Metagenomic and single-cell RNA-seq survey of the H. pylori-infected stomach in asymptomatic individuals
Authors: Sorini Chiara , Tripathi Kumar P. , Wu Shengru , Higdon Shawn M. , Wang Jing , Cheng Liqin , Banerjee Sanghita , Reinhardt Annika , Kreslavsky Taras , Thorell Anders , Engstrand Lars , Du Juan , Villablanca Eduardo J. 
Published: December 2021

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.

SIGNIFICANCE OF THE STUDY

What is already known on this subject?

Previous studies on the gastric microbiome were performed via 16S rRNA gene sequencing.

Acute Helicobacter spp. infection in murine models and symptomatic H. pylori-driven pathology in humans result in remodeling of the stomach immune cell compartment.

ILC2 is the dominant ILC population in the murine stomach.

What are the new findings?

We described the effect of chronic asymptomatic H. pylori infection on the gastric microbiome via whole-genome sequencing.

Single cell census of the gastric mucosa reveals ILC3 to be the dominant ILC population in the human stomach, whereas ILC2 were virtually absent.

scRNA-seq reveals the gastric immune cell programs in asymptomatic H. pylori-infected individuals, which is characterized by the formation of tertiary lymphoid structures.

How might it impact on clinical practice in the foreseeable future?

Whole genome sequencing of uninfected and H. pylori-infected gastric mucosa bolsters collective knowledge of stomach physiology with respect to the gastric microbiome and microbiota function.

We present a comprehensive immune cellular landscape of the human stomach, which will be a valuable resource to interrogate pathology of gastric diseases.