (11p15, 4) (i.e., procalcitonin is encoded by the Calc-I gene located on chromosome 11, with a coding region length of 426bp). The gene consists of 2800 base pairs, including 6 exons and 5 introns. After transcription, it is translated into procalcitonin precursor (Preprocalciton in) in the rough endoplasmic reticulum of thyroid parafollicular cells, including three parts: 84 amino acids at the N-terminus, active calcitonin, and calcitonin. Under the action of endogenous peptidase, the single sequence at the nPro-CT end of procalcitonin precursor is cut off to generate 116 amino acids of procalcitonin with a molecular weight of about 13kD. Procalcitonin and calcitonin have the same 32 amino acid sequence (60-91).

[0003] Procalcitonin can be used as a raw material in the research and development of procalcitonin diagnostic kits, but the expression level of procalcitonin prepared by existing methods is low, which hinders its large-scale application.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] Based on the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide nucleic acid fragments, recombinant vectors, recombinant cells and recombinant procalcitonin antigens and preparation methods and applications thereof, aiming to solve the problem of low expression level of procalcitonin prepared by existing methods.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect of the present invention, a recombinant procalcitonin antigen is provided, wherein the amino acid sequence of the recombinant procalcitonin antigen is as shown in SEQ ID NO: 1, or the amino acid sequence of the recombinant procalcitonin antigen is an amino acid sequence obtained by connecting a protein purification tag to the C-terminus or N-terminus of the amino acid sequence shown in SEQ ID NO: 1.

[0008] The second aspect of the present invention provides a nucleic acid fragment, wherein the nucleic acid fragment comprises a nucleotide sequence encoding the recombinant procalcitonin antigen of the present invention as described above.

[0009] Optionally, the nucleotide sequence of the nucleic acid fragment is shown in SEQ ID NO:2.

[0010] The third aspect of the present invention provides a recombinant vector, wherein the recombinant vector contains the nucleic acid fragment of the present invention as described above.

[0011] A fourth aspect of the present invention provides a recombinant cell, wherein the recombinant cell contains the recombinant vector of the present invention as described above.

[0012] A fifth aspect of the present invention provides a method for preparing a recombinant procalcitonin antigen, comprising the following steps:

[0013] Inserting the nucleotide sequence encoding the recombinant procalcitonin antigen of the present invention as described above into a plasmid to obtain a recombinant plasmid;

[0014] The recombinant plasmid is transformed into competent Escherichia coli cells, and then an inducer is added to induce expression. After purification, the recombinant procalcitonin antigen is obtained.

[0015] Optionally, the step of transforming the recombinant plasmid into competent Escherichia coli cells and then adding an inducer to induce expression to obtain the recombinant procalcitonin antigen specifically includes:

[0016] Transforming the recombinant plasmid into Escherichia coli competent cells to obtain recombinant competent cells;

[0017] Inoculating the recombinant competent cells into LB liquid culture medium, and then adding an inducer to induce expression to obtain a bacterial liquid;

[0018] After the bacterial solution is centrifuged, the bacterial bodies are collected, the bacterial bodies are resuspended, ultrasonically disrupted, the supernatant is collected, and the recombinant procalcitonin antigen is obtained after purification.

[0019] Optionally, the plasmid is a pET series plasmid, and the Escherichia coli competent cell is an Escherichia coli BL21 (DE3) competent cell.

[0020] Optionally, the temperature for inducing expression is 30°C, and the inducer includes isopropyl-β-D-thiogalactoside;

[0021] The purification is firstly carried out His-tag nickel column purification and then anion purification.

[0022] The sixth aspect of the present invention provides the use of the recombinant procalcitonin antigen as described above or the recombinant procalcitonin antigen prepared by the preparation method as described above in the preparation of calibrators and / or quality control products for a procalcitonin antigen immunoassay kit.

[0023] Beneficial effects: The present invention intercepts the amino acid sequence UniProtKB-P01258 found on the Uniprot website, and then, on the basis of the intercepted amino acid sequence, replaces the 37th lysine with arginine, and replaces the 71st tyrosine with cysteine ​​to obtain a recombinant procalcitonin antigen with an amino acid sequence as shown in SEQ ID NO: 1, or further connects a protein purification tag to the N-terminus or C-terminus of the amino acid sequence as shown in SEQ ID NO: 1 to obtain the amino acid sequence of the recombinant procalcitonin antigen. The recombinant procalcitonin antigen provided by the present invention has a higher expression level and purity than the procalcitonin antigen before the amino acid replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the SDS-PAGE electrophoresis result of the product in Example 1.

[0025] Figure 2 This is the SDS-PAGE electrophoresis result of the product in Example 2. DETAILED DESCRIPTION

[0026] The present invention provides nucleic acid fragments, recombinant vectors, recombinant cells and recombinant procalcitonin antigens and preparation methods and applications thereof. To make the purpose, technical scheme and effects of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] An embodiment of the present invention provides a recombinant procalcitonin antigen, wherein the amino acid sequence of the recombinant procalcitonin antigen is as shown in SEQ ID NO: 1, or the amino acid sequence of the recombinant procalcitonin antigen is an amino acid sequence obtained by connecting a protein purification tag to the C-terminus or N-terminus of the amino acid sequence shown in SEQ ID NO: 1.

[0029] The present invention intercepts the amino acid sequence UniProtKB-P01258 (as shown in SEQ ID NO: 3) found on the Uniprot website, and then replaces the 37th lysine with arginine and the 71st tyrosine with cysteine ​​on the basis of the intercepted amino acid sequence to obtain a recombinant procalcitonin antigen with an amino acid sequence as shown in SEQ ID NO: 1, or further connects a protein purification tag (such as a His tag, etc., to facilitate the purification of the recombinant procalcitonin antigen) to the C-terminus or N-terminus of the amino acid sequence as shown in SEQ ID NO: 1 to form an amino acid sequence of the recombinant procalcitonin antigen. The recombinant procalcitonin antigen has a higher expression level and purity than the procalcitonin antigen before the amino acid replacement, and is easy to purify. The embodiment of the present invention increases the expression level of the recombinant procalcitonin antigen by amino acid replacement.

[0030] An embodiment of the present invention further provides a nucleic acid fragment, wherein the nucleic acid fragment comprises a nucleotide sequence encoding the recombinant procalcitonin antigen of the present invention as described above.

[0031] In some embodiments, the nucleotide sequence of the nucleic acid fragment is shown in SEQ ID NO:2.

[0032] In order to facilitate the purification of the recombinant procalcitonin antigen, in this embodiment, a His tag is connected to the N-terminus of the amino acid sequence shown in SEQ ID NO: 1 to obtain the amino acid sequence of the recombinant procalcitonin antigen, and the nucleotide sequence encoding the recombinant procalcitonin antigen is shown in SEQ ID NO: 2. The use of the nucleic acid fragment is conducive to the purification of the recombinant procalcitonin antigen.

[0033] The embodiment of the present invention further provides a recombinant vector, wherein the recombinant vector contains the nucleic acid fragment described in the embodiment of the present invention. The recombinant vector includes a plasmid and a nucleic acid fragment (nucleotide sequence as shown in SEQ ID NO: 2) inserted into the plasmid, and the plasmid can be a pET series plasmid, specifically a pET28a (+) plasmid, but is not limited thereto.

[0034] The pET series of plasmids are currently the most widely used recombinant protein expression vectors, with advantages such as low price and high expression. When constructing the vector, the target fragment is cloned into the vector bacteriophage T7 transcription and translation system, and is expressed under the induction of the host T7 RNA polymerase after transformation. T7 RNA polymerase has a super strong and specific function of initiating T7 promoter gene expression. When it is fully induced, the host's own expression can be almost completely converted into the expression of the target gene.

[0035] The embodiment of the present invention further provides a recombinant cell, wherein the recombinant cell contains the recombinant vector described above in the embodiment of the present invention. The recombinant cell includes an Escherichia coli cell and a recombinant vector located in the Escherichia coli cell.

[0036] The present invention also provides a method for preparing a recombinant procalcitonin antigen, wherein the method for preparing the recombinant procalcitonin antigen comprises the following steps:

[0037] S1, inserting the nucleotide sequence encoding the recombinant procalcitonin antigen described in the embodiment of the present invention into a plasmid to obtain a recombinant plasmid;

[0038] S2. Transforming the recombinant plasmid into competent E. coli cells, and then adding an inducer to induce expression to obtain the recombinant procalcitonin antigen.

[0039] The preparation method provided by the present invention has simple steps and low cost, can improve the expression amount and purity of recombinant procalcitonin antigen, and increase the yield of recombinant procalcitonin antigen, which is conducive to the large-scale application of recombinant procalcitonin antigen.

[0040] In step S1, in some embodiments, the plasmid is a pET28a(+) plasmid.

[0041] Specifically, in this embodiment, the nucleotide sequence shown in SEQ ID NO: 2 is inserted into the pET28a(+) plasmid to obtain a recombinant plasmid.

[0042] In step S2, in some embodiments, the step of transforming the recombinant plasmid into Escherichia coli competent cells and then adding an inducer to induce expression to obtain the recombinant procalcitonin antigen specifically includes:

[0043] S21, transforming the recombinant plasmid into Escherichia coli competent cells to obtain recombinant competent cells;

[0044] S22, inoculating the recombinant competent cells into LB liquid culture medium, and then adding an inducer to induce expression to obtain a bacterial liquid;

[0045] S23, after centrifuging the bacterial solution, collecting the bacterial cells, resuspending the bacterial cells, and then ultrasonically disrupting them, collecting the supernatant, and purifying them to obtain the recombinant procalcitonin antigen.

[0046] In some embodiments, the E. coli competent cells are E. coli BL21 (DE3) competent cells.

[0047] In some embodiments, the temperature for inducing expression is 30° C., and the inducer includes isopropyl-β-D-thiogalactoside (IPTG).

[0048] In step S23, in some embodiments, the ultrasonic fragmentation is performed in an ice bath;

[0049] During the ultrasonic disruption process, ultrasonic waves are performed 6 times in total, with a 1-minute pause between each ultrasonic wave.

[0050] During each ultrasonic process, the ultrasonication lasted for 2 seconds and then stopped for 3 seconds, with a total time of 5 minutes.

[0051] In some embodiments, the purification is firstly His-tag (histidine tag) nickel column purification and then anion purification. After these two steps of purification, a recombinant procalcitonin antigen with high purity can be obtained.

[0052] The present invention also provides the use of the recombinant procalcitonin antigen described above in the present invention or the recombinant procalcitonin antigen prepared by the preparation method described above in the present invention in the preparation of calibrators and / or quality control products for a procalcitonin antigen immunoassay kit.

[0053] The present invention will be further described below by means of specific examples.

[0054] Example 1

[0055] The amino acid sequence UniProtKB-P01258 (as shown in SEQ ID NO: 3, wherein the first 1-25 amino acids are signal peptides, 85C and 91C form a disulfide bond) found on the Uniprot website was truncated to obtain the 26-141 amino acid sequence, i.e. the truncated amino acid sequence (i.e. the amino acid sequence of the mature PCT, the corresponding procalcitonin antigen is denoted as PCT2, and the nucleotide sequence of the PCT2 gene is shown in SEQ ID NO: 4). Then, based on the truncated amino acid sequence (i.e. the amino acid sequence of the mature PCT), the lysine at position 37 was replaced with arginine, and the tyrosine at position 71 was replaced with cysteine ​​to obtain the amino acid sequence shown in SEQ ID NO: 1, and then a His tag was added to its N-terminus, and the obtained amino acid sequence was shown in SEQ ID NO: 5, which is the amino acid sequence of the recombinant procalcitonin antigen (denoted as PCT1), and the nucleotide sequence of the PCT1 gene is shown in SEQ ID NO: 2.

[0056] The PCT1 gene (its nucleotide sequence is shown in SEQ ID NO: 2) and the PCT2 gene (its nucleotide sequence is shown in SEQ ID NO: 4) were synthesized by chemical synthesis and sequenced by Shanghai Bioengineering. Restriction sites (NcoI and XhoI) were designed and pET28a (+) was used as an expression vector to obtain PCT1 recombinant plasmid and PCT2 recombinant plasmid.

[0057] The PCT1 recombinant plasmid was transformed into Escherichia coli BL21 (DE3) competent cells to obtain recombinant competent cells, and the recombinant competent cells were inoculated into 100 mL of LB liquid culture medium, and then 0.05 mmol / L, 0.1 mmol / L, and 0.25 mmol / L of IPTG were added respectively, and the cells were placed at 250 rpm and 30°C overnight (i.e., the expression time was > 12 h) to induce the expression of the recombinant protein to obtain PCT1 bacterial liquid;

[0058] The PCT1 bacterial solution was collected and centrifuged at 3000 rpm for 20 min to collect the precipitated PCT1 bacteria and the supernatant (i.e., the supernatant before PCT1 crushing);

[0059] The PCT1 cells were resuspended with a cell resuspension buffer (containing 20 mM PB (phosphate buffer) and 0.5 M NaCl) with a volume of 1 / 10 PCT1 bacterial solution, and then ultrasonicated 6 times with a cell ultrasonic disruptor to break the PCT1 cells. The ultrasonication was stopped for 1 minute between each ultrasonication to avoid the generation of foam. The process parameters for each ultrasonication were 2 seconds per ultrasonication, 3 seconds for stopping, and a total time of 5 minutes. The ultrasonication temperature was 0°C (ice bath), and the ultrasonic probe was at least 1 cm below the surface of the resuspended bacterial solution. Then, the supernatant (i.e., the supernatant after PCT1 was broken) was collected and analyzed for solubility using SDS-PAGE electrophoresis (sodium dodecyl sulfate-polyacrylamide gel electrophoresis).

[0060] The PCT2 recombinant plasmid was transformed into Escherichia coli BL21 (DE3) competent cells, and the supernatant before and after PCT2 disruption was obtained by the same method as above, and the solubility was analyzed by SDS-PAGE electrophoresis.

[0061] The results are as follows Figure 1 As shown, lanes 1 to 3 are electrophoretic bands of the supernatant after PCT2 disruption (lanes 1 to 3 are obtained from PCT2 bacteria under 0.05mmol / L, 0.1mmol / L, and 0.25mmol / L IPTG conditions, respectively); lane 4 is the supernatant before PCT2 disruption; lane 5 is a protein molecular weight standard (marker); lanes 6 to 8 are electrophoretic bands of the supernatant after PCT1 disruption (lanes 6 to 8 are obtained from PCT1 bacteria under 0.05mmol / L, 0.1mmol / L, and 0.25mmol / L IPTG conditions, respectively); lane 9 is the supernatant before PCT1 disruption.

[0062] The electrophoresis diagram shows that PCT1 has a wider band than PCT2 and has a higher purity. After concentration determination, the concentration of PCT1 is higher than that of PCT2. From the electrophoresis diagram, it can be seen that most of the bacterial protein is in the supernatant after ultrasonic disruption, which contains recombinant procalcitonin antigen. The recombinant procalcitonin antigen protein is expressed in a soluble form.

[0063] Example 2

[0064] According to the optimal conditions obtained by optimization: IPTG concentration is 0.05mmol / L, bacterial solution OD600 is between 0.5-0.6 during induction, induction temperature is 30℃, induction time is greater than 12h, and rotation speed is 250rpm. Large-scale induction expression of recombinant protein was carried out, and His-tag nickel column was used to purify PCT1, and the purified product was collected and anion purified. The purity of the sample obtained after two-step purification can reach 100%. After boiling the sample, SDS-PAGE electrophoresis and PCT detection kit were used for identification. The purification steps are shown in Table 1.

[0065] Table 1. Purification steps

[0066]

[0067] The results are as follows Figure 2 As shown, the meanings of the different lanes are as follows:

[0068] Lane 1: marker (protein molecular weight standard); Lane 2: PCT1 loading; Lane 3, PCT1 flow-through; Lane 4: PCT1-Na0.1 (i.e., elution 2 condition); Lane 5: PCT1-Na0.2 (i.e., elution 3 condition); Lane 6: PCT1-Na0.5 (i.e., elution 4 condition); Lane 7: PCT-Na0.7 (i.e., elution 5 condition); Lane 8: PCT-Na1 (i.e., elution 6 condition).

[0069] After purification at different Na ion concentrations, electrophoresis results showed that PCT1 had the highest purity under elution condition 4 (20 mM PB, 0.5 M NaCl).

[0070] Test of PCT1 prepared in Example 2 (anion purification using elution condition 4):

[0071] (1) Stability test

[0072] a. Prepare PCT1 solutions with different concentrations (PCT1 concentrations are 0 ng / mL, 0.2 ng / mL, 0.5 ng / mL, 2 ng / mL, 10 ng / mL, 50 ng / mL and 110 ng / mL), which are respectively recorded as PCT-1-1, PCT-1-2, PCT-1-3, PCT-1-4, PCT-1-5, PCT-1-6 and PCT-1-7;

[0073] The above solution was placed at a temperature of 2-8°C, and its light intensity value was tested on the 7th, 14th, 21st, 28th and 42nd days. The results are shown in Table 2.

[0074] Table 2. Data results of samples placed at 2-8℃ for different days

[0075]

[0076] Among them, CV in Table 2 represents the coefficient of variation of repeatability.

[0077] b. Prepare solutions of PCT1 with different concentrations (PCT1 concentrations are 0 ng / mL, 0.2 ng / mL, 0.5 ng / mL, 2 ng / mL, 10 ng / mL, 50 ng / mL and 110 ng / mL), which are respectively recorded as PCT-1-1, PCT-1-2, PCT-1-3, PCT-1-4, PCT-1-5, PCT-1-6 and PCT-1-7;

[0078] The above solution was placed at a temperature of 37°C, and its light intensity value was tested on the 7th, 14th and 21st days. The results are shown in Table 3.

[0079] Table 3. Data results of samples placed at 37°C for different days

[0080]

[0081] Among them, CV in Table 3 represents the coefficient of variation of repeatability.

[0082] c. Prepare solutions of PCT1 with different concentrations (PCT1 concentrations are 0 ng / mL, 0.2 ng / mL, 0.5 ng / mL, 2 ng / mL, 10 ng / mL, 50 ng / mL and 110 ng / mL), which are respectively recorded as PCT-1-1, PCT-1-2, PCT-1-3, PCT-1-4, PCT-1-5, PCT-1-6 and PCT-1-7;

[0083] After freeze-drying, test its light value;

[0084] The freeze-dried powder was then placed at temperatures of 2-8°C and -20°C, and its light intensity values ​​were tested after re-dissolving on the 7th, 14th, 21st, 28th and 42nd day, respectively. The results are shown in Table 4.

[0085] Table 4. Data results of freeze-dried powder samples reconstituted after being placed for different days at 2-8℃ and -20℃

[0086]

[0087]

[0088] Among them, CV in Table 4 represents the coefficient of variation of repeatability.

[0089] It can be seen that PCT1 has good stability and re-dissolution stability.

[0090] (2) Assignment accuracy test

[0091] PCT1 was prepared into different concentrations as primary calibrators (serial numbers were PCT-1, PCT-2, PCT-3, PCT-4, PCT-5, PCT-6, PCT-7), and then at another time PCT1 was prepared into different concentrations as new primary calibrators (serial numbers were PCT-1-1, PCT-1-2, PCT-1-3, PCT-1-4, PCT-1-5, PCT-1-6, PCT-1-7, PCT-2-1, PCT-2-2, PCT-2-3, PCT-2-4, PCT-2-5, PCT-2-6, PCT-2-7), and light intensity detection was performed to test the accuracy of its assignment. The results are shown in Table 5.

[0092] Table 5. PCT1 assignment accuracy test data

[0093]

[0094]

[0095] Wherein, fitting deviation = (fitting concentration - theoretical concentration) / theoretical concentration.

[0096] It can be seen that PCT1 has good assignment stability.

[0097] (3) PCT1 was prepared as a master calibrator and then clinically tested. The clinical sample tested was positive serum. The results are shown in Table 6.

[0098] Table 6. PCT clinical test data

[0099]

[0100] Eligibility requirements are:

[0101] Compared with qualified batches of reagents (i.e., competing reagents):

[0102] a. For clinical samples with a value less than 0.046 ng / mL, the absolute deviation (i.e., the absolute deviation between the full-point return value of the main calibration 1 and the full-point assignment of the qualified batch, and the absolute deviation between the full-point return value of the main calibration 2 and the full-point assignment of the qualified batch) is within the range of [-0.005, 0.005] ng / mL;

[0103] b. For clinical samples with a range of 0.046 to 0.25 ng / mL, the absolute deviation (the absolute deviation between the full-point return value of the main calibration 2 and the full-point assignment value of the qualified batch) is within the range of [-0.01, 0.01] ng / mL;

[0104] c. ≥0.25ng / mL, relative deviation (i.e. the ratio of the difference between the full-point return value of the main calibration 1 and the full-point value of the qualified batch to the full-point value of the qualified batch) is within ±5%;

[0105] d. The proportion of clinical samples that meet the above requirements accounts for ≥ 95% of all samples.

[0106] From the above clinical test results, it can be seen that the test data of the PCT1 main calibrator is basically the same as that of the competing product, meeting the qualification requirements, and the clinical compliance rate is ≥95%. In addition, the above clinical data can also show that PCT1 is reactive and has no functional changes compared to the competing product (or PCT2).

[0107] It can be seen that after the main calibrator is prepared using PCT1, the stability and value assignment accuracy meet the requirements, and the clinical compliance rate is ≥95%. The recombinant procalcitonin antigen prepared by the present invention can be used for the preparation of calibrators and quality control products in the procalcitonin antigen immunoassay kit, and can be used in the field of immunoluminescent diagnostic reagents, which can significantly reduce the research and development costs and avoid the risk of out-of-stock procurement of raw materials.

[0108] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A recombinant procalcitonin antigen, characterized in that: The amino acid sequence of the recombinant procalcitonin antigen is as shown in SEQ ID NO: 1, or the amino acid sequence of the recombinant procalcitonin antigen is the amino acid sequence obtained by connecting a protein purification tag to the C-terminus or N-terminus of the amino acid sequence shown in SEQ ID NO:

1.

2. A nucleic acid fragment, characterized in that The nucleic acid fragment comprises a nucleotide sequence encoding the recombinant procalcitonin antigen according to claim 1.

3. The nucleic acid fragment according to claim 2, characterized in that The nucleotide sequence of the nucleic acid fragment is shown in SEQ ID NO:

2.

4. A recombinant vector, characterized in that: The recombinant vector contains the nucleic acid fragment according to any one of claims 2-3.

5. A recombinant cell, characterized in that The recombinant cell contains the recombinant vector according to claim 4.

6. A method for preparing a recombinant procalcitonin antigen, characterized in that , including the following steps: Inserting the nucleotide sequence encoding the recombinant procalcitonin antigen according to claim 1 into a plasmid to obtain a recombinant plasmid; The recombinant plasmid is transformed into competent Escherichia coli cells, and then an inducer is added to induce expression to obtain the recombinant procalcitonin antigen.

7. The preparation method according to claim 6, characterized in that: The step of transforming the recombinant plasmid into competent Escherichia coli cells and then adding an inducer to induce expression to obtain the recombinant procalcitonin antigen specifically includes: Transforming the recombinant plasmid into Escherichia coli competent cells to obtain recombinant competent cells; Inoculating the recombinant competent cells into LB liquid culture medium, and then adding an inducer to induce expression to obtain a bacterial liquid; After the bacterial solution is centrifuged, the bacterial bodies are collected, the bacterial bodies are resuspended, ultrasonically disrupted, the supernatant is collected, and the recombinant procalcitonin antigen is obtained after purification.

8. The preparation method according to claim 6, characterized in that: The plasmid is a pET series plasmid, and the Escherichia coli competent cell is an Escherichia coli BL21 (DE3) competent cell.

9. The preparation method according to claim 6, characterized in that: The temperature for inducing expression is 30°C, and the inducing agent includes isopropyl-β-D-thiogalactoside; The purification is firstly carried out His-tag nickel column purification and then anion purification.

10. Use of the recombinant procalcitonin antigen according to claim 1 or the recombinant procalcitonin antigen prepared by the preparation method according to claim 6 in the preparation of calibrators and / or quality control products for a procalcitonin antigen immunoassay kit.

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