Why are tribal populations free from clinical symptoms infection with H pylori strains?

Helicobacter pylori is of growing concern today because of its crucial role in the pathogenesis of chronic gastritis, peptic ulcer diseases and in the multi-step carcinogenic process of gastric cancer. However, it is still an enigma why few strains are associated with ulcer formation with relevant clinical symptoms while others are not associated with any disease manifestation. H pylori infection and duodenal ulcer disease is common among ethnic Bengali population in West Bengal, India. In contrast, although H pylori infection is equally or more common in the ethnic tribal minorities (Santhals and Orans) of West Bengal, symptomatic disease is extremely rare. A research article to be published on March 7, 2009 in the World Journal of Gastroenterology addresses different histological parameters occurring in the stomach tissue of H pylori infected tribal populations and duodenal ulcer patients among ethnic Bengalis for getting insights of the cause for near absence of H pylori associated overt disease in these tribal populations and correlation of the genotypes of H pylori with different histological parameters.

This study showed almost similar distribution of inflammatory cells among asymptomatic tribals and DU Bengali patients. Interestingly, the tribal population are free from any clinical symptoms despite evidence of active histologic gastritis and infection with H pylori strains carrying similar virulence markers as of strains isolated from patients with DU. There was increased cellular response specially in terms of neutrophil infiltration but much lower risk of developing atrophy and metaplastic changes among tribal population.

Apparent avirulence among tribal group might reflect features of the host. Our study raised two important questions – (i) why tribal groups are free from any clinical symptoms in spite of evidence of active histologic gastritis and (ii) identification of the host factors (Tribal), which may provide immunity to resist the pathogenic effects of putatively virulent H pylori strains. Such kind of studies may uncover new genetic factor/factors that affect human infection, increase our understanding of bacterium-host interactions in colonization and disease.

Source: World Journal of Gastroenterology