IL-22-induced antimicrobial peptides are key determinants of mucosal vaccine-induced protection against H-pylori in mice

Despite the recent description of themucosal vaccine-induced reduction of Helicobacter pylori natural infection in a phase 3 clinical trial, the absence of immune correlates of protection slows the final development of the vaccine. In this study, we evaluated the role of interleukin (IL)-22 inmucosal vaccine-induced protection. Gastric IL-22 levels were increased in mice intranasally immunized with urease+cholera toxin and challenged with H. felis, as compared with controls. Flow cytometry analysis showedthat a peak of CD4(+)IL-22(+)IL-17(+) Tcells infiltrating the gastric mucosa occurred in immunized mice in contrast to controlmice. The inhibition of the IL-22 biological activity prevented the vaccine-induced reduction of H. pylori infection. Remarkably, anti-microbial peptides (AMPs) extracted from the stomachs of vaccinated mice, but not from the stomachs of non-immunized or immunized mice, injected with anti-IL-22 antibodies efficiently killed H. pylori in vitro. Finally, H. pylori infection in vaccinated RegIII beta-deficient mice was not reduced as efficiently as in wild-type-mice. These results demonstrate that IL-22 has a critical role in vaccine-induced protection, by promoting the expression of AMPs, such as RegIII beta, capable of killing Helicobacter. Therefore, it can be concluded that urease-specific memory Th17/Th22 cells could constitute immune correlates of vaccine protection in humans.