Immunogenicity of a Canine Parvovirus 2 Capsid Antigen (VP2-S1) surface-expressed on Lactobacillus casei

Canine parvovirus (CPV2) is one of the most virulent virus causing acute hemorrhagic enteritis and myocarditis in dogs. Infection mainly caused by the ingestion of virus through the mucosal route. Therefore, induction of mucosal immunity is essential in prevention of Canine Parvovirus (CPV2) infection. For safe and effective delivery of viral antigens to the mucosal immune system, a novel surface antigen display system for lactic acid bacteria using the poly-γ-glutamic acid synthetase A protein (pgsA) of Bacillus subtilis as an anchoring matrix was applied in order to display CPV2 antigen on the surface of the recombinant L. casei. Recombinant fusion proteins comprised of pgsA and the capsid protein (VP2-S1) showed stable expression in Lactobacillus casei. Surface localization of the fusion protein was verified by cellular fractionation analyses. Oral and nasal inoculations of recombinant L. casei into mice resulted in high levels of serum immunoglobulin G (IgG) and mucosal IgA, as demonstrated by ELISA using recombinant VP2-S1 proteins. Mice receiving intranasal immunization mounted higher antibody response than those receiving oral immunization. These results indicate that mucosal immunization with recombinant L. casei expressing CPV2 VP2-S1 protein on its surface provides an effective means for elicitation of strong antibody responses against CPV 2 VP2-S1.