Preventive and therapeutic vaccines against Helicobacter pylori: Current status and future challenges

Approximately 50% of humanity is infected with Helicobacter pylori. Normall y, this is a life-long infection indicating that the host response to natur al infection fails to yield protective immunity. Moreover, the chronic infl ammatory response associated with this infection can contribute to tissue d amage and the pathogenesis of gastroduodenal disease including atrophic gas tritis, peptic ulcer and gastric cancer. These damaging immune responses ar e attributed to a subset of helper T cells, so-called Th1 cells, that enhan ce cell-mediated immunity and induce damage to the gastric epithelium. Thus , it is desirable to have effective vaccines that could prevent and cure in fection or at least, modify the host response in a manner that prevents imm une-mediated disease. Using animal models as a tool to understand the immun obiology of Helicobacter infections, several investigators have shown that effective vaccines can be developed. Thus, prophylactic and even therapeuti c vaccines have been described in various animal models. The basis for the effectiveness of these vaccines seems to be found in their ability to alter the gastric immune response, perhaps away from a homogeneous Th1 response towards a mixed Th1 and Th2 response. Using these encouraging approaches, v accines are being developed for use in humans for the treatment and prevent ion of H. pylori infection and the gastroduodenal diseases associated with this infection.