Novel insights on the role of CD8+ T cells and cytotoxic responses during Helicobacter pylori infection

Effects of Helicobacter pylori infection on intestinal microbiota, immunity and colorectal cancer risk

Infecting about half of the world´s population, Helicobacter pylori is one of the most prevalent bacterial infections worldwide and the strongest known risk factor for gastric cancer. Although H. pylori colonizes exclusively the gastric epithelium, the infection has also been associated with various extragastric diseases, including colorectal cancer (CRC). Epidemiological studies reported an almost two-fold increased risk for infected individuals to develop CRC, but only recently, direct causal and functional links between the chronic infection and CRC have been revealed. Besides modulating the host intestinal immune response, H. pylori is thought to increase CRC risk by inducing gut microbiota alterations. It is known that H. pylori infection not only impacts the gastric microbiota at the site of infection but also leads to changes in bacterial colonization in the distal large intestine. Considering that the gut microbiome plays a driving role in CRC, H. pylori infection emerges as a key factor responsible for promoting changes in microbiome signatures that could contribute to tumor development. Within this review, we want to focus on the interplay between H. pylori infection, changes in the intestinal microbiota, and intestinal immunity. In addition, the effects of H. pylori antibiotic eradication therapy will be discussed.

Mucosal Immunity Related to CD8+ T Lymphocytes in Children with Helicobacter pylori Gastritis

Purpose

We investigated the role of CD8+T cells as host immune factors in pediatric patients with Helicobacter pylori gastritis.

Methods

Gastric mucosal tissue and blood samples were collected from 39 children, including 11 children with H. pylori infection and 28 children as controls. Anti-CD8 and anti-T-bet antibodies were used for immunohistochemistry of the gastric mucosa. For the cell surface and intracellular staining, peripheral blood mononuclear cells were stained with anti-IL7Rα, anti-CX3CR1, anti-CD8, anti-T-bet, and anti-IFN-γ antibodies. Cytokines of sera such as tumor necrosis factor alpha (TNF-α) and CX3CL1 were analyzed using enzyme- linked immunosorbent assay (ELISA).

Results

In the immunohistochemistry of gastric mucosa, the frequency of CD8+ and T-bet+ T cells cells was higher in the H. pylori-positive group than in the control group (26.9± 7.8% vs. 16.9±3.3%, p<0.001; 5.0±2.5% vs. 2.2±0.7%, p=0.001). Between the control and H. pylori-positive groups, the frequency of IL-7RαlowCX3CR1+ CD8+ and T-bet+ INF-γ+ CD8+ T cells were not significantly different between surface and intracellular staining, respectively (40.4±24.0% vs. 38.2±17.8%, p=0.914; 40.4±24.0% vs. 38.2±17.8%, p=0.914). In the ELISA, no significant differences in TNF-α and CX3CL1 concentrations were observed between the control and H. pylori-positive groups (34.3±12.1 pg/mL vs. 47.0±22.6 pg/mL, p=0.114/0.5± 0.1 pg/mL vs. 0.5±0.1 pg/mL, p=0.188).

Conclusion

CD8+ T and Th1 cells, which secrete IFN-γ, might play important roles in the mucosal immunity of the stomach in children with H. pylori infection.

Prebiotic-mediated gastroprotective potentials of three bacterial levans through NF-κB-modulation and upregulation of systemic IL-17A

This study aimed to investigate whether the gastroprotective effects of three types of bacterial levans are correlated with their prebiotic-associated anti-inflammatory/antioxidant potentials. Three levans designated as LevAE, LevP, and LevZ were prepared from bacterial honey isolates; purified, and characterized using TLC, NMR, and FTIR. The anti-inflammatory properties of levan preparations were assessed in LPS-stimulated RAW 264.7 cell lines, while their safety and gastroprotective potentials were assessed in Wistar rats. The three levans significantly reduced ulcer number (22.29-70.05 %) and severity (31.76-80.54 %) in the ethanol-induced gastric ulcer model compared to the control (P < 0.0001/each), with the highest effect observed in LevAE and levZ (200 mg/each) (P < 0.0001). LevZ produced the highest levels of glutathione; catalase activity, and the lowest MDA levels (P = 0.0001/each). The highest anti-inflammatory activity was observed in LevAE and levZ in terms of higher inhibitory effect on IL-1β and TNF-α production (P < 0.0001 each); COX2, PGE2, and NF-κB gene expression. The three levan preparations also proved safe with no signs of toxicity, with anti-lipidemic properties as well as promising prebiotic activity that directly correlated with their antiulcer effect. This novel study highlights the implication of prebiotic-mediated systemic immunomodulation exhibited by bacterial levans that directly correlated with their gastroprotective activity.

UreB immunodominant epitope-specific CD8+ T-cell responses were beneficial in reducing gastric symptoms in Helicobacter pylori-infected individuals

BACKGROUND AND AIMS

Although Helicobacter pylori is recognized as an extracellular infection bacterium, it can lead to an increase in the number of CD8⁺ T cells after infection. At present, the characteristics of H. pylori antigen-specific CD8⁺ T cells and the epitope response have not been elucidated. This study was focused on putative protective antigen UreB to detect specific CD8⁺ T-cell responses in vitro and screen for predominant response epitopes.

METHODS

The PBMCs collected from H. pylori-infected individuals were stimulated by UreB peptide pools in vitro to identify the immunodominant CD8⁺ T-cell epitopes. Furthermore, their HLA restriction characteristics were detected accordingly by NGS. Finally, the relationship between immunodominant responses and appearance of gastric symptoms after H. pylori infection was conducted.

RESULTS

UreB-specific CD8⁺ T-cell responses were detected in H. pylori-infected individuals. Three of UreB dominant epitopes (A-2 (UreB_443-451 : GVKPNMIIK), B-4 (UreB_420-428 : SEYVGSVEV), and C-1 (UreB_5-13 : SRKEYVSMY)) were firstly identified and mainly presented by HLA-A*1101, HLA-B*4001 and HLA-C*0702 alleles, respectively. C-1 responses were mostly occurred in H. pylori-infected subjects without gastric symptoms and may alleviate the degree of gastric inflammation.

CONCLUSIONS

The UreB dominant epitope-specific CD8⁺ T-cell response was closely related to the gastric symptoms after H. pylori infection, and the C-1 (UreB_5-13 ) dominant peptides may be protective epitopes.

Breastfeeding Is Associated with Lower Likelihood of Helicobacter Pylori Colonization in Babies, Based on a Prospective USA Maternal-Infant Cohort

BACKGROUND

Mother-to-child transmission of Helicobacter pylori (H. pylori) is the primary source of intrafamilial spread in early childhood in regions of high H. pylori prevalence. However, early-in-life H. pylori colonization and associated protective or risk factors have not been fully evaluated in lower prevalence regions, such as the USA.

AIMS

Therefore, from a well-characterized prospective US cohort, we selected women who provided fecal samples during pregnancy and had paired fecal samples from their babies up to 24 months postpartum. We evaluated maternal and baby factors associated with likelihood of H. pylori colonization in the babies. Fecal antigen testing was used to determine H. pylori status. We also evaluated the association between maternal breastmilk cytokines and H. pylori colonization in breastfed babies.

RESULTS

Among included mother-baby pairs (n = 66), H. pylori prevalence was 31.8% in mothers and 19.7% in their babies. Dominant breastfeeding (adjusted odds ratio [aOR] 0.17, 95% CI 0.03-0.98) and maternal IBD (aOR 0.05, 95% CI 0.01-0.27) were associated with significantly lower likelihood of H. pylori colonization among babies; no other clinical factors were associated with H. pylori colonization in the babies. Matrix metalloproteinase-10 (MMP-10) and tumor necrosis factor-related activation-induced cytokine expression were significantly higher in breastmilk of mothers with H. pylori positive vs negative babies.

CONCLUSIONS

Consistent with data from high H. pylori prevalence regions, our findings suggest dominant breastfeeding may protect against early H. pylori colonization. Downregulation of pro-inflammatory cytokines such as MMP-10 may be relevant in mediating this protection among breastfed babies, but more data are needed.

Helicobacter urease suppresses cytotoxic CD8 + T cell responses through activating Myh9-dependent induction of PD-L1

As a key virulence factor for persistent colonization, Urease B subunit (UreB) is considered to be an ideal vaccine antigen against Helicobacter pylori (H. pylori) infection. However, the role and molecular mechanisms of UreB involved in immune microenvironment dysregulation still remains largely unknown. In the present study, we evaluated the effects of UreB on macrophage activation and found that UreB induced PD-L1 accumulation on Bone marrow-derived macrophages (BMDMs). Co-culture assays further revealed that UreB-induced PD-L1 expression on BMDMs significantly decreased the proliferation and secretion of cytolytic molecules (granzyme B and perforin) of splenic CD8 + T cells isolated from inactivated H. pylori-immunized mice. More importantly, myosin heavy chain 9 (Myh9) was confirmed to be a direct membrane receptor of UreB via using LC-MS/MS and Co-immunoprecipitation and required for PD-L1 upregulation on BMDMs. Molecular studies further demonstrated that the interaction between UreB and Myh9 decreased GCN2 autophosphorylation and enhanced intracellular pool of amino acids, leading to the upregulation of S6K phosphorylation, a commonly used marker for monitoring activation of mTORC1 signaling activity. Furthermore, blocking mTORC1 activation with its inhibitor Temsirolimus reversed UreB-induced PD-L1 upregulation and the subsequently inhibitory effects of BMDMs on activation of cytotoxic CD8 + T cell responses. Overall, our data unveil a novel immunosuppressive mechanism of UreB during H. pylori infection, which may provide valuable clue for the optimization of H. pylori vaccine.

Programmed Death Ligand 1-Expressing Classical Dendritic Cells MitigateHelicobacter-Induced Gastritis

BACKGROUND & AIMS

Helicobacter pylori has been reported to modulate local immune responses to colonize persistently in gastric mucosa. Although the induced expression of programmed cell death ligand 1 (PD-L1) has been suggested as an immune modulatory mechanism for persistent infection of H pylori, the main immune cells expressing PD-L1 and their functions in Helicobacter-induced gastritis still remain to be elucidated.

METHODS

The blockades of PD-L1 with antibody or PD-L1-deficient bone marrow transplantation were performed in Helicobacter-infected mice. The main immune cells expressing PD-L1 in Helicobacter-infected stomach were determined by flow cytometry and immunofluorescence staining. Helicobacter felis or H pylori-infected dendritic cell (DC)-deficient mouse models including Flt3-/-, Zbtb46-diphtheria toxin receptor, and BDCA2-diphtheria toxin receptor mice were analyzed for pathologic changes and colonization levels. Finally, the location of PD-L1-expressing DCs and the correlation with H pylori infection were analyzed in human gastric tissues using multiplexed immunohistochemistry.

RESULTS

Genetic or antibody-mediated blockade of PD-L1 aggravated Helicobacter-induced gastritis with mucosal metaplasia. Gastric classical DCs expressed considerably higher levels of PD-L1 than other immune cells and co-localized with T cells in gastritis lesions from Helicobacter-infected mice and human beings. H felis- or H pylori-infected Flt3-/- or classical DC-depleted mice showed aggravated gastritis with severe T-cell and neutrophil accumulation with low bacterial loads compared with that in control mice. Finally, PD-L1-expressing DCs were co-localized with T cells and showed a positive correlation with H pylori infection in human subjects.

CONCLUSIONS

The PD-1/PD-L1 pathway may be responsible for the immune modulatory function of gastric DCs that protects the gastric mucosa from Helicobacter-induced inflammation, but allows persistent Helicobacter colonization.

Swine as biomedical animal model for T-cell research-Success and potential for transmittable and non-transmittable human diseases

Swine is biologically one of the most relevant large animal models for biomedical research. With its use as food animal that can be exploited as a free cell and tissue source for research and its high susceptibility to human diseases, swine additionally represent an excellent option for both the 3R principle and One Health research. One of the previously most limiting factors of the pig model was its arguably limited immunological toolbox. Yet, in the last decade, this toolbox has vastly improved including the ability to study porcine T-cells. This review summarizes the swine model for biomedical research with focus on T cells. It first contrasts the swine model to the more commonly used mouse and non-human primate model before describing the current capabilities to characterize and extend our knowledge on porcine T cells. Thereafter, it not only reflects on previous biomedical T-cell research but also extends into areas in which more in-depth T-cell analyses could strongly benefit biomedical research. While the former should inform on the successes of biomedical T-cell research in swine, the latter shall inspire swine T-cell researchers to find collaborations with researchers working in other areas - such as nutrition, allergy, cancer, transplantation, infectious diseases, or vaccine development.

The important role played by chemokines influence the clinical outcome of Helicobacter pylori infection

The extended infection with Helicobacter pylori (H. pylori), one of the most frequent infectious agents in humans, may cause gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer. During H. pylori infection, different kinds of inflammatory cells such as dendritic cells, macrophages, neutrophils, mast cells, eosinophils, T cells and B cells are accumulated into the stomach. The interactions between chemokines and their respective receptors recruit particular types of the leukocytes that ultimately determine the nature of immune response and therefore, have a main influence on the consequence of infection. The suitable production of chemokines especially in the early stages of H. pylori infection shapes appropriate immune responses that contribute to the H. pylori elimination. The unbalanced expression of the chemokines can contribute in the induction of inappropriate responses that result in the tissue damage or malignancy. Thus, chemokines and their receptors may be promising potential targets for designing the therapeutic strategies against various types H. pylori-related gastrointestinal disorders. In this review, a comprehensive explanation regarding the roles played by chemokines in H. pylori-mediated peptic ulcer, gastritis and gastric malignancies was provided while presenting the potential utilization of these chemoattractants as therapeutic elements.

Immune response and immune escape mechanism in Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a Gram-negative bacterium which is parasitic on the surface of the gastric mucosa, and it is a causative agent in the development of chronic gastritis, gastric and duodenal peptic ulcer, gastric adenocarcinoma, and lymphoid tissue lymphoma associated with the gastric mucosa. After H. pylori infection, the bacterium is first recognized by the pattern recognition receptors of immune cells, which in turn causes the innate immune and adaptive immune responses, but these responses are usually insufficient to eliminate bacterial infections. H. pylori can evade the identification and clearance by the immune system by modifying and attenuating the immunogenicity of its pathogen-associated molecular patterns, regulating the immune responses of innate immune cells and T cells, and leading to persistent infection. A thorough understanding of the immune response and immune escape mechanism in H. pylori infection is of great significance for eliminating H. pylori infection and controlling the occurrence of H. pylori infection-related diseases.

The importance of TH22 and TC22 cells in the pathogenesis of Helicobacter pylori-associated gastric diseases

BACKGROUND

An association exists between Helicobacter pylori (H. pylori), peptic ulcers, gastritis, and sometimes gastric carcinomas. Th22 cells have protective and inflammatory roles in defense against microbes.

AIM

We investigated the frequencies of Th22, Tc22, Th22/17, and Tc22/17 cells in addition to the changes in levels of cytokines IL-22, IL-6, IL-23, TNF-α, IL-1β, and TGF-β in sera from patients with H. pylori-associated gastritis, and peptic ulcer, and in uninfected patients.

METHODS

A total of 76 patients with H. pylori-associated disorders formed the studied group. Frequencies of T-cell subsets were determined by flow cytometry. Levels of cytokines IL-22, IL-6, IL-23, TNF-α, IL-1β, and TGF-β in the sera and supernatants of patients were measured by ELISA and flow cytometry.

RESULTS

The study participants included 32 males and 44 females with a mean age of 38.5±15.3 years. We divided the infected group into peptic ulcer and gastritis (mild, moderate, active chronic, and chronic). The frequencies of Th22, Tc22, and Tc22/17 increased significantly in the peptic ulcer, moderate, active chronic, and chronic gastritis groups compared to the uninfected group. Th22/17 only increased significantly in the chronic gastritis group. We observed significant increases in IL-22 in the moderate and active chronic gastritis, IL-23 in the active chronic and chronic gastritis, and TNF-α in the peptic ulcer and moderate gastritis groups. Following in vitro antigenic stimulation, we observed significantly higher levels of IL-1β, IL-23, and IL-6 in the active chronic gastritis group, as well as IL-6 and IL-1β in the chronic gastritis group compared to the uninfected group.

CONCLUSION

Increased Th22, Tc22, and Tc22/17 cells and IL-22 levels appear to be influential in progression and severity of H. pylori infection. Th22/17 can be an interesting therapeutic target for chronic H. pylori infections where eradication is more difficult.

Dual epithelial and immune cell function of Dvl1 regulates gut microbiota composition and intestinal homeostasis

Homeostasis of the gastrointestinal (GI) tract is controlled by complex interactions between epithelial and immune cells and the resident microbiota. Here, we studied the role of Wnt signaling in GI homeostasis using Disheveled 1 knockout (Dvl1^-/-) mice, which display an increase in whole gut transit time. This phenotype is associated with a reduction and mislocalization of Paneth cells and an increase in CD8⁺ T cells in the lamina propria. Bone marrow chimera experiments demonstrated that GI dysfunction requires abnormalities in both epithelial and immune cells. Dvl1^-/- mice exhibit a significantly distinct GI microbiota, and manipulation of the gut microbiota in mutant mice rescued the GI transit abnormality without correcting the Paneth and CD8⁺ T cell abnormalities. Moreover, manipulation of the gut microbiota in wild-type mice induced a GI transit abnormality akin to that seen in Dvl1^-/- mice. Together, these data indicate that microbiota manipulation can overcome host dysfunction to correct GI transit abnormalities. Our findings illustrate a mechanism by which the epithelium and immune system coregulate gut microbiota composition to promote normal GI function.

Modeling-Enabled Systems Nutritional Immunology

This review highlights the fundamental role of nutrition in the maintenance of health, the immune response, and disease prevention. Emerging global mechanistic insights in the field of nutritional immunology cannot be gained through reductionist methods alone or by analyzing a single nutrient at a time. We propose to investigate nutritional immunology as a massively interacting system of interconnected multistage and multiscale networks that encompass hidden mechanisms by which nutrition, microbiome, metabolism, genetic predisposition, and the immune system interact to delineate health and disease. The review sets an unconventional path to apply complex science methodologies to nutritional immunology research, discovery, and development through “use cases” centered around the impact of nutrition on the gut microbiome and immune responses. Our systems nutritional immunology analyses, which include modeling and informatics methodologies in combination with pre-clinical and clinical studies, have the potential to discover emerging systems-wide properties at the interface of the immune system, nutrition, microbiome, and metabolism.

Systems-wide analyses of mucosal immune responses to Helicobacter pylori at the interface between pathogenicity and symbiosis

Helicobacter pylori is the dominant member of the gastric microbiota in over half of the human population of which 5-15% develop gastritis or gastric malignancies. Immune responses to H. pylori are characterized by mixed T helper cell, cytotoxic T cell and NK cell responses. The presence of Tregs is essential for the control of gastritis and together with regulatory CX3CR1+ mononuclear phagocytes and immune-evasion strategies they enable life-long persistence of H. pylori. This H. pylori-induced regulatory environment might contribute to its cross-protective effect in inflammatory bowel disease and obesity. Here we review host-microbe interactions, the development of pro- and anti-inflammatory immune responses and how the latter contribute to H. pylori's role as beneficial member of the gut microbiota. Furthermore, we present the integration of existing and new data into a computational/mathematical model and its use for the investigation of immunological mechanisms underlying initiation, progression and outcomes of H. pylori infection.

Modeling the Regulatory Mechanisms by Which NLRX1 Modulates Innate Immune Responses to Helicobacter pylori Infection

Helicobacter pylori colonizes half of the world’s population as the dominant member of the gastric microbiota resulting in a lifelong chronic infection. Host responses toward the bacterium can result in asymptomatic, pathogenic or even favorable health outcomes; however, mechanisms underlying the dual role of H. pylori as a commensal versus pathogenic organism are not well characterized. Recent evidence suggests mononuclear phagocytes are largely involved in shaping dominant immunity during infection mediating the balance between host tolerance and succumbing to overt disease. We combined computational modeling, bioinformatics and experimental validation in order to investigate interactions between macrophages and intracellular H. pylori. Global transcriptomic analysis on bone marrow-derived macrophages (BMDM) in a gentamycin protection assay at six time points unveiled the presence of three sequential host response waves: an early transient regulatory gene module followed by sustained and late effector responses. Kinetic behaviors of pattern recognition receptors (PRRs) are linked to differential expression of spatiotemporal response waves and function to induce effector immunity through extracellular and intracellular detection of H. pylori. We report that bacterial interaction with the host intracellular environment caused significant suppression of regulatory NLRC3 and NLRX1 in a pattern inverse to early regulatory responses. To further delineate complex immune responses and pathway crosstalk between effector and regulatory PRRs, we built a computational model calibrated using time-series RNAseq data. Our validated computational hypotheses are that: 1) NLRX1 expression regulates bacterial burden in macrophages; and 2) early host response cytokines down-regulate NLRX1 expression through a negative feedback circuit. This paper applies modeling approaches to characterize the regulatory role of NLRX1 in mechanisms of host tolerance employed by macrophages to respond to and/or to co-exist with intracellular H. pylori.

Sensitivity Analysis of an ENteric Immunity SImulator (ENISI)-Based Model of Immune Responses to Helicobacter pylori Infection

Agent-based models (ABM) are widely used to study immune systems, providing a procedural and interactive view of the underlying system. The interaction of components and the behavior of individual objects is described procedurally as a function of the internal states and the local interactions, which are often stochastic in nature. Such models typically have complex structures and consist of a large number of modeling parameters. Determining the key modeling parameters which govern the outcomes of the system is very challenging. Sensitivity analysis plays a vital role in quantifying the impact of modeling parameters in massively interacting systems, including large complex ABM. The high computational cost of executing simulations impedes running experiments with exhaustive parameter settings. Existing techniques of analyzing such a complex system typically focus on local sensitivity analysis, i.e. one parameter at a time, or a close “neighborhood” of particular parameter settings. However, such methods are not adequate to measure the uncertainty and sensitivity of parameters accurately because they overlook the global impacts of parameters on the system. In this article, we develop novel experimental design and analysis techniques to perform both global and local sensitivity analysis of large-scale ABMs. The proposed method can efficiently identify the most significant parameters and quantify their contributions to outcomes of the system. We demonstrate the proposed methodology for ENteric Immune SImulator (ENISI), a large-scale ABM environment, using a computational model of immune responses to Helicobacter pylori colonization of the gastric mucosa.

Intraepithelial lymphocytes in relation to NIH category IV prostatitis in autopsy prostate

BACKGROUND

Quantitative analysis of the number, normal and pathologic ratios between lymphocytes and epithelial cells (ECs), and the significance of intraepithelial lymphocytes (IELs) in normal prostatic epithelium, benign prostatic hyperplasia (BPH), and high grade prostatic intraepithelial neoplasia (PIN) in relation to NIH category IV prostatitis (histologic prostatitis: HP) was studied in autopsy prostate.

METHODS

IELs were analysed in 59 autopsy prostates, which was routinely embedded in paraffin and immunohistochemically stained for CD3. An average of 300-500 ECs were counted per case. The number of IELs was calculated as the mean/100 ECs. Category IV prostatitis was evaluated using NIH consensus grading system in terms of anatomical localization and grade.

RESULTS

In healthy individuals the mean number of IELs/100 ECs was 0.61 ± 0.34% or ≤1 lymphocyte/100 ECs, which is considered as the normal basal level of prostate IELs. In category IV prostatitis, the mean number of IELs/100 ECs was 8.53 ± 3.25% or 5-11 lymphocytes/100 ECs. The number of IELs in both around and inside inflammation areas correlated to the grade and location of HP (P < 0.0001 and P < 0.0003), the presence of acute glandular inflammation (P < 0.0001), the scattered stromal lymphocytes (P = 0.029), and BPH and PIN associated prostatic inflammation (P < 0.0001).

CONCLUSION

The study presents the first attempt to examine and score the basic quantitative values of prostatic IELs in normal prostate and in relation to category IV prostatitis. The detected normal upper limit of CD3+ IELs is 1 lymphocyte/100 ECs in the normal prostate epithelium. This is considered as an organ specific characteristic of the prostate-associated lymphoid tissue (PALT). Values >5 IELs/100 ECs indicate the presence of category IV prostatitis. The severity of inflammation correlates to the number of IELs. There is an intimate link between the quantity of the IELs, the degree of the severity and the localization of category IV prostatitis. HP is a chronic and dynamic inflammatory process affecting the whole prostate gland. The increased number of IELs suggests the immune or autoimmune character of category IV prostatitis, BPH and inflammatory preneoplastic (PIN) lesions in the prostatic tumor environment.

Immunology and vaccines and nanovaccines for Helicobacter pylori infection

Helicobacter pylori infection is very common worldwide and is an important cause of gastritis, peptic ulcer disease, gastric mucosa-associated lymphoid tissue lymphoma, and gastric adenocarcinoma. Since the eradication requires treatment with multidrug regimens, prevention of primary infection by a suitable vaccine is attractive. Developing vaccines on the spot when and where an infection is breaking out might be possible, thanks to engineered nanoparticles. In this review, the nature of the host immune response to H. pylori infection is considered. We explain recent candidate vaccines and prophylactic or therapeutic immunization strategies for use against H. pylori. We also describe identification of different types of immune responses that may be related to protection against H. pylori infection. Thus, it seems that there is still a strong need to clarify the main protective immune response against H. pylori.