30th World Congress on Vaccines and Immunization
Beijing Academy of Agricultural and Forestry Sciences, China
Title: Avian Meta Pneumo Virus subgroup C attenuates the immune system of SPF chickens and enhances the susceptibility to Avibacterium paragallinarum
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Biography: Jun Chu
Statement of the Problem: Avian Meta Pneumo Virus (aMPV) and Avibacterium paragallinarum are frequently isolated from chickens with respiratory disease, especially Swollen Head Syndrome (SHS). However, the roles of these pathogens in co-infection remain unclear. We hypothesized that aMPV/C may enhance A. paragallinarum infection via suppression of host immunity.
Method: 21-days-old SPF chickens were inoculated with the aMPV/C JC strain or the A. paragallinarum Page serovar B strain/isolates and simultaneously vaccinated against Newcastle Disease Virus (NDV). The second experimental group of birds was inoculated with aMPV/C and A. paragallinarum simultaneously, inoculated with aMPV/C 3 days prior to A. paragallinarum infection, or inoculated with aMPV/C 3 days after A. paragallinarum infection; infection with aMPV/C or A. paragallinarum alone was also performed.
Findings: There was a significant decrease in the NDV antibody titer after aMPV/C infection. As for the second group, the body weights, immune organ indices, pathological changes, histopathological lesions, pathogenic loads, cellular and humoral immunity levels, the expression levels of IFNs, pro inflammatory cytokines, as well as anti-inflammatory cytokines were tested. Co-infection significantly reduced the body weight and thymus index of SPF chickens, significantly aggravating pathological changes and pathological damage. Simultaneously, prior infection with aMPV/C significantly decreased the cellular and humoral immunity, down-regulated the levels of the proinflammatory cytokine TNF-α and up-regulated the levels of the anti-inflammatory cytokine IL-4 in SPF chickens in response to A. paragallinarum.
Conclusion & Significance: In summary, aMPV/C infection suppresses the immune response by inhibiting cellular and humoral immune responses and altering the pro-/anti-inflammatory cytokine balance of SPF chickens, thereby enhancing the susceptibility of infected birds to A. paragallinarum.