Neuropathogenicity of newly isolated avian leukosis viruses from chickens with osteopetrosis and mesenchymal neoplasms.

Abstract

The prototype fowl glioma-inducing virus (FGVp) causes fowl glioma and cerebellar hypoplasia in chickens. In this study, we investigated whether a strain of avian leukosis virus (ALV), associated with avian osteopetrosis and mesenchymal neoplasms, is able to induce fowl glioma. We encountered avian osteopetrosis and mesenchymal neoplasms, including myxosarcoma and rhabdomyosarcoma, in Japanese native chickens used for both egg-laying and meat production. These birds were also affected by non-suppurative encephalitis and glioma in their brains. Four ALV strains (GifN_001, GifN_002, GifN_004, GifN_005) were isolated, and a phylogenic analysis ofSU showed that these isolates were classified into different clusters from FGVp and the variants previously reported. Whereas theSU shared a high identity (94.7%) with that of Rous sarcoma virus (strain Schmidt-Ruppin B) (RSV-SRB), the identity betweenTM of GifN_001 and that of FGVp was high (94.5%), indicating that GifN_strains may emerge by recombination between FGVp and other exogenous ALVs. Specific-pathogen-free chickens inoculatedwith GifN_001 revealed fowl glioma and cerebellar hypoplasia. These results suggest that the newly isolated strains have acquired neuropathogenicity to chickens.