Recombinant chicken interferon-alpha inhibits the replication of exogenous avian leukosis virus (ALV) in DF-1 cells

Chickeninterferon alpha (ChIFNα) belongs to type I IFNs that are important antiviral cytokines. We investigated whether ChIFNα plays a role in avian leukosis virus (ALV) infections of chickens. Firstly, we explored the immune response to ALV in vivo by measuring cytokine expression profiles in the spleens and bursas of chickens during the late stages of ALV-J infection. The results indicated that ALV-J infection could induce a mixed Th1/Th2 cytokine response by elevating levels of both interleukin-2 (IL-2) and IL-10. In contrast, tumor necrosis factor alpha (TNF-α) levels decreased in the spleen while interferon beta (IFNβ) and Toll-like receptor 7 (TLR7) expression levels in the bursa increased significantly. This indicated that ALV-J stimulates a Type I IFN response. Next, we found that different ALV subgroups or strains up-regulated chicken IFN regulatory factor 3 (ChIRF-3) promoter activity, suggesting that ALV infection could trigger Type I IFNs pathway in vitro. Accordingly, we further investigated ChIFNα antiviral effects on ALV replication in DF-1 cells by successfully expressing recombinant ChIFNα in Escherichia coli (E. coli) strain BL21. The specific activity of the purified rChIFNα protein was determined to be 4 × 10⁷ U/mL. When added at 4000 U/mL, the recombinant protein restrained ALV replication as measured by decreases in viral protein p27 levels and mRNA expression. This new reagent may be useful for prophylactic and therapeutic drug design.