Attenuated live vaccine against mycoplasmal pneumonia of swine (MPS) and use thereof

Abstract

Disclosed are an attenuated live vaccine against mycoplasmal pneumonia of swine (MPS) and use thereof. In the present invention, pathological lung tissues of swine having typical Mycoplasma hyopneumoniae (Mhp) infection and no obvious other pathogenic infections are screened, and subcultured 100 generations in lungs of newborn rabbits; then, Mhp strains are isolated and serially subcultured in a medium; and the Mhp strain AN306 is obtained by screening a plurality of strains, which is deposited with an accession number: CCTCC NO. M2012431. Also disclosed is a live vaccine formulation against MPS prepared on the basis of the attenuated strain and comprising live attenuated strain, a pharmaceutically acceptable carrier or excipient, and optionally an adjuvant and immunogens of other pathogens.

Claims

1. An attenuated Mycoplasma hyopneumoniae (Mhp) strain AN306, which is deposited in China Center for Type Culture Collection (CCTCC) with an accession number: CCTCC NO. M2012431.

2. A method comprising: administering an effective amount of the attenuated Mhp strain AN306 according to claim 1 to a pig in order to treat an Mhp infection.

3. An immunogenic composition against mycoplasmal pneumonia of swine (MPS), comprising the attenuated Mhp strain AN306 according to claim 1.

4. The immunogenic composition against MPS according to claim 3, further comprising a pharmaceutically acceptable carrier or excipient.

5. The immunogenic composition against MPS according to claim 3, further comprising an immunization adjuvant.

6. The immunogenic composition against MPS according to claim 3, further comprising an immunogen of an additional pathogen.

7. The immunogenic composition against MPS according to claim 6, wherein the additional pathogen includes at least one of viruses, bacteria, fungi, and parasites.

8. The immunogenic composition against MPS according to claim 7, wherein the additional pathogen is porcine circovirus, Haemophilus parasuis, porcine reproductive and respiratory syndrome virus, Mycoplasma hyorhinis, Mycoplasma hyosynoviae, or swine influenza virus.

9. The immunogenic composition against MPS according to claim 3, wherein the vaccine is in the form of an intrapulmonary injectable formulation, an intramuscular injectable formulation, an aerosol, an oral formulation, or a nasal drop.

10. A method for preparing the immunogenic composition against MPS according to claim 3, comprising combining an effective amount of the Mhp strain AN306 with a pharmaceutically acceptable carrier or excipient, an immunization adjuvant, and an immunogen of an additional pathogen.

11. The method according to claim 2, wherein the effective amount of the attenuated Mhp strain AN306 is administered in the form of an intrapulmonary injectable formulation, an intramuscular injectable formulation, an aerosol, an oral formulation, or a nasal drop.

Description

DETAILED DESCRIPTION

(1) The present invention is further described and discussed with reference to specific embodiments; however, the present invention is not limited thereto.

(2) For the purpose of illustrating the screening, subculture, and identification of the live vaccine strain against MPS according to the present invention as well as the immunogenicity and safety of the live vaccine strain, and confirming that by using the live vaccine formulations against MPS according to the present invention that are inoculated through various routes of immunization and contain various adjuvants and immunogens of additional different pathogens, the Mhp infection can be effectively prevented and the incidence of MPS can be controlled, the following experiments and preparations are conducted.

Example 1: Acquisition of Mhp AN306

(3) Acquisition of Virulent Strain:

(4) In 1975, Jiangsu Academy of Agricultural Sciences carried out the screening of virulent and pathogenic Mhp strains by collecting the typical MPS affected tissue samples from agricultural universities and national and provincial academy of science in more than 20 provinces all over the country, according to the requirements of the Ministry of agriculture. A total of over 2 hundreds of suspected MPS affected lung tissue samples were collected all over the country, from which 10 samples having typical Mhp infection and no obvious other pathogenic infections were screened out, and lyophilized and stored as virulent MPS tissular strains. Also, the tests of disease development upon challenge and attenuation by serial subculture were conducted in animals.

(5) The selected 10 virulent tissular strains were inoculated to healthy and susceptible pigs of local variety by nasal drip, and after challenge, the test animals were observed to have clinical symptoms of MPS such as cough, shortness of breath, asarcia, and dog sitting, and typical shrimp meat like consolidation was found in the apical and cardiac lobes of the lungs of the animals after necropsy. 3 strains that have the most potent virulence and the highest immunogenicity were selected from the 10 virulent tissular strains for subculture, according to the latency prior to attack, the clinical symptoms, the incidence rate, the severity of the disease, and the titer of the haemagglutination antibody of the challenged animals.

(6) Attenuation by Subculture:

(7) The virulent tissular strains were inoculated to healthy newborn rabbits by intrapulmonary injection. The lung tissues of challenged rabbits were collected, homogenized, and then inoculated to healthy newborn rabbits. The subculture was conducted as such. Only 1 of the 3 virulent strains was successful in subculture in rabbits. During the subculture of the strain, a parallel subculture group was additionally set respectively at Generations 20, 40, 60, and 80, and the strain was serially subcultured 100 generations.

(8) Mhp was isolated from the generation 100 lung tissue of the newborn rabbits by “affected lung block immersion method”. Specifically, the animals were sacrificed by bleeding, the lung tissue was aseptically removed, cut into small blocks with a size of ½ sesame, washed with Hank's solution, and immersed in KM2 medium. Antibiotics were added, and incubation was continued at 37° C. The change in pH and the turbidity were observed every day. When the pH had an obvious change (dropped to 7.0-6.8) and homogenous turbidness was formed (at about 48 hrs), the culture was serially subcultured 4-5 generations by inoculating at a ratio of 1:5, and then subcultured by inoculating at a ratio of 1:10. After staining following Gurr's modified Giemsa staining method and examination under oil immersion microscope, the isolated microorganism was found to have a polymorphic mycelium, and have the typical morphological features of Mhp, and identified to be Mhp by particle agglutination reaction and metabolism inhibition test with standard Mhp positive serum. The isolated Mhp was purified by three times of solid cloning, identified again, lyophilized and stored.

(9) The lyophilized and stored Mhp strain of generation F100 was revived, and continuously attenuated by serially subculturing in KM2 medium by inoculating at a ratio of 1:10. The strain was identified by PCR every five generations, and lyophilized and stored every 20 generations. The strain of generations F100, F140, F180, F220, F240, F280, and F320 was additionally subcultured different generations.

(10) TABLE-US-00001 TABLE 1 Preliminary screening of attenuated strains Growth during in-vitro Disease development of Strain Generation culture challenged animals Remark AN301 F240 Grow well, 10.sup.9 CCU/mL No apparent lesion and no pathological changes AN302 F110 Grow slowly, — Loss in subculture 10.sup.2 CCU/mL in medium AN303 F280 Grow well, 10.sup.8 CCU/mL No apparent lesion and no pathological changes AN304 F240 Grow well, 10.sup.7 CCU/mL No apparent lesion and no pathological changes AN305 F32 — — Loss in subculture in newborn rabbits AN306 F280 Grow well, 10.sup.9 CCU/mL No apparent lesion and no pathological changes AN307 F140 Grow well, 10.sup.8 CCU/mL No apparent lesion and mild inflammatory pathological changes AN308 F300 Grow well, 10.sup.9 CCU/mL No apparent lesion and no pathological changes AN309 F360 Grow well, 10.sup.8 CCU/mL No apparent lesion and no pathological changes AN310 F12 — — Loss in subculture in newborn rabbits AN311 F260 Grow slowly, No apparent lesion and no 10.sup.4 CCU/mL pathological changes AN312 F64 — — Loss in subculture in newborn rabbits

(11) The various strains subjected to subculture was comprehensively analyzed in terms of subculture and growth abilities, and virulence, and 5 strains AN301, AN303, AN306, AN308, AN309 that grow rapidly, and have high titer and attenuated virulence were selected for the following virulence recovery test and immunoprotection assay.

(12) Virulence Recovery Test of Attenuated Strain:

(13) The screened strains were subjected to consecutive five-generation virulence recovery test. 3 mL of 10.sup.8 CCU/mL Mhp culture was injected to the tracheas of 3 healthy pigs. The animals were isolated and raised for 28 days, subjected to necropsy to observe whether lesions occur to the lungs of the test pigs, and pathologically sectioned to observe whether inflammatory changes occur. The apical and cardiac lobes and 5-7 g anterior portion of the diaphragm of the lung were aseptically removed, chopped, and ground into a paste. 100 mL of Hank's solution containing 1000 IU/mL penicillin was added, to formulate a 50 g/L lung suspension. The supernatant was aspirated and inoculated to 3 healthy pigs in an amount of 3 mL/pig on the same day. The strain was subcultured 5 generations as such, to observe whether virulence recovery takes places.

(14) TABLE-US-00002 TABLE 2 Screening of attenuated strains by virulence recovery test Strain AN301 AN303 AN306 AN308 AN309 Generation F240 F280 F280 F300 F360 1.sup.st test 0/3 0/3 0/3 0/3 0/3 2.sup.nd test 0/3 0/3 0/3 0/3 0/3 3.sup.rd test 0/3 0/3 0/3 0/3 0/3 4.sup.th test 1/3 0/3 0/3 0/3 0/3 5.sup.th test 2/3 0/3 0/3 0/3 0/3

(15) The results show that the strain AN301 leads to inflammatory pathological changes of the lung of the animals at the fourth and fifth generations; and no obvious clinical symptoms of MPS are observed for the animals experiencing 5 inoculations of the remaining 4 strains, no consolidation of the lung is found after necropsy, and no inflammatory pathological changes such as lymphadenosis and lymphocyte and macrophage infiltration are found through pathological section examination, suggesting that the 4 strains subcultured are attenuated strains and have no virulence recovery ability.

(16) Immunoassay of Attenuated Strains:

(17) The screened strains were determined for immunogenicity and assayed for immunoprotection after challenge. Lyophilized strains were prepared and determined for the titer. The lyophilized strain was dissolved in a sterile phosphate buffer, and adjusted with the sterile phosphate buffer to have the same concentrations for test.

(18) Immunoprotection after challenge was assayed in healthy and negative Meishan pigs at an age of 5-7 days. The animals were grouped at random, each group having 5 animals. The animals in the immunization group was inoculated with 0.5 mL of attenuated strain (10.sup.5 CCU/pig) by intrapulmonary injection, and challenged by intratracheal injection with virulent Mhp strain 8 weeks after immunization, and subjected to necropsy 28 days later. A healthy control group and a challenged control group were additionally set.

(19) The serum antibody was detected by indirect hemagglutination test. 1:10“++” or above is determined to be positive.

(20) Score at necropsy: The animals were sacrificed 28 days after challenge, and the damage to the lung of the test pigs was scored following the method reported by MADEC and KOBISCH (1982). The whole lung includes a left cardiac lobe (LCL), a left apical lobe (LAL), a left diaphragmatic lobe (LDL), a right cardiac lobe (RCL), a right apical lobe (RAL), a right diaphragmatic lobe (RDL), and an accessory lobe (IL), and there are 7 lobes in total. The damage score of the lung is a sum of the damage scores for the dorsal surface and the ventral surface of the 7 lobes, and the total score is 28. Each lobe is scored 0-4 according to the injured area, where no damage is scored 0, 1-25% of area being damaged is scored 1, 26-50% of area being damaged is scored 2, 51-75% of area being damaged is scored 3, and 76-100% of area being damaged is scored 4.

(21) TABLE-US-00003 TABLE 3 Screening of attenuated strain by immunoassay Strain for immunization AN303 AN306 AN308 AN309 Healthy Generation Challenged control F280 F280 F300 F360 control Antibody − − + + − − Score for 0.24 ± 0.15 6.23 ± 3.39 3.01 ± 1.45 7.73 ± 4.38 11.10 ± 6.77 20.29 ± 5.42 lesions of lung of pigs

(22) It can be known from analysis of the results that the attenuated strain AN306 has a high immunogenicity, and a high protection effect as confirmed by the challenge test. Moreover, the test shows that the strain grows rapidly when cultured in vitro, and has a high titer and a high safety. Therefore, the strain AN306 is selected and used as the live vaccine strain, and the primary generation is F280.

Example 2: Culture of Attenuated Mhp Strain AN306

(23) Preparation of KM2 liquid medium (2050 mL): 1000 mL of Eagles medium, 10 g of hydrolyzed milk protein, 400 mL of swine serum, 20 mL of fresh yeast extract, 600 mL of Dulbecco phosphate buffer, 4,000,000 units of penicillin, and 3.5 mL of 0.4% phenol red, pH 7.4 7.6 (adjusted with 10 g/L NaOH).

(24) 1 vial of lyophilized attenuated Mhp strain AN306 was dissolved in 0.5 mL medium, and then 0.5 mL was inoculated in 4.5 mL medium, and incubated in a closed penicillin bottle at 37° C. When the color of the medium was changed from red to yellow, the culture was harvested in time, and inoculated into a fresh medium at a volume ratio of 1:10 for expansion culture. When the color of the medium was changed from red to yellow, the culture was harvested in time. Following this process, the strain was expansion cultured to 5000 mL and the culture was collected.

(25) A lyoprotectant was formulated, which comprised 1.5 g of gelatine, 12.5 g of sucrose, 100 mL of double distilled water, and was sterilized in an autoclave for 15 min at 115° C., and adjusted to pH 7.0 with sterilized 1% NaOH. The culture was harvested and determined for the CCU level. The culture to be inoculated was added with the sterilized lyoprotectant at a volume ratio of 3:2, mixed fully, and packaged in ampoules in an amount of 0.5 mL/ampoule. The ampoule with packaged culture therein was placed in a lyophilizer, and lyophilized. After lyophilization, the bottle was sealed with nitrogen, and stored at −40° C. 1 mL culture was removed for DNA extraction and identification by PCR.

(26) The culture of the attenuated strain AN306 thus obtained has a titer up to 10.sup.9 CCU/mL, and a production at liter level.

Example 3: Evaluation of Immunoprotection of Attenuated Live Vaccine Strain AN306 Against MPS Inoculated by Intrapulmonary Injection, and Comparison with Other Commercial Live and Inactivated Vaccines

(27) Preparation of Vaccines:

(28) Lyophilized attenuated live vaccine strain AN306 against MPS was dissolved in a sterile phosphate buffer, to formulate a vaccine solution in which the live vaccine has a titer of 2×10.sup.5 CCU/mL. Each animal was dosed 0.5 mL by intrapulmonary injection, that is, 10.sup.5 CCU/animal.

(29) Commercial live vaccines: In this test, the only two live vaccines against MPS available in the market were used as control live vaccines, that is, (1) the live vaccine against MPS manufactured by Jilin Zhengye Biological Products Co., Ltd, which is chick embryo yolk sac tissue containing lapinized attenuated Mhp strain, referred to as Commercial vaccine 1 hereinafter, and used following the operations described in the instruction of the vaccine; and (2) Zhibining (trade name), which is a in-vitro culture of attenuated Mhp strain 168, referred to as Commercial vaccine 2 hereinafter, and used following the operations described in the instruction of the vaccine.

(30) Commercial inactivated vaccine: In this test, two inactivated vaccines against MPS currently widely available in the market were used as control inactivated vaccines, that is (1) RespiSure (trade name), which is referred to as Commercial vaccine 3 hereinafter, and used following the operations described in the instruction of the vaccine; and (2) MycoFLEX (trade name), which is referred to as Commercial vaccine 4 hereinafter, and used following the operations described in the instruction of the vaccine.

(31) Immunization and Challenge of Animals:

(32) 70 healthy piglets were assigned to 7 groups at random, where Group G1 is a healthy control group, which is not immunized and challenged; Group G7 is a challenged control group, which is not immunized, but challenged; and Groups G2-G6 are groups with immunization of vaccines. The specific grouping and immunization method was as shown in a table below. The animals were immunized and then challenged. 8 weeks after immunization, the animals in Groups G2-G7 were challenged by intratracheal injection with virulent Mhp strain, and subjected to necropsy 28 days later.

(33) The test was the experiments were done in duplicate with two varieties including Suzhong pig and Topigs.

(34) Result:

(35) The MPS lesion in the lung of the animals was scored following the method described in Example 1. The result shows that the animals immunized with attenuated live vaccine strain AN306 against MPS have obviously lessened lesions in the lung, and the statistical difference is highly significant (P<0.01) compared with the challenged control group (by One-way ANOVA). The average disease index is obviously lower than that of the commercial live and inactivated vaccines (Commercial vaccine 1, P<0.01; Commercial vaccine 2, P<0.05; Commercial vaccine 3, P<0.01; and Commercial vaccine 4, P<0.01) currently widely available in the market, suggesting that the attenuated live vaccine strain AN306 can help the immunized animals to resist Mhp infection effectively, with a protection being superior to that of the vaccines widely available in the market.

(36) TABLE-US-00004 TABLE 4 Evaluation of immunoprotection of attenuated live vaccine strain AN306 against MPS inoculated by intrapulmonary injection, and comparison with other commercial live and inactivated vaccines Group No. G1 G2 G3 G4 G5 G6 G7 Group Healthy Live vaccine Commercial Commercial Commercial Commercial Challenged division control group vaccine 1 vaccine 2 vaccine 3 vaccine 4 control group group Route of — Intrapulmonary Intrathoracic Intrapulmonary Intramuscular Intramuscular — immunization injection injection injection injection injection Score of 0.50 ± 0.71 2.60 ± 0.84 5.00 ± 1.15 3.80 ± 1.14 10.60 ± 2.37 11.90 ± 3.41 21.90 ± 2.02 lesions of the lung (test 1) Score of 0.40 ± 0.70 2.80 ± 1.40 5.10 ± 2.18 4.00 ± 1.25  8.30 ± 2.41  6.00 ± 2.17 17.90 ± 3.21 lesions of the lung (test 2)

Example 4: Evaluation of Immunoprotection of Attenuated Live Vaccine Strain AN306 Against MPS Inoculated by Aerosol Immunization

(37) Preparation of Vaccine Diluent:

(38) Sterilized 5%-10% glycerol solution in deionized water, pH 6.8-7.5.

(39) Formulation of Vaccines:

(40) Lyophilized attenuated live vaccine strain AN306 against MPS was dissolved in the vaccine diluent, to formulate a vaccine solution in which the live vaccine has a titer of 10.sup.6 CCU/mL.

(41) Immunization and Challenge of Animals:

(42) 40 healthy and negative Topigs at an age of 5-7 days were assigned to 4 groups at random, where Group G1 is a healthy control group, which is not immunized and challenged; Group G2 is a group with aerosol immunizations of live vaccine strain AN306 in an amount of 0.5 mL (5×10.sup.5 CCU/animal), in which 2 weeks after the first immunization, the immunization is conducted again, followed by challenge; Group G3 is a commercial vaccine group, in which the commercial inactivated vaccine RespiSure against MPS currently widely available in the market is inoculated, the operation is following the instruction of the vaccine, and challenge is performed after immunization; and Group G4 is a challenged control group, which is not immunized, but challenged. The animals in Groups G2, G3, and G4 were challenged by intratracheal injection with virulent Mhp strain 8 weeks after the first immunization, and subjected to necropsy 28 days later.

(43) Result:

(44) The MPS lesion in the lung of the animals was scored following the method described in Example 1, specifically as shown in a table below. The result shows that the animals with aerosol immunization of attenuated live vaccine strain AN306 against MPS have obviously lessened lesions in the lung, the statistical difference is highly significant (P<0.01) compared with the challenged control group, and the lesions are obviously reduced compared with the case in which the commercial inactivated vaccine is inoculated (P<0.01), suggesting that the attenuated live vaccine strain can help the immunized animals to resist Mhp infection through aerosol immunization, with a protection being superior to that of the inactivated vaccine widely available in the market.

(45) TABLE-US-00005 TABLE 5 Evaluation of immunoprotection of attenuated live vaccine strain AN306 against MPS inoculated by aerosol immunization Group Division G3 G4 G1 G2 Commercial Challenged Healthy Live vaccine inactivated control control group group vaccine group group Score of 1.08 ± 0.27 3.83 ± 2.48 8.25 ± 4.14 20.34 ± 3.45 lesions of the lung

Example 5: Evaluation of Immunoprotection of Attenuated Live Vaccine Strain AN306 Against MPS Inoculated by Intramuscular Injection

(46) Preparation of Vaccines:

(47) Lyophilized attenuated live vaccine strain AN306 against MPS was used. The adjuvant used was a mixed adjuvant of 5 mg/mL carbomers and 30 mg/mL. Astragalus polysaccharides formulated in a sterile phosphate buffer. The lyophilized vaccine strain was dissolved in the adjuvant solution, to formulate a vaccine solution in which the live vaccine has a titer of 2.5×10.sup.5 CCU/mL.

(48) Immunization and Challenge of Animals:

(49) 40 healthy and negative Suzhong pigs at an age of 5-7 days were assigned to 4 groups at random, where Group G1 is a healthy control group, which is not immunized and challenged; Group G2 is a group immunized with a live vaccine by intramuscular injection in an amount of 2 mL (5×10.sup.5 CCU/animal), in which 2 weeks after the first immunization, the immunization is conducted again, followed by challenge; Group G3 is a commercial vaccine group, in which the commercial inactivated vaccine RespiSure against MPS currently widely available in the market is inoculated, the operation is following the instruction of the vaccine, and challenge is performed after immunization; and Group G4 a challenged control group, which is not immunized, but challenged. The animals in Groups G2, G3, and G4 were challenged by intratracheal injection with virulent Mhp strain 8 weeks after the first immunization, and subjected to necropsy 28 days later.

(50) Result:

(51) The MPS lesion in the lung of the animals was scored following the method described in Example 1, specifically as shown in a table below. The result shows that the animals immunized with attenuated live vaccine strain AN306 against MPS by intramuscular injection have obviously lessened lesions in the lung, the statistical difference is highly significant (P<0.01) compared with the challenged control group, and the lesions are obviously reduced compared with the case in which the commercial inactivated vaccine is inoculated (P<0.01), suggesting that the attenuated live vaccine strain can help the immunized animals to resist Mhp infection through intramuscular injection, with a protection being superior to that of the inactivated vaccine widely available in the market.

(52) TABLE-US-00006 TABLE 6 Evaluation of immunoprotection of attenuated live vaccine strain AN306 against MPS inoculated by intramuscular injection Group Division G3 G4 G1 G2 Commercial Challenged Healthy control Live vaccine inactivated control group group vaccine group group Score of 0.98 ± 0.43 4.57 ± 2.32 7.88 ± 4.78 20.65 ± 7.51 lesions of the lung

Example 6: Evaluation of Immunoprotection of Attenuated Live Vaccine Strain AN306 Against MPS Inoculated by Nasal Immunization

(53) Preparation of Vaccines:

(54) Fresh culture of Mhp strain AN306 having a titer of 5×10.sup.6 CCU/mL was used. A vaccine containing chitosan as an adjuvant was prepared as follows. Chitosan was dissolved in a 1% acetic acid solution, to formulate a stock solution containing 1% chitosan, which was adjusted to pH 6.5 with a 0.1 M NaOH solution. The stock solution containing chitosan was diluted with 0.1 M NaAc—HAc (pH 6.5) solution to give a final concentration of chitosan of 0.2%. The fresh culture of the Mhp strain AN306 was concentrated at 12000 rpm for 30 min, to collect the pellet, which was resuspended in 1 mL of 50 mM Na.sub.2SO.sub.4, to give a titer of 6.66×10.sup.6 CCU/mL. 5 mL of 0.2% chitosan solution was added with 1 mL of the Na.sub.2SO.sub.4 solution containing Mhp, and mixed by stirring. 660 μL of sodium tripolyphosphate (4 mg/mL) solution was added slowly with stirring, to obtain a cream white homogeneous suspension.

(55) Immunization and Challenge of Animals:

(56) 32 healthy and negative Topigs at an age of 5-7 days were assigned to 4 groups at random, where Group G1 is a healthy control group, which is not immunized and challenged; Group G2 is a group with nasal immunizations of live vaccine strain AN306 in an amount of 0.5 mL (5×10.sup.5 CCU/animal), in which 2 weeks after the first immunization, the immunization is conducted again, followed by challenge; Group G3 is a commercial vaccine group, in which the commercial inactivated vaccine RespiSure against MPS currently widely available in the market is inoculated, the operation is following the instruction of the vaccine, and challenge is performed after immunization; and Group G4 is a challenged control group, which is not immunized, but challenged. The animals in Groups G2, G3, and G4 were challenged by intratracheal injection with virulent Mhp strain 8 weeks after the first immunization, and subjected to necropsy 28 days later.

(57) Result:

(58) The MPS lesion in the lung of the animals was scored following the method described in Example 1, specifically as shown in a table below. The result shows that the animals immunized with attenuated live vaccine strain AN306 against MPS have obviously lessened lesions in the lung, the statistical difference is highly significant (P<0.01) compared with the challenged control group, and the lesions are obviously reduced compared with the case in which the commercial inactivated vaccine is inoculated (P<0.01), suggesting that the attenuated live vaccine strain can help the immunized animals to resist Mhp infection through nasal immunization, with a protection being superior to that of the inactivated vaccine widely available in the market.

(59) TABLE-US-00007 TABLE 7 Evaluation of immunoprotection of attenuated live vaccine strain AN306 against MPS inoculated by nasal immunization Group division G3 G4 G1 G2 Commercial Challenged Healthy control Live vaccine inactivated control group group vaccine group group Score of 0.21 ± 0.18 3.03 ± 2.68 8.72 ± 4.19 22.68 ± 4.67 lesions of the lung

Example 7: Evaluation of Immunoprotection of Divalent Vaccine of Attenuated Live Vaccine Strain AN306 Against MPS and Inactivated HPS Vaccine

(60) Preparation of Vaccines:

(61) Fresh culture of Mhp strain AN306 having a titer of 1×10.sup.6 CCU/mL was used.

(62) Fresh culture of HPS strain XX0306 serotype 5 (which is isolated by Veterinary Research Institute, Jiangsu Academy of Agricultural Sciences, has a good immunogenicity, and is proved through tests to be suitable for the preparation of inactivated vaccines of HPS, with the protection effect being good) was inactivated for 12 hrs with a formaldehyde solution having a final concentration of 0.2% after viable count. Then the inactivation was terminated by adding 0.2% sodium metabisulfite. The cells were concentrated to 1×10.sup.10 CFU/mL.

(63) The adjuvant used was a mixed adjuvant of 5 mg/mL carbomers and immunostimulating complex matrix (containing QuilA 500 μg/mL, cholesterol 100 μg/mL, and phospholipid 100 μg/mL) formulated in a sterile phosphate buffer.

(64) 0.5 mL of fresh Mhp culture was mixed fully with 0.5 mL of inactivated HPS strain XX0306 serotype 5 and the adjuvant at a ratio of 1:1:2, with which the animals were immunized.

(65) Immunization and Challenge of Animals:

(66) 30 healthy and negative Suzhong pigs at an age of about 10 days were assigned to 4 groups at random, where Group G1 is a healthy control group having 10 animals, which is not immunized and challenged, and in which 5 of 10 animals are subjected to necropsy at the same time with the animals in Groups G2 and G3, and the other 5 animals are subjected to necropsy at the same time with the animals in Groups G4 and G5; Group G2 is a group having 5 animals and immunized with the bivalent vaccine and challenged with Mhp, where the immunization is performed by intramuscular injection of 2 mL of the prepared bivalent vaccine (AN306 live vaccine: 2.5×10.sup.5 CCU/mL, inactivated HPS strain XX0306 serotype 5: 2.5×10.sup.9 CFU/mL), immunization is performed again 3 weeks after the first immunization, and challenge with virulent Mhp is conducted by intratracheal injection 8 weeks after the first immunization; Group G3 is a control group challenged with Mhp and having 5 animals, which is not immunized, but challenged in the same way as that for the animals in Group G2; Group G4 is a group having 5 animals and immunized with the bivalent vaccine and challenged with HPS, where the immunization is performed by intramuscular injection of 2 mL of the prepared bivalent vaccine (AN306 live vaccine: 2.5×10.sup.5 CCU/mL, inactivated HPS strain XX0306 serotype 5: 2.5×10.sup.9 CFU/mL), immunization is performed again 3 weeks after the first immunization, and challenge with virulent HPS is conducted by intraperitoneal injection 6 weeks after the first immunization; and Group G5 is a control group having 5 animals and challenged with HPS, which is not immunized, but challenged in the same way as that for the animals in Group G4.

(67) Result:

(68) (1) Protection Against Mhp Infection

(69) The animals were subjected to necropsy 28 days after challenge, and the MPS lesion in the lung of the animals was scored following the method described in Example 1. The results are shown in a table below and suggest that after immunization with the bivalent vaccine, the lesion in the lung is obviously lessened (P<0.01).

(70) (2) Protection Against HPS Infection

(71) The clinical symptoms of HPS infection include reduced appetite, roughened hair coats, ear and body skin flushing, increased nasal discharge, and respiratory distress, swelling joint, and failure to stand occurring in a later stage. At necropsy, pleural effusion, abdominal effusion, different degrees of pleural and peritoneal adhesion, swelling joint, increased mucus in articular cavity, bleeding lung, lymph node enlargement and other physiological changes may be found. The disease status of HPS infection in the animals in each group was determined based on the above criteria, and outlined in a table below. The results suggest that after immunization with the bivalent vaccine, the incidence of HPS infection in the animals are obviously lessened (P<0.01).

(72) TABLE-US-00008 TABLE 8 Evaluation of immunoprotection of divalent vaccine of attenuated live vaccine strain AN306 against MPS and inactivated HPS Live vaccine Group division G2 G4 Group immunized Group immunized with the bivalent G3 with the bivalent G5 G1 vaccine and Control group vaccine and Control group Healthy challenged with challenged challenged with challenged control group Mhp with Mhp HPS with HPS Immunization Not Immunized with Not immunized Immunized with Not immunized immunized the bivalent the bivalent vaccine vaccine Challenge with Not Challenged Challenged Not challenged Not challenged Mhp challenged Challenge with Not Not challenged Not challenged Challenged Challenged HPS challenged Score of MPS 0.54 ± 0.28 5.37 ± 4.36 19.81 ± 6.57 Not evaluated Not evaluated lesion Evaluation of 0/5 Not evaluated Not evaluated 1/5 5/5 disease status of HPS infection

Example 8: Evaluation of Immunoprotection of Divalent Vaccine of Attenuated Live Vaccine Strain AN306 Against MPS and Live PRRSV Vaccine

(73) Preparation of Vaccines:

(74) A mixed adjuvant containing 10 mg/mL chitosan and 10 mg/mL levamisole was formulated in a sterile phosphate buffer. Lyophilized live vaccine strain AN306 against MPS was dissolved in 1.5 mL adjuvant, to obtain a live vaccine against MPS as a solution having a specification of 1 dose (5×10.sup.5 CCU)/1.5 mL.

(75) Commercial live PRRSV vaccine (strain ATCCVR-2332) was dissolved in saline, to obtain a live PRRSV vaccine as a solution having a specification of 2 dose/mL.

(76) The two vaccine solutions were mixed at a ratio (by volume) of 3:1, with which the animals were immunized by inoculating 2 mL per animal, that is, 1 dose of the live vaccine against MPS and 1 dose of the live PRRSV vaccine.

(77) Immunization and Challenge of Animals:

(78) 30 healthy and negative Suzhong pigs at an age of about 10 days were assigned to 4 groups at random, where Group G1 is a healthy control group having 10 animals, which is not immunized and challenged, and in which 5 of 10 animals are subjected to necropsy at the same time with the animals in Groups G2 and G3, and the other 5 animals are subjected to necropsy at the same time with the animals in Groups G4 and G5; Group G2 is a group having 5 animals and immunized with the bivalent vaccine and challenged with Mhp, where the immunization is performed by intramuscular injection of 2 mL of the prepared bivalent vaccine, immunization is performed again 2 weeks after the first immunization, and challenge with virulent Mhp is conducted by intratracheal injection 8 weeks after the first immunization; Group G3 is a control group challenged with Mhp and having 5 animals, which is not immunized, but challenged in the same way as that for the animals in Group G2; Group G4 is a group having 5 animals and immunized with the bivalent vaccine and challenged with PRRSV, where the immunization is performed by intramuscular injection of 2 mL of the prepared bivalent vaccine, immunization is performed again 2 weeks after the first immunization, and challenge with virulent PRRSV is conducted by intraperitoneal injection at the neck 6 weeks after the first immunization; and Group G5 is a control group having 5 animals and challenged with PRRSV, which is not immunized, but challenged in the same way as that for the animals in Group G4.

(79) Result:

(80) (1) Protection Against Mhp Infection

(81) The animals were subjected to necropsy 28 days after challenge, and the MPS lesion in the lung of the animals was scored following the method described in Example 1. The results are shown in a table below and suggest that after immunization with the bivalent vaccine, the lesion in the lung is obviously lessened (P<0.01).

(82) (2) Protection Against PRRSV Infection

(83) After challenge, the animals were observed and detected for the body temperature every day. The criteria for determining the attack of PRRSV infection include consecutive 3 or more days of high fever of 41° C. or higher, lassitude, reduced appetite, occurrence of conjunctivitis and respiratory symptoms such as cough and shorthness of breath, death, and lamellar consolidation of the lung at necropsy. The results show that the animals in the control group challenged with PRRSV all suffer from the disease, and two of them are dead; and the animals in the group immunized with the bivalent vaccine have no obvious symptoms of the disease and all survive.

(84) TABLE-US-00009 TABLE 9 Evaluation of immunoprotection of divalent vaccine of attenuated live vaccine strain AN306 against MPS and live PRRSV vaccine Group division G2 G4 Group immunized Group immunized with the bivalent G3 with the bivalent G5 G1 vaccine and Control group vaccine and Control group Healthy challenged with challenged challenged with challenged control group Mhp with Mhp PRRSV with PRRSV Immunization Not Immunized with Not Immunized with the Not immunized immunized the bivalent immunized bivalent vaccine vaccine Challenge with Not Challenged Challenged Not challenged Not challenged Mhp challenged Challenge with Not Not challenged Not challenged Challenged Challenged PRRSV challenged Score of MPS 0.22 ± 0.15 5.05 ± 3.89 23.24 ± 3.72 Not evaluated Not evaluated lesion Evaluation of 0/5 Not evaluated Not evaluated 0/5 5/5 disease status of PRRS