Metagenomic and single-cell RNA-seq survey of the H. pylori-infected stomach in asymptomatic individuals

Objective. Helicobacter pylori colonization of the gastric niche can persist for years in asymptomatic individuals. Although latent H. pylori infection can progress to cancer, a detailed survey of the microbiome and immune composition in the chronically infected stomach is still lacking. Design. We collected human gastric tissues and performed metagenomic sequencing, single-cell RNA sequencing (scRNA-seq), flow cytometry and fluorescent microscopy to deeply characterize the host-microbiota environment in H. pylori-infected (HPI) stomachs. Results. HPI asymptomatic individuals showed dramatic changes in the composition of gastric microbiome and immune cells compared to non-infected individuals. With metagenomic data, we also demonstrated antibiotic resistant genes, enzymes and pathway alterations related to metabolism and immune response. scRNA-seq and flow cytometry data revealed that in contrast to murine stomachs, ILC2 are virtually absent in the human gastric mucosa, whereas ILC3 are the dominant population in asymptomatic HPI individuals. Specifically, NKp44+ ILC3s were highly increased in the gastric mucosa of asymptomatic HPI individuals, and their proportions correlated with the abundance of selected microbial taxa found to be enriched in the infected mucosa. In addition, CD11c+ myeloid cells, activated CD4 T cells and B cells were expanded in HPI individuals. In HPI individuals, B cells acquired an activated phenotype and progressed into a highly proliferating germinal center stage and plasmablast maturation, which correlated with the presence of tertiary lymphoid structures within the gastric lamina propria. Conclusion. Our study provides a comprehensive atlas of the gastric mucosa-associated microbiome and immune cell landscape when comparing asymptomatic HPI and uninfected individuals.