| Porcine pleuropneumonia, called porcine contagious pleuropneumonia or haemophilus pleuropneumonia in the past,is a highly contagious and lethal respiratory disease with high morbidity and mortality.Actinobacillus pleuropneumoniae(APP), is the etiological agent of porcine pleuropneumonia. Previous study found that there are some homology gene fragments between A.pleuropneumoniae immune-related genes and Propionibacterium acnes genes, the homology rates are 93 ~ 100%.And there is efficient immune-cross-reaction between them by using serological detection. In order to investigate the prevention effect of P.acnes against A.pleuropneumoniae infection, several Gram-positive bacillus brevis were isolated from skin in human face. Observation of culture characters, biochemical tests and PCR identification were carried on.The results showed that 7 isolated strains were Gram-positive, Catalase test-positive, Nitrate test-positive, Indole test-positive, maltose-negative, sucrose-negative and Glucose test-negative.The 16SrRNA sequence that amplified by PCR was sequenced and compared with 16SrRNA sequence of P.acnes representative strains registered in GenBank,the homology rates reached more than 97%.Toxicity experiments have been carried out on the 7 isolated strains, the results showed the 7 isolated strains were no lethal to mice and pigs.The mice were respectively immunized with seven isolated strains of P. acnes. After 15 days,the mice were challenged with A.pleuropneumoniae serotype 1 and serotype 5 (10×LD50), then observed 1 week. The results showed that there was significant difference between P.acnes isolates in protection effect of against A.pleuropneumoniae infection, consist with anti-A.pleuropneumoniae antibody titer and the highest protection rate was 60%. The mice were injected with high titer of anti- P.acnes serum and respectively challenged with A.pleuropneumoniae serotype 1 and serotype 5 (10×LD50). The results showed that anti- P.acnes serum provided 100% protection against A.pleuropneumoniae infection,but it did not protect mice against E.col infection. The results indicated that P.acnes could provide good protection against A.pleuropneumoniae serotype 1 and serotype5 infection,and the protection effect was specific to mice infected with A.pleuropneumoniae serotype 1 and serotype 5As the main susceptible animals of A.pleuropneumoniae, healthy Duroc pigs of 5-week-old and about 10 Kg-weight were immunized with P. acnes of activated whole-cell. After 21 days,the pigs were immunized with PA again. In the 21st day after second immunization, the pigs were challenged with A.pleuropneumoniae serotype 1. Antibody titers of anti-P. acnes and anti-A.pleuropneumoniae were determinated after immunization. Temperature of the pigs were determinated before and after immunization. The serum of the immune pigs were obtained before infection of A.pleuropneumoniae. The antibody titers in serum were detected and the concentrations of IgG, IgM, IgA, IL-2, IL-4 and lysozyme were determinated.The results showed that there was no significant difference in temperature between immune group and control group before and after the immunization. There was significant difference in temperature between immune group and control group after infection.Temperature of control group increased significantly, reaching 38.5℃, 39.1℃, 39.1℃, 39.2℃, 39.2℃, 39.2℃after infection 1,3,4,5,6,7 days respectively.But the temperature of immune group did not increase. Compared with control group, the concentrations of IgG, IgM, IgA, IL-2, IL-4 in serum of immune group increased significantly.But there was no significant difference in lysozyme concentration between immune group and control group. After infection, the clinical symptoms of the control group were more serious than immune group. The average area of lung lesions from pigs in immune group were less than control group.The results showed that P. acnes plays significant role in immune protection from A.pleuropneumoniae serotype 1 infection. After immunized with P. acnes, the concentrations of IL-2 and IL-4 in serum of pigs increased significantly, indicating that P. acnes provide the specific humoral immunity protection against A.pleuropneumoniae infection, in addition , the cell-mediated immunity also play a role .In order to screen common antigen between P. acnes and A.pleuropneumoniae, SDS-PAGE electrophoresis analysis was used to compare the whole-cell proteins of P. acnes and A.pleuropneumoniae. By using anti- A.pleuropneumoniae specific antibody, Western-bloting was carried out on the whole-cell proteins of P. acnes to screen common antigen. Two bands with strong immune reaction were screened, confirming that the cross-reactive immunity exists between P. acnes and A.pleuropneumoniae and laying the foundation for further study of common antigens.Thus, P. acnes can used in the animals without obvious side effects and it will supply new ideas and new methods for to study on prevention of Porcine Pleuropneumonia.
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