Potent Neutralization of Vacuolating Cytotoxin (VacA) of Helicobacter pylori by Immunoglobulins Against the Soluble Recombinant VacA

Background: The recombinant vacuolating cytotoxin (rVacA) of Helicobacter pylori that retains native conformational epitopes was evaluated as a vaccine antigen for anti-H. pylori treatment. Methods: s1m1 vacA gene fraction encoding the mature VacA protein was expressed as a soluble protein in E. coli at low temperature. The efficacy of anti-rVacA antibody against VacA or H. pylori was assessed in vitro using AGS cells and in vivo using a murine model. Results: The rabbit antisera against rVacA completely neutralized the vacuolating activity and partially inhibited the cell death induced by VacA in AGS cells. Oral immunization of C57BL/6 mice with rVacA plus CpG- oligodeoxynucleotide (ODN) as an ajuvant stimulated specific anti-VacA antibody and mucosal immune responses which correlated with decreased systemic immune responses and gastric urease activities (p>0.05). Conclusion: The rVacA antigen possessing conformational epitopes may have potential as a vaccine component and may be useful in serological and histopathological analysis.