Frequency and immunological consequences of Helicobacter pylori and intestinal parasite co-infections: a brief review

Helicobacter pylori is a Gram-negative, spiral bacterium capable of colonizing the gastric mucosa. Infections caused by this microorganism often lead to the development of various gastrointestinal complaints. Simultaneous human colonization by H. pylori and intestinal parasites is a common phenomenon. Moreover, the two groups of pathogens share the similar predisposing factors. The presence of parasites together with H. pylori can significantly influence the modulation of the host immune response. During H. pylori infection, strong polarization of Th1 cells is observed. The presence of protozoa, also contributing to the recruitment of Th1 cells, may well aggravate this response and exacerbate gastric mucosal damage. In contrast, intestinal helminth infection is associated with the polarization of lymphocytes towards Th2; their presence enhances the regenerative processes within the digestive tract and lowers the host overresponse. A literature review suggests that co-infection with intestinal helminths may serve as a buffering mechanism against the effects of H. pylori and/or protozoan infection, alleviating the Th1-dependent response and protecting against inflammations within the gastrointestinal tract.