Heterologous expression, immunogenic evaluation, and subunit vaccine potential of the σC protein from the Xinjiang avian reovirus (ARV) strain xj-1.1

Avian reovirus (ARV) causes a range of diseases in poultry and results in significant economic losses for the poultry industry. To address the epidemic of ARV infection in yellow-feathered broilers in Xinjiang, this study conducted genetic and evolutionary analyses of a chicken-origin ARV field strain, designated ARV xj-1.1. The σC gene of this strain was expressed in vitro using both Escherichia coli and Pichia pastoris systems to compare expression characteristics and immunogenicity. Phylogenetic analysis revealed that ARV xj-1.1 belongs to genotype IV. The σC gene was successfully cloned and efficiently expressed in both prokaryotic and eukaryotic systems. After purification by nickel affinity chromatography, recombinant proteins pET-σC and GS115/pPIC9K-σC were obtained. Post-translational modification analysis indicated that neither recombinant protein exhibited glycosylation; however, phosphorylation levels differed, with values of 5.9% and 21.7%, respectively. Immunogenicity evaluation showed that both recombinant proteins induced high antibody titers in mice (1:51,200 for pET-σC and 1:102,400 for GS115/pPIC9K-σC). In immunized chicks, antibody levels peaked in the third week post-vaccination, and neutralizing antibody titers were significantly higher than in the control group (P < 0.01). Challenge experiments confirmed that vaccinated chicks exhibited no clinical symptoms or gross lesions, whereas the challenged controls displayed classic signs such as depression, swollen footpads, and visceral hemorrhage. These results demonstrate that the σC protein possesses strong potential as a subunit vaccine antigen. Although the eukaryotically expressed protein exhibited higher phosphorylation, the prokaryotically expressed σC protein induced a stronger neutralizing antibody response. This study provides a theoretical and experimental foundation for the development of regional ARV subunit vaccines and has important implications for controlling ARV infections among poultry in Xinjiang.