The immune response to a B-cell epitope delivered by Salmonella is enhanced by prior immunological experience

Attenuated, heterologous strains of Salmonella have shown potential as live, recombinant vaccines against foreign pathogens. Studies in animal models have demonstrated that immunization with these heterologous vaccines is an effective way to induce both cellular and humoral immune responses against Salmonella and the foreign antigen. We studied the consequence of priming mice with Salmonella dublin 3-6 months before intraperitoneal administration with the same strain carrying a model B-cell epitope. Mice primed with the carrier strain demonstrated enhanced serum Ig titres against the foreign antigen. This immune enhancement was observed up to approximately 6 months after priming. These findings suggest that previous immunological experience with Salmonella does not limit the immune response to a foreign antigen carried by the same organism. In fact, prior exposure to Salmonella appears to enhance the response to the foreign antigen.