Systemic immunization with an epitope-based vaccine elicits a Th1-biased response and provides protection against Helicobacter pylori in mice

Vaccine-mediated Th1-biased CD4+ T cell responses have been shown to be crucial for protection against Helicobacter pylori (H. pylori). In this study, we investigated whether a vaccine composed of CD4+ T cell epitopes together with Th1 adjuvants could confer protection against H. pylori in a mouse model. We constructed an epitope-based vaccine, designated Epivac, which was composed of predicted immunodominant CD4+ T cell epitopes from H. pylori adhesin A (HpaA), urease B (UreB) and cytotoxin-associated gene A product (CagA). Together with four different Th1 adjuvants, Epivac was administered subcutaneously and the prophylactic potential was examined. Compared to non-immunized mice, immunization with Epivac alone or with a Th1 adjuvant significantly reduced H. pylori colonization, and better protection was observed when an adjuvant was used. Immunized mice exhibited a strong local and systemic Th1-biased immune response, which may contribute to the inhibition of H. pylori colonization. Though a significant specific antibody response was induced by the vaccine, no correlation was found between the intensity of the humoral response and the protective effect. Our results suggest that a vaccine containing CD4+ T cell epitopes is a promising candidate for protection against H. pylori infection.