Abstract: Avian reticuloendotheliosis virus (REV) infection was reported to be very common in chicken flocks in China, but its economic impact on the poultry industry was not clear. The results in this study indicated that REV infection could severely inhibit immune reactions to inactivated vaccines against Newcastle disease virus (NDV) and avian influenza virus (AIV, H9 and H5) in 1-day-old broilers without maternal antibodies specific to REV. Four weeks after vaccination at 1 week of age, the hemagglutination inhibition (HI) antibody titers to NDV, AIV-H9 and AIV-H5 in REV-infected and control birds were: 1.58±1.69 vs 4.40±2.17(p<0.01), 0.71±1.60 vs 6.20±3.55(p<0.01)和0.54±1.44 vs 7.10±2.77(p<0.01). In birds with maternal antibodies, REV infection only slightly decreased antibody reactions to AIV-H9 and AIV-H5. Four weeks after vaccination, the HI titers to H9 and H5 in REV-inoculated and control broilers were 6.27±3.87 Vs 6.62±1.85(p>0.05)和6.72±3.9 Vs 7.00±2.51(p>0.05)) respectively。But inhibitory effect of REV infection on antibody reactions to NDV vaccine was still demonstrated. However, maternal antibody did very effectively protected birds from REV infection and its immunosuppressive effect. Four weeks after vaccination, the HI titers to NDV、AIV-H9和AIV-H5 in maternal antibody positive groups and control groups were 3.36±2.04 vs 1.58±1.69(p<0.01)，6.27±3.87 vs 0.71±1.60(p<0.01)和6.72±3.92 vs 0.54±1.44(p<0.01)。 This study demonstrated that early REV infection could interfere immune responses seriously to NDV and AIV vaccines, especially to AIV vaccine. The study also demonstrated that maternal antibodies from breeders was able to prevent or decrease the immunosuppression induced by REV infection in broilers.

Key words: reticuloendotheliosis virus, maternal antibody, immunosuppression, NDV, AIV