The Anti-infectious Bursal Disease Virus Effect Of Recombinant Chicken Interferon Alpha/Chicken Interleukin-2Fusion Protein In Vivo And In Vitro

Interferon α (IFN-α) and interleukin2(IL-2) are important cytokines, and havesignificant activities of immune enhancement and anti-virus in chickens. To clarifyanti-virus activities of recombinant complex protein of ChIFN-α-Linker-ChIL-2invivo and in vitro, the following tests were performed in the present study:50%cytopathic effect inhibition (CPEI) of CEF cells was used to examine efficacy ofrChIFN-α-Linker-ChIL-2against vesicular stomatitis virus (VSV) and virulent strainLX of infectious bursal disease virus (IBDV). MTS method was employed todetermine the immune enhancement of the recombinant protein on both spleenic andperipheral lymphocytes.24-day-old SPF chickens were intramuscularly injected withrChIFN-α-Linker-ChIL-2at the pro-3d,0d, and24h post challeng with virulent strainLX of IBDV to screen the optimal time of inoculation.21-day-old SPF chickens wereintramuscularly injected and ocularly and nasally inoculated with rChIFN-α-Linker-ChIL-2at the0day post challeng with virulent strain LX of IBDV to determine theoptimal inoculation route.Results: The anti-virus activities of rChIFN-α-Linker-ChIL-2against VSV andIBDV in CEF cells were5.24105IU/mL and1.64104IU/mL, respectively. TherChIFN-α-Linker-ChIL-2was capable of distinctly improving the profilerationactivities of both spleenic lymphocytes and peripheral ones. The duration of typicalsymptoms, case fatality rate, secreting virus rate, and peripheral blood loading virusrate of chickens injected with rChIFN-α-Linker-ChIL-2at the0day post challengewere72h,20%,31.6%,31.6%, respectively; those of chickens injected3days beforechallenged were96h,30%,36.8%,36.2%, respectively; those of chickens injected24hours post challenge were120h,40%,42.1%,47.4%; those of positive control groupwere168h,70%,57.9%,52.6%, respectively. The durations of tissue loaded withIBDV in chickens injected with the recombinant complex protein pro-3d and0d post challenge was shorter than that of chickens injected24hours post challenge andpositive control group. The rate of tissue loaded with IBDV and specific antibodyconcentration against IBDV in chickens injected with the rChIFN-α-Linker-ChIL-20day post challenge were lower than other groups. The expression level of ChIL-2,ChIFN-γ, ChIL-6, ChIL-4, ChIFN-α, the profileration activities of both spleeniclymphocytes and peripheral ones, ratio of CD4+/CD8+T cells in chickens injected withrChIFN-α-Linker-ChIL-2were significant higher than other groups. In addition, Theduration of typical symptoms, case fatality rate, secreting virus rate, and peripheralblood loading virus rate of chickens intramuscularly injected with rChIFN-α-Linker-ChIL-2(96h,30%,54.5%,32%) were distinctly lower than those of chickensinoculated via ocular and nasal routes (120h,50%,81.8%,48%). The rate of tissueloaded with IBDV and specific antibody concentration against IBDV in chickensintramuscularly injected were lower than those of chickens inoculated via ocular andnasal routes. The expression level of ChIL-2, ChIFN-γ, ChIL-6, ChIL-4(7dpc~21dpc),ChIFN-α (7dpc~14dpc), the profileration activities of both spleeniclymphocytes and peripheral ones, ratio of CD4+/CD8+T cells in chickensintramuscularly injected were significantly higher than those of chickens inoculatedvia ocular and nasal routes.Conclusions: The rChIFN-α-Linker-ChIL-2protein has distinct anti-virus activitiesagainst IBDV and VSV, and enhances the profileration activities of both spleeniclymphocytes and peripheral ones in vitro tests. More importly, this recombinantcomplex protein is able to improve humoral and cellular immune responses and anti-virus efficacy in chickens through enhancing expression level of cytokines, theprofileration activities of lymphocytes and ratio of CD4+/CD8+T cells. The rChIFN-α-Linker-ChIL-2protein has the strongest anti-virus activities when it is intramuscularlyinjected to chickens simultaneously at the day post challenging with IBDV.