Summary The Helicobacter pylori adhesin BabA binds mucosal ABO/Leb blood group (bg) carbohydrates. BabA facilitates bacterial attachment to gastric surfaces, increasing strain virulence and forming a recognized risk factor for peptic ulcers and gastric cancer. High sequence variation causes BabA functional diversity, but the underlying structural-molecular determinants are unknown. We generated X-ray structures of representative BabA isoforms that reveal a polymorphic, three-pronged Leb binding site. Two diversity loops, DL1 and DL2, provide adaptive control to binding affinity, notably ABO versus O bg preference. H. pylori strains can switch bg preference with single DL1 amino acid substitutions, and can coexpress functionally divergent BabA isoforms. The anchor point for receptor binding is the embrace of an ABO fucose residue by a disulfide-clasped loop, which is inactivated by reduction. Treatment with the redox-active pharmaceutic N-acetylcysteine lowers gastric mucosal neutrophil infiltration in H. pylori-infected Leb-expressing mice, providing perspectives on possible H. pylori eradication therapies.

BackgroundThe gastric pathogen Helicobacter pylori is extraordinary in its genetic diversity, the differences between strains from well-separated human populations, and the range of diseases that infection promotes.Principal FindingsHousekeeping gene sequences from H. pylori from residents of an Amerindian village in the Peruvian Amazon, Shimaa, were related to, but not intermingled with, those from Asia. This suggests descent of Shimaa strains from H. pylori that had infected the people who migrated from Asia into The Americas some 15,000+ years ago. In contrast, European type sequences predominated in strains from Amerindian Lima shantytown residents, but with some 12% Amerindian or East Asian-like admixture, which indicates displacement of ancestral purely Amerindian strains by those of hybrid or European ancestry. The genome of one Shimaa village strain, Shi470, was sequenced completely. Its SNP pattern was more Asian- than European-like genome-wide, indicating a purely Amerind ancestry. Among its unusual features were two cagA virulence genes, each distinct from those known from elsewhere; and a novel allele of gene hp0519, whose encoded protein is postulated to interact with host tissue. More generally, however, the Shi470 genome is similar in gene content and organization to those of strains from industrialized countries.ConclusionsOur data indicate that Shimaa village H. pylori descend from Asian strains brought to The Americas many millennia ago; and that Amerind strains are less fit than, and were substantially displaced by, hybrid or European strains in less isolated communities. Genome comparisons of H. pylori from Amerindian and other communities should help elucidate evolutionary forces that have shaped pathogen populations in The Americas and worldwide.

Early regulators of disease may increase understanding disease mechanisms, and serve as markers for pre-symptomatic diagnosis and treatment. However, early regulators are difficult to identify because patients generally present after they are symptomatic. We hypothesized that early regulators of T-cell associated diseases could be found by identifying upstream transcription factors (TFs) in T-cell differentiation, and by prioritizing hub TFs that were enriched for disease associated This analytical strategy to identify early regulators of disease by combining gene regulatory networks with GWAS may be generally applicable for functional and clinical studies of early disease development.

SUMMARY The BabA adhesin mediates high-affinity binding of Helicobacter pylori to the ABO blood-group antigen-glycosylated gastric mucosa. Here we show that BabA is acid responsive but binding is restored by pH neutralization. Acid responsiveness differs among strains; often correlates with different intragastric regions; changes during chronic infection and disease progression; and depends on pH sensor sequences in BabA and on pH reversible formation of high-affinity binding BabA multimers. We propose that BabA’s extraordinary reversible acid-responsiveness enables tight mucosal bacterial adherence while at the same time allowing an effective escape from epithelial cells and mucus that are shed into the acidic bactericidal lumen and that bio-selection and changes in BabA binding properties through mutations and recombination with babA-related genes are selected by differences among individuals and by changes in gastric acidity over time. These processes generate diverse H. pylori subpopulations, and BabA’s adaptive evolution contributes importantly to H. pylori persistence and to overt gastric disease.