Development and immunogenicity evaluation of attenuated Salmonella typhimurium delivering porcine Deltacoronavirus S1 gene.

Abstract

Porcine deltacoronavirus (PDCoV) is a swine enteropathogenic coronavirus that causes severe diarrhea in piglets, the development of novel vaccines is of great value in the prevention and control of PDCoV. Here, we selected attenuated Salmonella typhimurium SL7207 to deliver pVAX1-S1, resulting in the oral vaccine strain, SL7207 (pVAX1-S1). In immunized mice, SL7207 (pVAX1-S1) induced PDCoV-specific humoral IgG, IgA, neutralizing antibodies, mucosal sIgA, up-regulation of CD8T cells, and increased levels of Th1 cytokines (IFN-γ and IL-2). In piglets, SL7207 (pVAX1-S1) induced high levels of PDCoV-specific humoral IgG and neutralizing antibodies but no detectable IgA, and only low levels of mucosal sIgA. SL7207 (pVAX1-S1) also promoted T cell differentiation into CD4and CD8T cells, and increased the expression level of IFN-γ and IL-4 in peripheral blood. Challenge experiments in piglets showed SL7207 (pVAX1-S1) alleviated diarrhea, decreased fecal virus load and intestinal lesions compared with control groups. In conclusion, this study systematically evaluated the immunogenicity and feasibility of attenuated Salmonella typhimurium delivering PDCoV S1 gene, which will provide helpful reference information for further exploration of novel PDCoV oral vaccine.