Analysis of transcriptional and translational activities of Marek's disease (MD) virus genes in MD central nervous system lesions in chickens

The expression of Marek's disease virus (MDV) gene products and transcripts was observed in tissues obtained from the central nervous system (CNS) of chickens experimentally infected with a very virulent strain (Md/5) of MDV, Many cells antigen-positive for MDV early gene products, but not for late gene products, were detected immunohistochemically in the necrotizing lymph omatous lesions, The positive signals were found only in necrotic or degene rated neoplastic lymphoblasts, Abundant transcriptional activity of MDV gen es was observed in the necrotizing lymphomatous lesions for immediate-early and early genes, but not for late ones, by the reverse-transcription polym erase chain reaction. In the non-necrotizing lymphomatous lesions, as well as non-suppurative ones, there were no or very few antigen-positive lymphob lasts for early and late genes, and little transcriptional activity of MDV genes, The necrotizing lesions of the lymphoma were associated with necroti zing vasculitis in which endothelial cells exhibited up-regulation of MHC c lass II antigen but no viral antigens, The present results indicate that on ly necrotizing lymphomatous lesions revealed abundant incomplete cytolytic cycle in MDV latently infected neoplastic lymphoblasts.