| Highly pathogenic avian influenza(HPAI) is a notifiable disease to the World Organization for Animal Health(OIE) and is the list A animal disease in China. H5 subtype avian influenza virus(AIV) always caused outbreaks in poultry with huge economic losses for the poultry industry and threatened public health. Many countries, including China, effectively controlled the H5 HPAI by taking the measures of culling plus vaccination in poultry. However, H5 AIV still existed in nature and resulted in sporadic outbreaks in poultry with the compromised protection efficacy of the vaccine. Many factors may contribute to the decreased immune efficacy, beside the virus antigenicity shift. In this study, we investigated the immunosuppression caused by Avian Leukosis Virus(ALV) and Chicken Infectious Anemia Virus(CIAV) in order to give advice for implication of the vaccine and analyzing the reason of immune failure.To investigate the impact of ALV and CIAV on immune efficacy of the AI vaccines, one-day-old SPF chickens were infected with ALV(HLJR0901) or CIAV(WDNE110501) and then immunized AI vaccines at 21-day-old. The items, as following: HI antibody titers, stimulation index(SI) of peripheral blood monoculear cells(PBMCs) and splenic lymphocytes, CD4+/CD8+ of PBMCs and splenic lymphocytes, cytokine content and protective efficacy, will be evaluated on the schedule. And the normal one-day-old SPF chickens were immunized AI vaccines at the same day and all the items as mentioned above will be detected at the same time.The results showed that both ALV and CIAV suppressed the humoral immunity and decreased protection efficacy of the inactivated vaccine and the live vaccine. The peak of average HI antibody titers in the groups infected with ALV or CIAV were delayed and the titers were lower than the control groups only immunized with AI vaccine. The significant difference(p<0.05) of the HI antibody titers between the immunosuppression groups and the control groups were observed during two months detection. The peak of HI antibody titers in vaccinated group infected with ALV were 5.4 log2 on 35 days post-vaccinated with inactivated AI vaccine(Re-8), while the peak of HI antibody titers were 8.7 log2 on 28 days post-vaccination in the control group only vaccinated with Re-8. The peak of HI antibody titers in the group infected with ALV were 1.8 log2 on 42 days post-vaccinated with live AI vaccine(rLH5-8), while the peak of the HI antibody titers in the control group only vaccinated with rLH5-8 AI vaccine were 3.9 log2 on 35 days post-vaccination. On 21 days post vaccination, the HI antibody titers in Re-8 vaccination group infected with CIAV and the control group were 3.0 log2 and 7.8 log2, respectively, and the HI antibody titers in r LH5-8 vaccination group infected with CIAV and the control group were 1.2 log2 and 2.7 log2, respectively. The protection efficacy of the inactivated vaccine and the live vaccine in SFP chickens was decreased by the influence of the infection of ALV and CIAV. With the infection of ALV, the survival percent(100%) of the inactivated vaccine group and the live vaccine group was reduced to 90% and 0%, respectively, and the virus shedding percent(0%) were increased to 40% and 100%, respectively, in the inactivated vaccine group and the live vaccine group. With the infection of CIAV, the survival percent(100%) of the inactivated vaccine group and the live vaccine group was reduced to 80% and 0%, respectively, and the virus shedding percent(0%) were increased to 40% and 100%, respectively, in the inactivated vaccine group and the live vaccine group.The detection of cell-mediated immunity showed both ALV and CIAV suppressed the cellular immunity in the vaccination group. The infection ALV and CIAV reduced the value of CD4+/CD8+ and increased the value of IFN-γand IL-2.Our study demonstrated that both ALV and CIAV infection could significant impact on the immune efficacy of the inactivated and live AI vaccines, and CIAV infection could induce significant impact on live AI vaccines. This date suggested that it is necessary to pay more attention to the infection of ALV and CIAV in chickens during the control of the H5 HPAI by vaccination. |
