Effect Of RFPV-IFN-γ On Active Immunization Induced By Infectious Bursal Diease Live Vaccine In Chickens

Infections caused by IBD virus (IBDV) may exacerbate infections with other etiologic agents, and reduce the chicken's ability to respond to vaccination. The economic impact of IBD is influenced by strain of virus, susceptibility and breed of flock, intercurrent primary and secondary pathogens, and environmental and managemental factors. In addition to mortality, IBDV is immunosuppressive. In broilers, immunosuppression is denoted by a high prevalence of viral respiratory infections and elevated mortality due to airsacculitis and colisepticemia during the terminal third of the 6–8-week growing cycle. Both, broiler and pullet flocks may become refractory to live attenuated vaccines against respiratory diseases such as infectious bronchitis and Newcastle disease. The importance of IFNs in innate resistance is not only owing to their antiviral activity,but also to their ability to regulate the functions of cells of innate and adaptive immunity.It is synthesized and excreted by T lymphocyte activated by antigen or mitogen.IFN-II can boost the expression of MHC in APC,and so magnify humor immunity,but also be used singly to prevent diseases.Vaccination trials using live IBD MB43 vaccines were carried out in SPF chickens to evaluate the potential use of chickenγ-interferon expressed by recombinant fowlpox virus (rFPV-IFN-γ) .The results showed that broilers vaccinated with MB43+rFPV-IFN-γ(103U)or MB43+rIFN-γ(rIFN-γ,200U) produced ELISA antibody two weeks after immunization , about one week earlier than those vaccinated with MB43 lonely. Pathological findings could be seen in bursae, spleen, thymus, cecal tonsils in all groups, broilers injected with MB43+rFPV-IFN-γ(103U)or MB43+rIFN-γ(rIFN-γ,200U) performed better than others after challenge with the IBDV GX strain, the proportion of CD8+ T cell in three vaccinated group rise obviously ,but no apparent change in CD4+ T cell population one week after vaccination. the proportion of CD4+ CD8+ T cell in three vaccinated group rise obviously,no apparent differences among them two week after challenge with the IBDV Gx strain .These results showed that rFPV-IFN-γor rIFN-γcan enhance immune response in chickens vaccinated with MB43.