B-cell and T-cell immune responses to experimental Helicobacter pylori infection in humans

Implications of lncRNAs in Helicobacter pylori-associated gastrointestinal cancers: underlying mechanisms and future perspectives

Helicobacter pylori (H. pylori) is a harmful bacterium that is difficult to conveniently diagnose and effectively eradicate. Chronic H. pylori infection increases the risk of gastrointestinal diseases, even cancers. Despite the known findings, more underlying mechanisms are to be deeply explored to facilitate the development of novel prevention and treatment strategies of H. pylori infection. Long noncoding RNAs (lncRNAs) are RNAs with more than 200 nucleotides. They may be implicated in cell proliferation, inflammation and many other signaling pathways of gastrointestinal cancer progression. The dynamic expression of lncRNAs indicates their potential to be diagnostic or prognostic biomarkers. In this paper, we comprehensively summarize the processes of H. pylori infection and the treatment methods, review the known findings of lncRNA classification and functional mechanisms, elucidate the roles of lncRNAs in H. pylori-related gastrointestinal cancer, and discuss the clinical perspectives of lncRNAs.

CCR6+ T helper cells and regulatory T cells in the blood and gastric mucosa during Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H. pylori) can evade the host's immune response and persist for a long time on the gastric mucosa. T helper (Th) cells appear to be involved in the control of H. pylori bacteria but promote mucosal inflammation. In contrast, regulatory T cells (Tregs) may reduce inflammation but promote H. pylori persistence. CC motif chemokine receptor 6 (CCR6) is involved in the migration of various cells into inflamed gastric mucosa. In this study, we examined CCR6+ Th cells and CCR6+ Tregs during H. pylori infection in humans.

MATERIALS AND METHODS

Isolation of cells from blood and mucosal biopsies, magnetic separation of В cells, CD4+ and CD4+CCR6+CD45RO+ T cells, antigen-specific activation, B cell response in vitro, flow cytometry, determination of CD4+CD25hiFoxP3+ Tregs and various groups of Th cells.

RESULTS

CD4+CCR6+ blood lymphocytes from healthy donors included Th cells and Tregs. These CCR6+ Th cells produced proinflammatory cytokines and also stimulated plasma cell maturation and antibody production in vitro. H. pylori gastritis and peptic ulcer disease were associated with an increase in the number of circulate CD4+CCR6+CD45RO+ cells and the percentage of Th1, Th17 and Th1/17 cells in this lymphocyte subgroup. In H. pylori-positive patients, circulating CD4+CCR6+ cells contained a higher proportion of H. pylori-specific cells compared with their CD4+CCR6- counterparts. H. pylori infection strongly increased the content of CD4+ lymphocytes in the inflamed gastric mucosa, with the majority of these CD4+ lymphocytes expressing CCR6. CD4+CCR6+ lymphocytes from H. pylori-infected stomach included Tregs and in vivo activated T cells, some of which produced interferon-γ without ex vivo stimulation.

CONCLUSION

H. pylori infection causes an increase in the number of mature CD4+CCR6+ lymphocytes in the blood, with a pro-inflammatory shift in their composition and enrichment of the gastric mucosa with CD4+CCR6+ lymphocytes, including CCR6+ Th1 cells and Tregs.

Helicobacter pylori: A Contemporary Perspective on Pathogenesis, Diagnosis and Treatment Strategies

Helicobacter pylori (H. pylori) is a Gram-negative bacterium that colonizes the gastric mucosa and is associated with various gastrointestinal disorders. H. pylori is a pervasive pathogen, infecting nearly 50% of the world's population, and presents a substantial concern due to its link with gastric cancer, ranking as the third most common cause of global cancer-related mortality. This review article provides an updated and comprehensive overview of the current understanding of H. pylori infection, focusing on its pathogenesis, diagnosis, and treatment strategies. The intricate mechanisms underlying its pathogenesis, including the virulence factors and host interactions, are discussed in detail. The diagnostic methods, ranging from the traditional techniques to the advanced molecular approaches, are explored, highlighting their strengths and limitations. The evolving landscape of treatment strategies, including antibiotic regimens and emerging therapeutic approaches, is thoroughly examined. Through a critical synthesis of the recent research findings, this article offers valuable insights into the contemporary knowledge of Helicobacter pylori infection, guiding both clinicians and researchers toward effective management and future directions in combating this global health challenge.

Helicobacter pylori

Helicobacter pylori (H. pylori) is an important human pathogen etiologically associated with peptic ulcers and gastric cancer. The infection is present in approximately one-half of the world's population. Population-based H. pylori eradiation has confirmed that cure or prevention of the infection produces a marked reduction in gastric cancer and peptic ulcer disease. Antimicrobial therapy has become increasingly ineffective, and complexity and costs of antimicrobial therapy for infected individuals residing in and, immigrating from, the developing world combined with the cost of treatment for cancer make vaccine development a cost-effective alternative. Challenge studies allowed making a "go-no go" decision regarding vaccine effectiveness. We provide detailed protocols regarding challenge strain selection and administration as well as guidance regarding the clinical and laboratory tests used to confirm and monitor experimental infection. Experience shows that reliance of noninvasive methods led to the erroneous conclusion that some subjects were not infected. The current data suggests that histologic assessment of gastric mucosal biopsies may be one of the most sensitive and specific means of assessment of the presence of experimental infection as well as of successful H. pylori eradication. We recommend detailed recommendations for acquiring, processing, embedding, sectioning, and examining the gastric biopsies.

An Evaluation of Urease A Subunit Nanocapsules as a Vaccine in a Mouse Model of Helicobacter pylori Infection

Using removable silica templates, protein nanocapsules comprising the A subunit of Helicobacter pylori urease (UreA) were synthesised. The templates were of two sizes, with solid core mesoporous shell (SC/MS) silica templates giving rise to nanocapsules of average diameter 510 nm and mesoporous (MS) silica templates giving rise to nanocapsules of average diameter 47 nm. Both were shown to be highly monodispersed and relatively homogenous in structure. Various combinations of the nanocapsules in formulation were assessed as vaccines in a mouse model of H. pylori infection. Immune responses were evaluated and protective efficacy assessed. It was demonstrated that vaccination of mice with the larger nanocapsules combined with an adjuvant was able to significantly reduce colonisation.

Helicobacter pylori infection increases the risk of carotid plaque formation: Clinical samples combined with bioinformatics analysis

Objective

Infection with Helicobacter pylori (H. pylori) may increase atherosclerosis, which can lead to carotid plaque formation. Our study examined the relationship between H. pylori infection and carotid plaque formation, and its underlying mechanisms.

Methods

A total of 36,470 people who underwent physical examination in Taizhou Hospital Health Examination Center from June 2017 to June 2022 were included in this study. All people participated in the urease test, neck ultrasound, blood pressure detection, anthropometric measurement and biochemical laboratory examination. In addition, the GSE27411 and GSE28829 datasets in the Gene Expression Omnibus (GEO) database were used to analyze the mechanism of H. pylori infection and atherosclerosis progression.

Results

H. pylori infection, sex, age, blood lipids, blood pressure, fasting blood glucose, glycated hemoglobin and body mass index were risk factors for carotid plaque formation. An independent risk factor was still evident in the multivariate logistic regression analysis, indicating H. pylori infection. Furthermore, after weighted gene coexpression network analysis (WGCNA), we discovered 555 genes linked to both H. pylori infection and the advancement of atherosclerosis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed a strong correlation between these genes and immunity, infection, and immune disorders. SsGSEA analysis showed that H. pylori infection and atherosclerosis included changes in the immune microenvironment. Finally, three genes MS4A6A, ADAMDEC1 and AQP9 were identified to be involved in the formation of atherosclerosis after H. pylori infection. Conclusion: Our research affirms that H. pylori is a unique contributor to the formation of carotid plaque, examines the immune microenvironment associated with H. pylori infection and advanced carotid atherosclerosis, and offers fresh perspectives on how H. pylori infection leads to atherosclerosis.

Outer Membrane Vesicles (OMVs) as Biomedical Tools and Their Relevance as Immune-Modulating Agents against H. pylori Infections: Current Status and Future Prospects

Outer membrane vesicles (OMVs) are lipid-membrane-bounded nanoparticles that are released from Gram-negative bacteria via vesiculation of the outer membrane. They have vital roles in different biological processes and recently, they have received increasing attention as possible candidates for a broad variety of biomedical applications. In particular, OMVs have several characteristics that enable them to be promising candidates for immune modulation against pathogens, such as their ability to induce the host immune responses given their resemblance to the parental bacterial cell. Helicobacter pylori (H. pylori) is a common Gram-negative bacterium that infects half of the world's population and causes several gastrointestinal diseases such as peptic ulcer, gastritis, gastric lymphoma, and gastric carcinoma. The current H. pylori treatment/prevention regimens are poorly effective and have limited success. This review explores the current status and future prospects of OMVs in biomedicine with a special focus on their use as a potential candidate in immune modulation against H. pylori and its associated diseases. The emerging strategies that can be used to design OMVs as viable immunogenic candidates are discussed.

Gastric immune homeostasis imbalance: An important factor in the development of gastric mucosal diseases

The gastric mucosal immune system is a unique immune organ independent of systemic immunity that not only maintains nutrient absorption but also plays a role in resisting the external environment. Gastric mucosal immune disorder leads to a series of gastric mucosal diseases, including autoimmune gastritis (AIG)-related diseases, Helicobacter pylori (H. pylori)-induced diseases, and various types of gastric cancer (GC). Therefore, understanding the role of gastric mucosal immune homeostasis in gastric mucosal protection and the relationship between mucosal immunity and gastric mucosal diseases is very important. This review focuses on the protective effect of gastric mucosal immune homeostasis on the gastric mucosa, as well as multiple gastric mucosal diseases caused by gastric immune disorders. We hope to offer new prospects for the prevention and treatment of gastric mucosal diseases.

CagA-specific Gastric CD8+ Tissue-Resident T Cells Control Helicobacter pylori During the Early Infection Phase

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 characterize gastric H pylori-specific CD8⁺ T-cell responses in mice and humans by flow cytometry, RNA-sequencing, immunohistochemistry, and ChipCytometry, applying functional analyses including T-cell depletion, H pylori eradication, and ex vivo restimulation.

RESULTS

We define CD8⁺ T-cell populations bearing a tissue-resident memory (T_RM) phenotype, which infiltrate the gastric mucosa shortly after infection and mediate pathogen control by executing antigen-specific effector properties. These induced CD8⁺ tissue-resident memory T cells (T_RM 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 progresses, we observe a loss of the T_RM 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 unknown role of CD8⁺ T-cell response in this bacterial infection, which may have important clinical implications for treatment and vaccination strategies against H pylori.

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.

Inflammation and Gastric Cancer

Gastric cancer remains a major killer globally, although its incidence has declined over the past century. It is the fifth most common cancer and the third most common reason for cancer-related deaths worldwide. Gastric cancer is the outcome of a complex interaction between environmental, host genetic, and microbial factors. There is significant evidence supporting the association between chronic inflammation and the onset of cancer. This association is particularly robust for gastrointestinal cancers in which microbial pathogens are responsible for the chronic inflammation that can be a triggering factor for the onset of those cancers. Helicobacter pylori is the most prominent example since it is the most widespread infection, affecting nearly half of the world’s population. It is well-known to be responsible for inducing chronic gastric inflammation progressing to atrophy, metaplasia, dysplasia, and eventually, gastric cancer. This review provides an overview of the association of the factors playing a role in chronic inflammation; the bacterial characteristics which are responsible for the colonization, persistence in the stomach, and triggering of inflammation; the microbiome involved in the chronic inflammation process; and the host factors that have a role in determining whether gastritis progresses to gastric cancer. Understanding these interconnections may improve our ability to prevent gastric cancer development and enhance our understanding of existing cases.

Two Distinct Etiologies of Gastric Cancer: Infection and Autoimmunity

Gastric cancer is a leading cause of mortality worldwide. The risk of developing gastric adenocarcinoma, which comprises >90% of gastric cancers, is multifactorial, but most associated with Helicobacter pylori infection. Autoimmune gastritis is a chronic autoinflammatory syndrome where self-reactive immune cells are activated by gastric epithelial cell autoantigens. This cause of gastritis is more so associated with the development of neuroendocrine tumors. However, in both autoimmune and infection-induced gastritis, high risk metaplastic lesions develop within the gastric mucosa. This warrants concern for carcinogenesis in both inflammatory settings. There are many similarities and differences in disease progression between these two etiologies of chronic gastritis. Both diseases have an increased risk of gastric adenocarcinoma development, but each have their own unique comorbidities. Autoimmune gastritis is a primary cause of pernicious anemia, whereas chronic infection typically causes gastrointestinal ulceration. Both immune responses are driven by T cells, primarily CD4⁺ T cells of the IFN-γ producing, Th1 phenotype. Neutrophilic infiltrates help clear H. pylori infection, but neutrophils are not necessarily recruited in the autoimmune setting. There have also been hypotheses that infection with H. pylori initiates autoimmune gastritis, but the literature is far from definitive with evidence of infection-independent autoimmune gastric disease. Gastric cancer incidence is increasing among young women in the United States, a population at higher risk of developing autoimmune disease, and H. pylori infection rates are falling. Therefore, a better understanding of these two chronic inflammatory diseases is needed to identify their roles in initiating gastric cancer.

Cytokine Profile of CCR6+ T-Helpers Isolated from the Blood of Patients with Peptic Ulcer Associated with Helicobacter pylori Infection

We previously found that the number of CCR6⁺ T-helpers with the phenotype of effector/effector memory T cells increases in the blood of patients with H. pylori-associated peptic ulcer. The mature phenotype and the expression of the chemokine receptor CCR6, which is involved in migration of lymphocytes to the inflamed mucous membrane of the gastrointestinal tract, suggests that these cells are involved in the immune response observed in this clinical condition. To better understand the pathogenetic role of these cells, it is necessary to study their functional activity, specifically, the production of pro-inflammatory cytokines involved in the pathogenesis of the disease.

The aim of the study was to evaluate changes in the blood level of pro-inflammatory types of mature CCR6⁺ T-helpers in H. pylori-associated peptic ulcer disease.

DNA vaccine containing Flagellin A gene induces significant immune responses against Helicobacter pylori infection: An in vivo study

Objective(s):

Helicobacter pylori is one of the most prevalent human infectious agents that is directly involved in various upper digestive tract diseases. Although antibiotics-based therapy and proton pump inhibitors eradicate the bacteria mostly, their effectiveness has been declined recently due to emergence of antibiotic-resistant strains. Development of a DNA vaccine is a promising approach against bacterial pathogens. Genes encoding motility factors are promising immunogens to develop a DNA vaccine against H. pylori infection due to critical role of these genes in bacterial attachment and colonization within the gastric lumen. The present study aimed to synthesize a DNA vaccine construct based on the Flagellin A gene (flaA), the predominant flagellin subunit in H. pylori flagella.

Materials and Methods:

The coding sequence of flaA was amplified through PCR and sub-cloned in the pBudCE4.1 vector. The recombinant vector was introduced into the human dermal fibroblast cells, and its potency to express the flaA protein was analyzed using SDS-PAGE. The recombinant construct was intramuscularly (IM) injected into the mice, and the profiles of cytokines and immunoglobulins were measured using ELISA.

Results:

It has been found that flaA was successfully expressed in cells. Recombinant-vector also increased the serum levels of evaluated cytokines and immunoglobulins in mice.

Conclusion:

These findings showed that the pBudCE4.1-flaA construct was able to activate the immune responses. This study is the first step towards synthesis of recombinant-construct based on the flaA gene. Immunization with such construct may inhibit the H. pylori-associated infection; however, further experiments are urgent.

Evolved to vary: genome and epigenome variation in the human pathogen Helicobacter pylori

Helicobacter pylori is a Gram-negative, spiral shaped bacterium that selectively and chronically infects the gastric mucosa of humans. The clinical course of this infection can range from lifelong asymptomatic infection to severe disease, including peptic ulcers or gastric cancer. The high mutation rate and natural competence typical of this species are responsible for massive inter-strain genetic variation exceeding that observed in all other bacterial human pathogens. The adaptive value of such a plastic genome is thought to derive from a rapid exploration of the fitness landscape resulting in fast adaptation to the changing conditions of the gastric environment. Nevertheless, diversity is also lost through recurrent bottlenecks and H. pylori's lifestyle is thus a perpetual race to maintain an appropriate pool of standing genetic variation able to withstand selection events. Another aspect of H. pylori's diversity is a large and variable repertoire of restriction-modification systems. While not yet completely understood, methylome evolution could generate enough transcriptomic variation to provide another intricate layer of adaptive potential. This review provides an up to date synopsis of this rapidly emerging area of H. pylori research that has been enabled by the ever-increasing throughput of Omics technologies and a multitude of other technological advances.

H. pylori modulates DC functions via T4SS/TNFα/p38-dependent SOCS3 expression

Background

Helicobacter pylori (H. pylori) is a gram-negative bacterium that chronically infects approximately 50% of the world’s human population. While in most cases the infection remains asymptomatic, 10% of infected individuals develop gastric pathologies and 1–3% progress to gastric cancer. Although H. pylori induces severe inflammatory responses, the host’s immune system fails to clear the pathogen and H. pylori can persist in the human stomach for decades. As suppressor of cytokine signaling (SOCS) proteins are important feedback regulators limiting inflammatory responses, we hypothesized that H. pylori could modulate the host’s immune responses by inducing SOCS expression.

Methods

The phenotype of human monocyte-derived DCs (moDCs) infected with H. pylori was analyzed by flow cytometry and multiplex technology. SOCS expression levels were monitored by qPCR and signaling studies were conducted by means of Western blot. For functional studies, RNA interference-based silencing of SOCS1–3 and co-cultures with CD4⁺ T cells were performed.

Results

We show that H. pylori positive gastritis patients express significantly higher SOCS3, but not SOCS1 and SOCS2, levels compared to H. pylori negative patients. Moreover, infection of human moDCs with H. pylori rapidly induces SOCS3 expression, which requires the type IV secretion system (T4SS), release of TNFα, and signaling via the MAP kinase p38, but appears to be independent of TLR2, TLR4, MEK1/2 and STAT proteins. Silencing of SOCS3 expression in moDCs prior to H. pylori infection resulted in increased release of both pro- and anti-inflammatory cytokines, upregulation of PD-L1, and decreased T-cell proliferation.

Conclusions

This study shows that H. pylori induces SOCS3 via an autocrine loop involving the T4SS and TNFα and p38 signaling. Moreover, we demonstrate that high levels of SOCS3 in DCs dampen PD-L1 expression on DCs, which in turn drives T-cell proliferation.

Pathogenesis and clinical management of Helicobacter pylori gastric infection

Helicobacter pylori (H. pylori) is a gram-negative bacterium that infects approximately 4.4 billion individuals worldwide. However, its prevalence varies among different geographic areas, and is influenced by several factors. The infection can be acquired by means of oral-oral or fecal-oral transmission, and the pathogen possesses various mechanisms that improve its capacity of mobility, adherence and manipulation of the gastric microenvironment, making possible the colonization of an organ with a highly acidic lumen. In addition, H. pylori presents a large variety of virulence factors that improve its pathogenicity, of which we highlight cytotoxin associated antigen A, vacuolating cytotoxin, duodenal ulcer promoting gene A protein, outer inflammatory protein and gamma-glutamyl transpeptidase. The host immune system, mainly by means of a Th1-polarized response, also plays a crucial role in the infection course. Although most H. pylori-positive individuals remain asymptomatic, the infection predisposes the development of various clinical conditions as peptic ulcers, gastric adenocarcinomas and mucosa-associated lymphoid tissue lymphomas. Invasive and non-invasive diagnostic methods, each of them with their related advantages and limitations, have been applied in H. pylori detection. Moreover, bacterial resistance to antimicrobial therapy is a major challenge in the treatment of this infection, and new therapy alternatives are being tested to improve H. pylori eradication. Last but not least, the development of effective vaccines against H. pylori infection have been the aim of several research studies.

Identification of common highly expressed genes of Salmonella Enteritidis by in silico prediction of gene expression and in vitro transcriptomic analysis

Chickens are the reservoir host of Salmonella Enteritidis. Salmonella Enteritidis colonizes the gastro-intestinal tract of chickens and replicates within macrophages without causing clinically discernable illness. Persistence of S. Enteritidis in the hostile environments of intestinal tract and macrophages allows it to disseminate extra-intestinally to liver, spleen, and reproductive tract. Extra-intestinal dissemination into reproductive tract leads to contamination of internal contents of eggs, which is a major risk factor for human infection. Understanding the genes that contribute to S. Enteritidis persistence in the chicken host is central to elucidate the genetic basis of the unique pathobiology of this public health pathogen. The aim of this study was to identify a succinct set of genes associated with infection-relevant in vitro environments to provide a rational foundation for subsequent biologically-relevant research. We used in silico prediction of gene expression and RNA-seq technology to identify a core set of 73 S. Enteritidis genes that are consistently highly expressed in multiple S. Enteritidis strains cultured at avian physiologic temperature under conditions that represent intestinal and intracellular environments. These common highly expressed (CHX) genes encode proteins involved in bacterial metabolism, protein synthesis, cell-envelope biogenesis, stress response, and a few proteins with uncharacterized functions. Further studies are needed to dissect the contribution of these CHX genes to the pathobiology of S. Enteritidis in the avian host. Several of the CHX genes could serve as promising targets for studies towards the development of immunoprophylactic and novel therapeutic strategies to prevent colonization of chickens and their environment with S. Enteritidis.

Activation of CD3+ T cells by Helicobacter pylori DNA vaccines in potential immunotherapy of gastric carcinoma

Most of gastric carcinoma (GC) is attributed to infection by Helicobacter pylori (H. pylori) but there is increasing evidence that the positive H. pylori status correlates with better prognosis in GC. The H. pylori-induced cellular immune response may suppress cancer and in this work, recombinant pcDNA3 plasmids encoding various fragments of H. pylori virulence genes of cagA, vacA and babA are constructed and combined into groups to immunize BALB/c mice. The activated splenic CD3⁺ T cells are purified and the anticancer effects are investigated in vitro and in vivo. The H. pylori DNA vaccines induce a shift in the response from Th1 to Th2 that mimicks the immune status in patients of GC with chronic H. pylori infection. The stimulated CD3⁺ T cells inhibit the growth of human GC cells in vitro and adoptive transfusions of the CD3⁺ T cells suppress the growth of GC xenograft in vivo. The effects may be caused by the larger ratios of infiltrated CD8⁺/CD4⁺ T cells, reduced infiltration of regulatory FOXP3⁺ T cells, and enhanced apoptosis induced by upregulation of Caspase-9/Caspase-3 and downregulation of Survivin. Our results reveal the potential immunotherapeutic value of H. pylori vaccine-activated CD3⁺ T cells in those with advanced GC.

Beyond the antibody: B cells as a target for bacterial infection

It is well established that B cells play an important role during infections beyond antibody production. B cells produce cytokines and are APCs for T cells. Recently, it has become clear that several pathogenic bacterial genera, such as Salmonella, Brucella, Mycobacterium, Listeria, Francisella, Moraxella, and Helicobacter, have evolved mechanisms such as micropinocytosis induction, inflammasome down-regulation, inhibitory molecule expression, apoptosis induction, and anti-inflammatory cytokine secretion to manipulate B cell functions influencing immune responses. In this review, we summarize our current understanding of B cells as targets of bacterial infection and the mechanisms by which B cells become a niche for bacterial survival and replication away from extracellular immune responses such as complement and antibodies.

Helicobacter pylori Deregulates T and B Cell Signaling to Trigger Immune Evasion

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4⁺ T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell-cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.

Gastric lymphoma: association with Helicobacter pylori outer membrane protein Q (HopQ) and cytotoxic-pathogenicity activity island (CPAI) genes

B-cell non-Hodgkin lymphoma (B-cell NHL) is the second commonest malignancy in the stomach. We determined the distribution of Helicobacter pylori outer membrane protein Q (HopQ) allelic type, cytotoxin-associated gene (cag)-pathogenicity activity island (cag-PAI) and vacuolation activating cytotoxin A (vacA) genes, respectively, in patients with B-cell NHL. We also compared them with their distribution in non-ulcer dyspepsia (NUD). H. pylori was cultured from gastric biopsy tissue obtained at endoscopy. Polymerase chain reaction was performed. Of 170 patients enrolled, 114 (63%) had NUD and 56 (37%) had B-cell NHL. HopQ type 1 was positive in 66 (58%) in NUD compared with 46 (82%) (P = 0·002) in B-cell NHL; HopQ type 2 was positive in 93 (82%) with NUD compared with 56 (100%) (P < 0·001) in B-cell NHL. Multiple HopQ types were present in 46 (40%) in NUD compared with 46 (82%) (P < 0·001) in B-cell NHL. CagA was positive in 48 (42%) in NUD vs. 50 (89%) (P < 0·001) in B-cell NHL; cagT was positive in 35 (31%) in NUD vs. 45 (80%) (P < 0·001) in B-cell NHL; left end of the cagA gene (LEC)1 was positive in 23 (20%) in NUD vs. 43 (77%) (P < 0·001) in B-cell NHL. VacAs1am1 positive in B-cell NHL in 48 (86%) (P < 0·001) vs. 50 (44%) in NUD, while s1am2 was positive in 20 (17%) in NUD vs. 46 (82%) (P < 0·001) in B-cell NHL. H. pylori strains with multiple HopQ allelic types, truncated cag-PAI evidenced by expression of cagA, cagT and cag LEC with virulent vacAs1 alleles are associated with B-cell NHL development.

Helicobacter pylori γ-glutamyl transferase contributes to colonization and differential recruitment of T cells during persistence

Helicobacter pylori γ-glutamyl transferase (gGT) is a key bacterial virulence factor that is not only important for bacterial gastric colonization but also related to the development of gastric pathology. Despite accumulating evidence for pathogenic and immunologic functions of H. pylori gGT, it is still unclear how it supports gastric colonization and how its specific effects on the host’s innate and adaptive immune responses contribute to colonization and pathology. We have compared mice showing similar bacterial load after infection with gGT-proficient or gGT-deficient H. pylori to analyse the specific role of the enzyme during infection. Our data indicate that H. pylori gGT supports initial colonization. Nevertheless, bacteria lacking gGT can still colonize and persist. We observed that the presence of gGT during infection favoured a proinflammatory innate and adaptive immune response. Notably, H. pylori gGT activity was linked to increased levels of IFNγ, which were attributed to a differential recruitment of CD8⁺ T cells to the stomach. Our data support an essential role for H. pylori gGT in gastric colonization and further suggest that gGT favours infiltration of CD8⁺ cells to the gastric mucosa, which might play an important and yet overlooked role in the pathogenesis of H. pylori.

Gastric TFF1 Expression from Acute to Chronic Helicobacter Infection

TFF1, a mucin-associated secreted peptide of gastric mucous cells, is known as a protective agent for stomach epithelium under different stimuli, but its role upon Helicobacter infection is still not clear. In this paper we characterized TFFs expression, with particular attention to TFF1, under Helicobacter infection in gastric cell lines. A mouse model was used to distinguish TFF1 mRNA expression between acute and chronic stages of Helicobacter infection. Our results show that TFF1 expression is induced in infected cells; in addition, the inflammatory response upon Helicobacter infection is inversely associated to pre-existing TFF1 protein levels. In infected mice, TFF1 is initially upregulated in gastric antrum in the acute phase of infection, along with IL-1β and IL-6. Then, expression of TFF1 is gradually silenced when the infection becomes chronic and IFN-γ, CXCL5, and CXCL15 reach higher levels. Our data suggest that TFF1 might help cells to counteract bacteria colonization and the development of a chronic inflammation.

Helicobacter pylori Infection Increases Frequency of PDCA-1(+) (CD317(+)) B-cell Subsets

BACKGROUND AND AIMS

As a newly discovered B-cell subset, PDCA-1(+) B cells have been shown to participate in the immune clearance of invading pathogens. The prominence of PDCA-1(+) B cell immunity in the pathogenesis of Helicobacter pylori infection prompted us to explore the potential role of this subset in gastric H. pylori infection.

METHODS

H. pylori infection was determined by (14)C-urea breath test and Western blot. The frequency of the different sub-compartments of PDCA-1(+) B cells and their relation to serum cytokines was determined in 33 H. pylori-infected and 14 uninfected patients and in 12 healthy controls (HC).

RESULTS

In comparison to uninfected individuals, there was a significantly increased frequency of PDCA-1(+) B cells, PDCA-1(+)IgM(+) B cells, CD93(+)PDCA-1(+) B cells, CD93(+)PDCA-1(+)IgM(+) B cells, CD137(+)PDCA-1(+) B cells and CD137(+)PDCA-1(+)IgM(+) B cells were detected in patients with H. pylori infection, corresponding to increased levels of serum IFN-α and IgM in this group. Compared with H. pylori-positive (HP(+)) chronic non-atrophic gastritis patients, a larger proportion of PDCA-1(+) B cells, CD93(+)PDCA-1(+) B cells and CD137(+)PDCA-1(+) B cells were observed in HP(+) patients suffering from atrophic gastritis or HP(+) peptic ulcers.

CONCLUSIONS

The frequency of the PDCA-1(+) B cell compartment is increased during H. pylori infection. Our data support the potential role of this B-cell subset in the pathogenesis of H. pylori-dependent gastritis.

Helicobacter pylori Eradication in Patients with Immune Thrombocytopenic Purpura: A Review and the Role of Biogeography

Idiopathic thrombocytopenic purpura (ITP) is typically a diagnosis of exclusion, assigned by clinicians after ruling out other identifiable etiologies. Since a report by Gasbarrini et al. in 1998, an accumulating body of evidence has proposed a pathophysiological link between ITP and chronic Helicobacter pylori (H. pylori) infection. Clinical reports have described a spontaneous resolution of ITP symptoms in about 50% of chronic ITP patients following empirical treatment of H. pylori infection, but response appears to be geography dependent. Studies have also documented that ITP patients in East Asian countries are more likely to express positive antibody titers against H. pylori-specific cytotoxic-associated gene A (CagA), a virulence factor that is associated with an increased risk for gastric diseases including carcinoma. While a definitive mechanism by which H. pylori may induce thrombocytopenia remains elusive, proposed pathways include molecular mimicry of CagA by host autoantibodies against platelet surface glycoproteins, as well as perturbations in the phagocytic activity of monocytes. Traditional treatments of ITP have been largely empirical, involving the use of immunosuppressive agents and immunoglobulin therapy. However, based on the findings of clinical reports emerging over the past 20 years, health organizations around the world increasingly suggest the detection and eradication of H. pylori as a treatment for ITP. Elucidating the exact molecular mechanisms of platelet activation in H. pylori-positive ITP patients, while considering biogeographical differences in response rates, could offer insight into how best to use clinical H. pylori eradication to treat ITP, but will require well-designed studies to confirm the suggested causative relationship between bacterial infection and an autoimmune disease state.

Immune responses to Helicobacter pylori infection

Helicobacter pylori (H. pylori) infection is one of the most common infections in human beings worldwide. H. pylori express lipopolysaccharides and flagellin that do not activate efficiently Toll-like receptors and express dedicated effectors, such as γ-glutamyl transpeptidase, vacuolating cytotoxin (vacA), arginase, that actively induce tolerogenic signals. In this perspective, H. pylori can be considered as a commensal bacteria belonging to the stomach microbiota. However, when present in the stomach, H. pylori reduce the overall diversity of the gastric microbiota and promote gastric inflammation by inducing Nod1-dependent pro-inflammatory program and by activating neutrophils through the production of a neutrophil activating protein. The maintenance of a chronic inflammation in the gastric mucosa and the direct action of virulence factors (vacA and cytotoxin-associated gene A) confer pro-carcinogenic activities to H. pylori. Hence, H. pylori cannot be considered as symbiotic bacteria but rather as part of the pathobiont. The development of a H. pylori vaccine will bring health benefits for individuals infected with antibiotic resistant H. pylori strains and population of underdeveloped countries.

Bacterial urease and its role in long-lasting human diseases

Urease is a virulence factor found in various pathogenic bacteria. It is essential in colonization of a host organism and in maintenance of bacterial cells in tissues. Due to its enzymatic activity, urease has a toxic effect on human cells. The presence of ureolytic activity is an important marker of a number of bacterial infections. Urease is also an immunogenic protein and is recognized by antibodies present in human sera. The presence of such antibodies is connected with progress of several long-lasting diseases, like rheumatoid arthritis, atherosclerosis or urinary tract infections. In bacterial ureases, motives with a sequence and/or structure similar to human proteins may occur. This phenomenon, known as molecular mimicry, leads to the appearance of autoantibodies, which take part in host molecules destruction. Detection of antibodies-binding motives (epitopes) in bacterial proteins is a complex process. However, organic chemistry tools, such as synthetic peptide libraries, are helpful in both, epitope mapping as well as in serologic investigations.

In this review, we present a synthetic report on a molecular organization of bacterial ureases - genetic as well as structural. We characterize methods used in detecting urease and ureolytic activity, including techniques applied in disease diagnostic processes and in chemical synthesis of urease epitopes. The review also provides a summary of knowledge about a toxic effect of bacterial ureases on human body and about occurrence of anti-urease antibodies in long-lasting diseases.

Association between HLA-DQ genotypes and haplotypes vs Helicobacter pylori infection in an Indonesian population

BACKGROUND

Helicobacter pylori is an important gastrointestinal pathogen related to the development of not only atrophic gastritis and peptic ulcer, but also gastric cancer. Human leukocyte antigens (HLA) may play particular roles in host immune responses to bacterial antigens. This study aimed to investigate the association between HLA-DQA1 and DQB1 genotypes and haplotypes vs H. pylori infection in an Indonesian population.

METHODS

We selected 294 healthy participants in Mataram, Lombok Island, Indonesia. H. pylori infection was determined by urea breath test (UBT). We analyzed HLA-DQA1 and DQB1 genotypes by PCR-RFLP and constructed haplotypes of HLA-DQA1 and DQB1 genes. Multiple comparisons were conducted according to the Bonferroni method.

RESULTS

The H. pylori infection rate was 11.2% in this Indonesian population. The DQB1*0401 genotype was noted to be associated with a high risk of H. pylori infection, compared with the DQB1*0301 genotype. None of the HLA-DQA1 or DQB1 haplotypes were related to the risk of H. pylori infection.

CONCLUSIONS

The study suggests that HLADQB1 genes play important roles in H. pylori infection, but there was no statistically significant association between HLA-DQA1 or DQB1 haplotypes and H.pylori infection in our Lombok Indonesian population.

Clinical Significance of Peripheral Blood T Lymphocyte Subsets in Helicobacter pylori-Infected Patients

Background. Helicobacter pylori chronically colonizes gastric/duodenal mucosa and induces gastroduodenal disease and vigorous humoral and cellular immune responses. Methods. In order to clarify the immunological changes induced by this infection, we determined the percentage and, as indicated, ratios of the following cells in peripheral blood of 45 H. pylori-infected patients and 21 control subjects: CD4⁺ T cell, CD8⁺ T cells, T helper 1 cells (Th1), T helper 2 cells (Th2), CD4⁺CD25⁺ T cells, Foxp3⁺ regulatory T cells (Tregs), CD4/CD8 ratio, and Th1/Th2 ratio. Results. The percentage of CD8⁺ T cells was significantly lower in H. pylori-infected patients (mean ± SD; 18.0 ± 7.1%) compared to control subjects (mean ± SD; 23.2 ± 7.8%) (P < 0.05). The CD4/CD8 ratio was significantly higher in H. pylori-infected patients (mean ± SD; 3.1 ± 2.4) compared to control subjects (mean ± SD; 2.1 ± 1.0) (P < 0.05). The Th1/Th2 ratio was significantly lower in H. pylori-infected patients (mean ± SD; 10.0 ± 8.5) compared to control subjects (mean ± SD; 14.5 ± 9.0) (P < 0.05). The percentage of CD4⁺CD25⁺ T cells in H. pylori-infected patients (mean ± SD; 13.2 ± 6.2%) was significantly higher than that in control subjects (mean ± SD; 9.8 ± 3.4%) (P < 0.05). However, there was no significant difference in Tregs. Conclusion. Tregs did not decrease, but the activation of humoral immunity and Th2 polarization were observed in the peripheral blood of H. pylori-infected patients. In some cases, these changes may induce systemic autoimmune diseases.

H. pylori vaccines: why we still don't have any

Helicobacter pylori was appreciated as the major cause of peptic ulcers about 30 years ago and the most significant etiological agent in gastric cancer in the mid-1990s. Since that time, progress in the development of a preventive or therapeutic H. pylori vaccine has been relatively slow. The impediments to rapid advances in the field include a luke-warm enthusiasm among clinicians, research scientists, and public health authorities concerning the need for a vaccine, rudimentary understanding of the correlates of gastric immunity to H. pylori and of gastric mucosal immunology in general, the geographical heterogeneity of the H. pylori genome and insufficient pharmaceutical industry support. Recent enhancements in our understanding of the gastric immune response together with advances in H. pylori genomics now provide the potential to accelerate progress in H. pylori vaccine development. Whether an H. pylori vaccine becomes a reality will likely depend upon our ability to appropriately target the populations at highest risk of the adverse sequelae of infection.

Role of virulence factors and host cell signaling in the recognition of Helicobacter pylori and the generation of immune responses

Helicobacter pylori colonizes a large proportion of the world's population, with infection invariably leading to chronic, lifelong gastritis. While the infection often persists undiagnosed and without causing severe pathology, there are a number of host, bacterial and environmental factors that can influence whether infection provokes a mild inflammatory response or results in significant morbidity. Intriguingly, the most virulent H. pylori strains appear to deliberately induce the epithelial signaling cascades responsible for activating the innate immune system. While the reason for this remains unclear, the resulting adaptive immune responses are largely ineffective in clearing the bacterium once infection has become established and, as a result, inflammation likely causes more damage to the host itself.

The effect of Helicobacter pylori infection on growth velocity in young children from poor urban communities in Ecuador

OBJECTIVE

To characterize the potential effects of Helicobacter infections on growth velocity in low socioeconomic status young children in a developing country.

METHODS

Children were recruited in poor suburbs of Quito, Ecuador. Normally nourished, mildly and substantially malnourished children (defined using weight-for-age Z-scores at recruitment) formed equal strata. Six height and weight measurements were collected during one year. Enrollment and exit serum samples were analyzed for anti-Helicobacter IgG and exit non-diarrheal feces tested for Helicobacter antigen.

RESULTS

Among 124 participants (enrollment age 19 ± 9 months), 76 (61%) excreted fecal antigen at exit (were infected). Of these, 44 were seropositive at least once (chronic infections) and 32 tested seronegative both times (new or acute phase infections). The adjusted linear growth velocity during follow-up in children with new infections was reduced by 9.7 (3.8, 15.6) mm/year compared to uninfected controls and 6.4 (0.0, 12.9) mm/year compared to children with chronic infections. The effects of Helicobacter infections on ponderal growth were not significant.

CONCLUSION

These results suggest that linear growth velocity is reduced in young children during the initial phase of Helicobacter infection.

Advances in vaccination against Helicobacter pylori

A vaccination against Helicobacter pylori may represent both prophylactic and therapeutic approaches to the control of H. pylori infection. Different protective H. pylori-derived antigens, such as urease, vacuolating cytotoxin A, cytotoxin-associated antigen, neutrophil-activating protein and others can be produced at low cost in prokaryote expression systems and most of these antigens have already been administered to humans and shown to be safe. The recent development by Graham et al. of the model of H. pylori challenge in humans, the recent published clinical trials and the last insight generated in animal models of H. pylori infection regarding the immune mechanisms leading to vaccine-induced Helicobacter clearance will facilitate the evaluation of immunogenicity and efficacy of H. pylori vaccine candidates in Phase II and III clinical trials.

Development of vaccines against Helicobacter pylori

Helicobacter pylori is a Gram-negative, microaerophilic bacterium adapted to survive in the stomach of humans where it can cause peptide ulcers and gastric cancer. Although effective antibiotic treatment exists, there is a consensus that vaccines are necessary to limit the severity of this infection. Great progress has been made since its discovery 25 years ago in understanding the virulence factors and several aspects of the pathogenesis of the H. pylori gastric diseases. Several key bacterial factors have been identified: urease, vacuolating cytotoxin, cytotoxin-associated antigen, the pathogenicity island, neutrophil-activating protein, and among others. These proteins, in their native or recombinant forms, have been shown to confer protection against infectious challenge with H. pylori in experimental animal models. It is not known, however, through which effector mechanisms this protection is achieved. Nevertheless, a number of clinical trials in healthy volunteers have been conducted using urease given orally as a soluble protein or expressed in bacterial vectors with limited results. Recently, a mixture of H. pylori antigens was reported to be highly immunogenic in H. pylori-negative volunteers following intramuscular administration of the vaccine with aluminium hydroxide as an adjuvant. These data show that vaccination against this pathogen is feasible. More research is required to understand the immunological mechanisms underlying immune-mediate protection.

Analysis of peripheral blood lymphocyte phenotypes and Th1/Th2 cytokines profile in the systemic immune responses of Helicobacter pylori infected individuals

H. pylori elicits specific humoral and cellular immune responses in the mucosal immune system. However, the type and extent of T lymphocyte response in the systemic immune system is not clear for H. pylori positive patients. In this study, peripheral blood T lymphocyte phenotypes and serum Th1/Th2 based cytokines of 32 H. pylori positive patients were analyzed and compared to those of healthy controls. While alphabeta TCR(+) lymphocytes and their phenotype analysis were not significantly different to those of healthy controls, the percentage of pan gammadelta TCR(+) lymphocytes was up to 2.4 times greater in the H. pylori positive group then in healthy controls. Furthermore, significant increases in IL-10 concentrations in serum samples of H. pylori patients indicated that their immune systems had switched toward a Th2 type immune response. The correlation between phenotype and type of T cell response in the peripheral blood during H. pylori infection is discussed.

Correspondence between Helicobacter pylori antibodies and urea breath test results in a US-Mexico birth cohort

The uncertain accuracy of methods for detecting Helicobacter pylori infection in young children complicates research on this infection in early life. The aim of the present report was to describe the correspondence between positive serology and positive urea breath test (UBT) in children followed from age 0 to 24 months in the Pasitos Cohort Study, conducted along the US-Mexico border at El Paso and Juarez. Children were recruited before birth during 1998-2000 and examined at target ages of 6, 12, 18 and 24 months. H. pylori infection was detected using an enzyme immunoassay for serum immunoglobulin G antibodies and the (13)C-urea breath test corrected for age-dependent variation in CO(2) production. Of 472 children, 125 had one or more positive UBT results and 46 had one or more positive serology results. The prevalence of H. pylori infection at target ages of 6, 12, 18 and 24 months was 7%, 14%, 16% and 19%, respectively, by UBT and 8%, 2%, 3% and 3%, respectively, by serology. Few (<1%) of those tested on both tests were positive on both at any age. Among UBT-positive children, 6% were concurrently seropositive and 6% became seropositive later. Because UBT positivity cut points were selected to minimise false positives, these results suggest that H. pylori infection occurred frequently in this cohort, but rarely produced detectable antibodies. For clinical or epidemiological investigations, serology should not be used as the sole method for detecting H. pylori infection in children aged 2 years or less.

Colonization and infection by Helicobacter pylori in humans

When Helicobacter pylori arrives in the human stomach, it may penetrate the mucin layer and adhere to the gastric epithelial cells or it may pass through the stomach without colonizing the mucosa. In this paper, the colonization process and the ensuing immunological response will be briefly described. Urease production is necessary for H. pylori to establish a pH-neutral microenvironment around the bacteria. The flagella enable the bacteria to move and the shape of H. pylori makes it possible to penetrate the mucin layer where it comes into contact with the gastric epithelial cells. H. pylori contains several adhesins that enable it to adhere to the epithelial cells. This adherence activates IL-8 which, together with bacterial antigens, attracts polymorphs and monocytes and causes acute gastritis. Antigen-presenting cells activate lymphocytes and other mononuclear cells that are attracted to the inflamed mucosa, causing chronic superficial gastritis and initiating a cytotoxic or an antigen-producing Th response. The infection is established within a few weeks after the primary exposure to H. pylori. After this initial colonization, many chemical, biochemical, and immunologic reactions take place that are of importance in the progress of the infection and the development of disease.

Helicobacter pylori as a vaccine delivery system

For more than 10 years a vaccine against Helicobacter pylori has been the elusive goal of many investigators. The need for a vaccine was highlighted when eradication attempts in developing countries were foiled by reinfection rates of 15-30% per annum. In addition, physicians in developed countries were concerned that attempts at total eradication of H. pylori would result in widespread macrolide resistance in both H. pylori and other important pathogens. Although attempts to produce vaccines against H. pylori have failed in their ultimate goal, considerable knowledge has been developed on the pathogenesis and immunology of Helicobacter infections. In this article we describe an alternative use for this new knowledge, i.e. a plan to use live Helicobacter species to deliver vaccines against other organisms. Because of its intimate attachment to the gastric mucosa and long-term residence there, H. pylori might succeed as an antigen delivery system, a goal which has eluded most other strategies of nonparenteral vaccination.

Host response to Helicobacter pylori infection before initiation of the adaptive immune response

Helicobacter pylori persistently colonizes the human stomach. In this study, immune responses to H. pylori that occur in the early stages of infection were investigated. Within the first 2 days after orogastric infection of mice with H. pylori, there was a transient infiltration of macrophages and neutrophils into the glandular stomach. By day 10 postinfection, the numbers of macrophages and neutrophils decreased to baseline levels. By 3 weeks postinfection, an adaptive immune response was detected, marked by gastric infiltration of T lymphocytes, macrophages, and neutrophils, as well as increased numbers of H. pylori-specific T cells, macrophages, and dendritic cells in paragastric lymph nodes. Neutrophil-attracting and macrophage-attracting chemokines were expressed at higher levels in the stomachs of H. pylori-infected mice than in the stomachs of uninfected mice. Increased expression of TNFalpha and IFNgamma (Th1-type inflammatory cytokines) and IL-17 (a Th17-type cytokine) was detected in the stomachs of H. pylori-infected mice, but increased expression of IL-4 (a Th2-type cytokine) was not detected. These data indicate that a transient gastric inflammatory response to H. pylori occurs within the first few days after infection, before the priming of T cells and initiation of an adaptive immune response. It is speculated that inappropriate waning of the innate immune response during early stages of infection may be a factor that contributes to H. pylori persistence.

Immune and proliferative cellular responses to Helicobacter pylori infection in the gastric mucosa of Mexican children

BACKGROUND

Helicobacter pylori infection occurs mostly during childhood, but few studies on this age group have addressed the innate immune and the proliferative response to this infection. Mexico has a high H. pylori prevalence in children, but a low risk of gastric cancer. The aim of this work was to study the cellular responses of the gastric mucosa to this infection in Mexican children.

METHODS

Antral and corpus gastric biopsies were obtained from 44 H. pylori-infected children (mean age 12 +/- 3.2 years) and 44 uninfected children (mean age 10 +/- 3 years). Mucosal cellular responses were studied by immunohistochemistry, using anti-Ki67 antibodies for proliferation studies, antihuman tryptase for mast cells, and antihuman CD68 for macrophages. T and B lymphocytes were stained with a commercial integrated system. The intensity of cellular responses was estimated histologically using the software KS300.

RESULTS

Epithelium proliferation and infiltration of macrophages and T and B lymphocytes were significantly higher in H. pylori-infected than in uninfected children. A balanced increase of CD4, CD8, and CD20 lymphocytes was observed in infected children. However, activated mast cells were decreased, and infiltration of neutrophil and mononuclear cells was low. Epithelial proliferation was associated with polymorphonuclear infiltration but not with infiltration of macrophages or lymphocytes. Inflammation and proliferation was higher in CagA (+)-infected children.

CONCLUSIONS

Mexican children respond to H. pylori infection with a low inflammatory response, a balanced increase of T and B lymphocytes, and a high regenerative activity.

Progress in vaccine development against Helicobacter pylori

Based on the very high prevalence of diseases caused by Helicobacter pylori, particularly in the developing world, and the rapid emergence of antibiotic resistance among clinical isolates, there is a strong rationale for an effective vaccine against H. pylori. In this review we describe recent promising candidate vaccines and prophylactic or therapeutic immunization strategies for use against H. pylori, as well as studies to identify immune responses that are related to protection in experimental animals. We also describe identification of different types of immune responses that may be related to protection against symptoms based on comparisons of H. pylori-infected patients with duodenal ulcers or gastric cancer and asymptomatic carriers. We conclude that there is still a strong need to clarify the main protective immune mechanisms against H. pylori as well as to identify a cocktail of strong protective antigens, or recombinant bacterial strains that express such antigens, that could be administered by a regimen that gives rise to effective immune responses in humans.

The transmission of Helicobacter pylori: the effects of analysis method and study population on inference

Although much is known about the virulence of Helicobacter pylori, the transmission pathways for this bacterium are still unresolved. Transmission has been addressed through: (1) prevalence within families; (2) detection in fecal/oral environments; (3) detection in the abiotic/biotic environment; and (4) direct inference from strain similarity. Here, we review the molecular and biochemical methods used and discuss the relative merits of each. Furthermore, as there are differences between developing and developed nations, we discuss the results obtained from transmission studies in light of the study population. We conclude that H. pylori is probably transmitted person-to-person, facilitated by fecal-oral transmission during episodes of diarrhea or gastro-oral contact during periods of vomiting. The persistence of H. pylori in abiotic and biotic environments remains unproven but possible reactivation from viable, non-culturable coccoid forms should be further investigated. Finally, we speculate on the effect of host-pathogen interactions in confounding the inference of transmission.

The current status of Helicobacter pylori vaccines: a review

Helicobacter pylori, a Gram-negative flagellate bacterium that infects the stomach of more than half of the global population, is regarded as the leading cause of chronic gastritis, peptic ulcer disease, and even gastric adenocarcinoma in some individuals. Although the bacterium induces strong humoral and cellular immune responses, it can persist in the host for decades. It has several virulence factors, some of them having vaccine potential as judged by immunoproteomic analysis. A few vaccination studies involving a small number of infected or uninfected humans with various H. pylori formulations such as the recombinant urease, killed whole cells, and live Salmonella vectors presenting the subunit antigens have not provided satisfactory results. One trial that used the recombinant H. pylori urease coadministered with native Escherichia coli enterotoxin (LT) demonstrated a reduction of H. pylori load in infected participants. Although extensive studies in the mouse model have demonstrated the feasibility of both therapeutic and prophylactic immunizations, the mechanism of vaccine-induced protection is poorly understood as several factors such as immunoglobulin and various cytokines do not contribute to protection. Transcriptome analyses in mice have indicated the role of nonclassical immune factors in vaccine-induced protection. The role of regulatory T cells in the persistence of H. pylori infection has also been suggested. A recently developed experimental H. pylori infection model in humans may be used for testing several new adjuvants and vaccine delivery systems that have been currently obtained. The use of vaccines with appropriate immunogens, routes of immunization, and adjuvants along with a better understanding of the mechanism of immune protection may provide more favorable results.

Helicobacter pylori persistence: an overview of interactions between H. pylori and host immune defenses

Helicobacter pylori is a gram-negative bacterium that persistently colonizes more than half of the global human population. In order to successfully colonize the human stomach, H. pylori must initially overcome multiple innate host defenses. Remarkably, H. pylori can persistently colonize the stomach for decades or an entire lifetime despite development of an acquired immune response. This review focuses on the immune response to H. pylori and the mechanisms by which H. pylori resists immune clearance. Three main sections of the review are devoted to (i) analysis of the immune response to H. pylori in humans, (ii) analysis of interactions of H. pylori with host immune defenses in animal models, and (iii) interactions of H. pylori with immune cells in vitro. The topics addressed in this review are important for understanding how H. pylori resists immune clearance and also are relevant for understanding the pathogenesis of diseases caused by H. pylori (peptic ulcer disease, gastric adenocarcinoma, and gastric lymphoma).