Oral Immunization with Recombinant Mycobacterium smegmatis Expressing the Outer Membrane Protein 26-Kilodalton Antigen Confers Prophylactic Protection against Helicobacter pylori Infection
ABSTRACTHelicobacter pyloriinfection is prevalent worldwide and results in chronic gastritis, which may lead to gastric mucosa-associated lymphoid tissue lymphoma and gastric cancer. We have previously reported that oral immunization with recombinantMycobacterium smegmatisexpressing theH. pyloriouter membrane protein 26-kilodalton (Omp26) antigen affords therapeutic protection againstH. pyloriinfection in mice. In the present study, we investigated the prophylactic effects of this vaccine candidate onH. pylorichallenge in mice. We found that oral immunization with recombinantMycobacteriumOmp26 significantly reducedH. pyloricolonization in the stomach compared to inoculation with wild-typeM. smegmatisin control mice. Six of the recombinantMycobacterium-immunized mice (60%) were completely protected fromH. pyloriinfection. The severity ofH. pylori-associated chronic gastritis assessed histologically was significantly milder in mice vaccinated with recombinantMycobacteriumthan in control animals. Mice immunized with recombinantMycobacteriumshowed enhanced antigen-specific lymphocyte proliferation and antibody responses. Moreover, immunization with recombinantMycobacteriumresulted in an increased expression of interleukin-2 and gamma interferon in the stomach and spleen, as determined by reverse transcription-PCR analysis. Our results collectively suggest that vaccination with recombinantMycobacteriumOmp26 confers prophylactic protection againstH. pyloriinfection. The inhibition ofH. pyloricolonization is associated with the induction of antigen-specific humoral and cell-mediated immune responses.