Gastric Subserous Vaccination With Helicobacter pylori Vaccine: An Attempt to Establish Tissue-Resident CD4+ Memory T Cells and Induce Prolonged Protection

IL-17A in gastric carcinogenesis: good or bad?

Cytokines, which are important to the tumor microenvironment (TME), play critical roles in tumor development, metastasis, and immune responses. Interleukin-17(IL-17) has emerged as a key biomarker in many malignancies; however, its precise involvement in gastric cancer is less fully understood. Elevated levels of IL-17 have been observed in stomach diseases such as Helicobacter pylori infection and autoimmune gastritis, indicating that a sustained Th17 response may precede the development of gastric cancer. While IL-17 is related to inflammatory processes that may lead to cancer, its specific influence on gastric cancer development and therapy needs to be completely understood. Specifically, the release of IL-17A by diverse immune cells has been associated with both tumor development and inhibition in gastric cancer. It may impact tumor development through mechanisms such as boosting cell proliferation, inducing angiogenesis, and enabling immune cell recruitment or, conversely, suppressing tumor growth via the activation of anti-tumor immune responses. The dual role of IL-17 in cancer, along with its various effects depending on the TME and immune cell composition, highlights the complexity of its activity. Current research reveals that although IL-17 might serve as a target for immunotherapy, its therapeutic potential is hindered by its various activities. Some studies have shown that anti-IL-17 drugs may be helpful, especially when paired with immune checkpoint inhibitors, whereas others point to concerns about the validity of IL-17 in gastric cancer therapy. The lack of clinical trials and the heterogeneity of human tumors underscore the necessity for individualized treatment approaches. Further studies are needed to identify the specific mechanisms of IL-17 in gastric cancer and to design targeted therapeutics appropriately.

CD38 and extracellular NAD+ regulate the development and maintenance of Hp vaccine-induced CD4+ TRM in the gastric epithelium

Tissue-resident memory T cells (TRM) can be induced by infection and vaccination, and play a key role in maintaining long-term protective immunity against mucosal pathogens. Our studies explored the key factors and mechanisms affecting the differentiation, maturation, and stable residence of gastric epithelial CD4+ TRM induced by Helicobacter pylori (Hp) vaccine and optimized Hp vaccination to promote the generation and residence of TRM. Cluster of differentiation (CD)38 regulated mitochondrial activity and enhanced transforming growth factor-β signal transduction to promote the differentiation and residence of gastric epithelial CD4+ TRM by mediating the expression of CD105. Extracellular nucleotides influenced the long-term maintenance of TRM in gastric epithelium by the P2X7 receptor (P2RX7). Vitamin D3 and Gram-positive enhancer matrix (GEM) particles as immune adjuvants combined with Hp vaccination promoted the production of CD69+CD103+CD4+ TRM.

Recombinant outer membrane vesicles delivering eukaryotic expression plasmid of cytokines act as enhanced adjuvants against Helicobacter pylori infection in mice

The widespread prevalence of Helicobacter pylori (H. pylori) infection remains a great challenge to human health. The existing vaccines are not ideal for preventing H. pylori infection; thus, exploring highly effective adjuvants may improve the immunoprotective efficacy of H. pylori vaccines. In a previous study, we found that the outer membrane vesicles (OMVs), a type of nanoscale particle spontaneously produced by Gram-negative bacteria, could act as adjuvants to boost the immune responses to vaccine antigens. In this study, we explored the potential application of OMVs as delivery vectors for adjuvant development. We constructed recombinant OMVs containing eukaryotic expression plasmid of cytokines, including interleukin 17A or interferon-γ, and evaluated their function as adjuvants in combination with inactivated whole-cell vaccine (WCV) or UreB as vaccine antigens. Our results showed that recombinant OMVs as adjuvants could induce stronger humoral and mucosal immune responses in mice than wild-type H. pylori OMVs and the cholera toxin (CT) adjuvant. Additionally, the recombinant OMVs significantly promoted Th1/Th2/Th17-type immune responses. Furthermore, the recombinant OMV adjuvant induced more potent clearance of H. pylori than CT and wild-type OMVs. Our findings suggest that the recombinant OMVs coupled with cytokines may become potent adjuvants for the development of novel and effective vaccines against H. pylori infection.

Vaccination against Helicobacter pylori - An approach for cancer prevention?

The gram-negative bacterium Helicobacter pylori is the most common chronic bacterial infection and the main cause of gastric cancer. Due to the increasing antimicrobial resistance of H. pylori, the development of an efficacious vaccine is a valid option to protect from disease or infection and ultimately prevent gastric cancer. However, despite more than 30 years of research, no vaccine has entered the market yet. This review highlights the most relevant previous preclinical and clinical studies to allow conclusions to be drawn on which parameters need special attention in the future to develop an efficacious vaccine against H. pylori and thus prevent gastric cancer.

Immune Biology and Persistence of Helicobacter pylori in Gastric Diseases

Helicobacter pylori is a prevalent pathogen, which affects more than 40% of the global population. It colonizes the human stomach and persists in its host for several decades or even a lifetime, if left untreated. The persistent infection has been linked to various gastric diseases, including gastritis, peptic ulcers, and an increased risk for gastric cancer. H. pylori infection triggers a strong immune response directed against the bacterium associated with the infiltration of innate phagocytotic immune cells and the induction of a Th1/Th17 response. Even though certain immune cells seem to be capable of controlling the infection, the host is unable to eliminate the bacteria as H. pylori has developed remarkable immune evasion strategies. The bacterium avoids its killing through innate recognition mechanisms and manipulates gastric epithelial cells and immune cells to support its persistence. This chapter focuses on the innate and adaptive immune response induced by H. pylori infection, and immune evasion strategies employed by the bacterium to enable persistent infection.

Immune Memory in Aging: a Wide Perspective Covering Microbiota, Brain, Metabolism, and Epigenetics

Non-specific innate and antigen-specific adaptive immunological memories are vital evolutionary adaptations that confer long-lasting protection against a wide range of pathogens. Adaptive memory is established by memory T and B lymphocytes following the recognition of an antigen. On the other hand, innate immune memory, also called trained immunity, is imprinted in innate cells such as macrophages and natural killer cells through epigenetic and metabolic reprogramming. However, these mechanisms of memory generation and maintenance are compromised as organisms age. Almost all immune cell types, both mature cells and their progenitors, go through age-related changes concerning numbers and functions. The aging immune system renders the elderly highly susceptible to infections and incapable of mounting a proper immune response upon vaccinations. Besides the increased infectious burden, older individuals also have heightened risks of metabolic and neurodegenerative diseases, which have an immunological component. This review discusses how immune function, particularly the establishment and maintenance of innate and adaptive immunological memory, regulates and is regulated by epigenetics, metabolic processes, gut microbiota, and the central nervous system throughout life, with a focus on old age. We explain in-depth how epigenetics and cellular metabolism impact immune cell function and contribute or resist the aging process. Microbiota is intimately linked with the immune system of the human host, and therefore, plays an important role in immunological memory during both homeostasis and aging. The brain, which is not an immune-isolated organ despite former opinion, interacts with the peripheral immune cells, and the aging of both systems influences the health of each other. With all these in mind, we aimed to present a comprehensive view of the aging immune system and its consequences, especially in terms of immunological memory. The review also details the mechanisms of promising anti-aging interventions and highlights a few, namely, caloric restriction, physical exercise, metformin, and resveratrol, that impact multiple facets of the aging process, including the regulation of innate and adaptive immune memory. We propose that understanding aging as a complex phenomenon, with the immune system at the center role interacting with all the other tissues and systems, would allow for more effective anti-aging strategies.

Recent strategies driving oral biologic administration

INTRODUCTION

High patient compliance, noninvasiveness, and self-administration are the leading features of vaccine delivery through the oral route. The implementation of swift mass vaccination campaigns in pandemic outbreaks fascinates the use of oral vaccination. This approach can elicit both mucosal and systemic immune responses to protect against infection at the surface of the mucosa.

AREA COVERED

As pathogen entry and spread mainly occurs through the gastrointestinal tract (GIT) mucosal surfaces, oral vaccination may protect and limit disease spread. Oral vaccines target various potential mucosal inductive sites in the GIT, such as the oral cavity, gastric area, and small intestine. Orally delivered vaccines having subunit and nucleic acid pass through various GIT-associated risks, such as the biodegradation of biologics and their reduced absorption. This article presents a summarized review of the existing technologies and prospects for oral vaccination.

EXPERT OPINION

The intestinal mucosa focuses on current approaches, while future strategies target new mucosal sites, i.e. oral cavity and stomach. Recent developments in biologic delivery through the oral route and their potential use in future oral vaccination are mainly considered.

CD4+ CD8αα+ T cells in the gastric epithelium mediate chronic inflammation induced by Helicobacter felis

CD4⁺ CD8αα⁺ double-positive intraepithelial T lymphocytes (DP T cells), a newly characterized subset of intraepithelial T cells, are reported to contribute to local immunosuppression. However, the presence of DP T cells in Helicobacter. pylori -induced gastritis and their relationship with disease prognosis has yet to be elucidated. In this study, a chronic gastritis model was established by infecting mice with Helicobacter felis. Gastric-infiltrating lymphocytes were isolated from these mice and analyzed by flow cytometry. The frequency of DP T cells in H. felis-induced gastritis mice was higher than that in uninfected mice. The gastric DP T cells were derived from lamina propria cells but were predominantly distributed in the gastric epithelial layer. These gastric DP T cells also exhibited anti-inflammatory functions, and they inhibited the maturation of dendritic cells and proliferation of CD4⁺ T lymphocytes in vitro. Elimination of DP T cells simultaneously resulted in severe gastritis and a reduction of H. felis load in vivo. Finally, vaccine mixed with different adjuvants was used to explore the relationship between vaccine efficacy and DP cells. Silk fibroin as the vaccine delivery system enhanced vaccine efficacy by reducing the number of DP T cells. This study demonstrated that DP T cells perform an immunosuppressive role in Helicobacter felis-induced gastritis, and consequently, DP T cells may affect disease prognosis and vaccine efficacy.

Helicobacter pylori induces gastric cancer via down-regulating miR-375 to inhibit dendritic cell maturation

BACKGROUND

Recent studies and clinical samples have demonstrated that Helicobacter pylori could induce the downregulation of miR-375 in the stomach and promote gastric carcinogenesis. However, whether the immune cells are affected by Helicobacter pylori due to the downregulation of miR-375 is unclear.

MATERIALS AND METHODS

In this study, we constructed an overexpression and knockdown of miR-375 and Helicobacter pylori infection cell models in vitro. In addition, the maturity of dendritic cells (DCs) and the expression of IL-6, IL-10, and VEGF at the transcriptional and translational levels were analyzed. Changes in the JAK2-STAT3 signaling pathway were detected. In vivo, the number changes in CD4+ T and CD8+ T cells and the size changes of tumors via models of transplantable subcutaneous tumors were also analyzed.

RESULTS

A cell model of Helicobacter pylori and gastric cancer was used to identify the expression of miR-375 and the maturity of dendritic cells. This study found that Helicobacter pylori could downregulate miR-375, which regulates the expression of cytokines IL-6, IL-10, and VEGF in the stomach. MiR-375 regulated the expression of cytokines IL-6, IL-10, and VEGF through the JAK2-STAT3 signaling pathway in vitro. In addition, we found that Helicobacter pylori regulates the maturation of dendritic cells through miR-375. These results were further verified in vivo, and miR-375 diminishes tumor size was also demonstrated. This study showed that immature DCs caused a decrease in the number of CD4+ and CD8+ T cells.

CONCLUSIONS

This study demonstrated that Helicobacter pylori can inhibit miRNA-375 expression in the stomach. Downregulated miR-375 activates the JAK2-STAT3 pathway. Activating the JAK2-STAT3 signaling pathway promotes the secretion of IL-6, IL-10, and VEGF, leading to immature differentiation of DCs and induction of gastric cancer.

Gastric eosinophils are detrimental for Helicobacter pylori vaccine efficacy

Helicobacter pylori (Hp) colonizes the human gastric mucosa with a high worldwide prevalence. Currently, Hp can be eradicated by the use of antibiotics. Due to the increase of antibiotic resistance, new therapeutic strategies need to be devised: one such approach being prophylactic vaccination. Pre-clinical and clinical data showed that a urease-based vaccine is efficient in decreasing Hp infection through the mobilization of T helper (Th)-dependent immune effectors, including eosinophils. Preliminary data have shown that upon vaccination and subsequent Hp infection, eosinophils accumulate in the gastric mucosa, suggesting a possible implication of this granulocyte subset in the vaccine-induced reduction of Hp infection. In our study, we confirm that activated eosinophils, expressing CD63, CD40, MHCII and PD-L1 at their cell surface, infiltrate the gastric mucosa during vaccine-induced reduction of Hp infection. Strikingly, we provide evidence that bone marrow derived eosinophils efficiently kill Hp in vitro, suggesting that eosinophils may participate to the vaccine-induced reduction of Hp infection. However, conversely to our expectations, the absence of eosinophils does not decrease the efficacy of this Hp vaccine in vivo. Indeed, vaccinated mice that have been genetically ablated of the eosinophil lineage or that have received anti-Sialic acid-binding immunoglobulin-like lectin F eosinophil-depleting antibodies, display a lower Hp colonization when compared to their eosinophil sufficient counterparts. Although the vaccine induces similar urease-specific humoral and Th responses in both eosinophil sufficient and deficient mice, a decreased production of anti-inflammatory cytokines, such as IL-10, TGFβ, and calgranulin B, was specifically observed in eosinophil depleted mice. Taken together, our results suggest that gastric eosinophils maintain an anti-inflammatory environment, thus sustaining chronic Hp infection. Because eosinophils are one of the main immune effectors mobilized by Th2 responses, our study strongly suggests that the formulation of an Hp vaccine needs to include an adjuvant that preferentially primes Hp-specific Th1/Th17 responses.

Oral Biologic Delivery: Advances Toward Oral Subunit, DNA, and mRNA Vaccines and the Potential for Mass Vaccination During Pandemics

Oral vaccination enables pain-free and self-administrable vaccine delivery for rapid mass vaccination during pandemic outbreaks. Furthermore, it elicits systemic and mucosal immune responses. This protects against infection at mucosal surfaces, which may further enhance protection and minimize the spread of disease. The gastrointestinal (GI) tract presents a number of prospective mucosal inductive sites for vaccine targeting, including the oral cavity, stomach, and small intestine. However, currently available oral vaccines are effectively limited to live-attenuated and inactivated vaccines against enteric diseases. The GI tract poses a number of challenges,including degradative processes that digest biologics and mucosal barriers that limit their absorption. This review summarizes the approaches currently under development and future opportunities for oral vaccine delivery to established (intestinal) and relatively new (oral cavity, stomach) mucosal targets. Special consideration is given to recent advances in oral biologic delivery that offer promise as future platforms for the administration of oral vaccines.

Infiltration of Immunoinflammatory Cells and Related Chemokine/Interleukin Expression in Different Gastric Immune Microenvironments

Gastric mucosal immune microenvironment plays an important role in the occurrence and development of diseases such as inflammation and cancer. In the present study, single-sample gene set enrichment analysis (ssGSEA) was used to evaluate the expression of cytokines and the degree of immune cell infiltration in four different gastric mucosa tissues from normal gastric mucosa, simple gastritis, and atrophic gastritis to gastric cancer. Here, we show the immune microenvironments of these four gastric mucosae were significantly different. From inflammation to gastric cancer, most immunoinflammatory cells showed a downward trend such as central memory CD4 T cell. Instead, several cells showed an upward trend such as macrophage. Additionally, we found some chemokines/interleukins were illustrated to be low expressed (or highly expressed) in precancerous stage and highly expressed (or low expressed) in postcancerous stage, which demonstrated an opposite expression characteristic in pre-/postcancerous stage.

Silk fibroin hydrogel as mucosal vaccine carrier: induction of gastric CD4+TRM cells mediated by inflammatory response induces optimal immune protection against Helicobacter felis

Tissue-resident memory T (T_RM) cells, located in the epithelium of most peripheral tissues, constitute the first-line defense against pathogen infections. Our previous study reported that gastric subserous layer (GSL) vaccination induced a “pool” of protective tissue-resident memory CD4+T (CD4+T_RM) cells in the gastric epithelium. However, the mechanistic details how CD4+T_RM cells form in the gastric epithelium are unknown. Here, our results suggested that the vaccine containing CCF in combination with Silk fibroin hydrogel (SF) broadened the distribution of gastric intraepithelial CD4+T_RM cells. It was revealed that the gastric intraepithelial T_RM cells were even more important than circulating memory T cells against infection by Helicobacter felis. It was also shown that gastric-infiltrating neutrophils were involved as indispensable mediators which secreted CXCL10 to chemoattract CXCR3+CD4+T cells into the gastric epithelium. Blocking of CXCR3 or neutrophils significantly decreased the number of gastric intraepithelial CD4+T_RM cells due to reduced recruitment of CD4+T cells. This study demonstrated the protective efficacy of gastric CD4+T_RM cells against H. felis infection, and highlighted the influence of neutrophils on gastric intraepithelial CD4+T_RM cells formation.

Tumor-Infiltrating Lymphocyte-Based Risk Score for Predicting Prognosis in Gastric Cancer

Tumor-infiltrating lymphocytes (TILs) in gastric cancer are closely related to clinical prognosis; however, little is known regarding the immune microenvironment in this disease. Thus, RNA-sequencing data from gastric cancer patients were downloaded from the Gene Expression Omnibus (GEO). The proportion of immune cells was determined based on a deconvolution algorithm (CIBERSORT), and gene expression profiles were analyzed in the context of clinical outcomes to construct an immune risk score. Data were analyzed using least absolute shrinkage and selection operator (LASSO) and multivariable Cox regression, to identify prognostic markers of gastric cancer survival. The model included four immune cell types: neutrophils, plasma cells, activated CD4+ memory T cells, and T follicular helper cells. Patients were classified into two subgroups based on risk score, and a significant difference in overall survival (OS) was seen between the subgroups in both the training and testing cohorts, particularly in patients with tumor stages ≥T3. Multivariable analysis revealed that both T-stage and risk score were independent prognostic factors for gastric cancer survival [hazard ratio (HR) 1.505; 95% confidence interval (CI) 1.043-2.173, HR 1.686; 95% CI 1.367-2.080]. Risk scores and clinical factors were then integrated into a nomogram to build a model with both good discriminatory power and accuracy in predicting clinical outcomes. Further analysis using gene set enrichment analysis (GSEA) identified strong associations of immune risk with TGF-β and tumor metastasis-related pathways, which could inform research on the molecular mechanisms of gastric cancer. Collectively, the data presented here suggest that an immune risk model can make an important contribution to predictions prognosis in gastric cancer patients.

Effect of the cagW-based gene vaccine on the immunologic properties of BALB/c mouse: an efficient candidate for Helicobacter pylori DNA vaccine

BACKGROUND

Helicobacter pylori (H. pylori) infect more than half of the world population, and they cause different serious diseases such as gastric carcinomas. This study aims to design a vaccine on the basis of cagW against H. pylori infection. After pcDNA3.1 (+)-cagW-CS-NPs complex is produced, it will be administered into the muscles of healthy BALB/c mice in order to study the effect of this DNA vaccine on the interleukin status of mice, representing its effect on the immune system. After that, the results will be compared with the control groups comprising the administration of cagW-pCDNA3.1 (+) vaccine, the administration of chitosan and the administration of PBS in the muscles of mice.

METHODS

The cagW gene of H. pylori was amplified by employing PCR, whose product was then cloned into the pcDNA3.1 (+) vector, and this cloning was confirmed by PCR and BamHI/EcoRV restriction enzyme digestion. CagW gene DNA vaccine was encapsulated in chitosan nanoparticles (pcDNA3.1 (+)-cagW-CS-NPs) using a complex coacervation method. The stability and in vitro expression of chitosan nanoparticles were studied by DNase I digestion and transfection, and the immune responses elicited in specific pathogen-free (SPF) mice by the pcDNA3.1 (+)-cagW-CS-NPs were evaluated. Apart from that, the protective potential pcDNA3.1 (+)-cagW-CS-NPs was evaluated by challenging with H. pylori.

RESULTS

The pcDNA3.1 (+)-cagW-CS-NPs comprises cagW gene of H. pylori that is encapsulated in chitosan nanoparticles, produced with good morphology, high stability, a mean diameter of 117.7 nm, and a zeta potential of + 5.64 mV. Moreover, it was confirmed that chitosan encapsulation protects the DNA plasmid from DNase I digestion, and the immunofluorescence assay showed that the cagW gene could express in HDF cells and maintain good bioactivity at the same time. In comparison to the mice immunized with the control plasmid, in vivo immunization revealed that mice immunized with pcDNA3.1 (+)-cagW-NPs showed better immune responses and prolonged release of the plasmid DNA.

CONCLUSIONS

This research proves chitosan-DNA nanoparticles as potent immunization candidates against H. pylori infection and paves the way for further developments in novel vaccines encapsulated in chitosan nanoparticles.

Memory CD4+ T Cells in Immunity and Autoimmune Diseases

CD4⁺ T helper (Th) cells play central roles in immunity in health and disease. While much is known about the effector function of Th cells in combating pathogens and promoting autoimmune diseases, the roles and biology of memory CD4⁺ Th cells are complex and less well understood. In human autoimmune diseases such as multiple sclerosis (MS), there is a critical need to better understand the function and biology of memory T cells. In this review article we summarize current concepts in the field of CD4⁺ T cell memory, including natural history, developmental pathways, subsets, and functions. Furthermore, we discuss advancements in the field of the newly-described CD4⁺ tissue-resident memory T cells and of CD4⁺ memory T cells in autoimmune diseases, two major areas of important unresolved questions in need of answering to advance new vaccine design and development of novel treatments for CD4⁺ T cell-mediated autoimmune diseases.

Perivascular Lymphocyte Clusters Induced by Gastric Subserous Layer Vaccination Mediate Optimal Immunity against Helicobacter through Facilitating Immune Cell Infiltration and Local Antibody Response

Background

In situ vaccination-induced local inflammatory response resulted in the establishment of a pool of tissue-resident memory T (T_RM) cells and new vessels after the resolution of inflammation. T_RM cells have received increasing attention; however, the role of new vessels in protective response is still unknown.

Materials and Methods

We performed the laparotomy to access the stomach and injected alum-based vaccine into the gastric subserous layer (GSL). At 28 days post vaccination, a parabiosis mouse model along with depletion of anti-CD90.2 antibody was employed to explore the function of perivascular lymphocyte clusters in recall responses. The composition of the gastric lymphocyte clusters was analyzed by immunofluorescence staining. Antibody responses were detected using ELISA. Gastric lymphocytes were analyzed using flow cytometry.

Results

GSL vaccination induced the formation of new vessels in the inflamed region. These new vessels were different from native vessels in that they were generally accompanied by perivascular lymphocyte clusters that mainly consisted of CD90-expressing cells. Additionally, histological analysis revealed the presence of CD4⁺ and CD8⁺ T cells in the perivascular lymphocyte clusters. Administration of a dose of an anti-CD90.2 antibody to GSL-vaccinated mice resolved these clusters. The efficacy of protection was compared in the parabiosis mice. Upon challenge, the presence of perivascular lymphocyte clusters was responsible for the fast recall response, as depletion of these clusters by CD90.2 antibody administration resulted in decreased expressions of VCAM-1, Madcam-1, and TNF-α, as well as lower recruitment of proinflammatory immune cells, decreased antibody levels, and poor protection.

Conclusions

Our research demonstrates that in situ vaccination-induced regional inflammatory response contributes to optimal recall response not only by establishing a CD4⁺ T_RM pool but also by creating an “expressway,” i.e., perivascular lymphocyte cluster.

Vaccine-induced gastric CD4+ tissue-resident memory T cells proliferate in situ to amplify immune response against Helicobacter pylori insult

BACKGROUND

Tissue-resident memory T cells accelerate the clearance of pathogens during recall response. However, whether CD4⁺ TRM cells themselves can provide gastric immunity is unclear.

MATERIALS AND METHODS

We established a parabiosis model between the enhanced green fluorescent protein and wild-type mice that the circulation system was shared, and the wild-type partner was vaccinated with H pylori vaccine composed of CCF and silk fibroin in gastric subserous layer to induce gastric EGFP⁺ CD4⁺ TRM cells. Antigen-specific EGFP⁺ CD4⁺ T cells and proliferous TRM cells were analyzed by flow cytometry. The colonization of H pylori was detected by quantitative real-time PCR. EGFP⁺ CD4⁺ TRM cells and the inflammation of the stomach were observed by histology.

RESULTS

A parabiosis animal model was employed to identify the cells that introduced by vaccination in GSL. Antigen-specific EGFP⁺ CD4⁺ T cells could be detected at day 7 post-vaccination. Thirty days later, EGFP⁺ CD4⁺ TRM cells were established with a phenotype of CD69⁺ CD103^- . Of note, we found that when circulating lymphocytes were depleted by FTY720 administration, these TRM cells could proliferate in situ and differentiate into effector Th1 cells after H pylori challenge. A decrease in H pylori colonization was observed in the vaccinated mice but not unvaccinated mice. Further, we found that although FTY720 was administrated, mounted pro-inflammatory myeloid cells still emerged in the stomach of the vaccinated mice, which might contribute to the reduction of H pylori colonization.

CONCLUSIONS

Our study reveals that H pylori vaccine-induced CD4⁺ TRM cells can proliferate and differentiate in situ to enhance gastric local immunity during recall response.