Immunogenic properties of the Salmonella atypical fimbriae in Balb/c mice.

Components of the Salmonella atypical fimbriae (Saf) were investigated for potential inclusion in a Salmonella vaccine. Recombinant histidine-tagged SafB chaperone complexed with SafD adhesin was expressed in Escherichia coli and purified. Starch microparticles were used, as an adjuvant and recombinant cholera toxin B subunit (rCTB) was included as a mucosal antigen-uptake enhancer. BALB/c mice were immunized orally or subcutaneously with SafB/D- and rCTB-conjugated microparticles and nasally or subcutaneously with SafB/D mixedwith rCTB. The systemic and mucosal immune responses were studied, and an oral challenge with Salmonella enteritidis
was performed. All immunized groups except that receiving oral immunization responded with high IgM-IgG titers to SafB/D. Analysis of the subclass ratio (IgG1/IgG2a + IgG2b) indicated a mixed Th1 and Th2 response, with Th1 predominating. The mucosal response, measured as specific IgA/total IgA (from fecal samples), was significantly greater than that in the untreated control group only in the group receiving intranasal immunization (P < 0.05). Spleens were removed 6 days after oral challenge and Salmonella colony-forming units (CFU) were counted. The group immunized subcutaneously with SafB/D- and rCTB-conjugated microparticles had significantly lower
CFU counts than the untreated control group (P < 0.05).