Significance of Marek's disease virus serotype 1‐specific phosphorylated proteins in Marek's disease skin lesions

Abstract

Summary Skin tissues were obtained from 12 chickens showing Marek's disease (MD) skin tumour induced by a very virulent MD/5 strain of Marek's disease virus serotype 1 (MDVl) and taken from 24 field broiler chickens (8 to 9‐weeks‐old) manifesting MD skin tumour. They were examined by the immunohistochemical method in order to examine the topographic expression of MDV1‐specific phosphorylated proteins (PP) and by the reverse‐transcription polymerase chain reaction following Southern hybridization to analyse their gene transcriptional activity. PP were massively detected and their gene transcripts were abundantly expressed only in the necrotic areas of some experimentally‐induced MD cutaneous lymphoma lesions. Strong PP‐positive cells were degenerate or necrotic lymphoblasts. The other field or experimentally‐induced MD cutaneous lymphoma lesions, even those consisting almost completely of tumorous lymphoblasts, had only a few PP‐positive lymphoid cells and few gene transcripts. Necrotic areas of feather pulp MD lymphoma lesions consisting mainly of degenerate or necrotic lymphoblasts and cytolytic feather follicle epithelium (FFE) were also strongly positive for PP. PPs and their gene transcripts were detectable only in the cytolytically infected cells such as FFE and tumorous lymphoblasts converting to the abortic state.