Identification Of Fowlpox Virus (FPV) Integrated With Reticuloendotheliosisrus (REV) Gene And Study On Pathology Of Chickens Infected With REV-integrated FPV

To exame integration of reticuloendotheliosis virus (REV) gene in FPV genome, and study on the changes of the specific antibody against REV in FP flocks, the cytopathic effect in tissue cells infected by FPV and the histopathological changes in FP chickens. Fowlpox viruses (FPV) were isolated from 9 typical fowlpox (FP) clinical cases identified in Taian and surrounding areas, PCR to amplify REV-env,LTR sequence, ELISA to test the changes of the specific antibody against REV in FP flocks, electron microscopy to observe the morphous of FPV, and histopathological examination of FP chicken. The results showed that all of the 9 FPV isolates were integrated with REV gene, the tight sphere of the nucleus in infected tissue cells transformed into helix pattern, antibody levels against REV in FP chickens increased significantly. Besides common pathological changes caused by FP, severe atrophy of spleen, thymus, bursa and Reticuloendothelial cell proliferation were observed. Pathologic changes of liver, duodenum and lung were also found; In summary, integration of FPV with REV gene is common in chickens from Taian and surrounding areas, and the pathogenicity of the wild FPV strains integrated with REV gene has changed to some extent.CEF inoculated with one of the isolation FPV tested negative for REV by IFA. Furthermore, SPF chickens were inoculated with the virus. viraemia and antibody were dynamically detected in blood of inoculated chickens. After two weeks'infection, REV and antibody were consistently positive. The data suggest that in vivo testing of FPV by chick inoculation is a more sensitive test than in vitro testing in CEF. The histological changes, the ratios of immune organs to body weight, immune responses and cell apoptosis of the immune organs were dynamically observed also. The results showed that the infection caused severe atrophy of central immune organs, and especially, had a significant impacts on thymus. After two weeks'infection, the ratios of thymus to body weight in infected birds were significantly lower than that in the control birds (P<0.05). The immune organs revealed transient hyperemia, edema and gradually atrophy. The interstitial proliferation was found. It's mechanism would be the apoptosis with a certain degree of degenerative necrosis. The immune responses to ND vaccine were profoundly suppressed. In summary, the integration of FPV with REV gene can obviously change the pathogenicity and manifest some pathogenic characters of REV. REV provirus integrated into FPV provides additional transmission routes for the retrovirus by way of the infectious cycle of FPV.