Induction of CTLA-4-mediated anergy contributes to persistent colonization in the murine model of gastric Helicobacter pylori infection

Impact of Modern Lifestyle on Circadian Health and Its Contribution to Adipogenesis and Cancer Risk

BACKGROUND

Recent research underscores a crucial connection between circadian rhythm disruption and cancer promotion, highlighting an urgent need for attention.

OBJECTIVES

Explore the molecular mechanisms by which modern lifestyle factors-such as artificial light exposure, shift work, and dietary patterns-affect cortisol/melatonin regulation and cancer risk.

METHODS

Employing a narrative review approach, we synthesized findings from Scopus, Google Scholar, and PubMed to analyze lifestyle impacts on circadian health, focusing on cortisol and melatonin chronobiology as molecular markers. We included studies that documented quantitative changes in these markers due to modern lifestyle habits, excluding those lacking quantitative data or presenting inconclusive results. Subsequent sections focused solely on articles that quantified the effects of circadian disruption on adipogenesis and tumor microenvironment modifications.

RESULTS

This review shows how modern habits lead to molecular changes in cortisol and melatonin, creating adipose microenvironments that support cancer development. These disruptions facilitate immune evasion, chemotherapy resistance, and tumor growth, highlighting the critical roles of cortisol dysregulation and melatonin imbalance.

CONCLUSIONS

Through the presented findings, we establish a causal link between circadian rhythm dysregulation and the promotion of certain cancer types. By elucidating this relationship, the study emphasizes the importance of addressing lifestyle factors that contribute to circadian misalignment, suggesting that targeted interventions could play a crucial role in mitigating cancer risk and improving overall health outcomes.

Tumor-associated macrophages: an effective player of the tumor microenvironment

Cancer progression is primarily caused by interactions between transformed cells and the components of the tumor microenvironment (TME). TAMs (tumor-associated macrophages) make up the majority of the invading immune components, which are further categorized as anti-tumor M1 and pro-tumor M2 subtypes. While M1 is known to have anti-cancer properties, M2 is recognized to extend a protective role to the tumor. As a result, the tumor manipulates the TME in such a way that it induces macrophage infiltration and M1 to M2 switching bias to secure its survival. This M2-TAM bias in the TME promotes cancer cell proliferation, neoangiogenesis, lymphangiogenesis, epithelial-to-mesenchymal transition, matrix remodeling for metastatic support, and TME manipulation to an immunosuppressive state. TAMs additionally promote the emergence of cancer stem cells (CSCs), which are known for their ability to originate, metastasize, and relapse into tumors. CSCs also help M2-TAM by revealing immune escape and survival strategies during the initiation and relapse phases. This review describes the reasons for immunotherapy failure and, thereby, devises better strategies to impair the tumor-TAM crosstalk. This study will shed light on the understudied TAM-mediated tumor progression and address the much-needed holistic approach to anti-cancer therapy, which encompasses targeting cancer cells, CSCs, and TAMs all at the same time.

A case of acute lymphocytic gastritis related to treatment with pembrolizumab for metastatic urothelial carcinoma

Introduction

Immune checkpoint inhibitors such as programmed cell death/-ligand 1 inhibitor and cytotoxic T-lymphocyte-associated antigen-4 inhibitors have been widely used for various advanced malignancies. The mechanism of action for these inhibitors is the improvement of antitumor immunity via T-cell modulation. On the contrary, immune-related adverse events such as autoimmune colitis might arise in association with T-cell activation. Upper gastrointestinal adverse events related to pembrolizumab have rarely been reported.

Case presentation

A 72-year-old man underwent laparoscopic radical cystectomy for muscle-invasive bladder cancer (pT2N0M0). Multiple lymph node metastases appeared in the paraaortic region. First-line chemotherapy comprising gemcitabine and carboplatin failed to stop disease progression. After the administration of pembrolizumab as second-line treatment, the patient showed symptomatic gastroesophageal reflux disease. Esophagogastroduodenoscopic biopsy of the gastric body showed severe lymphoplasmacytic and neutrophilic infiltration.

Conclusion

We present acute gastritis related to pembrolizumab. Early eradication therapy may be able to control immune checkpoint inhibitor-related gastritis.

Manipulation and exploitation of host immune system by pathogenic Mycobacterium tuberculosis for its advantage

Mycobacterium tuberculosis (Mtb) can become a long-term infection by evading the host immune response. Coevolution of Mtb with humans has resulted in its ability to hijack the host's immune systems in a variety of ways. So far, every Mtb defense strategy is essentially dependent on a subtle balance that, if shifted, can promote Mtb proliferation in the host, resulting in disease progression. In this review, the authors summarize many important and previously unknown mechanisms by which Mtb evades the host immune response. Besides recently found strategies by which Mtb manipulates the host molecular regulatory machinery of innate and adaptive immunity, including the intranuclear regulatory machinery, costimulatory molecules, the ubiquitin system and cellular intrinsic immune components will be discussed. A holistic understanding of these immune-evasion mechanisms is of foremost importance for the prevention, diagnosis and treatment of tuberculosis and will lead to new insights into tuberculosis pathogenesis and the development of more effective vaccines and treatment regimens.

sCD28, sCD80, sCTLA-4, and sBTLA Are Promising Markers in Diagnostic and Therapeutic Approaches for Aseptic Loosening and Periprosthetic Joint Infection

Aseptic prosthetic loosening and periprosthetic joint infections (PJI) are among the most frequent complications after total knee/hip joint arthroplasty (TJA). Current research efforts focus on understanding the involvement of the immune system in these frequent complications. Different immune cell types have already been implicated in aseptic prosthetic loosening and PJI. The aim of this study was to systematically analyze aspirates from knee and hip joints, evaluating the qualitative and quantitative composition of soluble immunoregulatory markers, with a focus on co-inhibitory and co-stimulatory markers. It has been shown that these molecules play important roles in immune regulation in cancer and chronic infectious diseases, but they have not been investigated in the context of joint replacement. For this purpose, aspirates from control joints (i.e., native joints without implanted prostheses), joints with TJA (no signs of infection or aseptic loosening), joints with aseptic implant failure (AIF; i.e., aseptic loosening), and joints with PJI were collected. Fourteen soluble immunoregulatory markers were assessed using bead-based multiplex assays. In this study, it could be shown that the concentrations of the analyzed immunoregulatory molecules vary between control, TJA, AIF, and PJI joints. Comparing TJA patients to CO patients, sCD80 was significantly elevated. The marker sBTLA was significantly elevated in AIF joints compared to TJA joints. In addition, a significant difference for eight markers could be shown when comparing the AIF and CO groups (sCD27, sCTLA-4, sCD137, sCD80, sCD28, sTIM-3, sPD-1, sBTLA). A significant difference was also reached for nine soluble markers when the PJI and CO groups were compared (sLAG-3, sCTLA-4, sCD27, sCD80, sCD28, sTIM-3, sPD-1, IDO, sBTLA). In summary, the analyzed immunoregulatory markers could be useful for diagnostic purposes as well as to develop new therapeutic approaches for AIF and PJI.

Revisiting Current Concepts on the Tolerogenicity of Steady-State Dendritic Cell Subsets and Their Maturation Stages

The original concept stated that immature dendritic cells (DC) act tolerogenically whereas mature DC behave strictly immunogenically. Meanwhile, it is also accepted that phenotypically mature stages of all conventional DC subsets can promote tolerance as steady-state migratory DC by transporting self-antigens to lymph nodes to exert unique functions on regulatory T cells. We propose that in vivo 1) there is little evidence for a tolerogenic function of immature DC during steady state such as CD4 T cell anergy induction, 2) all tolerance as steady-state migratory DC undergo common as well as subset-specific molecular changes, and 3) these changes differ by quantitative and qualitative markers from immunogenic DC, which allows one to clearly distinguish tolerogenic from immunogenic migratory DC.

Macrophage Polarization States in the Tumor Microenvironment

The M1/M2 macrophage paradigm plays a key role in tumor progression. M1 macrophages are historically regarded as anti-tumor, while M2-polarized macrophages, commonly deemed tumor-associated macrophages (TAMs), are contributors to many pro-tumorigenic outcomes in cancer through angiogenic and lymphangiogenic regulation, immune suppression, hypoxia induction, tumor cell proliferation, and metastasis. The tumor microenvironment (TME) can influence macrophage recruitment and polarization, giving way to these pro-tumorigenic outcomes. Investigating TME-induced macrophage polarization is critical for further understanding of TAM-related pro-tumor outcomes and potential development of new therapeutic approaches. This review explores the current understanding of TME-induced macrophage polarization and the role of M2-polarized macrophages in promoting tumor progression.

Sustained Helicobacter pylori infection accelerates gastric dysplasia in a mouse model

More than 80% of gastric cancer is attributable to stomach infection with Helicobacter pylori (Hp). Gastric preneoplastic progression involves sequential tissue changes, including loss of parietal cells, metaplasia and dysplasia. In transgenic mice, active KRAS expression recapitulates these tissue changes in the absence of Hp infection. This model provides an experimental system to investigate additional roles of Hp in preneoplastic progression, beyond its known role in initiating inflammation. Tissue histology, gene expression, the immune cell repertoire, and metaplasia and dysplasia marker expression were assessed in KRAS+ mice +/-Hp infection. Hp+/KRAS+ mice had severe T-cell infiltration and altered macrophage polarization; a different trajectory of metaplasia; more dysplastic glands; and greater proliferation of metaplastic and dysplastic glands. Eradication of Hp with antibiotics, even after onset of metaplasia, prevented or reversed these tissue phenotypes. These results suggest that gastric preneoplastic progression differs between Hp+ and Hp- cases, and that sustained Hp infection can promote the later stages of gastric preneoplastic progression.

The immune-related gene CD52 is a favorable biomarker for breast cancer prognosis

Background

An increasing number of studies have demonstrated a role for the tumor microenvironment in tumorigenesis, disease progression, and therapeutic response. This present study aimed to screen the significant immune-related genes and their possible role in the prognosis of breast cancer (BRCA).

Methods

The transcriptome data and clinical data of breast cancer were collected from The Cancer Genome Atlas (TCGA), and the immune scores and stromal scores were calculated by ESTIMATE algorithm. The differentially expressed genes were screened base on immune and stromal scores (high score vs. low score), than the intersected genes were used for subsequent functional enrichment analysis and protein-protein interaction (PPI) analysis. Furthermore, the key gene was identified by the intersection of the hub genes of PPI network and the prognostic genes of breast cancer. Finally, we explored the infiltration of immune cells of BRCA base on the CIBERSORT algorithm, and analysis the relationship between key gene and immune cells.

Results

High levels of CD52 expression were detected in the early stages of breast cancer and were associated with favorable prognosis. Overexpression of CD52 led to higher infiltrations of M1 macrophages, monocytes, T follicular helper cells, and resting memory CD4 T cells. Downregulation of CD52 resulted in high infiltrations of M2 macrophages. Therefore, high expression of CD52 may negatively regulate the infiltration of M2 macrophages but accelerate the infiltration of anti-cancer immune cells, and thus, high expression of CD52 may have a protective effect in breast cancer patients.

Conclusions

CD52 can increase the infiltration of anti-cancer immune cells but inhibit the infiltration of M2 macrophages, thereby improving the prognosis of breast cancer patients.

The Role of PD-1 in Acute and Chronic Infection

PD-1 as an immune checkpoint molecule down-regulates T cell activity during immune responses in order to prevent autoimmune tissue damage. In chronic infections or tumors, lasting antigen-exposure leads to permanent PD-1 expression that can limit immune-mediated clearance of pathogens or degenerated cells. Blocking PD-1 can enhance T cell function; in cancer treatment PD-1 blockade is already used as a successful therapy. However, the role of PD-1 expression and blocking in the context of acute and chronic infections is less defined. Building on its success in cancer therapy leads to the hypothesis that blocking PD-1 in infectious diseases is also beneficial in acute or chronic infections. This review will focus on the role of PD-1 expression in acute and chronic infections with virus, bacteria, and parasites, with a particular focus on recent studies regarding PD-1 blockade in infectious diseases.

Cytotoxic T-Lymphocyte-Associated Antigen 4 (CTLA-4)- and Programmed Death 1 (PD-1)-Mediated Regulation of Monofunctional and Dual Functional CD4+ and CD8+ T-Cell Responses in a Chronic Helminth Infection

Chronic helminth infections are known to be associated with the modulation of antigen-specific T-cell responses. Strongyloides stercoralis infection is characterized by the downmodulation of antigen-specific Th1 and Th17 responses and the upregulation of Th2 and Th9 responses. Immune homeostasis is partially maintained by negative regulators of T-cell activation, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death 1 (PD-1), which dampen effector responses during chronic infections. However, their roles in S. stercoralis infection are yet to be defined. Therefore, we sought to determine the role of CTLA-4 and PD-1 in regulating CD4⁺ and CD8⁺ T-cell responses and examined the frequencies of monofunctional and dual functional Th1/T cytotoxic type 1 (Tc1), Th17/Tc17, Th2/Tc2, and Th9/Tc9 cells in S. stercoralis infection in 15 infected individuals stimulated with parasite antigen following CTLA-4 or PD-1 blockade. Our data reveal that CTLA-4 or PD-1 blockade results in significantly enhanced frequencies of monofunctional and dual functional Th1/Tc1 and Th17/Tc17 cells and, in contrast, diminishes the frequencies of monofunctional and dual functional Th2/Tc2 and Th9/Tc9 cells with parasite antigen stimulation in whole-blood cultures. Thus, we demonstrate that CTLA-4 and PD-1 limit the induction of particular T-cell subsets in S. stercoralis infection, which suggests the importance of CTLA-4 and PD-1 in immune modulation in a chronic helminth infection.

Pathogenicity of Helicobacter pylori in cancer development and impacts of vaccination

Helicobacter pylori affect around 50% of the population worldwide. More importantly, the gastric infection induced by this bacterium is deemed to be associated with the progression of distal gastric carcinoma and gastric mucosal lymphoma in the human. H. pylori infection and its prevalent genotype significantly differ across various geographical regions. Based on numerous virulence factors, H. pylori can target different cellular proteins to modulate the variety of inflammatory responses and initiate numerous "hits" on the gastric mucosa. Such reactions lead to serious complications, including gastritis and peptic ulceration, gastric cancer and gastric mucosa-associated lymphoid structure lymphoma. Therefore, H. pylori have been considered as the type I carcinogen by the Global Firm for Research on Cancer. During the two past decades, different reports revealed that H. pylori possess oncogenic potentials in the gastric mucosa through a complicated interplay between the bacterial factors, various facets, and the environmental factors. Accordingly, numerous signaling pathways could be triggered in the development of gastrointestinal diseases (e.g., gastric cancer). Therefore, the main strategy for the treatment of gastric cancer is controlling the disease far before its onset using preventive/curative vaccination. Increasing the efficiency of vaccines may be achieved by new trials of vaccine modalities, which is used to optimize the cellular immunity. Taken all, H. pylori infection may impose severe complications, for resolving of which extensive researches are essential in terms of immune responses to H. pylori. We envision that H. pylori-mediated diseases can be controlled by advanced vaccines and immunotherapies.

Severe Gastritis after Administration of Nivolumab and Ipilimumab

Immune checkpoint inhibitors such as ipilimumab, a cytotoxic T-lymphocyte-associated antigen-4 inhibitor, have been widely used for advanced malignancies. As these inhibitors improve antitumor immunity via T-cell modulation, immune-mediated adverse events associated with T-cell activation, such as colitis, might occur. Herein, we describe a 75-year-old Japanese woman with metastatic malignant melanoma who developed hemorrhagic gastritis after ipilimumab treatment. There was no macroscopic or clinical improvement of gastritis after proton pump inhibitor treatment. However, her condition improved after approximately 3 weeks of corticosteroid therapy and Helicobacter pylori eradication. This case suggests a potential association between severe gastritis and immune checkpoint inhibitor treatment. Although several reports have mentioned ipilimumab-associated colitis, gastritis is considered to be rare. In the present case, H. pylori-associated gastritis might have been exacerbated by the T-cell modulation effect of ipilimumab. To date, no report has clarified the mechanism by which ipilimumab modifies H. pylori infection. The present treatment course provides a helpful perspective for similar cases.

Novel Systemic Therapies for Advanced Gastric Cancer

Gastric cancer (GC) is the second leading cause of cancer mortality and the fourth most commonly diagnosed malignant diseases. While continued efforts have been focused on GC treatment, the introduction of trastuzumab marked the beginning of a new era of target-specific treatments. Considering the diversity of mutations in GC, satisfactory results obtained from various target-specific therapies were expected, yet most of them were unsuccessful in controlled clinical trials. There are several possible reasons underlying the failures, including the absence of patient selection depending on validated predictive biomarkers, the inappropriate combination of drugs, and tumor heterogeneity. In contrast to targeted agents, immuno-oncologic agents are designed to regulate and boost immunity, are not target-specific, and may overcome tumor heterogeneity. With the successful establishment of predictive biomarkers, including Epstein-Barr virus pattern, microsatellite instability status, and programmed death-ligand 1 (PD-L1) expression, as well as ideal combination regimens, a new frontier in the immuno-oncology of GC treatment is on the horizon. Since the field of immuno-oncology has witnessed innovative, practice-changing successes in other cancer types, several trials on GC are ongoing. Among immuno-oncologic therapies, immune checkpoint inhibitors are the mainstay of clinical trials performed on GC. In this article, we review target-specific agents currently used in clinics or are undergoing clinical trials, and highlight the future clinical application of immuno-oncologic agents in inoperable GC.

T cell subsets play an important role in the determination of the clinical outcome of Helicobacter pylori infection

Helicobacter pylori (H. pylori) is one of the most prevalent human pathogen and a persistent infection with this bacterium causes common pathologies, such as gastritis or peptic ulcers, and also less common but more serious pathologies, such as gastric cancer or gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The clinical outcome of gastrointestinal infection sustained by H. pylori is determined by the reciprocal interactions between virulence factors of the bacterium and host factors, including immune response genes. Although H. pylori induces a strong immune response, the bacterium is not eliminated. The eradication failure could be attributed to the bacterial capability to regulate helper T (Th) cell-related responses. H. pylori specific CD4⁺ T cells play a fundamental role in regulating host immunity and immunopathologic events. It has been documented that Th1, Th2, Th9, Th17, Th22 and T regulatory (Treg) cells, separately or in coordination with each other, can affect the outcome of the infection sustained by of H. pylori. Some studies indicated that both Th1 and Th17 cells may be protective or pathogenic, whereas Treg and Th2 cells perform anti-inflammatory impacts during H. pylori infection. This review gathers recent information regarding the association of the CD4⁺ T cells-mediated immunological responses and the clinical consequence of H. pylori infection.

Persistent infection due to a small-colony variant of Burkholderia pseudomallei leads to PD-1 upregulation on circulating immune cells and mononuclear infiltration in viscera of experimental BALB/c mice

Background

Melioidosis is a neglected tropical disease endemic across South East Asia and Northern Australia. The etiological agent, Burkholderia pseudomallei (B.pseudomallei), is a Gram-negative, rod-shaped, motile bacterium residing in the soil and muddy water across endemic regions of the tropical world. The bacterium is known to cause persistent infections by remaining latent within host cells for prolonged duration. Reactivation of the recrudescent disease often occurs in elders whose immunity wanes. Moreover, recurrence rates in melioidosis patients can be up to ~13% despite appropriate antibiotic therapy, suggestive of bacterial persistence and inefficacy of antibiotic regimens. The mechanisms behind bacterial persistence in the host remain unclear, and hence understanding host immunity during persistent B. pseudomallei infections may help designing potential immunotherapy.

Methodology/Principal findings

A persistent infection was generated using a small-colony variant (SCV) and a wild-type (WT) B. pseudomallei in BALB/c mice via intranasal administration. Infected mice that survived for >60 days were sacrificed. Lungs, livers, spleens, and peripheral blood mononuclear cells were harvested for experimental investigations. Histopathological changes of organs were observed in the infected mice, suggestive of successful establishment of persistent infections. Moreover, natural killer (NK) cell frequency was increased in SCV- and WT-infected mice. We observed programmed death-1 (PD-1) upregulation on B cells of SCV- and WT-infected mice. Interestingly, PD-1 upregulation was only observed on NK cells and monocytes of SCV-infected mice. In contrast, cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) downregulation was seen on NK cells of WT-infected mice, and on monocytes of SCV- and WT-infected mice.

Conclusions/Significance

The SCV and the WT of B. pseudomallei distinctly upregulated PD-1 expression on B cells, NK cells, and monocytes to dampen host immunity, which likely facilitates bacterial persistence. PD-1/PD-L1 pathway appears to play an important role in the persistence of B. pseudomallei in the host.

B. pseudomallei is a bacterium that causes melioidosis, a disease endemic in Southeastern Asia and Northern Australia. It is estimated that melioidosis leads to 89,000 deaths worldwide each year. Nevertheless, melioidosis continues to remain a neglected tropical disease that is not even on the list of neglected tropical diseases of the World Health Organization. Furthermore, the disease has a high mortality and recurrence rate, which can be up to 40% and 13%, respectively. It has also been well documented that B. pseudomallei causes latent/persistent infections for a prolonged period without showing apparent symptoms in the infected individual. The mechanisms that are responsible for bacterial persistence in the host remain unclear. Our results demonstrated that B. pseudomallei were able to upregulate PD-1 expression on B cells, NK cells, and/or monocytes during persistent diseases, which likely diminish optimal host immunity. The weakened host immunity in turns facilitates persistence of the bacterium. Interestingly, the SCV had a higher PD-1 expression on distinct immune cells compared to the WT, which might explain its frequent association with persistent infections. Immunotherapies by targeting PD-1/PD-L1 pathway could serve as a better treatment than the conventional antibiotic regimens, which cause a high rate of recurrence in melioidosis patients.

E-M, an Engineered Endostatin with High ATPase Activity, Inhibits the Recruitment and Alternative Activation of Macrophages in Non-small Cell Lung Cancer

Endostatin recently was reported by our laboratory to possess ATPase activity that is indispensable for its anti-angiogenesis and anti-tumor effects. An engineered endostatin, E-M, which owns higher ATPase activity exhibits stronger inhibitory effects on angiogenesis. Tumor-associated macrophages (TAMs), especially M2-polarized TAMs, contribute to tumor progression by promoting tumor cell proliferation, metastasis, angiogenesis, and immunosuppression, thus emerging as crucial targets for therapeutic intervention. Endostatin reportedly modulated functions of TAMs, but the detailed mechanisms remain unclear. Here, in our study, we demonstrated that E-M exhibited stronger inhibitory effects on macrophages than endostatin and other low ATPase mutants, which indicates that the ATPase activity is required for the inhibitory effects of endostatin on TAMs. Moreover, we elucidated that endostatin co-receptor, nucleolin and integrin α5β1, overexpressed on the surface of M2 macrophages, facilitated the internalization of E-M via the caveolae/lipid raft- and clathrin-dependent pathways. E-M inhibited the migration of TAMs through blockade of p38 MAP kinase and Erk1/2 signaling pathways, and prevented the alternative activation of TAMs. As a result, TAM-induced tumor cell proliferation and angiogenic activities in vitro were dramatically suppressed by E-M. In a transplanted non-small cell lung cancer model, E-M remarkably decreased the density of intratumoral macrophages and blood vessels, leading to tumor regression. This study unravels a novel mechanism of endostatin on regulating TAM recruitment and polarization, and suggests that E-M is a remarkably promising and multifunctional anti-tumor agent.

Increased Expression of Cytotoxic T-Lymphocyte-Associated Protein 4 by T Cells, Induced by B7 in Sera, Reduces Adaptive Immunity in Patients With Acute Liver Failure

BACKGROUND & AIMS

Patients with acute liver failure (ALF) have defects in innate immune responses to microbes (immune paresis) and are susceptible to sepsis. Cytotoxic T-lymphocyte-associated protein 4 (CTLA4), which interacts with the membrane receptor B7 (also called CD80 and CD86), is a negative regulator of T-cell activation. We collected T cells from patients with ALF and investigated whether inhibitory signals down-regulate adaptive immune responses in patients with ALF.

METHODS

We collected peripheral blood mononuclear cells from patients with ALF and controls from September 2013 through September 2015 (45 patients with ALF, 20 patients with acute-on-chronic liver failure, 15 patients with cirrhosis with no evidence of acute decompensation, 20 patients with septic shock but no cirrhosis or liver disease, and 20 healthy individuals). Circulating CD4⁺ T cells were isolated and analyzed by flow cytometry. CD4⁺ T cells were incubated with antigen, or agonist to CD3 and dendritic cells, with or without antibody against CTLA4; T-cell proliferation and protein expression were quantified. We measured levels of soluble B7 molecules in supernatants of isolated primary hepatocytes, hepatic sinusoidal endothelial cells, and biliary epithelial cells from healthy or diseased liver tissues. We also measured levels of soluble B7 serum samples from patients and controls, and mice with acetaminophen-induced liver injury using enzyme-linked immunosorbent assays.

RESULTS

Peripheral blood samples from patients with ALF had a higher proportion of CD4⁺ CTLA4⁺ T cells than controls; patients with infections had the highest proportions. CD4⁺ T cells from patients with ALF had a reduced proliferative response to antigen or CD3 stimulation compared to cells from controls; incubation of CD4⁺ T cells from patients with ALF with an antibody against CTLA4 increased their proliferative response to antigen and to CD3 stimulation, to the same levels as cells from controls. CD4⁺ T cells from controls up-regulated expression of CTLA4 after 24-48 hours culture with sera from patients with ALF; these sera were found to have increased concentrations of soluble B7 compared to sera from controls. Necrotic human primary hepatocytes exposed to acetaminophen, but not hepatic sinusoidal endothelial cells and biliary epithelial cells from patients with ALF, secreted high levels of soluble B7. Sera from mice with acetaminophen-induced liver injury contained high levels of soluble B7 compared to sera from mice without liver injury. Plasma exchange reduced circulating levels of soluble B7 in patients with ALF and expression of CTLA4 on T cells.

CONCLUSIONS

Peripheral CD4⁺ T cells from patients with ALF have increased expression of CTLA4 compared to individuals without ALF; these cells have a reduced response to antigen and CD3 stimulation. We found sera of patients with ALF and from mice with liver injury to have high concentrations of soluble B7, which up-regulates CTLA4 expression by T cells and reduces their response to antigen. Plasma exchange reduces levels of B7 in sera from patients with ALF and might be used to restore antimicrobial responses to patients.

Adjuvanticity of a CTLA-4 3' UTR complementary oligonucleotide for emulsion formulated recombinant subunit and inactivated vaccines

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is recognized as a critical inhibitory regulator of T-cell proliferation and activation, opposing the action of CD28-mediated co-stimulation. Interfering or blocking CTLA-4 can result in continuous T-cell activation required for the full immune response to pathogenic microbes and vaccines. To test if nucleic acid-based CTLA-4 inhibitors could be developed into a novel adjuvant, we designed two oligonucleotides, CMD-1 and CMD-2, with the sequences complementary to the conserve regions identical between human and mouse CTLA-4 mRNA 3' untranslated region (3' UTR), and tested their in vitro effects on CTLA-4 production and their adjuvanticity for vaccines in mice. We found that CMD-1 inhibited the antigen-induced CTLA-4 up-regulation on the CD4⁺ T cells by interfering its mRNA expression, maintained higher levels of CD80 and CD86 on the CD11c⁺ cells and promoted the recalled proliferation of the CD4⁺ T cells and CD19⁺ B cells, and that the CMD-1 enhanced the antibody response against recombinant PCV2b capsid protein or inactivated foot-and-mouth disease virus in both ICR and BALB/c mice. These data suggest that the CMD-1 could be used as a novel vaccine adjuvant capable of inhibiting inhibitory signals rather than inducing stimulatory signals of immune cells.

Tumor-associated macrophages: Potential therapeutic targets for anti-cancer therapy

The macrophage is known to be a multifunctional antigen presenting cells and playing a central role in inflammation. Macrophages infiltrate into malignant tumor tissues in high numbers (the so-called tumor-associated macrophages [TAMs]) and many studies over the past decade have demonstrated that macrophages have protumor functions and are closely related to tumor progression. It has been shown that protumor macrophages that have differentiated through interaction with tumor cells are involved in stem cell niches, immunosuppression, invasion, and metastasis. Consistent with these functions, studies using human tumor samples have demonstrated that a higher density of macrophages, especially macrophages with the M2 phenotype, is closely associated with worse clinical prognosis in many kinds of malignant tumors. Infiltrating TAMs themselves or polarization pathway of TAMs are considered as new therapeutic targets for the therapy of malignant tumors.

Role of Helicobacter pylori infection in gastric carcinogenesis: Current knowledge and future directions

Helicobacter pylori (H. pylori) plays a role in the pathogenesis of gastric cancer. The outcome of the infection depends on environmental factors and bacterial and host characteristics. Gastric carcinogenesis is a multistep process that is reversible in the early phase of mucosal damage, but the exact point of no return has not been identified. Therefore, two main therapeutic strategies could reduce gastric cancer incidence: (1) eradication of the already present infection; and (2) immunization (prior to or during the course of the infection). The success of a gastric cancer prevention strategy depends on timing because the prevention strategy must be introduced before the point of no return in gastric carcinogenesis. Although the exact point of no return has not been identified, infection should be eradicated before severe atrophy of the gastric mucosa develops. Eradication therapy rates remain suboptimal due to increasing H. pylori resistance to antibiotics and patient noncompliance. Vaccination against H. pylori would reduce the cost of eradication therapies and lower gastric cancer incidence. A vaccine against H. pylori is still a research challenge. An effective vaccine should have an adequate route of delivery, appropriate bacterial antigens and effective and safe adjuvants. Future research should focus on the development of rescue eradication therapy protocols until an efficacious vaccine against the bacterium becomes available.

Immunosuppression associated with chronic inflammation in the tumor microenvironment

Chronic inflammation contributes to cancer development via multiple mechanisms. One potential mechanism is that chronic inflammation can generate an immunosuppressive microenvironment that allows advantages for tumor formation and progression. The immunosuppressive environment in certain chronic inflammatory diseases and solid cancers is characterized by accumulation of proinflammatory mediators, infiltration of immune suppressor cells and activation of immune checkpoint pathways in effector T cells. In this review, we highlight recent advances in our understanding of how immunosuppression contributes to cancer and how proinflammatory mediators induce the immunosuppressive microenvironment via induction of immunosuppressive cells and activation of immune checkpoint pathways.

Current Status and Prospects for a Helicobacter pylori Vaccine

Helicobacter pylori infection contributes to a variety of gastric diseases. H pylori-associated gastric cancer is diagnosed in advanced stages, and a vaccine against H pylori is desirable in parts of the world where gastric cancer remains a common form of cancer. Some of the strategies of vaccine development used in animals have been tested in several phase 3 clinical trials; these trials have been largely unsuccessful, although H pylori-specific immune responses have been induced. New insights into promoting immunity and overcoming the immunosuppressive nature of H pylori infection are required to improve the efficacy of an H pylori vaccine.

Vaccinating against Helicobacter pylori in the developing world

Helicobacter pylori infects more than half the world's population and in developing nations the incidence can be over 90%. The morbidity and mortality associated with H. pylori-associated diseases including ulcers and gastric cancer therefore, disproportionately impact the developing world. Mice have been used extensively to demonstrate the feasibility of developing a vaccine for H. pylori infection, and for testing antigens, routes of immunization, dose, and adjuvants. These successes however, have not translated well in clinical trials. Although there are examples where immune responses have been activated, there are few instances of achieving a reduced bacterial load. In vivo and in vitro analyses in both mice and humans demonstrates that the host responds to H. pylori infection through the activation of immunoregulatory mechanisms designed to suppress the anti-H. pylori response. Improved vaccine efficacy therefore, will require the inclusion of factors that over-ride or re-program these immunoregulatory rersponse mechanisms.

A Case of Persistent Helicobacter pylori Infection Occurring with Anti-IgE Immunosuppression

The increasingly widespread use of novel immunosuppressive drugs may lead to unexpected infectious complications. We report a case of persistent Helicobacter pylori (H. pylori) infection that failed to respond to antimicrobial therapy in a patient receiving omalizumab (Xolair™, Genentech USA Inc., San Francisco, CA and Novartis Pharmaceuticals, Basel, Switzerland), an anti-IgE monoclonal antibody approved by the FDA for treatment of severe persistent asthma. To our knowledge, this is the first case report linking an immunosuppressive regimen containing anti-IgE biologic therapy to persistent H. pylori infection.

Th1-mediated immunity against Helicobacter pylori can compensate for lack of Th17 cells and can protect mice in the absence of immunization

Helicobacter pylori (H. pylori) infection can be significantly reduced by immunization in mice. Th17 cells play an essential role in the protective immune response. Th1 immunity has also been demonstrated to play a role in the protective immune response and can compensate in the absence of IL-17. To further address the potential of Th1 immunity, we investigated the efficacy of immunization in mice deficient in IL-23p19, a cytokine that promotes Th17 cell development. We also examined the course of Helicobacter infection in unimmunized mice treated with Th1 promoting cytokine IL-12. C57BL/6, IL-12 p35 KO, and IL-23 p19 KO mice were immunized and challenged with H. pylori. Protective immunity was evaluated by CFU determination and QPCR on gastric biopsies. Gastric and splenic IL-17 and IFNγ levels were determined by PCR or by ELISA. Balb/c mice were infected with H. felis and treated with IL-12 therapy and the resulting gastric bacterial load and inflammatory response were assessed by histologic evaluation. Vaccine induced reductions in bacterial load that were comparable to wild type mice were observed in both IL-12 p35 and IL-23 p19 KO mice. In the absence of IL-23 p19, IL-17 levels remained low but IFNγ levels increased significantly in both immunized challenged and unimmunized/challenged mice. Additionally, treatment of H. felis-infected Balb/c mice with IL-12 resulted in increased gastric inflammation and the eradication of bacteria in most mice. These data suggest that Th1 immunity can compensate for the lack of IL-23 mediated Th17 responses, and that protective Th1 immunity can be induced in the absence of immunization through cytokine therapy of the infected host.

IRAK-M expression limits dendritic cell activation and proinflammatory cytokine production in response to Helicobacter pylori

Helicobacter pylori (H. pylori) infects the gastric mucosa and persists for the life of the host. Bacterial persistence may be due to the induction of regulatory T cells (T_regs) whichmay have protective effects against other diseases such as asthma. It has been shown that H. pylori modulates the T cell response through dendritic cell reprogramming but the molecular pathways involved are relatively unknown. The goal of this study was to identify critical elements of dendritic cell (DC) activation and evaluate potential influence on immune activation. Microarray analysis was used to demonstrate limited gene expression changes in H. pylori stimulated bone marrow derived DCs (BMDCs) compared to the BMDCs stimulated with E. coli. IRAK-M, a negative regulator of TLR signaling, was upregulated and we selectedit for investigation of its role in modulating the DC and T cell responses. IRAK-M^−/− and wild type BMDC were compared for their response to H. pylori. Cells lacking IRAK-M produced significantly greater amounts of proinflammatory MIP-2 and reduced amounts of immunomodulatory IL-10 than wild type BMDC. IRAK-M^−/− cells also demonstrated increased MHC II expression upon activation. However, IRAK-M^−/− BMDCs were comparable to wild type BMDCs in inducing T-helper 17 (T_H17) and T_reg responses as demonstrated in vitro using BMDC CD4+ T cells co-culture assays,and in vivo though the adoptive transfer of CD4⁺ FoxP3-GFP T cells into H. pylori infected IRAK-M^−/− mice. These results suggest that H. pylori infection leads to the upregulation of anti-inflammatory molecules like IRAK-M and that IRAK-M has a direct impact on innate functions in DCs such as cytokine and costimulation molecule upregulation but may not affect T cell skewing.

The systemic immune state of super-shedder mice is characterized by a unique neutrophil-dependent blunting of TH1 responses

Host-to-host transmission of a pathogen ensures its successful propagation and maintenance within a host population. A striking feature of disease transmission is the heterogeneity in host infectiousness. It has been proposed that within a host population, 20% of the infected hosts, termed super-shedders, are responsible for 80% of disease transmission. However, very little is known about the immune state of these super-shedders. In this study, we used the model organism Salmonella enterica serovar Typhimurium, an important cause of disease in humans and animal hosts, to study the immune state of super-shedders. Compared to moderate shedders, super-shedder mice had an active inflammatory response in both the gastrointestinal tract and the spleen but a dampened T(H)1 response specific to the secondary lymphoid organs. Spleens from super-shedder mice had higher numbers of neutrophils, and a dampened T cell response, characterized by higher levels of regulatory T cells (T(regs)), fewer T-bet(+) (T(H)1) T cells as well as blunted cytokine responsiveness. Administration of the cytokine granulocyte colony stimulating factor (G-CSF) and subsequent neutrophilia was sufficient to induce the super-shedder immune phenotype in moderate-shedder mice. Similar to super-shedders, these G-CSF-treated moderate-shedders had a dampened T(H)1 response with fewer T-bet(+) T cells and a loss of cytokine responsiveness. Additionally, G-CSF treatment inhibited IL-2-mediated TH1 expansion. Finally, depletion of neutrophils led to an increase in the number of T-bet(+) T(H)1 cells and restored their ability to respond to IL-2. Taken together, we demonstrate a novel role for neutrophils in blunting IL-2-mediated proliferation of the TH1 immune response in the spleens of mice that are colonized by high levels of S. Typhimurium in the gastrointestinal tract.

Blockade of the negative co-stimulatory molecules PD-1 and CTLA-4 improves survival in primary and secondary fungal sepsis

Introduction

Fungal sepsis is an increasingly common problem in intensive care unit patients.Mortality from fungal sepsis remains high despite antimicrobial therapy that is highly active against most fungal pathogens, a finding consistent with defective host immunity that is present in many patients with disseminated fungemia.One recently recognized immunologic defect that occurs in patients with sepsis is T cell "exhaustion" due to increased expression of programmed cell death -1 (PD-1).This study tested the ability of anti-PD-1 and anti-programmed cell death ligand -1 (anti-PD-L1) antagonistic antibodies to improve survival and reverse sepsis-induced immunosuppression in two mouse models of fungal sepsis.

Methods

Fungal sepsis was induced in mice using two different models of infection, that is, primary fungal sepsis and secondary fungal sepsis occurring after sub-lethal cecal ligation and puncture (CLP).Anti-PD-1 and anti-PD-L1 were administered 24 to 48 h after fungal infection and effects on survival, interferon gamma production, and MHC II expression were examined.

Results

Anti-PD-1 and anti-PD-L1 antibodies were highly effective at improving survival in primary and secondary fungal sepsis.Both antibodies reversed sepsis-induced suppression of interferon gamma and increased expression of MHC II on antigen presenting cells.Blockade of cytotoxic T-lymphocyte antigen-4 (CTLA-4), a second negative co-stimulatory molecule that is up-regulated in sepsis and acts like PD-1 to suppress T cell function, also improved survival in fungal sepsis.

Conclusions

Immuno-adjuvant therapy with anti-PD-1, anti-PD-L1 and anti-CTLA-4 antibodies reverse sepsis-induced immunosuppression and improve survival in fungal sepsis.The present results are consistent with previous studies showing that blockade of PD-1 and CTLA-4 improves survival in bacterial sepsis.Thus, immuno-adjuvant therapy represents a novel approach to sepsis and may have broad applicability in the disorder.Given the relative safety of anti-PD-1 antibody in cancer clinical trials to date, therapy with anti-PD-1 in patients with life-threatening sepsis who have demonstrable immunosuppression should be strongly considered.

Lack of genetic influence on the innate inflammatory response to helicobacter infection of the gastric mucosa

Helicobacter pylori (H. pylori) is a bacterial pathogen that resides at the gastric mucosa and has a world-wide prevalence of over 50%. Infection usually lasts for the life of the host, and although all infected individuals will develop histologic gastritis only a subset will develop symptomatic gastritis, peptic ulcer disease, gastric MALT lymphoma, or gastric adenocarcinoma. The bacterial and host factors that determine clinical outcome and influence the development of widely varying diseases have not been elucidated. We compared disease in Helicobacter-infected severe combined immunodeficient (SCID) mice on different genetic backgrounds with their corresponding immunocompetent partners to determine if the genetics of the host significantly impacts the innate inflammatory outcome, independent of variations in bacterial virulence factors. BALB/c SCID and C57BL/6 SCID mice developed equivalent histologic gastritis by 8 weeks of infection. Immunocompetent BALB/c mice and C57BL/6 mice developed significantly lower or higher degrees of inflammation respectively. Innate inflammation in immunodeficient mice on the C57BL/6 background remained low even in the absence of the regulatory cytokine IL-10. These results demonstrate that adaptive immunity is not required for the generation of low level inflammation in response to Helicobacter infection and that the degree of inflammation is consistent among different genetic backgrounds. Additionally, this inflammation is limited even in the absence of regulatory T cells.

Manipulation of costimulatory molecules by intracellular pathogens: veni, vidi, vici!!

Some of the most successful pathogens of human, such as Mycobacterium tuberculosis (Mtb), HIV, and Leishmania donovani not only establish chronic infections but also remain a grave global threat. These pathogens have developed innovative strategies to evade immune responses such as antigenic shift and drift, interference with antigen processing/presentation, subversion of phagocytosis, induction of immune regulatory pathways, and manipulation of the costimulatory molecules. Costimulatory molecules expressed on the surface of various cells play a decisive role in the initiation and sustenance of immunity. Exploitation of the “code of conduct” of costimulation pathways provides evolutionary incentive to the pathogens and thereby abates the functioning of the immune system. Here we review how Mtb, HIV, Leishmania sp., and other pathogens manipulate costimulatory molecules to establish chronic infection. Impairment by pathogens in the signaling events delivered by costimulatory molecules may be responsible for defective T-cell responses; consequently organisms grow unhindered in the host cells. This review summarizes the convergent devices that pathogens employ to tune and tame the immune system using costimulatory molecules. Studying host-pathogen interaction in context with costimulatory signals may unveil the molecular mechanism that will help in understanding the survival/death of the pathogens. We emphasize that the very same pathways can potentially be exploited to develop immunotherapeutic strategies to eliminate intracellular pathogens.

The CTLA-4 and PD-1/PD-L1 inhibitory pathways independently regulate host resistance to Plasmodium-induced acute immune pathology

The balance between pro-inflammatory and regulatory immune responses in determining optimal T cell activation is vital for the successful resolution of microbial infections. This balance is maintained in part by the negative regulators of T cell activation, CTLA-4 and PD-1/PD-L, which dampen effector responses during chronic infections. However, their role in acute infections, such as malaria, remains less clear. In this study, we determined the contribution of CTLA-4 and PD-1/PD-L to the regulation of T cell responses during Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM) in susceptible (C57BL/6) and resistant (BALB/c) mice. We found that the expression of CTLA-4 and PD-1 on T cells correlates with the extent of pro-inflammatory responses induced during PbA infection, being higher in C57BL/6 than in BALB/c mice. Thus, ECM develops despite high levels of expression of these inhibitory receptors. However, antibody-mediated blockade of either the CTLA-4 or PD-1/PD-L1, but not the PD-1/PD-L2, pathways during PbA-infection in ECM-resistant BALB/c mice resulted in higher levels of T cell activation, enhanced IFN-γ production, increased intravascular arrest of both parasitised erythrocytes and CD8⁺ T cells to the brain, and augmented incidence of ECM. Thus, in ECM-resistant BALB/c mice, CTLA-4 and PD-1/PD-L1 represent essential, independent and non-redundant pathways for maintaining T cell homeostasis during a virulent malaria infection. Moreover, neutralisation of IFN-γ or depletion of CD8⁺ T cells during PbA infection was shown to reverse the pathologic effects of regulatory pathway blockade, highlighting that the aetiology of ECM in the BALB/c mice is similar to that in C57BL/6 mice. In summary, our results underscore the differential and complex regulation that governs immune responses to malaria parasites.

T cells are part of the body's defense system in response to infection. However, once the infection has been suitably controlled, these T cells must be switched off. Inhibitory pathways, such as CTLA-4 and PD-1, are known to send the ‘turn off’ signal to T cells during chronic infections. However, their roles in acute infections, such as malaria, are unclear. We compared the function of these inhibitory pathways in mice that are either susceptible or resistant to severe malarial disease (cerebral malaria). Strikingly, we found that receptors for CTLA-4 and PD-1 are more highly expressed in T cells from susceptible mice than from resistant mice. Therefore, cerebral malaria develops despite the high expression of these inhibitory receptors. Moreover, we demonstrated that blocking these inhibitory receptors in the resistant mice increased the function of T cells, which in turn led to the characteristic signs of cerebral malaria. Finally, reminiscent of what is known for the susceptible strain, we confirmed that certain T cells (CD8⁺) and molecules (IFN-γ) are crucial to the development of cerebral malaria in the otherwise resistant mice. Thus, the CTLA-4 and PD-1 inhibitory pathways have essential, independent and non-redundant roles in regulating the body's complex response to malaria.

Dose-dependent effect of anti-CTLA-4 on survival in sepsis

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is one of the critical inhibitory regulators of early stages of T-cell activation and proliferation, which opposes the actions of CD28-mediated costimulation. Anti-CTLA-4 therapy has been effective clinically in enhancing immunity and improving survival in patients with metastatic cancer. Sepsis is a lethal condition that shares many of the same mechanisms of immune suppression with cancer. Given the similarities in immune defects in cancer and sepsis, we examined the ability of anti-CTLA-4 antibody to block apoptosis, reverse the immunosuppression of sepsis, and improve survival in the cecal ligation and puncture model. Mice underwent sham or cecal ligation and puncture, and spleens harvested at various time points after surgery. Expression of CTLA-4 on CD4, CD8, and regulatory T cells was quantitated. Anti-CTLA-4 was administrated 6 and 24 h after surgery. Spleens were harvested at 48 h after surgery, and apoptosis and cytokine production determined. Seven-day survival studies were also conducted. Expression of CTLA-4 on CD4, CD8, and regulatory T cells increased during sepsis. Anti-CTLA-4 therapy decreased sepsis-induced apoptosis but had little effect on proinflammatory or anti-inflammatory cytokines. There was a dose-dependent effect of anti-CTLA-4 on survival. At high dose, anti-CTLA-4 worsened survival, but at lower doses, survival was significantly improved. Survival in sepsis depends on the proper balance between the proinflammatory and anti-inflammatory/immunologic systems. Anti-CTLA-4-based immunotherapy offers promise in the treatment of sepsis, but care must be used in the timing and dose of administration of the drug to prevent adverse effects.

The dynamics of T cells during persistent Staphylococcus aureus infection: from antigen-reactivity to in vivo anergy

Staphylococcus aureus is an important human pathogen that can cause long-lasting persistent infections. The mechanisms by which persistent infections are maintained involve both bacterial escape strategies and modulation of the host immune response. So far, the investigations in this area have focused on strategies used by S. aureus to persist within the host. Here, we used an experimental mouse model to investigate the host response to persistent S. aureus infection. Our results demonstrated that T cells, which are critical for controlling S. aureus infection, gradually lost their ability to respond to antigenic stimulation and entered a state of anergy with the progression of infection towards persistence. The T cell hyporesponsiveness was reverted by co-stimulation with the phorbol ester PMA, an activator of protein kinase C, suggesting that a failure in the T cell receptor (TCR)-proximal signalling events underlie the hyporesponsive phenotype. The presence of these anergic antigen-specific T cells may contribute to the failure of the host immune response to promote sterilizing immunity during persistent S. aureus infection and also offers new possibilities for novel immunotherapeutic approaches.

Papillomavirus-specific CD4+ T cells exhibit reduced STAT-5 signaling and altered cytokine profiles in patients with recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is caused by human papillomavirus type 6 (HPV-6) or HPV-11. Specific HLA-DR haplotypes DRB1*01:02 and DRB1*03:01 are associated with the development of RRP, disease severity, and Th2-like responses to HPV early proteins. Th1-like responses to HPV proteins have been shown to be protective in animal models. Therefore, we investigated the hypothesis that RRP patients have dysfunctional Th1-like, HPV-specific T cell responses. Using MHC class II tetramers, we identified immunogenic peptides within HPV-11 early proteins. Two distinct peptides (E6(113-132) and E2(1-20)) contained DRB1*01:02- or DRB1*03:01-restricted epitopes, respectively. An additional peptide (E2(281-300)) contained an epitope presented by both alleles. Peptide binding, tetramer, and proliferation assays identified minimal epitopes within these peptides. These epitopes elicited E2/E6-specific CD4(+) T cell responses in RRP patients and healthy control subjects, allowing the isolation of HPV-specific T cell lines using tetramers. The cytokine profiles and STAT signaling of these tetramer-positive T cells were measured to compare the polarization and responsiveness of HPV-specific T cells from patients with RRP and healthy subjects. HPV-specific IFN-γ secretion was substantially lower in T cells from RRP patients. HPV-specific IL-13 secretion was seen at modest levels in T cells from RRP patients and was absent in T cells from healthy control subjects. HPV-specific T cells from RRP patients exhibited reduced STAT-5 phosphorylation and reduced IL-2 secretion, suggesting anergy. Levels of STAT-5 phosphorylation and IFN-γ secretion could be improved through addition of IL-2 to HPV-specific T cell lines from RRP patients. Therapeutic vaccination or interventions aimed at restoring Th1-like cytokine responses to HPV proteins and reversing anergy could improve clinical outcomes for RRP patients.

Vaccinating against Helicobacter pylori infection

Helicobacter pylori infection of the gastric mucosa remains a cause of significant morbidity and mortality almost 30 years after its discovery. H. pylori infection can lead to several gastric maladies, including gastric cancer, and although antimicrobial therapies for the infection exist, the cost of treatment for gastric cancer and the prognosis of individuals who present with this disease make vaccine development a cost effective alternative to bacterial eradication. Experimental mucosal and systemic H. pylori vaccines in mice significantly reduce bacterial load and sometimes provide sterilizing immunity. Clinical trials of oral vaccines consisting of H. pylori proteins with bacterial exotoxin adjuvants or live attenuated bacterial vectors expressing H. pylori proteins induce adaptive immune mechanisms but fail to consistently reduce bacterial load. Clinical trials and murine studies demonstrate that where H. pylori is killed, either spontaneously or following vaccination, the host demonstrated cellular immunity. Improved efficacy of vaccines may be achieved in new trials of vaccine formulations that include multiple antigens and use methods to optimize cellular immunity. Unfortunately, the industrial sponsors that served as the primary engine for much of the previous animal and human research have withdrawn their support. A renewed or expanded commitment from the biotechnology or pharmaceutical industry that could exploit recent advances in our understanding of the host immune response to H. pylori is necessary for the advancement of an H. pylori vaccine.

Helicobacter pylori and gastric cancer: factors that modulate disease risk

Helicobacter pylori is a gastric pathogen that colonizes approximately 50% of the world's population. Infection with H. pylori causes chronic inflammation and significantly increases the risk of developing duodenal and gastric ulcer disease and gastric cancer. Infection with H. pylori is the strongest known risk factor for gastric cancer, which is the second leading cause of cancer-related deaths worldwide. Once H. pylori colonizes the gastric environment, it persists for the lifetime of the host, suggesting that the host immune response is ineffective in clearing this bacterium. In this review, we discuss the host immune response and examine other host factors that increase the pathogenic potential of this bacterium, including host polymorphisms, alterations to the apical-junctional complex, and the effects of environmental factors. In addition to host effects and responses, H. pylori strains are genetically diverse. We discuss the main virulence determinants in H. pylori strains and the correlation between these and the diverse clinical outcomes following H. pylori infection. Since H. pylori inhibits the gastric epithelium of half of the world, it is crucial that we continue to gain understanding of host and microbial factors that increase the risk of developing more severe clinical outcomes.

Local recall responses in the stomach involving reduced regulation and expanded help mediate vaccine-induced protection against Helicobacter pylori in mice

Helicobacter pylori is recognised as the chief cause of chronic gastritis, ulcers and gastric cancer in humans. With increased incidence of treatment failure and antibiotic resistance, development of prophylactic or therapeutic vaccination is a desirable alternative. Although the results of vaccination studies in animal models have been promising, studies in human volunteers have revealed problems such as 'post-immunisation gastritis' and comparatively poor responses to vaccine antigens. The focus of this study was to compare the gastric and systemic cellular immune responses induced by recombinant attenuated Salmonella Typhimurium-based vaccination in the C57BL/6 model of H. pylori infection. Analysis of lymphocyte populations in the gastric mucosa, blood, spleen, paragastric LN and MLN revealed that the effects of vaccination were largely confined to the parenchymal stomach rather than lymphoid organs. Vaccine-induced protection was correlated with an augmented local recall response in the gastric mucosa, with increased proportions of CD4(+) T cells, neutrophils and reduced proportions of CD4(+) Treg. CD4(+) T cells isolated from the stomachs of vaccinated mice proliferated ex vivo in response to H. pylori antigen, and secreted Th1 cytokines, particularly IFN-γ. This detailed analysis of local gastric immune responses provides insight into the mechanism of vaccine-induced protection.

Role of innate immunity in Helicobacter pylori-induced gastric malignancy

Helicobacter pylori colonizes the majority of persons worldwide, and the ensuing gastric inflammatory response is the strongest singular risk factor for peptic ulceration and gastric cancer. However, only a fraction of colonized individuals ever develop clinically significant outcomes. Disease risk is combinatorial and can be modified by bacterial factors, host responses, and/or specific interactions between host and microbe. Several H. pylori constituents that are required for colonization or virulence have been identified, and their ability to manipulate the host innate immune response will be the focus of this review. Identification of bacterial and host mediators that augment disease risk has profound ramifications for both biomedical researchers and clinicians as such findings will not only provide mechanistic insights into inflammatory carcinogenesis but may also serve to identify high-risk populations of H. pylori-infected individuals who can then be targeted for therapeutic intervention.

Cytotoxic T cells in H. pylori-related gastric autoimmunity and gastric lymphoma

Helicobacter pylori infection is the major cause of gastroduodenal pathologies, but only a minority of infected patients develop gastric B-cell lymphoma, gastric autoimmunity, or other life threatening diseases, as gastric cancer or peptic ulcer. The type of host immune response against H. pylori, particularly the cytolytic effector functions of T cells, is crucial for the outcome of the infection. T cells are potentially able to kill a target via different mechanisms, such as perforins or Fas-Fas ligand interaction. In H. pylori-infected patients with gastric autoimmunity cytolytic T cells, that cross-recognize different epitopes of H. pylori proteins and H(+)K(+)-ATPase autoantigen, infiltrate the gastric mucosa and lead to gastric atrophy via long-lasting activation of Fas ligand-mediated appotosis and perforin-induced cytotoxicity. On the other hand, gastric T cells from MALT lymphoma exhibit defective perforin- and Fas-Fas ligand-mediated killing of B cells, with consequent abnormal help for B-cell proliferation, suggesting that deregulated and exhaustive H. pylori-induced T cell-dependent B-cell activation can support both the onset and the promotion of low-grade B-cell lymphoma.

CD4+ T-cell anergy induced by lin- CD117(c-kit)+ stem cell-derived immature dendritic cells loaded with nuclear antigen derived from Trypanosoma equiperdum

Dendritic cells (DCs) are professional antigen-presenting cells, which have the extraordinary capacity to initiate naïve T-cell-mediated primary immune responses. To investigate the role of DCs in the induction of antigen-specific tolerance, the immature DCs (imDCs) and mature DCs (mDCs) were generated in vitro from lin(-)CD117(c-kit)(+) stem cells isolated from mice bone marrow. Flow cytometry and confocal microscopy were used to characterize the phenotypes of DCs. These cells were loaded with nuclear antigen derived from Trypanosoma equiperdum and then co-cultured with naïve CD4(+) T cells. It was found that imDC-treated T cells had lower proliferation level and cytokine expression of interleukin (IL)-2, IL-4, IL-12, and interferon-γ compared with mDC-treated T cells. These results demonstrated that the maturation status of DCs is critical for preventing the production of autoantibodies.

PD-1 and CTLA-4 inhibitory cosignaling pathways in HIV infection and the potential for therapeutic intervention

The balance between proinflammatory mechanisms and the dampening of excessive immune activation is critical for successful clearance of a pathogen without harm to the host. In particular, molecules of the B7:CD28 family play a critical role in regulating T cell activation and peripheral tolerance. Chronic pathogens like HIV, which is characterized by ongoing viral replication despite detectable virus-specific T cell responses, and cancer cells have exploited these pathways to attenuate Ag-specific T cell immunity. This review summarizes evidence that molecules of the B7:CD28 family, PD-1, CTLA-4, and their ligands, play an active and reversible role in virus-specific T cell exhaustion associated with HIV infection in humans and in the SIV model in macaques. We discuss the potential for immunotherapeutic interventions based on manipulation of these inhibitory networks, the promising data obtained with blockade of the PD-1 pathway in animal models, and the challenges to such therapies.

Cathepsin X prevents an effective immune response against Helicobacter pylori infection

Cathepsin X, a cysteine protease, has been shown to regulate an immune response by activating beta-2 integrin receptors. In this study we demonstrate its role in regulating the immune response to infection with H. pylori. The level of cathepsin X was determined in THP-1 monocyte cells primed with H. pylori antigens isolated from subjects suffering from gastritis, who had either eradicated or not the disease after the antibiotic therapy. We show that the specific clinical outcome of H. pylori eradication therapy correlates strongly with the membrane expression of cathepsin X in stimulated THP-1 cells, being significantly higher after stimulation with H. pylori strains from those subjects who did not respond to antibiotic therapy. The same antigens elicit a more vigorous immune response, increased expression of MHC II, however trigger inadequate cytokine profile (IFN-gamma and IL-4) to eradicate the pathogen. We propose that cathepsin X mediated activation of beta-2 integrin receptor Mac-1 suppresses the stimulatory signal in the form of cytokines. Cathepsin X co-localizes on the membrane of THP-1 cells with Mac-1 integrin receptor and its inhibition increases homotypic aggregation and mononuclear cell proliferation, events that are associated with low Mac-1 activity. Our study highlights the diversity of the innate immune response to H. pylori antigens leading to either successful eradication of the infection or maintenance of chronic inflammation, revealing cathepsin X location and activity as a regulator of the effectiveness of H. pylori eradication.

CD25+ T cells induce Helicobacter pylori-specific CD25- T-cell anergy but are not required to maintain persistent hyporesponsiveness

The gastric pathogen Helicobacter pylori infects over half the world's population. The lifelong infection induces gastric inflammation but the host fails to generate protective immunity. To study the lack of protective H. pylori immunity, CD4(+)CD25(+) T(reg) cells were investigated for their ability to down-regulate H. pylori-specific CD4(+)CD25(-) cells in a murine model. CD25(-) lymphocytes from infected mice were hyporesponsive to antigenic stimulation in vitro even in the absence of CD25(+) T(reg) cells unless treated with high-dose IL-2. Transfer of CD45RB(hi) naïve CD25(-) cells from infected mice into rag1(-/-) mice challenged with H. pylori resulted in severe gastritis and reduced bacterial loads, whereas transfer of CD45RB(lo) memory CD25(-) cells from H. pylori-infected mice resulted in only mild gastritis and persistent infection. CD25(-) cells stimulated in the absence of CD25(+) cells in rag1(-/-) mice promoted bacterial clearance, but lost this ability when subsequently transferred to WT mice harboring CD25(+) cells. These results demonstrate that CD25(+) cells induce anergy in CD25(-) cells in response to H. pylori infection but are not required to maintain hyporesponsiveness. In addition, CD25(+) cells are able to suppress previously activated CD25(-) cells when responding to H. pylori challenge in vivo.

Synergistic reversal of intrahepatic HCV-specific CD8 T cell exhaustion by combined PD-1/CTLA-4 blockade

Viral persistence is associated with hierarchical antiviral CD8 T cell exhaustion with increased programmed death-1 (PD-1) expression. In HCV persistence, HCV-specific CD8 T cells from the liver (the site of viral replication) display increased PD-1 expression and a profound functional impairment that is not reversed by PD-1 blockade alone. Here, we report that the inhibitory receptor cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is preferentially upregulated in PD-1(+) T cells from the liver but not blood of chronically HCV-infected patients. PD-1/CTLA-4 co-expression in intrahepatic T cells was associated with a profound HCV-specific effector dysfunction that was synergistically reversed by combined PD-1/CTLA-4 blockade in vitro, but not by blocking PD-1 or CTLA-4 alone. A similar effect was observed in circulating HCV-specific CD8 T cells with increased PD-1/CTLA-4 co-expression during acute hepatitis C. The functional response to combined blockade was directly associated with CTLA-4 expression, lost with CD28-depletion and CD4-independent (including CD4(+)FoxP3(+) Tregs). We conclude that PD-1 and CTLA-4 pathways both contribute to virus-specific T cell exhaustion at the site of viral replication by a redundant mechanism that requires combined PD-1/CTLA-4 blockade to reverse. These findings provide new insights into the mechanisms of virus-specific T cell dysfunction, and suggest that the synergistic effect by combined inhibitory receptor blockade might have a therapeutic application against chronic viral infection in vivo, provided that it does not induce autoimmunity.

Vaccination of mice against H pylori induces a strong Th-17 response and immunity that is neutrophil dependent

BACKGROUND & AIMS

Vaccine efficacy against gastric Helicobacter pylori infection has been shown in mice, but little is known about the mechanisms of bacterial clearance. Our aim was to investigate a possible T-cell/neutrophil pathway of vaccine-induced protection.

METHODS

Nonimmune and immunized mice were compared for their response to H pylori challenge. T-cell responses were assessed by recall assays. Interleukin (IL)-17-induced chemokine production was evaluated by cytokine enzyme-linked immunosorbent assay. In a kinetic study, biopsy specimens were collected at multiple time points postchallenge and assessed for bacterial load and inflammation. Relative levels of T cells, IL-17, interferon gamma, MIP-2, KC, and LIX were determined by quantitative polymerase chain reaction. The role of neutrophils was evaluated by antibody-mediated depletion of neutrophils following challenge.

RESULTS

Immunization induced strong interferon gamma- and IL-17-producing T-cell responses, and IL-17 was capable of inducing significant amounts of KC and MIP-2 from dendritic cells, macrophages, fibroblasts, and gastric epithelial cells. Challenge of immunized mice induced significantly greater gastritis than that of infected mice, preceding significantly lower bacterial loads by day 7. In immune mice, T-cell recruitment to the gastric mucosa correlated with a continuous rise in IL-17 and interferon gamma levels, followed by KC, MIP-2, and LIX production and the recruitment of significant numbers of neutrophils by day 5. Antibody-mediated depletion of neutrophils abrogated vaccine efficacy.

CONCLUSIONS

Vaccination of mice against H pylori results in a significant Th-17 cell recall response associated with increases in chemokines that attract neutrophils to the stomach, which are important for eradication of H pylori.

Cytotoxic T-lymphocyte antigen 4 blockade augments the T-cell response primed by attenuated Listeria monocytogenes resulting in more rapid clearance of virulent bacterial challenge

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) uniformly suppresses antigen-specific T cells during chronic infection with bacterial, parasitic or viral pathogens. However, the importance of CTLA-4 in controlling the T-cell response during acute infection or after priming with live attenuated vaccine vectors has not been well characterized. Since strategies aimed at blocking CTLA-4 are being actively developed to therapeutically augment T-cell-mediated immunity, the effects of CTLA-4 blockade on T-cell activation during these conditions need to be more clearly defined. We have examined the role of CTLA-4 in a prime-challenge model of acute bacterial infection using both attenuated and virulent strains of the intracellular bacterium Listeria monocytogenes. Although Foxp3(+) CD4(+) T cells are the predominant CTLA-4-expressing cell type in naïve mice, antigen-specific Foxp3(-) CD4(+) cells upregulate CTLA-4 expression after primary L. monocytogenes infection. Blockade of CTLA-4 results in increased numbers of L. monocytogenes-specific CD4 and CD8 T cells after primary infection with attenuated L. monocytogenes, and confers more rapid bacterial clearance after secondary challenge with virulent L. monocytogenes. Accordingly, CTLA-4 plays an important suppressive role in T-cell priming and protective immunity in a prime-challenge model of acute bacterial infection.

CD25+ T cells induce Helicobacter pylori-specific CD25- T-cell anergy but are not required to maintain persistent hyporesponsiveness

The gastric pathogen Helicobacter pylori infects over half the world's population. The lifelong infection induces gastric inflammation but the host fails to generate protective immunity. To study the lack of protective H. pylori immunity, CD4(+)CD25(+) T(reg) cells were investigated for their ability to down-regulate H. pylori-specific CD4(+)CD25(-) cells in a murine model. CD25(-) lymphocytes from infected mice were hyporesponsive to antigenic stimulation in vitro even in the absence of CD25(+) T(reg) cells unless treated with high-dose IL-2. Transfer of CD45RB(hi) naïve CD25(-) cells from infected mice into rag1(-/-) mice challenged with H. pylori resulted in severe gastritis and reduced bacterial loads, whereas transfer of CD45RB(lo) memory CD25(-) cells from H. pylori-infected mice resulted in only mild gastritis and persistent infection. CD25(-) cells stimulated in the absence of CD25(+) cells in rag1(-/-) mice promoted bacterial clearance, but lost this ability when subsequently transferred to WT mice harboring CD25(+) cells. These results demonstrate that CD25(+) cells induce anergy in CD25(-) cells in response to H. pylori infection but are not required to maintain hyporesponsiveness. In addition, CD25(+) cells are able to suppress previously activated CD25(-) cells when responding to H. pylori challenge in vivo.