Protective Immunity to Streptococcus sobrinus Induced by Nasal Immunization with Surface Protein Antigen

Abstract

In this study, mice were immunized nasally with surface protein antigen A (SpaA) of Streptococcus sobrinus and cholera toxin, as a mucosal adjuvant. Immunization of mice with SpaA plus cholera toxin elicited significant levels of SpaA-specific IgG and IgA in serum, and mucosal IgA antibodies in saliva. Antibody-forming cell analysis confirmed the antibody titers by detecting high numbers of SpaA-specific antibody-forming cells in spleen and salivary glands. Furthermore, CD4+ T cells from spleen and cervical lymph nodes exhibited significant proliferative responses when restimulated with SpaA in vitro. Importantly, mice that were nasally immunized with SpaA plus cholera toxin exhibited significantly reduced oral colonization by S. sobrinus. These results show that nasal administration of SpaA is potentially an effective nasal vaccine against dental caries and reduces the colonization of S. sobrinus in the oral cavity.