Peroral immunization with Helicobacter pylori adhesin protein genetically linked to cholera toxin A2B subunits

Helicobacter pylori is a major cause of gastric-associated diseases. To eva luate the efficacy of a possible vaccine antigen against H. pylori infectio n, the chimaeric construct adhesin-CTXA2B. derived from H. pylori adhesin g enetically coupled to cholera toxin (CTX) subunits A2 and B (CTXA2B), was e xpressed in Escherichia coli as an insoluble recombinant chimaeric protein. The protein was then purified by denaturation, renaturation and size-exclu sion chromatography. The com position of purified adhesin-CTXA2B was verifi ed by SDS/PAGE and Western blotting with antibodies to antigenic components of adhesin and CTXB. and confirmed as a chimaeric protein with G(MI)-gangl ioside binding activity and adhesin epitopes by a G(MI)-ELISA developed usi ng antibodies to adhesin. Oral immunization of mice with adhesin-CTXA2B ind uced higher levels of mucosal IgA and serum IgG antibodies to H. pylori adh esin and to CTXB than in mice immunized with adhesin or CTXA2B alone. Adhes in-CTXA2B was also demonstrated to be a potential protective antigen in a m ouse model of H. pylori infection. The immunization of mice with adhesin-CT XA2B protected 62.5% of mice infected with H. pylori SSI strain, whereas ad hesin immunization was not able to confer protection to mice. This protecti on may be correlated with high levels of mucosal IgA and serum IgG antibodi es against H. pylori adhesin. Taken together. the results indicate that the genetically linked CTXA2B acts as a useful mucosal adjuvant, and that the adhesin-CTXA2B chimaeric protein could be a potential component in future H . pylori vaccine development.