Vaccines.

Abstract

Extensive research with mice has shown that animals can be protected from or cured of Helicobacter infection by immunization. A therapeutic effect has also been demonstrated in ferrets. The possibility of developing a vaccine against H. pylori-associated diseases that will work in humans has been the stimulus for intense research activity. A major subset of lymphocytes involved in immunity against invading pathogens is the CD4+ T-lymphocytes, divided into Th1 and Th2 phenotypes. Th1 cells are involved in cell-mediated immunity and Th2 cells are involved in antibody formation, particularly IgA and IgG, which are most active at mucosal surfaces and thus most likely to be protective against bacteria trying to colonize that surface. H. pylori can exist for the life of its human host, despite the vigorous immune response that is mounted against it. Most infected humans have a Th1 response, which does not eradicate H. pylori. A Th2 response would logically be more effective. Experiments with mice deficient in the cytokines that drive the Th responses are confusing and indicate that a change in the balance of the Th1/Th2 response may have a therapeutic effect In the next 2-5 years, a number of anti-Helicobacter vaccines will be studied in humans and this will open up a completely new approach to the management of gastroduodenal diseases.