Prevention of Helicobacter pylori infection.

The only successful strategy for large-scale eradication of an infectious disease from whole populations has been through immunization. In societies fortunate enough to have a healthcare infrastructure that allows mass vaccination, diseases such as poliomyelitis, whooping cough and diphtheria have been virtually eliminated. But what about infection with Helicobacter pylori, which has now been proved to be a major worldwide pathogen? Infection by H. pylori is lifelong, despite a vigorous immune response. How, then, could immunization be feasible? Recent investigations using a mouse model of H. pylori infection have shown that protective immunity can indeed be induced with an oral vaccine. Furthermore, protection was lifelong in the animal model. Also, more importantly, the vaccine actually cured existing infection, raising the exciting possibility of therapeutic immunization. Stimulated by the medical need, the race is now on to produce the first vaccine. However, many critical questions remain to be answered before the first patients are immunized with the complete vaccine. For example, what is the best antigen to target? Urease is currently the favourite antigen, but others will be tested. What about the adjuvant? LT, the heat labile enterotoxin of diarrhoeaogenic strains of Escherichia coli, is the most likely candidate, but we need to examine alternatives. Is there any risk of immunopotentiation? The answer is probably no, but this has to be proved. A vaccine against H. pylori will be developed, and infection with H. pylori will be prevented--the question remains 'how long will it take'?