Vaccination and mucosal responses to Helicobacter pylori infection.

H. pylori infection persists for life if not treated, and is responsible for major morbidity and mortality throughout the world. Preventative immunization, once thought to be impossible, is now considered by many to be the only practical approach to large-scale elimination of the bacterium from susceptible populations. High rates of protection have been achieved in the H. felis mouse model, utilizing antigens ranging from whole cells to purified recombinant proteins selected on the basis of their role in pathogenicity. Immunization has also been shown to cure established infection. H. pylori mouse models have been developed and may become the model of choice. Urease remains the favourite antigen but combinations will most likely be required. A priority is to define alternate muscosal adjuvants, as some used in the animal models may be too toxic for use in humans. Also, there is a need to understand the basis of immunization. Why does the natural immune response to H. pylori fail while the artificially stimulated response succeeds? The first important steps towards a vaccine have been made but, given safety issues and regulatory requirements, it may be 5-8 years before the final product becomes available. Over these years antimicrobial resistance is likely to be an increasing problem in the treatment of H. pylori infections. Thus, when the vaccine comes, the time will be ripe for the completely new approach of therapeutic immunization.