Genome-wide association and Mendelian randomization analyses link Helicobacter pylori infection to Human Leukocyte Antigen polymorphisms and autoimmune diseases.

Helicobacter pylori (H. pylori) infects the gastric epithelium of approximately half of the global population, and is a well-known risk factor for developing gastric cancer. Despite the clinical significance of H. pylori infection, many genetic factors that contribute to susceptibility remain unidentified. While it is well-established that H. pylori infection can result in gastritis and peptic ulcers, which may progress to gastric cancer, its causal link to other diseases remains unclear. We performed the genome-wide association study (GWAS) for anti-H. pylori IgG antibody titers, which were validated as a surrogate marker for H. pylori infection by the correlation with clinical traits, followed by gene-based and pathway analyses, involving up to 140,863 individuals. This included 56,967 in the discovery phase, and 68,211 in the replication phase from Japanese cohorts, and an additional 15,685 from European populations in a cross-ancestry meta-analysis. We reveal significant associations between H. pylori infection and polymorphisms in Human Leukocyte Antigen (HLA) genes the Human Leukocyte Antigen (HLA) class II region within the Major Histocompatibility Complex (MHC), as well as genes related to innate immunity, including CCDC80, NFKBIZ, TIFA, PSCA, and TRAF3. Mendelian randomization (MR) analysis revealed that genetic liability to H. pylori infection has both positive and negative causal relationships with a variety of diseases, including autoimmune-related diseases such as Type 1 diabetes, Hashimoto's disease, atopic dermatitis, as well as traits like body height and weight. These genetic findings strongly support the notion that genetic liability to H. pylori infection influences not only gastrointestinal diseases, but also a broader spectrum of health issues, thereby providing valuable insights for public health strategies and personalized medicine approaches.