An Oral Salmonella-Based Vaccine Expressing Viral M43 Protein Elicits Effective Immunity Against Murine Cytomegalovirus in Mice

Human cytomegalovirus (HCMV) is the leading viral cause of congenital infections and causes substantial morbidity and mortality in neonates and immunosuppressed people. Generating an anti-HCMV vaccine is required for preventing viral-associated diseases and infections. Oral vaccines based on attenuated <i>Salmonella</i> are an attractive solution, since these vaccines can be applied orally and easily for mass immunization. In this report, we constructed an attenuated <i>Salmonella</i> strain for the expression of the murine cytomegalovirus (MCMV) M43 protein and studied its ability as an oral vaccine candidate to stimulate antiviral immunity in mice. In orally immunized mice, the constructed vaccine, Sal-M43, elicited both serum IgG and mucosal IgA levels as well as T cell responses that were specific against the MCMV M43 protein. Moreover, the Sal-M43 immunization substantially inhibited the viral growth and infection in various organs and tissues and offered complete immune protection against both intraperitoneal and intranasal MCMV challenges. Thus, the <i>Salmonella</i>-based vaccine expressing the M43 antigen is effective in inducing anti-MCMV immunity. These findings also reveal the promise of developing oral anti-CMV vaccines based on attenuated <i>Salmonella</i> vectors expressing different viral antigens.