Identification of a unique Env protein mutation associated with ALV-J-induced hemangioma

ALV-J is a retrovirus which can induce diverse tumors in chickens. In this study, ALV-J was identified as the causative agent of both hemangioma and lymphocyte-like tumors in Chinese indigenous layer hens. Microscopic analysis revealed significant vascular endothelial cell hyperplasia across multiple tissues. Viral isolation and sequencing identified unique insertion mutations in the env gene and the 3'UTR. The env insertion was found it enhances viral replication in vascular endothelial cells. Furthermore, infection with the mutant virus led to significant upregulation of vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth receptor subtype 2 (VEGFR-2) expression. Collectively, these findings provide important insights into the molecular mechanisms underlying the enhanced pathogenicity of ALV-J.