Innate immune activation and modulatory factors of Helicobacter pylori towards phagocytic and nonphagocytic cells

Helicobacter pylori reversing the landscape of neoadjuvant immunotherapy for microsatellite stable gastric cancer: a multicenter cohort study

BACKGROUND

Microsatellite stable (MSS) gastric cancer (GC) is largely unresponsive to immunotherapy, presenting a persistent and formidable challenge in the field. Patients with advanced GC and Helicobacter pylori (H. pylori) infection have shown benefits from immunotherapy. However, it remains unreported whether neoadjuvant immunotherapy is beneficial for H. pylori-positive MSS GC patients.

METHODS

This retrospective cohort study analyzed data from GC patients treated at three medical centers in China between January 1, 2014, and July 1, 2024. Patients with gastric adenocarcinoma or adenocarcinoma of the gastroesophageal junction underwent testing for H. pylori infection prior to receiving neoadjuvant therapy.

RESULTS

In this retrospective analysis, those positive for H. pylori had a higher objective response rate of 63.77% (95% CI, 51.98-74.11%) compared to 47.73% (95% CI, 39.39-56.19%) in H. pylori-negative patients. Pathological complete remission was higher in H. pylori-positive patients at 17.39% (95% CI, 10.24-27.98%) versus 15.91% (95% CI, 10.65-23.10%). Logistic regression analysis revealed a strong correlation between H. pylori positivity and increased objective remission rate (P = 0.031, OR = 1.928, 95% CI 1.06-3.51). In H. pylori-positive MSS GC patients receiving neoadjuvant immunotherapy pCR rates can reach 27.27% (95% CI, 15.07-44.21%), much higher than the 8.33% (95% CI, 2.87-21.82%) in neoadjuvant chemotherapy patients. Survival analysis showed a 3-year OS rate of 74.2% (95% CI, 56.75-86.30%) in the H. pylori-positive group and 64.3% (95% CI, 51.20-75.55%) in the H. pylori-negative group, and the hazard ratio (HR) of these two groups was 0.50 (95% CI, 0.28-0.87; P <.001). Multivariable analysis for OS further showed the survival benefit of H. pylori, with HRs of 0.51 (95% CI, 0.29-0.91; P = 0.02).

CONCLUSIONS

H. pylori infection has emerged as a favorable factor for neoadjuvant immunotherapy in MSS GC, underscoring the importance of considering H. pylori status in preoperative treatment strategies.

The role and mechanisms of Helicobacter pylori outer membrane vesicles in the pathogenesis of extra-gastrointestinal diseases

Helicobacter pylori (H. pylori) infection have been closely associated with several extra-gastrointestinal disorders. Outer membrane vesicles (OMVs), as lipid-membrane-bounded nanoparticles, are usually shed from Gram-negative both in vitro and in vivo. H. pylori is also capable of producing OMVs, which can enter the systemic circulation and be delivered to various cells, tissues or organs, eliciting a range of inflammatory and immune modulation responses. In this current review, we summarize the biogenesis and functions of H. pylori OMVs, describe the contribution of H. pylori OMVs to the generation and progression of extra-gastrointestinal diseases, such as neuronal damage, Alzheimer disease, hepatic fibrosis and atherosclerosis. We also explored the effect of H. pylori OMVs in inflammatory and immune modulation of diverse immune cells, including macrophages, mononuclear cells and dendritic cells. By elucidating the molecular mechanism of H. pylori OMVs-mediated extra-gastrointestinal diseases and immunomodulatory effect, it may promote the development of efficient treatments and vaccinations against H. pylori.

Helicobacter pylori outer membrane vesicles and infected cell exosomes: new players in host immune modulation and pathogenesis

Outer membrane vesicles (OMVs) and exosomes are essential mediators of host-pathogen interactions. Elucidating their mechanisms of action offers valuable insights into diagnosing and treating infectious diseases and cancers. However, the specific interactions of Helicobacter pylori (H. pylori) with host cells via OMVs and exosomes in modulating host immune responses have not been thoroughly investigated. This review explores how these vesicles elicit inflammatory and immunosuppressive responses in the host environment, facilitate pathogen invasion of host cells, and enable evasion of host defenses, thereby contributing to the progression of gastric diseases and extra-gastric diseases disseminated through the bloodstream. Furthermore, the review discusses the challenges and future directions for investigating OMVs and exosomes, underscoring their potential as therapeutic targets in H. pylori-associated diseases.

A glucose-rich heteropolysaccharide from Marsdenia tenacissima (Roxb.) Wight et Arn. and its zinc-modified complex enhance immunoregulation by regulating TLR4-Myd88-NF-κB pathway

A previously unreported immunological polysaccharide (MTP70-1) was obtained from Marsdenia tenacissima (Roxb.) Wight et Arn. MTP70-1 (2738 Da) is a heteropolysaccharide that mainly consists of (1 → 5)-linked-L-Araf, t-D-Glcp, (1 → 3,5)-linked-L-Araf, (1 → 4)-linked-D-Galp, (1 → 6)-linked-D-Glcp, and (1 → 3,6)-linked-D-Manp. In vitro cell assays revealed that MTP70-1 exhibits moderate immunomodulatory effects at the cellular level, and MTP70-1 was further modified with zinc to improve these effects. These modifications enhanced the immunomodulatory effects of MTP70-1, as phagocytosis was enhanced, the secretion of cytokines (TNF-α, IL-6, IL-1β, and IL-18) was increased, and the generation of chemokines (NO and ROS) in macrophages was enhanced. The intracellular mechanism by which MTP70-1 and MTP70-Zn activate macrophages was further revealed to be closely related to the TLR4-Myd88-NF-κB signaling pathway. In addition, a microscale thermophoresis binding (MST) assay confirmed that Zn modification can effectively enhance the binding affinity of MTP70-1 for TLR4. Ultimately, better immune-enhancing activity was attained with MTP70-Zn than MTP70-1. The immune-enhancing activity of MTP70-Zn was further demonstrated through zebrafish assays, which revealed that MTP70-Zn can effectively enhance the proliferation of macrophages and neutrophils.

Helicobacter pylori triggers inflammation and oncogenic transformation by perturbing the immune microenvironment

The immune microenvironment plays a critical regulatory role in the pathogenesis of Helicobacter pylori (H. pylori). Understanding the mechanisms that drive the transition from chronic inflammation to cancer may provide new insights for early detection of gastric cancer. Although chronic inflammation is frequent in precancerous gastric conditions, the monitoring function of the inflammatory microenvironment in the progression from H. pylori-induced chronic inflammation to gastric cancer remains unclear. This literature review summarizes significant findings on how H. pylori triggers inflammatory responses and facilitates cancer development through the immune microenvironment. Furthermore, the implications for future research and clinical applications are also addressed. The review is divided into four main sections: inflammatory response and immune evasion mechanisms induced by H. pylori, immune dysregulation associated with gastric cancer, therapeutic implications, and future perspectives on H. pylori-induced gastric carcinogenesis with a focus on the immune microenvironment.

Fusobacterium nucleatum carcinogenesis and drug delivery interventions

The microbiome has emerged as a significant biomarker and modulator in cancer development and treatment response. Recent research highlights the notable role of Fusobacterium nucleatum (F. nucleatum) in various tumor types, including breast, colorectal, esophageal, gastric, pancreatic, and lung cancers. Accumulating evidence suggests that the local microbial community forms an integral component of the tumor microenvironment, with bacterial communities within tumors displaying specificity to tumor types. Mechanistic investigations indicate that tumor-associated microbiota can directly influence tumor initiation, progression, and responses to chemotherapy or immunotherapy. This article presents a comprehensive review of microbial communities especially F. nucleatum in tumor tissue, exploring their roles and underlying mechanisms in tumor development, treatment, and prevention. When the tumor-associated F. nucleatum is killed, the host immune response is activated to recognize tumor cells. Bacteria epitopes restricted by the host antigens, can be identified for future anti-bacteria/tumor vaccine development.

Helicobacter pylori extract induces purified neutrophils to produce reactive oxygen species only in the presence of plasma

H. pylori is a bacterial pathogen infecting over half of the world's population and induces several gastric and extra-gastric diseases through its various virulence factors, especially cagA. These factors may be released from the bacteria during interactions with host immune cells. Neutrophils play key roles in innate immunity, and their activity is regulated by plasma factors, which can alter how these cells may interact with pathogens. The aim of the present study was to determine whether purified neutrophils could produce reactive oxygen species (ROS), one of the key functions of their anti-microbial functions, in response to extracts of cagA+ and cagA- H. pylori. Extracts from either cagA+ or cagA- H. pylori were co-cultured with human neutrophils in the presence or absence of plasma, and the neutrophil ROS production was measured. In the absence of plasma, extracts from cagA+ and cagA- H. pylori did not induce neutrophil ROS production, whereas in the presence of plasma, extracts from both cagA+ and cagA- H. pylori-induced ROS production. Furthermore, when peripheral blood mononuclear cells (PBMCs) were added to the purified neutrophils in the absence of plasma, there was no neutrophil ROS production after challenging with extracts from either cagA+ or cagA- H. pylori. Thus, it is suggested that plasma contains immunological components that change the responsiveness of neutrophils, such that when neutrophils encounter the bacterial antigens in H. pylori extracts, they become activated and produce ROS. This study also revealed a potential novel immunopathogenic pathway by which cagA activation of neutrophils contributed to inflammatory damage.

Innate activation of human neutrophils and neutrophil-like cells by the pro-inflammatory bacterial metabolite ADP-heptose and Helicobacter pylori

Lipopolysaccharide inner core heptose metabolites, including ADP-heptose, play a substantial role in the activation of cell-autonomous innate immune responses in eukaryotic cells, via the ALPK1-TIFA signaling pathway, as demonstrated for various pathogenic bacteria. The important role of LPS heptose metabolites during Helicobacter pylori infection of the human gastric niche has been demonstrated for gastric epithelial cells and macrophages, while the role of heptose metabolites on human neutrophils has not been investigated. In this study, we aimed to gain a better understanding of the activation potential of bacterial heptose metabolites for human neutrophil cells. To do so, we used pure ADP-heptose and, as a bacterial model, H. pylori, which can transport heptose metabolites into the human host cell via the Cag Type 4 Secretion System (CagT4SS). Main questions were how bacterial heptose metabolites impact on the pro-inflammatory activation, alone and in the bacterial context, and how they influence maturation of human neutrophils. Results of the present study demonstrated that neutrophils respond with high sensitivity to pure heptose metabolites, and that global regulation networks and neutrophil maturation are influenced by heptose exposure. Furthermore, activation of human neutrophils by live H. pylori is strongly impacted by the presence of LPS heptose metabolites and the functionality of its CagT4SS. Similar activities were determined in cell culture neutrophils of different maturation states and in human primary neutrophils. In conclusion, we demonstrated that specific heptose metabolites or bacteria producing heptoses exhibit a strong activity on cell-autonomous innate responses of human neutrophils.

Designed Ankyrin Repeat Proteins provide insights into the structure and function of CagI and are potent inhibitors of CagA translocation by the Helicobacter pylori type IV secretion system

The bacterial human pathogen Helicobacter pylori produces a type IV secretion system (cagT4SS) to inject the oncoprotein CagA into gastric cells. The cagT4SS external pilus mediates attachment of the apparatus to the target cell and the delivery of CagA. While the composition of the pilus is unclear, CagI is present at the surface of the bacterium and required for pilus formation. Here, we have investigated the properties of CagI by an integrative structural biology approach. Using Alpha Fold 2 and Small Angle X-ray scattering, it was found that CagI forms elongated dimers mediated by rod-shape N-terminal domains (CagIN) prolonged by globular C-terminal domains (CagIC). Three Designed Ankyrin Repeat Proteins (DARPins) K2, K5 and K8 selected against CagI interacted with CagIC with subnanomolar affinities. The crystal structures of the CagI:K2 and CagI:K5 complexes were solved and identified the interfaces between the molecules, thereby providing a structural explanation for the difference in affinity between the two binders. Purified CagI and CagIC were found to interact with adenocarcinoma gastric (AGS) cells, induced cell spreading and the interaction was inhibited by K2. The same DARPin inhibited CagA translocation by up to 65% in AGS cells while inhibition levels were 40% and 30% with K8 and K5, respectively. Our study suggests that CagIC plays a key role in cagT4SS-mediated CagA translocation and that DARPins targeting CagI represent potent inhibitors of the cagT4SS, a crucial risk factor for gastric cancer development.

Helicobacter pylori infection

Helicobacter pylori infection causes chronic gastritis, which can progress to severe gastroduodenal pathologies, including peptic ulcer, gastric cancer and gastric mucosa-associated lymphoid tissue lymphoma. H. pylori is usually transmitted in childhood and persists for life if untreated. The infection affects around half of the population in the world but prevalence varies according to location and sanitation standards. H. pylori has unique properties to colonize gastric epithelium in an acidic environment. The pathophysiology of H. pylori infection is dependent on complex bacterial virulence mechanisms and their interaction with the host immune system and environmental factors, resulting in distinct gastritis phenotypes that determine possible progression to different gastroduodenal pathologies. The causative role of H. pylori infection in gastric cancer development presents the opportunity for preventive screen-and-treat strategies. Invasive, endoscopy-based and non-invasive methods, including breath, stool and serological tests, are used in the diagnosis of H. pylori infection. Their use depends on the specific individual patient history and local availability. H. pylori treatment consists of a strong acid suppressant in various combinations with antibiotics and/or bismuth. The dramatic increase in resistance to key antibiotics used in H. pylori eradication demands antibiotic susceptibility testing, surveillance of resistance and antibiotic stewardship.

Genome and population dynamics during chronic infection with Helicobacter pylori

Helicobacter pylori is responsible for one of the most prevalent bacterial infections worldwide. Chronic infection typically leads to chronic active gastritis. Clinical sequelae, including peptic ulcers, mucosa-associated lymphoid tissue lymphoma or, most importantly, gastric adenocarcinoma develop in 10-15% of cases. H. pylori is characterized by extensive inter-strain diversity which is the result of a high mutation rate, recombination, and a large repertoire of restriction-modification systems. This diversity is thought to be a major contributor to H. pylori's persistence and exceptional aptitude to adapt to the gastric environment and evade the immune system. This review covers efforts in the last decade to characterize and understand the multiple layers of H. pylori's diversity in different biological contexts.