Co-Infection Dynamics of Helicobacter pylori and Helminths: A Double-Edged Sword

Helicobacter pylori (H. pylori) and intestinal helminthes are common in low- and middle-income countries, where co-infection is endemic due to similar modes of transmission and poor sanitation. Whereas H. pylori are recognized gastric pathogens that induce gastritis, ulcers, and gastric carcinoma, helminths possess systemic immunomodulatory functions. The immunological, epidemiological, and clinical features of H. pylori and helminth co-infections will be discussed in this review. Key findings include that helminths induce a Th2-biased and regulatory immune response, potentially counteracting the Th1/Th17 H. pylori-induced inflammation and therefore limiting gastric tissue damage and cancer risk. Certain human studies and animal models concluded that co-infection would be protective against extreme gastric pathology by modulating immunity, altering gut microbiota, and by helminth-secreted extracellular vesicles. Epidemiologic data show large regional heterogeneity in co-infection prevalence with higher rates in children and rural socioeconomically disadvantaged populations. Much of the research mechanisms, however, are limited to models in the lab, and few human studies exist. Lastly, helminth co-infection is also potentially immunoprotective against H. pylori-associated illnesses, but greater translational research and human clinical trials are necessary. Public health policy in endemic regions must consider the complex relationships between co-infecting parasites when developing control.