Enhancement of Helicobacter pylori outer inflammatory protein DNA vaccine efficacy by co-delivery of interleukin-2 and B subunit heat-labile toxin gene encoded plasmids

Development of an effective vaccine for controlling H. pylori-associated infection, which is present in about half the people in the world, is a priority. The H. pylori outer inflammatory protein (oipA) has been demonstrated to be a potential antigen for a vaccine. In the present study, use of oipA gene encoded construct (poipA) for C57BL/6 mice vaccination was investigated. Whether co-delivery of IL-2 gene encoded construct (pIL-2) and B subunit heat-labile toxin of Escherichia coli gene encoded construct (pLTB) can modulate the immune response and enhance DNA vaccine efficacy was also explored. Our results demonstrated that poipA administered intradermally (‘gene gun’ immunization) promoted a strong Th2 immune response, whereas co-delivery of either pIL-2 or pLTB adjuvant elicited a Th1-biased immune response. PoipA administered with both pIL-2 and pLTB adjuvants promoted a strong Th1 immune response. Regardless of the different immune responses promoted by the various vaccination regimes, all immunized mice had smaller bacterial loads after H. pylori challenge than did PBS negative and pVAX1 mock controls. Co-delivery of adjuvant(s) enhances poipA DNA vaccine efficacy by shifting the immune response from being Th2 to being Th1-biased, which results in a greater reduction in bacterial load after H. pylori challenge. Both prophylactic and therapeutic vaccination can achieve sterile immunity in some subjects.