Patent Publication Number: US-2022233671-A1

Title: Subunit vaccine of contagious caprine pleuropneumonia and preparation method and use thereof

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Chinese Patent Application No. 202110110937.4, entitled Subunit vaccine of contagious caprine pleuropneumonia and preparation method and use thereof filed with the China National Intellectual Property Administration on Jan. 26, 2021, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The disclosure belongs to the technology field of preparation of animal infectious disease vaccine, and in particular relates to a subunit vaccine of contagious caprine pleuropneumonia and preparation method and use thereof. 
     BACKGROUND ART 
     Contagious caprine pleuropneumonia (CCPP) is an important animal disease endangering the world&#39;s goat breeding industry and is a notifiable infectious disease of the World Organization for Animal Health (OIE). The main clinical manifestations of contagious caprine pleuropneumonia are fever, cough and dyspnea. The main necropsy lesions are cellulosic pleuropneumonia, pleural effusion and lung hepatization. Contagious caprine pleuropneumonia is a highly contagious infectious disease and has the characteristics of high incidence rate and high mortality in new epidemic areas, which brings serious threats and huge economic losses to the goat breeding industry. A variety of animals such as  Capra aegagrus  and  Pantholops hodgsonii  can be infected. Contagious caprine pleuropneumonia is distributed in more than 40 countries or regions around the world and is currently prevalent in Africa, the Middle East, Asia and other countries or regions, causing huge economic losses. The pathogen of the disease is Mycoplasma capricolum subsp. capripneumoniae (Mccp), which has extremely high nutritional requirements and is difficult to cultivate. Early in 1873, there were documents documenting the outbreak of contagious caprine pleuropneumonia, and it was not until 1976 that Macowan first isolated the pathogen Mccp. At present, contagious caprine pleuropneumonia is widespread in China. However, there are few reports on the isolation of Mycoplasma capricolum subsp. capripneumoniae due to the difficulty of pathogen isolation and cultivation and high technical requirements. 
     Vaccine immunization is an important means to prevent and control the contagious caprine pleuropneumonia. At present, the main vaccines for the prevention and control of the disease are inactivated whole-bacteria vaccines and inactivated tissue vaccines. The preparation methods of inactivated tissue vaccines generally include infecting healthy goats with infected tissue or bacteria culture, collecting tissues from infected goats&#39; lungs, removing trachea, bronchus and other tissues, grinding, filtering, inactivating the tissue, and other procedures. The preparation methods of inactivated tissue vaccines has problems such as complex process, high requirements for laboratory animals, tendency to pollute other pathogens, unstable quality, and limited scale production capacity. Inactivated whole-bacteria vaccines have many advantages over inactivated tissue vaccines, and have gradually become the main means for preventing and controlling contagious caprine pleuropneumonia. However, the inactivated vaccine in the prior arts has the problems such as difficulty in pathogen cultivation, low growth rate, low yield, complex process, high cost, limited scale production, risk of biosafety, and relatively larger adverse effects, which limits its promotion and application. Subunit vaccine is an important research direction of contagious caprine pleuropneumonia. However, to date, there is no report on effective contagious caprine pleuropneumonia subunit vaccine at home and abroad. 
     SUMMARY OF THE DISCLOSURE 
     In view of this, the purpose of the present disclosure is to provide a subunit vaccine of contagious caprine pleuropneumonia and preparation method and use thereof. The present disclosure combines the immune proteins with good immune protection effect widely existing in the Mycoplasma capricolum subsp. capripneumoniae strains into subunit vaccine of contagious caprine pleuropneumonia. The subunit vaccine has the advantages of high safety, good immune effect and stability, minor adverse effects and low cost. 
     The Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E involved in the present disclosure are classified and screened through comprehensive analysis of cell localization, protein hydrophilicity, antigenicity, signal peptide, transmembrane region, T cell epitope and B cell epitope, etc. based on the Mccp genomics, comparative genomics, proteomics and immunoproteomics, etc. and verified by in vitro and in vivo tests. The above immunoproteins combination may overcome the problems that a single protein is difficult to induce comprehensive humoral and cellular immunity and the protective effect is limited. The subunit vaccine prepared by screening the immunoproteins combination and by combining with adjuvant formulation may induce comprehensive immune response, and provide good protective effect for goats against Mccp infection. 
     In order to achieve the above-mentioned purpose of the present disclosure, the present disclosure provides the following technical solutions. 
     In one aspect, the present disclosure provides a combination of Mycoplasma capricolum sub sp. capripneumoniae immunoproteins, including Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E; the mass ratio of Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E is (0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5); the amino acid sequences of Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E are set forth in SEQ ID No. 1-SEQ ID No.5. 
     In one embodiment, concentrations of the Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E are independently 20-150 μg/mL. 
     In another aspect, the present disclosure provides a subunit vaccine of contagious caprine pleuropneumonia, wherein the subunit vaccine of contagious caprine pleuropneumonia includes the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and adjuvant. 
     In one embodiment, the adjuvant is a double adjuvant, and the double adjuvant includes saponin and ISA 201 VG adjuvant. 
     In one embodiment, final concentration of the saponin is 1.0-4.0 mg/mL. 
     In one embodiment, the volume of the ISA 201 VG adjuvant is 50%-55% of volume of the subunit vaccine of contagious caprine pleuropneumonia. 
     In one embodiment, the subunit vaccine of contagious caprine pleuropneumonia further includes a preservative solution, volume of the preservative solution accounts for 0.8%-1.2% of total volume of the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and the saponins, and mass percent content of the preservative in the preservative solution is 0.8%-1.2%. 
     In another aspect, the present disclosure provides a method for preparing the subunit vaccine of contagious caprine pleuropneumonia, including the following steps:
         1) mixing the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and the saponins to obtain a mixture, allowing the mixture to stand to obtain an antigen saponin mixture, temperature for the standing is 2-8° C., time for the standing is 18-48 h, and shaking the mixture once every 2-4 h during the standing;   2) mixing and emulsifying the antigen saponin mixture and the ISA 201 VG adjuvant to obtain the subunit vaccine of contagious caprine pleuropneumonia.       

     In one embodiment, the method further includes the following steps before mixing the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins with the saponins in the step 1): dissolving proteins in the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins in PBS buffer solution and mixing; and mixing the preservative solution with the solution after the standing in the step 1) to obtain the antigen saponin mixture. 
     In yet another aspect, the present disclosure provides the use of the subunit vaccine of contagious caprine pleuropneumonia in the preparation of drugs for preventing and/or treating contagious caprine pleuropneumonia 
     The subunit vaccine of contagious caprine pleuropneumonia provided by the disclosure combines the immune proteins which have with good immune protection effect and widely exist in the Mycoplasma capricolum subsp. capripneumoniae strains into a safe and effective subunit vaccine. Compared with the prior art, the subunit vaccine of contagious caprine pleuropneumonia has the following advantages: 
     High safety: the present disclosure can avoid the problems of possible incomplete inactivation of pathogen during the production of inactivated vaccine and possible contamination of other pathogens in the inactivated tissue vaccine. The present disclosure has better safety and minor adverse effects after immunization. The method for preparing the subunit vaccine of contagious caprine pleuropneumonia does not involve pathogen and its nucleic acids, which reduces the risk of spread and contamination of pathogens that may exist in the prior methods for preparing inactivated vaccine, and reduces the risk of biological safety. 
     High efficiency: the subunit vaccine of contagious caprine pleuropneumonia provided by the present disclosure provides good protective effect and significantly reduces the disease incidence rate and mortality, significantly reducing the lung lesions and bacterial load. The vaccine provided by the present disclosure induces goats to produce good protective effect, and the proteins A, B, C, D and E in the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins has good immunogenicity. Furthermore, the adjuvant is selected from saponin and a new type of genetically engineered vaccine adjuvant ISA 201 VG. Saponins are capable of enhancing immune response, stimulating immune reaction of cellular and humoral immune response, and the immune duration is long. ISA 201 VG is a new type of adjuvant, is a water-in-oil-in-water emulsion, which has the advantages of good immune effect, stability, low viscosity, easy injection and small stimulation reaction. Combined use of saponin and ISA 201 VG adjuvant may improve immune response, stimulate cellular and humoral immune response, improve immune protection effect, reduce immune adverse effects, and provide good immune protection effect. 
     Large-scale production: production of the inactivated whole-bacteria vaccine needs large-scale cultivation of pathogen Mccp which is difficult to cultivate and has a slow growth speed and a low yield. The inactivated whole-bacteria vaccine needs to be concentrated, inactivated, emulsified and subjected other steps to prepare, the process is complicated, and the large-scale production capacity is limited. The preparation methods of inactivated tissue vaccines generally includes infecting healthy goats with infected tissue or bacteria culture, collecting tissues from infected goats&#39; lungs, removing trachea, bronchus and other tissues, grinding, filtering, inactivating, and other procedures. The preparation methods of inactivated tissue vaccines are complicated and difficult to scale-up. The present disclosure directly adopts Mycoplasma capricolum subsp. capripneumoniae immunoproteins which may be highly expressed by prokaryotic system, and the process is relatively simple and prone to large-scale production. 
     High stability: compared with the inactivated vaccine, the subunit vaccine of contagious caprine pleuropneumonia provided by the present disclosure has less antigen components, higher antigen purity, and it is an water-in-oil-in-water emulsion and has good stability, and it is convenient to transport and preserve. 
     Minor adverse effects: the inactivated vaccines in the prior arts have many antigen components, because a large amount of animal serum is used in antigen culture, adverse effects are easy to occur after immunization. Because the inactivated tissue vaccine contains animal tissues has complex the compositions, and the adverse effects are relatively large. The subunit vaccine of contagious caprine pleuropneumonia provided by the present disclosure has less antigen components and higher antigen purity, and is made into water-in-oil-in-water emulsion with low viscosity. It is easy to inject and has minor stimulation and adverse effects. 
     Lower cost: the pathogen of Mccp is difficult to culture, having slow growth rate, low yield and high culture. The bacteria inactivated vaccines in the prior arts need to cultivate a large number of bacteria, and the production cost is high due to the need for concentration, inactivation and other steps. In the present disclosure,  Escherichia coli  is used to efficiently express antigen with high efficiency and low cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the SDS-PAGE electrophoretic map of recombinant proteins; in the figure, M is the standard for protein molecular weight, lanes  1 - 3  are for protein C, lane  4  is for protein D, lane  5  is for protein B, lane  6  is for protein A, and lanes  7 - 8  are protein E; 
         FIG. 2  shows the level of Mccp antibody in goat serum after immunization with the subunit vaccine of the present disclosure; 
         FIG. 3  shows the necropsy lesions of lung dissection; wherein A is the subunit vaccine group of the present disclosure, B is the inactivated vaccine group, C is the challenge control group, and D is the blank control group. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure provides a combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins, including Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E; the mass ratio of Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E is (0.5-1.5): (0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5); preferably 1:1:1:1:1. In the present disclosure, concentrations of the Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E are independently 20-150 μg/mL, more preferably 30-100 μg/mL. In the present disclosure, there is no special limitation on the solvents of the Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E, and any conventional protein solvent in the art can be used. During the specific implementation process of the present disclosure, the solvent is PBS buffer. In the present disclosure, there is no special limitation on the method for preparing the Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E. They can be prepared by conventional artificial synthesis and recombinant expression by prokaryotic or eukaryotic expression system in the art. During the specific implementation process of the present disclosure, the method for preparing the Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E is preferably the method of recombinant expression by prokaryotic expression system. In the present disclosure, there is no special limitation on the method of recombinant expression by prokaryotic expression system, and can adopt the conventional method in the art. The detailed steps are as described in the examples. 
     In the present disclosure, the amino acid sequences of Mycoplasma capricolum subsp. capripneumoniae immunoproteins A, B, C, D and E are set forth in SEQ ID No.1-SEQ ID No.5, and the details are as follows: 
     
       
         
           
               
               
            
               
                 The amino acid sequence of protein A (SEQ ID No. 1): 
                   
               
               
                 MKTKNQEEEIPNGDAFKGAKSLEKKLSPFSDNTIETQQAGLSRVFIKASKKAYSN 
               
               
                   
               
               
                 NQDDFKNAIERTGGLFILDKNYQDIFFNEELMKIIGVGEVYSKNSSDKRINKKLTLEEFLG 
               
               
                   
               
               
                 EAKAESLQPANFSNKNSPFVSFNLKNEYLKNLIDPKKNKDNNSLTMITSVGHVIETLRTY 
               
               
                   
               
               
                 YKKANSTNKQVIEKYLNTYFNQIIKPIQDYISSHLSDALAVKTLKDLFSIEYSTTTTEGTSG 
               
               
                   
               
               
                 NLAIQRTSLVDSKINKWWKSNQTGKIENTSDLKYVLFGTNNLDKKNDRHIFRFTNSANK 
               
               
                   
               
               
                 FLYDANASEKDFIKDDKGNVGKYYNKLKISSDNSISQDEELDYIDKVSNKLISIIMTEILFK 
               
               
                   
               
               
                 KDTTDKDHVVNRNLDQALFRNNVLLHNNQISPDNTRIVTTNPAIVTDRKTQTTKLYIPV 
               
               
                   
               
               
                 WSNTMAKQVESDILQTSLGYTFKVLSIKEFSSDILE. 
               
               
                   
               
               
                 The amino acid sequence of protein B (SEQ ID No. 2): 
               
               
                 MSNSSSDQITNFYKQKQDQIAEVKLSNKQDLEYYSLRDEYILFNQYQVNTGLCW 
               
               
                   
               
               
                 DFASIKSLETALMLANNEMYDFSEASISVLNEHWVADGVFFRTFDNLLNRNGIAFESDFR 
               
               
                   
               
               
                 FGDLYYFPNTGIYYDKLLDLYKSKYITNLANKLEAYSFYRYSILEKLKQIKEHISKHSALF 
               
               
                   
               
               
                 VGIDHWQVVKNKVNKQETFQITSGSMGAHAVSIIGWDDNYINNDNSKGAFIVLNSDGFY 
               
               
                   
               
               
                 DNNDGVNYLPYNSSTIYLDLQGYKFIGDKLISSKGINSSIKNKYFNYYNTKLAKKYTETK 
               
               
                   
               
               
                 PLNQNVFSWDDQVEIQYQLNDQIADFKRIQTSIFLWQTRCFRLE. 
               
               
                   
               
               
                 The amino acid sequence of protein C (SEQ ID No. 3): 
               
               
                 MSTTSIEKLGRKNFVDEESFKNAFIDPNALPVTEFSEVHNNKRSVKYDPEKNVVK 
               
               
                   
               
               
                 FNGKEISVDQYLQQYYQKYQALPYLNIRYGSFNFYNQYIEAVSPQEFYKFTKWFMKNVS 
               
               
                   
               
               
                 WGPEIITLKSFSIVKGVEMSGNSITLGAHSNKNKEETTIKFYPDAFFGTLPIYSNLSGRGNA 
               
               
                   
               
               
                 YESLTYKLNQQVLTQKDLEGFLANVGNYNSLVNLSQQTINKSYFRGITNVSFLKGQKVF 
               
               
                   
               
               
                 AYKQENWQSKFSKTYSELEKKRLEDRSSYLFVIPANSLQEARKKLEVKLSEYKKESDPFN 
               
               
                   
               
               
                 FFEKINPKNVVLEEKTISDAEVKQDNTNKIIDKKLVLTFNDKTNYIIHNAFSDVLTEQMTS 
               
               
                   
               
               
                 NNRRTYVALKNYVNFSSAKQKLEDKVKNFILQIKENIKLKSNGKEKELEELLKEFESYNN 
               
               
                   
               
               
                 VVSLLEQKNLTSDILKKVDKKIFESETKFNQILNKPNSNKTFNEKEYYKTDIAYSLPELITL 
               
               
                   
               
               
                 ETLVQHNNSNKLNWRDFYNLNEFVADRSNILKNGSTEFFVYSKFVKEINANENKKYEEL 
               
               
                   
               
               
                 KSENDLIAASSKVELIDILTKKSIIKPNISQEEINKIILKVDLFDLKKEGQNLLISLRNTTAEK 
               
               
                   
               
               
                 ASNKEKFGNKWINISINANAKKDVIRATNDLFAVLEYKKVVVPSVLKEESDLRNPITNKL 
               
               
                   
               
               
                 EKTFDVFVDAYENLIDELLEKVLYAAQWLEGPHIKKVLDENGVMQYKLENGKYLGFTK 
               
               
                   
               
               
                 DDRIGLWAILKMSDNNFKGISTDFLKFVGAHEYGHHITLNGAQDLGNKGSDPIFISALTP 
               
               
                   
               
               
                 GATPDISNYYNREVVDLFLKARTHIKLETKRLLDQFGAIKDYGEYAVFNFAKKDKNGNIN 
               
               
                   
               
               
                 FDTKDNIGIEKDSDIWGVDIEDPNIRKALSNKKRRFLQDFAGLLAAVKERQKENNLTTDD 
               
               
                   
               
               
                 DKKWLSAFLE. 
               
               
                   
               
               
                 The amino acid sequence of protein D (SEQ ID No. 4): 
               
               
                 MTLNPTVNSSDQQNQVVKYMYKDKKGVLRFQPASLKMLDGILKDGKGNPIKFD 
               
               
                   
               
               
                 ISNNGKSVEPIVVKGQKDSEGKYYKIDEVLVHNKDGSPIINVPIGVNLRDENSGYNDKKT 
               
               
                   
               
               
                 IDFINEKIKVVESTIKSLVVDKYSINGWNNENTRISLDSKIDLNYPAIKNIFGSKVPNNVSE 
               
               
                   
               
               
                 MYKNIYADYVLNRDVDKGSYKFDEHGEISKVKYYNLDSTKVDRYYNSDTPSSLIYANPS 
               
               
                   
               
               
                 NYKITDDNVELDFKTILWTLYAAGFVTYGNLINAGSSQVLWLSKDKMYMPNVKLQEAY 
               
               
                   
               
               
                 TDLYFLSSLPKEYEQIFEAKKVLKWISKYTPLFISSSSNKTGVWNMIDNEGKFVDFNLLIN 
               
               
                   
               
               
                 ENFTNSIKLQLNYSRVKTLDSNVLNGLFGTFKDFNDNSLEFDEYDKWLDFVTVDLRKAK 
               
               
                   
               
               
                 YNQKQDRVDWEIDYVKSKVDIDKFKEKYKSEVLDKLDSISSMNDNQKQAFKTFYEKAN 
               
               
                   
               
               
                 ADKTEQIWANEIMRRFSSSYFAMYNSALSIGEIESNKDLAWIFDSTHGYGDFKKAKFKIK 
               
               
                   
               
               
                 NPDKSKWEISTDDLLNAYKKLAKDLGVETKQLNLVDSLVFDNKTQLYTDQTMTHIYNR 
               
               
                   
               
               
                 KFDLLSIFSSLATAQFHTSPTRDVLDYFYKKTERKVNELFSNYTYNFAEVINRDNLQITYS 
               
               
                   
               
               
                 PSNHDFGNMPSFLSNISEATTGLEYVVDGTTTAKWKKRAIKINDRNGRNGIVNAILDYEK 
               
               
                   
               
               
                 LVDSEAKNKAEALNLKYRNSKLSQKSNLSDDSNYDNSYFGKFQSINNGWFKDRWYRDF 
               
               
                   
               
               
                 LDFKLYDDNGNPIKDETIRIKDLEGKKVDSRVNAFWQFYIQSQGVGKRNISGIWRDANK 
               
               
                   
               
               
                 DAVAMFGYLSSDVANKANYLAFKNQKTGEIKTIKINKQFSSNMFYYKTQNIENEAKYEA 
               
               
                   
               
               
                 AKTQEEKDKIRHTLAHEKYNYKDINGQHTGVGFVSWVSDYAIMSKYKNALLTPGQQYS 
               
               
                   
               
               
                 VYFSSDQKGTKDIIKTDLGNFESIAENGKTFSQAPVRMQKNKQVAKVDKDGTKYYENTL 
               
               
                   
               
               
                 YVYDQFNGVKLE. 
               
               
                   
               
               
                 The amino acid sequence of protein E (SEQ ID No. 5): 
               
               
                 MKSQGNFISYKQENSSSSSGTSSGGSDTGAGRNTDTGSGSNGGFETFNTRRNREK 
               
               
                   
               
               
                 DPSFNTFKETIKEKLKKGIEEVKKEIDSFLDKEIKEIGDLKTPDDKNKYFEKIERKTYLTEL 
               
               
                   
               
               
                 KKFFDKKDSNSFVDKPDEFGFNISFPYIIANLEKLYTATVKFDGKDYSDIKVGKSGDSAK 
               
               
                   
               
               
                 DIKGSDKKLDYSDVITNDVGKIITDTKAQDNFINSKEFDDVVKGYLATWKNEVKKMIYQ 
               
               
                   
               
               
                 KQDILEFGKDIFFEPTNGNTTTSENTTQVDQYKVYLDTKKYKSWSEYIKEKISKRFTHFD 
               
               
                   
               
               
                 LEQNQKFKIVDEAKPTPTPTKPTLPDPTNKPLVPTNPPSSQITQAVEALPNLEPYINYQFAS 
               
               
                   
               
               
                 YDLSSIGSQLSSSQDEEKDKYFFFLNPINTRFKYTVDSVNGNSVVVRITDQAKSGNSRTYI 
               
               
                   
               
               
                 YENVQVGKDWRFLMLLEKESKYIEQEFNKLYKALLLDEKINYNSLAHDSLQESVFSLVN 
               
               
                   
               
               
                 AATQIVSSSSFKSLWFENIINNYQKIDESDQLGDYTNWANKKAKYLFETLLKAISASKLN 
               
               
                   
               
               
                 NNPGWYVLVKAFNNVKYDLDQLTNDESTYNSHLKRAQEFDLDLKYYDQLYDALEHSIL 
               
               
                   
               
               
                 KLSTTANQLTKNLHISSWFNKYTDDIKDAREYVEILRNLLTGKPISKDSEDYKEFMTNYQ 
               
               
                   
               
               
                 KAIDKLNEKNQTTNKTLE. 
               
            
           
         
       
     
     The present disclosure further provides a subunit vaccine of contagious caprine pleuropneumonia, including the Mycoplasma capricolum sub sp. capripneumoniae immunoproteins and adjuvant. In the present disclosure, the adjuvant can be selected from one or more of a chemical immune adjuvant, a microbial immune adjuvant, a plant immune adjuvant and a biochemical immune adjuvant. In the present disclosure, the adjuvant is a double adjuvant, preferably saponin and ISA 201 VG double adjuvant. The mass-volume ratio of the saponins to the Mycoplasma capricolum subsp. capripneumoniae immunoproteins antigen solution is preferably 1-4 mg/mL, more preferably 2 mg/mL. In the present disclosure, there is no special limitation on the source of the saponin, and the conventional commercially available products in the art can be used. The volume of the ISA 201 VG adjuvant is 50%-55%, more preferably 50% of volume of the subunit vaccine of contagious caprine pleuropneumonia. In the present disclosure, there is no special limitation on the source of ISA 201 VG, and the conventional commercially available products in the art can be used. 
     In the present disclosure, the subunit vaccine of contagious caprine pleuropneumonia further includes a preservative solution, volume of the preservative solution accounts for 0.8%-1.2%, more preferably 1.0% of total volume of the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and saponins. The mass percent content of the preservative in the preservative solution is 0.8%-1.2%, more preferably 1.0%. In the specific implementation of the present disclosure, the preservative is preferably thimerosal. 
     The present disclosure further provides a method for preparing the subunit vaccine of contagious caprine pleuropneumonia, including the following steps: 1) mixing the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and the saponins to obtain a mixture, allowing the mixture to stand to obtain an antigen saponin mixture, temperature of the standing is 2-8° C., time for the standing is 18-48 h, and shaking the mixture once every 2-4 h during the standing; 2) mixing and emulsifying the antigen saponin mixture and the ISA 201 VG adjuvant to obtain the subunit vaccine of contagious caprine pleuropneumonia. 
     In the present disclosure, the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and the saponins are mixed to obtain a mixture, the mixture is allowed to stand to obtain an antigen saponin mixture. In the present disclosure, before mixing the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins and the saponins, the method preferably further includes the following steps: dissolving proteins of the combination of Mycoplasma capricolum subsp. capripneumoniae immunoproteins in PBS buffer solution and mixing to obtain an immunoprotein antigen solution. After obtaining the immunoprotein antigen solution, it is mixed with saponin, and the ratio of the saponin to the immunoprotein antigen solution is preferably 1-4 mg/mL. In the present disclosure, the temperature for mixing and standing the immunoprotein antigen solution and saponin is preferably 4° C., and time for the standing is preferably 24 hours. The mixture is shaken once every 2-4 h during the standing to promote the complete mixing of the saponins and the antigens. In the present disclosure, the solution after the standing is preferably mixed with a preservative solution to obtain an antigen-saponin mixture. 
     In the present disclosure, the antigen-saponin mixture is mixed with ISA 201 VG adjuvant and emulsified to obtain the subunit vaccine of contagious caprine pleuropneumonia. In the present disclosure, the volume ratio of the ISA 201 VG adjuvant to the antigen saponin mixture is preferably (50-55): (45-50). In the present disclosure, the emulsifying time is preferably 10-30 min. In the present disclosure, the emulsification is preferably carried out by using an emulsifier. The water-in-oil-in-water (w/o/w) emulsion with slight viscous force obtained after the emulsification is the subunit vaccine of contagious caprine pleuropneumonia. 
     The present disclosure further provides the use of the subunit vaccine of contagious caprine pleuropneumonia in preparation of drugs for preventing and/or treating contagious caprine pleuropneumonia. The drugs of the present disclosure are used for preventing and/or treating the Mycoplasma capricolum subsp. capripneumoniae infection and related diseases caused by the Mycoplasma capricolum subsp. capripneumoniae infection. The drugs provided by the present disclosure may reduce or prevent the lung damage caused by the Mycoplasma capricolum subsp. capripneumoniae, and reduce the settlement and infection of the Mycoplasma capricolum subsp. capripneumoniae in lung, lymph node and kidney. In the present disclosure, there is no special limitation on the dosage and excipients of the drugs, and the dosage and excipients that are acceptable to the subunit vaccine of contagious caprine pleuropneumonia can be adopted. 
     The technical solutions provided by the present disclosure will be described in detail below in combination with the embodiments, but they should not be understood as limiting the protection scope of the present disclosure. 
     Mycoplasma capricolum subsp. capripneumoniae M1601 strain, (GenBank accession number: CP017125.1), was obtained from Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, reference: Chen S, Hao H, Zhao P, Thiaucourt F, He Y, Gao P, Guo H, Ji W, Wang Z, Lu Z, Chu Y*, Liu Y*. Genome-Wide Analysis of the First Sequenced Mycoplasma capricolum subsp. capripneumoniae Strain M1601. G3 (Bethesda), 2017, 7(9): 2899-2906. 
     Main reagents: vector pET30a(+) from Novagen company.  Escherichia coli  BL21 (DE3), IPTG, and kanamycin were purchased from TransGen Biotech; Ni-NTA His bind resin was purchased from QIAGEN Company, and protein marker was purchased from Thermo Fisher Scientific. 
     The main instrument and equipment: low-temperature high-speed centrifuge was purchased from Eppendorf company, low-temperature and high-speed freezing centrifuge was purchased from Beckman company, ultrasonic disrupter was purchased from Ningbo Xinzhi Stock Biotechnology Co., Ltd., electrophoretic apparatus power supply was purchased from Beijing Liuyi company, protein electrophoretic apparatus, gel imager and microplate reader was purchased from Bio-Rad company, the emulsifying machine was purchased from Fluko company, the biological safety cabinet was purchased from Sujing Antai company, and the water-jacket thermostatic constant incubator was purchased from Shanghai Yiheng Company. 
     Mccp-infected serum and immune serum were prepared and preserved by Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences. The Mccp 1801 (M1801) of the present disclosure has been disclosed in the document (Wu Yaqin, Liu Baohong, Yuan Ting, etc. Identification and application of specific molecular target for detection of Mycoplasma capricolum subsp. capripneumoniae. Chinese Veterinary Science. 2020, 50 (10)): 1257-1262), and owned and preserved in Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences. 
     Experimental Animals: New Zealand white rabbits were purchased from the Experimental Animal Center of Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences. Healthy goats were purchased from a goat farm in Gansu Province. The Brucella antibody was tested negative, and the Mccp antigen and antibody were all tested negative before the experiment. 
     Ethics Statement: animal tests complied with guidelines of the ethical and technical specifications of People&#39;s Republic of China and approved by the Animal Ethics Committee and of Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences. 
     Example 1 
     Preparation of Protein A 
     The codon of the gene encoding Mccp protein A (GenBank: CP017125.1, M1601_02645, the 172-1524 nucleotide sequence from the 5′end, hypothetical protein) was optimized and ligated to the pET30a(+) restriction enzyme sites between NdeI and XhoI to express the protein set forth in sequence SEQ ID No.1. The obtained recombinant expression plasmid was transformed into  Escherichia coli  BL21 (DE3) to obtain recombinant bacteria. The recombinant bacteria were inoculated in a LB liquid medium (containing 50 μg/mL kanamycin), cultured at 37° C. and 200 rpm to OD 600  of 0.6. IPTG having a final concentration of 0.05 mM was added and induced for 12 h at 16° C. and 120 rpm, the recombinant protein culture was centrifuged for 30 minutes at 4° C. and 12000 rpm, bacteria precipitates were collected and resuspended with pre-cooled Lysis buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 10 mM imidazole, pH=8.0), and ultrasonically disrupted for 30 minutes (ultrasound 2s, interval 2s), centrifuged for 30 min at 4° C. and 7500 rpm. The supernatant was collected and filtered with a 0.45 μm filter for later use. The supernatant was purified with Ni-NTA His bind resin purchased from QIAGEN company, eluted with elution buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 250 mM imidazole, pH=8.0) to obtain the target protein. The target protein was dialyzed with a dialysis bag to remove imidazole and saved at −80° C. for later use. The SDS-PAGE results of protein A are shown in  FIG. 1 . 
     Preparation of Protein B 
     The codon of the gene encoding Mccp protein B (GenBank: CP017125.1, M1601_03335, the 85-1089 nucleotide sequence from the 5′end, hypothetical protein), was optimized and ligated to the pET30a(+) restriction enzyme sites between NdeI and XhoI to express the protein set forth in sequence SEQ ID No.2. The obtained recombinant expression plasmid was transformed into  Escherichia coli  BL21 (DE3) to obtain recombinant bacteria. The recombinant bacteria were inoculated in a LB liquid medium (containing 50 μg/mL kanamycin), cultured at 37° C. and 200 rpm to OD 600  of 0.6. IPTG having a final concentration of 0.05 mM was added. The recombinant bacteria were induced for 6 h at 26° C. and 180 rpm, the recombinant protein culture was centrifuged for at 12000 rpm for 30 minutes at 4° C. and bacteria precipitates were collected and resuspended with pre-cooled Lysis buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 10 mM imidazole, pH=8.0), and ultrasonically disrupted for 30 minutes (ultrasound 2s, interval 2s), centrifuged for 30 min at 4° C. and 7500 rpm. The precipitates were collected. Inclusion body proteins was purified using an inclusion body wash solution I (Tris 50 mM, NaCl 100 mM, EDTA 2 mM, 0.5% TritionX-100, pH8.0), inclusion body wash solution II (inclusion body wash solution, 1M urea), inclusion body wash solution III (inclusion body wash solution I, 2M urea), inclusion body wash solution IV (inclusion body wash solution I, 3M urea) and inclusion body wash solution V (inclusion body wash solution I, 4M urea) to remove the impure protein. The precipitates were resuspended with resuspension (Na 2 HPO 4  50 mM, Tris 1 mM, urea 8M, pH=8.0) and allowed to stand overnight. The inclusion bodies were denatured and dissolved. Dissolving solution was centrifuged for 15 min at 4° C. and 7000 rpm. The supernatant was collected. The purified protein was obtained, dialyzed with dialysis bag to remove urea, filtered with a 0.45 μm filter and saved at −80° C. for later use. The SDS-PAGE results of protein B are shown in  FIG. 1 . 
     Preparation of Protein C 
     The codon of the gene encoding Mccp protein C (GenBank: CP017125.1, M1601_00615, the 106-2823th nucleotide sequence from the 5′end, hypothetical protein) was optimized and ligated to the pET30a(+) restriction enzyme sites between NdeI and XhoI to express the protein set forth in sequence SEQ ID No.3. The obtained recombinant expression plasmid was transformed into  Escherichia coli  BL21 (DE3) to obtain recombinant bacteria. The monoclonal recombinant bacteria was inoculated in a LB liquid medium (containing 50 μg/mL kanamycin), cultured at 37° C. and 200 rpm to OD600 of 0.6. IPTG having a final concentration of 0.05 mM was added. The recombinant bacteria were induced for 12 h at 16° C. and 120 rpm, the recombinant protein culture was collected by high-speed centrifugation at 4° C. and 12000 rpm. The bacteria precipitates were resuspended with pre-cooled Lysis buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 10 mM imidazole, pH=8.0), and ultrasonically disrupted for 30 minutes (ultrasound 2s, interval 2s), centrifuged for 30 min at 4° C. and 7500 rpm after ultrasonic disruption. The supernatant was collected, and filtered by a 0.45 μm filter for later use. The supernatant was purified with Ni-NTA His bind resin purchased from QIAGEN company, eluted with elution buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 250 mM imidazole, pH=8.0) to obtain the target protein. The target protein was dialyzed with a dialysis bag to remove imidazole, filtered with a 0.45 μm filter, and saved at −80° C. for later use. The SDS-PAGE results of protein C are shown in  FIG. 1 . 
     Preparation of Protein D 
     The codon of the gene encoding Mccp protein D (GenBank: CP017125.1, M1601_00615, the 2862-5895 nucleotide sequence from the 5′end, hypothetical protein) was optimized and ligated to the pET30a(+) restriction enzyme sites between NdeI and XhoI to express the protein set forth in sequence SEQ ID No.4. The obtained recombinant expression plasmid was transformed into  Escherichia coli  BL21 (DE3) to obtain recombinant bacteria. The monoclonal recombinant bacteria was inoculated in LB liquid medium (containing 50 μg/mL kanamycin), cultured at 37° C. and 200 rpm to OD600 of 0.6. IPTG having a final concentration of 0.05 mM was added. The recombinant bacteria were induced for 12 h at 16° C. and 120 rpm, the recombinant protein culture was centrifuged at high speed, 4° C. and 12000 rpm and the bacteria precipitates were collected. The bacteria precipitates were resuspended with pre-cooled Lysis buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 10 mM imidazole, pH=8.0), and ultrasonically disrupted for 30 minutes (ultrasound 2s, interval 2s), centrifuged for 30 min at 4° C. and 7500 rpm. The supernatant was collected and filtered with a 0.45 μm filter for later use. The supernatant was purified with Ni-NTA His bind resin purchased from QIAGEN company, eluted with elution buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 250 mM imidazole, pH=8.0) to obtain the target protein. The target protein was dialyzed with dialysis bag to remove imidazole, filtered by a 0.45 μm filter, and saved at −80° C. for later use. The SDS-PAGE results of protein D are shown in  FIG. 1 . 
     Preparation of Protein E 
     The codon of the gene encoding Mccp protein E (GenBank: CP017125.1, M1601_01955, the 97-2109 nucleotide sequence from the 5′end, hypothetical protein) was optimized and ligated to the pET30a(+) restriction enzyme sites between NdeI and XhoI to express the protein set forth in sequence SEQ ID No.5. The obtained recombinant expression plasmid was transformed into  Escherichia coli  BL21 (DE3) to obtain recombinant bacteria. The monoclonal recombinant bacteria was inoculated in a LB liquid medium (containing 50 μg/mL kanamycin), cultured at 37° C. and 200 rpm to OD 600  of 0.6. IPTG having a final concentration of 0.05 mM was added and induced for 12 h at 16° C. and 120 rpm, the recombinant protein culture was centrifuged at high speed at 4° C. and 12000 rpm, the bacteria precipitates were collected and resuspended with pre-cooled Lysis buffer (50 mM Na 2 HPO 4, 0.3  M NaCl, 10 mM imidazole, pH=8.0), and ultrasonically disrupted for 30 minutes (ultrasound 2s, interval 2s), centrifuged at 4° C. and 7500 rpm for 30 min. The supernatant was collected, and filtered with a 0.45 μm filter for later use. The supernatant was purified with Ni-NTA His bind resin purchased from QIAGEN company, eluted with elution buffer (50 mM Na 2 HPO 4 , 0.3 M NaCl, 250 mM imidazole, pH=8.0) to obtain the target protein. The target protein was dialyzed with a dialysis bag to remove imidazole, filtered with a 0.45 μm filter, and saved at −80° C. for later use. The SDS-PAGE results of protein E are shown in  FIG. 1 . 
     Example 2 
     Three healthy New Zealand white rabbits each were immunized with the protein A, protein B, protein C, protein D, and protein E prepared in Example 1, and polyclonal antibodies were prepared. In the first immunization, protein A, protein B, protein C, protein D and protein E were respectively mixed with Freund&#39;s complete adjuvant in equal volume and emulsified. Rabbits were subcutaneously immunized at multiple points. Each rabbit was immunized with about 800 μg recombinant protein. The second immunization was carried out 2 weeks later, the third immunization was carried out 3 weeks later, and the fourth immunization was carried out 5 weeks later. The emulsions of protein A, protein B, protein C, protein D and protein E respectively mixed with Freund&#39;s incomplete adjuvant were used to enhance immune response. Each rabbit was immunized with 600 μg of recombinant protein. Blood was collected from the ear vein to separate the serum on the 7th day after the last immunization. The prepared polyclonal antibodies of protein A, protein B, protein C, protein D, and protein E were diluted at a dilution ratio of 1:80,000 and western test was carried out with the corresponding recombinant protein, and the results were all positive. The results showed that protein A, protein B, protein C, protein D and protein E can induce the body to produce antibodies at a high level. The polyclonal antibody to the recombinant protein reacts well with Mccp whole bacteria protein in western test. The prepared recombinant protein reacts well with Mccp-infected serum and immune serum in western test, indicating that the recombinant protein has good antigenicity and immunogenicity. 
     Example 3 
     The protein A, protein B, protein C, protein D, and protein E prepared in Example 1 were aseptically mixed at 1:1:1:1:1. The final concentration of protein A, protein B, protein C, protein D, and protein E in immunoprotein combination solution (27.88 mL) was 65 μg/mL; 0.54 mL of saponins having a final concentration of 2.0 mg/mL was added. The mixture was allowed to stand at 4° C. for 24 h, shaken once every 4 h during the period. 0.28 mL of 1% thimerosal aqueous solution was added at 1% of total volume of antigen to obtain a mixture of antigen saponins. 28.44 mL of ISA 201 VG adjuvant was taken and 28.44 mL of antigen saponins mixture was added to mix with the ISA 201 VG adjuvant. The mixture obtained was emulsified for 20 minutes with a small emulsifying machine Fluko at gear 1 (5000 rpm). As a result, a sterile slightly viscous water-in-oil-in-water type (w/o/w) vaccine was obtained. 
     Example 4 
     Ten (10) healthy goats (Mccp antibody, antigen negative) aged 8-9 months were divided into a vaccine group and a control group, each with 5 goats. Each goat in the vaccine group was injected 2 mL of the vaccine in Example 3 in the neck muscle. Each goat in the control group was injected the same amount of PBS. The goats were observed continuously for 14 days. The results show that after the vaccine of the present disclosure is injected, all the injected goat are healthy, the goat have no symptoms such as coughing, sneezing, no obvious lumps at the injection site, no obvious adverse effects, which indicates that the vaccine is safe. 
     Example 5 
     After immunization in Example 4, the non-anticoagulative blood was collected weekly, and the serum was separated. The Mccp antibody level in serum was determined by indirect ELISA method (coated with Mccp whole bacterial proteins) The operation method is outlined as follows: ultrasonic lysis of Mccp M1801 whole bacteria proteins were diluted to 1.6 μg/mL with 0.05M pH 9.6 carbonate coating solution, 100 μL per well, the ELISA plate was sealed, and incubated at 37° C. for 1 h and then incubated overnight at 4° C. 300 μL PBST wash solution was added to each well to wash 3 times at room temperature and the plate wells was patted dry. 100 μL of solution of 5% dry skim milk powder was added to each well. The plate was sealed for 2 h at 37° C., washed 3 times, patted dry. The primary antibody was incubated. The serum to be tested was diluted with blocking solution at the ratio of 1:200. Negative and positive controls were created and at least two replicates for each sample were made, 100 μL per well. The primary antibody was incubated at 37° C. for 1 h, washed 4 times, patted dry. A HRP-conjugated rabbit anti-goat IgG secondary antibody was diluted with blocking solution at a ratio of 1:5000, 100μL for each well, incubated for 1 h at 37° C., washed 4 times and patted dry. 100μL of TMB was added to each well in dark condition and color reaction was perform at 37° C. for 10 min. 100 μL of 2 M H2504 stop solution was added to each well, the solution turned from blue to yellow. The OD value at wave length 450 nm in the microplate reader was read to detect the antibody level in serum. As a result, the Mccp antibodies of the control group are all negative. The subunit vaccine provided by the present disclosure immunized animals can induce higher levels of antibodies ( FIG. 2 , Table 1, wherein 057, 059, 063, 073, and 105 are animal numbers). 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Mccp antibody level in serum for the goats after the immunization 
               
               
                 of subunit vaccine provided by the present disclosure 
               
            
           
           
               
               
            
               
                   
                 Animal No. 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 057 
                 059 
                 063 
                 073 
                 105 
               
            
           
           
               
               
            
               
                 Immu. day 
                 OD Value 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 day 0 
                 0.147 
                 0.189 
                 0.158 
                 0.222 
                 0.136 
               
               
                 day 7 
                 0.182 
                 0.313 
                 0.232 
                 0.274 
                 0.159 
               
               
                 day 14 
                 0.168 
                 0.597 
                 0.214 
                 0.244 
                 0.164 
               
               
                 day 21 
                 0.300 
                 0.516 
                 0.802 
                 0.400 
                 0.365 
               
               
                 day 28 
                 0.226 
                 0.544 
                 1.149 
                 0.312 
                 0.562 
               
               
                 day 35 
                 0.215 
                 0.498 
                 1.887 
                 1.350 
                 1.044 
               
               
                   
               
            
           
         
       
     
     Example 6 
     Immune and Protective Effect of Vaccine 
     Healthy goats (Mccp antibody, antigen negative) aged 8-9 months were divided into an inactivated vaccine group, a subunit vaccine group and a challenge control group, each with 5 goats, and 4 goats in blank control group. 
     Inactivated vaccine group: inactivated vaccine was injected intramuscularly at the neck on day 0 and day 14 of the experiment, 2 mL for each goat. The method for preparing the inactivated vaccine includes: the Mccp M1801 strain was proliferated and cultured in the modified MTB medium (glucose 2 g/L, sodium pyruvate 2g/L, PPLO broth 21 g/L, yeast extract 100 mL/L with 25% mass percentages, phenol red 2.5 mL/L with 1% mass percentages, horse serum 200 mL/L, 100000 IU penicillin, pH 7.4-7.6), the PBS buffer (0.01M, pH7.2-7.4) was added, and the mixture obtained was centrifuged 3 times, the concentration of the mixture is adjusted to 300 μg/mL, the final concentration of 2 mg/mL saponin was added, and the mixture obtained was inactivated for 24 h, and mixed with the ISA 201 VG adjuvant at a ratio of 1:1.1 and emulsified to prepare a inactivated whole-bacteria vaccine. 
     The subunit vaccine group: the vaccine prepared in Example 3 was injected intramuscularly at the neck on day 0 and day 14 of the experiment, 2 mL for each goat. 
     The challenge control group: PBS was injected intramuscularly at the neck on day 0 and day 14 of the experiment, 2 mL for each goat. 
     The blank control group was fed normally without any treatment. 
     On day 35 of the experiment, the test goats in inactivated vaccine group, the vaccine group and the challenge control group were challenged with Mycoplasma capricolum subsp. capripneumoniae, the culture of strain M1801 (preserved in Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, see the document: Wu Yaqin, Liu Baohong, Yuan Ting, etc. Identification and application of specific molecular target for detection of Mycoplasma capricolum subsp. capripneumoniae. Chinese Veterinary Science. 2020, 50 (10)): 1257-1262), and the challenge dose was 10 9  CCU/mL, the challenge approach was nasal spray of 2 mL for two consecutive days, following injection of 6 mL of bacteria culture through the trachea after 2 days. The results show that some goats have fever and develop symptoms such as cough, sneezing, depression, decreased food intake, etc. The vaccine of the present disclosure can significantly alleviate fever and clinical symptoms after immunization. The blank control group and the immunized animals immunized with subunit vaccine of the present disclosure survive 100%, the inactivated vaccine group survives 80%, and the challenge control group survives 40%. The results show that the vaccine of the present disclosure has good protective effect in the goats infected with Mccp, it can completely resist the attack of vicious Mccp and dramatically reduce the disease incidence and mortality of the goats. The vaccine of the present disclosure can effectively reduce the colonization of Mccp in the lungs of goats. The pathological changes by necropsy of the goats of the challenge control group are mainly pleural effusion, adhesion between lung and chest wall, lungs consolidation, caseous necrosis, gelatum exudates and other typical lesions of CCPP. There are no goats dying in the vaccine group. After the completion of the experimental observation period, there is no obvious pathological changes, only a few goats have slight pathological changes. The vaccine and inactivated vaccine of the present disclosure can significantly reduce lung and other tissue lesions ( FIG. 3 ), and the subunit vaccine of the present disclosure has better effect in improving lung lesions than the inactivated vaccine. Histopathological observation shows that the goats of the challenge control group mainly shows lymphofollicular hyperplasia in the lung tissue, hyperplasia in the alveolar epithelial cells, infiltration in inflammatory cells, fibroblast hyperplasia, fibrin exudation and other diseases. The serious pathological damage of the lung is detected in the challenge control group, and the subunit vaccine group can significantly reduce the pathological damage of the lung. The results show that the immune protection effect of the subunit vaccine of the present disclosure is better than that of the inactivated vaccine. 
     The above are only the preferred embodiments of the present disclosure. It should be pointed out that for ordinary persons skilled in the art, a number of improvements and modifications can be made without departing from the principle of the present disclosure, and these improvements and modifications should also be regarded as the protection scope of the present disclosure.