Recombinant human adenovirus type 5-vectored vaccine expressing avian reovirus σC protein protects against prevalent genotype I avian reovirus in chickens.

Avian reovirus (ARV) is a globally important poultry pathogen causing substantial economic losses due to viral arthritis, enteritis and immunosuppression. Traditional vaccines based on the S1133 strain are less effective against circulating ARV variants due to genetic divergence. The σC protein is the primary antigen inducing neutralizing antibodies against ARV, making it a key target for vaccine development. Here, we constructed a recombinant human adenovirus type 5 (rHAdV5) vector vaccine expressing the σC protein of a prevalent Chinese ARV field strain (SDAU-1) and evaluated its safety, immunogenicity and protective efficacy in specific-pathogen-free (SPF) chickens. The recombinant vaccine rHAdV5-ARV-σC stably expressed the ∼36 kDa σC protein and maintained genetic stability over 13 serial passages. Immunization of 1-day-old SPF chickens with 10⁹ PFU rHAdV5-ARV-σC elicited robust ARV-specific IgG antibodies (peak titer 1:3500 at 7 days post-immunization) and significantly elevated serum IFN-γ and IL-4 levels (P < 0.05), indicating activation of both humoral and cellular immune responses. Following challenge with the SDAU-1 strain at 7 days of age, the vaccine provided an 86% (26/30) protection rate, markedly reduced viral shedding and tissue viral loads, and alleviated pathological lesions and immune organ damage compared to unvaccinated controls. These results demonstrate that rHAdV5-ARV-σC is a safe, immunogenic, and effective vaccine candidate against prevalent ARV strains, with high potential for controlling ARV infections in commercial poultry production.