Immunogenicity of Salmonella vector vaccines expressing SBR of Streptococcus mutans under the control of a T7-nirB (dual) promoter system.

The purpose of the present study was to determine if a Salmonella vector expressing the cloned saliva-binding region (SBR) of Streptococcus mutans or SBR linked to the A2 and B subunits of cholera toxin (CTA2/B) under the control of both the T7 and nirB promoters (T7-nirB dual promoter) was more effective in inducing mucosal and systemic anti-SBR antibody responses than Salmonella clones expressing the same antigens but under the control of either the nirB or T7 promoter. Mice were immunized by the intranasal route on days 0, 18 and 320 with Salmonella enterica serovar Typhimurium strain BRD 509 containing one of six plasmids encoding SBR or SBR-CTA2/B under the control of the T7-nirB, T7, or nirB promoter. Serum, saliva and vaginal wash samples were collected throughout the experiment and assessed for antibody activity by ELISA. Evidence is provided that Salmonella clones expressing SBR or SBR-CAT2/B under the control of either the T7 or T7-nirB promoter induced a high and persistent mucosal and systemic anti-SBR antibody response. All Salmonella clones induced good anti-SBR responses following the boost on day 320.