Systemic and Mucosal Immunizations with Fibronectin-Binding Protein FBP54 Induce Protective Immune Responses againstStreptococcus pyogenesChallenge in Mice

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Abstract
The purpose of this study was to examine the suitability of fibronectin-binding protein FBP54 as a putative vaccine forStreptococcus pyogenesinfections. When the distribution of thefbp54gene among the clinical isolates representing various M serotypes was tested by PCR and Southern blot assays, it was found that all of the strains possess this gene. Furthermore, a significant increase in immunoglobulin G (IgG) antibody titers against FBP54 was observed in sera from patients withS. pyogenesinfections compared with those from healthy volunteers (P< 0.005). Mice were immunized with FBP54 subcutaneously, orally, or nasally. An enzyme-linked immunosorbent assay revealed that antigen-specific IgG antibodies were induced in the sera of immunized mice, while high salivary levels of IgA antibodies were detected after oral and nasal immunizations. Mice subcutaneously or orally immunized with FBP54 survived significantly longer following the challenge withS. pyogenesthan did nonimmunized mice (P< 0.001). These results indicate that FBP54 is a promising vaccine for the prevention ofS. pyogenesinfections.