Humoral immunity is the primary means of heterologous Propionibacterium acnes vaccination against Actinobacillus pleuropneumoniae infection in pig

Objective: To analyze the immunoprotection of pigs by heterologous P. acnes vaccination against A. pleuropneumoniae infection, by vaccine and infection in pig. Methods: : 12 five-week-old healthy pigs were randomly divided into 2 groups, of which 1 group (n=6) was vaccinated twice with living P. acnes and the other group served as a non-vaccinated control (n=6). Both groups were experimentally infected with A. pleuropneumoniae (serotype 1, 5*10 7 CFU, CCVC 259) then the clinical symptoms and pathological changes were monitored. Results: : Compared to the control group, the vaccination group showed significantly reduced clinical symptoms and pathological changes. The P. acnes -vaccinated group showed a significant increase in the levels of specific serum antibody titer against A. pleuropneumoniae soluble antigen and serum IL-2 and IL-4 concentration. Conclusion: Immunization with heterologous P. acnes enabled an effective humoral immune response against A. pleuropneumoniae infection in pigs.