Role of O-linked glycosylation modification on internalization and replication of avian leukosis virus subgroup J.

Upon infection, viruses reprogram the host metabolic system to hijack metabolic resources for proliferation. Avian leukosis virus subgroup J (ALV-J), an avian oncogenic virus, poses significant challenges to the poultry industry. ALV-J infection upgrades monosaccharide N-acetylgalactosamine (GalNAc) and galactosyltransferase (core 1 β3-Gal-T) in DF-1 cells, both of which are crucial for O-linked glycosylation. Addition of GalNAc or overexpression of core 1 β3-Gal-T in DF-1 cells can promote ALV-J replication. ALV-J envelope protein (Env) undergoes complex post-translational modifications. Two O-linked glycosylation sites (T32 and T271) located in the head region of the ALV-J Env have been identified for the first time using liquid chromatography-mass spectrometry (LC-MS). The results of coimmunoprecipitation and flow cytometry indicate that mutations in T32 or T271 diminish ALV-J infection by affecting viral internalization, rather than attachment. The viral internalization efficiency was partially restored under a low pH environment. Incorporation of T32A and T271A into ALV-J led to significantly reduced replication capacity in vivo and viral shedding of the recombinant virus. These findings are valuable for our understanding of the roles of glycans in the ALV-J infection cycle, as well as for providing potential anti-ALV-J strategies.