BACKGROUND:Helicobacter pylori infection is the most prevalent bacterial infection worldwide. Attempts to develop a vaccine have not been successful, partly due to the absence of well-defined immune correlates of protection. The inflammatory response to H. pylori infection is characterised by the recruitment of T cells expressing markers of tissue-resident memory T (TRM) cells to the gastric mucosa. However, the function of TRM cells in gastric tissue during H. pylori reinfection remained poorly understood. OBJECTIVE:We aimed to investigate the induction, development and function of gastric TRM cells during primary and secondary H. pylori infection. DESIGN:We characterised gastric H. pylori-specific TRM cells in mice and humans by flow cytometry, immunohistochemistry, immunofluorescence, ChipCytometry staining and single-cell RNA sequencing. The function of gastric TRM cells was established in H. pylori eradication and reinfection experiments as well as by targeted depletion of Hobit+ TRM cells and neutrophils in mice. RESULTS:Expression of the transcription factor Hobit governs the induction and development of gastric TRM cells, which largely depend on the presence of the H. pylori virulence factor Cytotoxin-associated gene A. H. pylori-specific CD4+ and CD8+ TRM cells resided long-term in the stomach and conferred complete protection from reinfection with the help of neutrophils. Gastric CD8+ TRM cells exhibited varying Hobit expression levels and clustered into distinct subgroups based on distinct transcriptomic and cytokine profiles, suggesting functional specialisation. CONCLUSION:These findings establish gastric TRM cells as bona fide correlates of protection against H. pylori, highlighting their potential for future prophylactic and therapeutic strategies.

Objective Helicobacter pylori infection is the most prevalent bacterial infection worldwide. Besides being the most important risk factor for gastric cancer development, epidemiological data show that infected individuals harbour a nearly twofold increased risk to develop colorectal cancer (CRC). However, a direct causal and functional connection between H. pylori infection and colon cancer is lacking. Design We infected two Apc-mutant mouse models and C57BL/6 mice with H. pylori and conducted a comprehensive analysis of H. pylori-induced changes in intestinal immune responses and epithelial signatures via flow cytometry, chip cytometry, immunohistochemistry and single cell RNA sequencing. Microbial signatures were characterised and evaluated in germ-free mice and via stool transfer experiments. Results H. pylori infection accelerated tumour development in Apc-mutant mice. We identified a unique H. pylori-driven immune alteration signature characterised by a reduction in regulatory T cells and pro-inflammatory T cells. Furthermore, in the intestinal and colonic epithelium, H. pylori induced pro-carcinogenic STAT3 signalling and a loss of goblet cells, changes that have been shown to contribute-in combination with pro-inflammatory and mucus degrading microbial signatures-to tumour development. Similar immune and epithelial alterations were found in human colon biopsies from H. pylori-infected patients. Housing of Apc-mutant mice under germ-free conditions ameliorated, and early antibiotic eradication of H. pylori infection normalised the tumour incidence to the level of uninfected controls. Conclusions Our studies provide evidence that H. pylori infection is a strong causal promoter of colorectal carcinogenesis. Therefore, implementation of H. pylori status into preventive measures of CRC should be considered.

Somatic mutations in the tumor suppressor Ring finger protein 43 ( RNF43 ) were frequently found in colitis-associated cancer (CAC) and related to the duration of chronic inflammation, but their significance in inflammation and inflammation-associated carcinogenesis remained elusive.We assessed the onset of RNF43 mutations at different stages of human CAC development by exome sequencing, and comprehensively characterized RNF43 loss-of-function-driven malignant transformation in mice by RNA sequencing, flow cytometry, immunohistochemistry, computational transcriptome-microbiome associations, and determined the underlying mechanisms by performing functional stem-cell derived organoid studies and fecal microbiota transfers.Mutations in RNF43 were frequent (12.9 %) in precancerous lesions of ulcerative colitis (UC) patients and eventually detectable in 24.4 % of CAC patients. In a bacterial-induced colitis mouse model, Rnf43 mutations caused invasive colorectal carcinomas by aggravating and perpetuating inflammation due to impaired epithelial barrier integrity and pathogen control. We could demonstrate that Rnf43 loss-of-function-mutations were even sufficient to cause spontaneous intestinal inflammation, resulting in UC-typical pathological features and subsequent invasive carcinoma development. In detail, mutant Rnf43 impaired intestinal epithelial and particularly goblet cell homeostasis in a cell-intrinsic manner, and caused dysbiosis. The altered microbiota composition induced epithelial DNA damage and spontaneous mucosal inflammation characterized by TGF-ß-activating dendritic cells and pro-inflammatory (IL-17+, IL-22+, TNFα+) T cells. Over time, the continuous epithelial and goblet cell dysfunction, combined with pro-tumorigenic and pro-inflammatory microbiota, resulted in accumulated epithelial damage with transformation into inflammation-associated cancer in the presence of constitutive WNT signaling activation.We identified mutant RNF43 as susceptibility gene for UC and bona fide driver of CAC.### Competing Interest StatementThe authors have declared no competing interest.Raw RNA sequencing and 16S rRNA sequencing data will be made available under the BioProject ID PRJNA951425.* dASVs : (differentially abundant amplicon sequence variants), CAC : (colitis-associated cancer), canonical correlation analysis (CCA) : C. rodentium ( Citrobacter rodentium ), CRC : (colorectal cancer), DCs : (dendritic cells), DEGs : (differentially expressed genes), ECM : (extracellular matrix), formalin-fixed and paraffin-embedded (FFPE) : Hematoxylin & Eosin (H&E), HGD : (high-grade dysplasia), IBD : (inflammatory bowel disease), LGD : (low-grade dysplasia), (PAS) : Periodic acid staining, (p.i.) : post-infection, RNF43 : (Ring finger protein 43), UC : (ulcerative colitis), WT : (wild type).

Combined anti-PD-L1+anti-CTLA-4 therapy has shown benefits over anti-PD-L1 monotherapy as a neoadjuvant treatment in head and neck cancer. In this issue of Immunity , Franken et al. report that CD4 + T cell trafficking from lymph nodes to tumors and expansion toward T helper 1 cells are features specific to combination therapy.

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers worldwide. While a close correlation between chronic Helicobacter pylori infection and CRC has been reported, the role of the virome has been overlooked. Here, we infected Apc-mutant mouse models and C57BL/6 mice with H. pylori and conducted a comprehensive metagenomics analysis of H. pylori-induced changes in lower gastrointestinal tract bacterial and viral communities. We observed an expansion of temperate phages in H. pylori infected Apc+/1638N mice at the early stage of carcinogenesis. Some of the temperate phages were predicted to infect bacteria associated with CRC, including Enterococcus faecalis. We also observed a high prevalence of virulent genes, such as flgJ, cwlJ, and sleB, encoded by temperate phages. In addition, we identified phages associated with pre-onset and onset of H. pylori-promoted carcinogenesis. Through co-occurrence network analysis, we found strong associations between the viral and bacterial communities in infected mice before the onset of carcinogenesis. These findings suggest that the expansion of temperate phages, possibly caused by prophage induction triggered by H. pylori infection, may have contributed to the development of CRC in mice by interacting with the bacterial community.

BACKGROUND & AIMS: Infection with Helicobacter pylori strongly affects global health by causing chronic gastritis, ulcer disease, and gastric cancer. Although extensive research into the strong immune response against this persistently colonizing bacterium exists, the specific role of CD8+ T cells remains elusive.METHODS: We comprehensively charac-terize gastric H pylori-specific CD8+ T-cell responses in mice and humans by flow cytometry, RNA-sequencing, immuno-histochemistry, and ChipCytometry, applying functional ana-lyses including T-cell depletion, H pylori eradication, and ex vivo restimulation.RESULTS: We define CD8+ T-cell populations bearing a tissue-resident memory (TRM) pheno-type, which infiltrate the gastric mucosa shortly after infec-tion and mediate pathogen control by executing antigen -specific effector properties. These induced CD8+ tissue -resident memory T cells (TRM cells) show a skewed T-cell receptor beta chain usage and are mostly specific for cytotoxin-associated gene A, the distinctive oncoprotein injected by H pylori into host cells. As the infection pro-gresses, we observe a loss of the TRM phenotype and replacement of CD8+ by CD4+ T cells, indicating a shift in the immune response during the chronic infection phase.CONCLUSIONS: Our results point toward a hitherto un-known role of CD8+ T-cell response in this bacterial infection, which may have important clinical implications for treatment and vaccination strategies against H pylori.

The understanding of gut virome and its role in Helicobacter pylori -driven colorectal cancer (CRC), as well as the long-term impact of H. pylori eradication via antibiotic treatment on it could contribute to better understanding the mechanisms of the disruption of gut bacteriome homeostasis involved in H. pylori -driven colorectal carcinogenesis and antibiotic therapy for H. pylori eradication. In the dynamic analysis of viral genome shotgun metagenomic of samples from lower gastrointestinal tract of the Apc +/1638N and C57BL/6 mice with H. pylori infection and eradication, stable viral abundance and replacement of bursted unique viral contigs in infected and uninfected Apc +/1638N mice were observed. Temperate phages, which encoding comprehensive microbial functional genes and targeting various susceptible hosts, were expanded extremely prior to cancer exacerbation. In addition, short-term antibiotic exposure for H. pylori eradication was able to alter the gut virome and thrive the antibiotic resistance genes (ARGs) in the viral genome for at least 6 months. Collectively, these results point toward a potential role of the altered, but dynamically balanced gut virome, characterized by the expanded temperate phages, in contributing to the H. pylori -driven CRC, and indicate that viral genome may act as ARG reservoir for the antibiotic resistance of bacteria after the antibiotics therapy to H. pylori eradication.

Murine Helicobacter species have gained increasing awareness in mouse facilities over the last years. Infections with Helicobacter species may have an impact effect on the health of mice and might pose a zoonotic risk to researchers. To minimize the interference with experiments and hence contribute to the 3Rs, a reliable method of monitoring Helicobacter infections in animal facilities needs to be available. The aim of this study was to improve and validate the detection of the most common murine Helicobacter species.

The gastric pathogen Helicobacter pylori infects half of the world’s population and is a major risk factor for gastric cancer development. In order to attach to human gastric epithelial cells and inject the oncoprotein CagA into host cells, H. pylori utilizes the outer membrane protein HopQ that binds to the cell surface protein CEACAM, which can be expressed on the gastric mucosa. Once bound, H. pylori activates a number of signaling pathways, including canonical and non-canonical NF-κB. We investigated whether HopQ–CEACAM interaction is involved in activating the non-canonical NF-κB signaling pathway. Different gastric cancer cells were infected with the H. pylori wild type, or HopQ mutant strains, and the activation of non-canonical NF-κB was related to CEACAM expression levels. The correlation between CEACAM levels and the activation of non-canonical NF-κB was confirmed in human gastric tissue samples. Taken together, our findings show that the HopQ–CEACAM interaction is important for activation of the non-canonical NF-κB pathway in gastric epithelial cells.