CTLA-4 blockade inhibits induction of Helicobacter pylori-associated gastritis in mice

Immune checkpoint blockade in experimental bacterial infections

Immune checkpoint inhibitors designed to reinvigorate immune responses suppressed by cancer cells have revolutionized cancer therapy. Similarities in immune dysregulation between cancer and infectious diseases have prompted investigations into the role of immune checkpoints in infectious diseases, including the therapeutic potential of immune checkpoint blockade and drug repurposing. While most research has centered around viral infections, data for bacterial infections are emerging. This systematic review reports on the in vivo effect of immune checkpoint blockade on bacterial burden and selected immune responses in preclinical studies of bacterial infection, aiming to assess if there could be a rationale for using immunotherapy for bacterial infections. Of the 42 analyzed studies, immune checkpoint blockade reduced the bacterial burden in 60% of studies, had no effect in 28% and increased the bacterial burden in 12%. Findings suggest that the effect of immune checkpoint blockade on bacterial burden is context-dependent and in part relates to the pathogen. Further preclinical research is required to understand how the therapeutic effect of immune checkpoint blockade is mediated in different bacterial infections, and if immune checkpoint blockade can be used as an adjuvant to conventional infection management strategies.

Antimicrobial immunotherapeutics: past, present and future

In this age of antimicrobial resistance (AMR) there is an urgent need for novel antimicrobials. One area of recent interest is in developing antimicrobial effector molecules, and even cell-based therapies, based on those of the immune system. In this review, some of the more interesting approaches will be discussed, including immune checkpoint inhibitors, Interferons (IFNs), Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF), Chimeric Antigen Receptor (CAR) T cells, Antibodies, Vaccines and the potential role of trained immunity in protection from and/or treatment of infection.

Association of immune checkpoint inhibitors with respiratory infections: A review

Treatment with immune-checkpoint inhibitors (ICIs) has shown efficacy against a variety of cancer types. The use of anti PD-1, anti PD-L1, and anti CTLA-4 antibodies is rapidly expanding. The side effects of ICIs are very different from conventional cytocidal anticancer and molecular target drugs, and may extend to the digestive organs, respiratory organs, thyroid gland, pituitary gland, skin, and others. Although the details of these adverse events are becoming increasingly apparent, much is unknown regarding the effects and adverse events related to infections. This review focuses specifically on the impact of ICIs on respiratory infections. The impact of ICIs on pathogens varies depending on the significance of the role of T-cell immunity in the immune response to the specific pathogen, as well as the different modes of infection (i.e., acute or chronic), although the impact of ICIs on the clinical outcome of infections in humans has not yet been well studied. Enhanced clearance of many pathogens has been shown because immune checkpoint inhibition activates T cells. In contrast, reactivation of tuberculosis associated with ICI use has been reported, and therefore caution is warranted. In COVID-19 pneumonia, ICI administration may lead to exacerbation; however, it is also possible that ICI may be used for the treatment of COVID-19. It has also been shown that ICI has potential in the treatment of intractable filamentous fungal infections. Therefore, expanded clinical applications are expected.

Identification of DEGs and transcription factors involved in H. pylori-associated inflammation and their relevance with gastric cancer

Background

Previous studies have indicated that chronic inflammation linked to H. pylori infection is the leading causes for gastric cancer (GC). However, the exact mechanism is not entirely clear until now.

Purpose

To identify the key molecules and TFs involved in H. pylori infection and to provide new insights into H. pylori-associated carcinogenesis and lay the groundwork for the prevention of GC.

Results

GO and KEGG analysis revealed that the DEGs of Hp⁺-NAG were mainly associated with the immune response, chemokine activity, extracellular region and rheumatoid arthritis pathway. The DEGs of Hp⁺-AG-IM were related to the apical plasma membrane, intestinal cholesterol absorption, transporter activity and fat digestion and absorption pathway. In Hp⁺-NAG network, the expression of TNF, CXCL8, MMP9, CXCL9, CXCL1, CCL20, CTLA4, CXCL2, C3, SAA1 and FOXP3, JUN had statistical significance between normal and cancer in TCGA database. In Hp⁺-AG-IM network the expression of APOA4, GCG, CYP3A4, XPNPEP2 and FOXP3, JUN were statistically different in the comparison of normal and cancer in TCGA database. FOXP3 were negatively associated with overall survival, and the association for JUN was positive.

Conclusion

The current study identified key DEGs and their transcriptional regulatory networks involved in H. pylori-associated NAG, AG-IM and GC and found that patients with higher expressed FOXP3 or lower expressed JUN had shorter overall survival time. Our study provided new directions for inflammation-associated oncogenic transformation involved in H. pylori infection.

Checkpoint Inhibition and Infectious Diseases: A Good Thing?

The mammalian immune system has evolved the capacity to detect and destroy tumor cells. Tumors utilize multiple strategies to evade host immune surveillance, including the induction of the checkpoint molecules cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) to suppress antitumor immunity. Pharmacologic blockade of these molecules with checkpoint inhibitors (CPIs) restores T cell function and prolongs survival in patients with various malignancies. Emerging evidence suggests that the same checkpoint pathways may play a crucial role during infections. Indeed, CPIs appear promising as immunotherapeutic agents in infectious diseases, although their efficacy varies depending on pathogen-, cell-, and organ-specific factors. More research will be necessary to clarify the effects and safety of CPIs on clinically relevant outcomes of human infection.

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.

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.

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.

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.

Anti-CTLA-4 treatment induces IL-10-producing ICOS+ regulatory T cells displaying IDO-dependent anti-inflammatory properties in a mouse model of colitis

BACKGROUND AND AIMS

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) has been shown to act as a negative regulator of T cell function and has been implicated in the regulation of T helper 1 (Th1)/Th2 development and the function of regulatory T cells. Tests were carried out to determine whether anti-CTLA-4 treatment would alter the polarisation of naive T cells in vivo.

METHODS

Mice were treated with anti-CTLA-4 monoclonal antibody (mAb) (UC10-4F10) at the time of immunisation or colonic instillation of trinitrobenzene sulfonic acid (TNBS). The cytokines produced by lymph node cells after in vitro antigenic stimulation and the role of indoleamine 2,3 dioxygenase (IDO) and of interleukin-10 (IL-10) were tested, and the survival of mice was monitored.

RESULTS

Injection of anti-CTLA-4 mAb in mice during priming induced the development of adaptive CD4(+) regulatory T cells which expressed high levels of ICOS (inducible co-stimulator), secreted IL-4 and IL-10. This treatment inhibited Th1 memory responses in vivo and repressed experimental intestinal inflammation. The anti-CTLA-4-induced amelioration of disease correlated with IDO expression and infiltration of ICOS(high) Foxp3(+) T cells in the intestine, suggesting that anti-CTLA-4 acted indirectly through the development of regulatory T cells producing IL-10 and inducing IDO.

CONCLUSIONS

These observations emphasise the synergy between IL-10 and IDO as anti-inflammatory agents and highlight anti-CTLA-4 treatment as a potential novel immunotherapeutic approach for inducing adaptive regulatory T cells.

Immunology of Helicobacter pylori: insights into the failure of the immune response and perspectives on vaccine studies

Helicobacter pylori infects the stomach of half of the human population worldwide and causes chronic active gastritis, which can lead to peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. The host immune response to the infection is ineffective, because the bacterium persists and the inflammation continues for decades. Bacterial activation of epithelial cells, dendritic cells, monocytes, macrophages, and neutrophils leads to a T helper cell 1 type of adaptive response, but this remains inadequate. The host inflammatory response has a key functional role in disrupting acid homeostasis, which impacts directly on the colonization patterns of H pylori and thus the extent of gastritis. Many potential mechanisms for the failure of the host response have been postulated, and these include apoptosis of epithelial cells and macrophages, inadequate effector functions of macrophages and dendritic cells, VacA inhibition of T-cell function, and suppressive effects of regulatory T cells. Because of the extent of the disease burden, many strategies for prophylactic or therapeutic vaccines have been investigated. The goal of enhancing the host's ability to generate protective immunity has met with some success in animal models, but the efficacy of potential vaccines in humans remains to be demonstrated. Aspects of H pylori immunopathogenesis are reviewed and perspectives on the failure of the host immune response are discussed. Understanding the mechanisms of immune evasion could lead to new opportunities for enhancing eradication and prevention of infection and associated disease.

CD4+ CD25+ regulatory T cells modulate the T-cell and antibody responses in helicobacter-infected BALB/c mice

Gastric Helicobacter spp. induce chronic gastritis that may lead to ulceration and dysplasia. The host elicits a T helper 1 (Th1) response that is fundamental to the pathogenesis of these bacteria. We analyzed immune responses in Helicobacter-infected, normal mice depleted of CD4+ CD25+ T cells to investigate the in vivo role of regulatory T cells (Tregs) in the modulation of Helicobacter immunopathology. BALB/c and transgenic mice were depleted of CD4+ CD25+ T cells by administration of an anti-CD25 antibody either at the time of infection with Helicobacter or during chronic infection and gastritis. Depletion of CD25+ Tregs prior to and during infection of mice with Helicobacter spp. did not affect either bacterial colonization or severity of gastritis. Depletion of CD25+ Tregs was associated with increased Helicobacter-specific antibody levels and an altered isotype distribution. Paragastric lymph node cells from CD25+ Treg-depleted and control infected mice showed similar proliferation to Helicobacter antigens, but only cells from anti-CD25-treated animals secreted Th2 cytokines. CD25+ Tregs do not control the level of gastritis induced by gastric Helicobacter spp. in normal, thymus-intact BALB/c mice. However, CD25+ Tregs influence the cytokine and antibody responses induced by infection. Autoimmune gastritis is not induced in Helicobacter-infected mice depleted of CD25+ Tregs but is induced in CD25+ Treg-depleted mice, which have a higher frequency of autoreactive T cells.

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

Helicobacter pylori infection induces gastric inflammation but the host fails to generate protective immunity. Therefore, we evaluated the immunologic mechanisms that contribute to the failure of the T cells to promote active immunity to H. pylori in the mouse model of H. pylori infection. Spleen cells from infected C57BL/6 mice underwent significantly less proliferation and cytokine production than cells from immune mice upon in vitro stimulation with H. pylori lysate. Similar results were observed when stimulating with Ag-pulsed macrophages demonstrating that hyporesponsiveness was not due to a direct effect of H. pylori virulence factors on the T cells. Ag-specific hyporesponsiveness could be reversed by the addition of high-dose IL-2 but not by removal of CD4(+)CD25(+) T cells, indicating that hyporesponsiveness was due to anergy and not due to active suppression. Cells from infected mice lacked significant suppressor activity as shown by the failure to reduce the recall response of cells from immune mice in coculture at physiologic ratios. Direct blockade of CTLA-4 using anti-CTLA-4 Fabs or indirect blockade using CTLA-4 Ig plus anti-CD28 Ab resulted in significantly increased T cell activation in vitro. The importance of CTLA-4 in establishing anergy was confirmed in an in vivo model of H. pylori infection in which mice that received anti-CTLA-4 Fabs responded to H. pylori challenge with significantly greater inflammation and significantly reduced bacterial load. These results suggest that CTLA-4 engagement induces and maintains functional inactivation of H. pylori-specific T cells during H. pylori infection resulting in a reduced immune response.

Response of IgG1 and IgG2 subclasses to Helicobacter pylori in subjects with chronic inflammation of the gastric mucosa, atrophy and gastric cancer in a country with high Helicobacter pylori infection prevalence

Polarized immune response to Helicobacter pylori and induction of chronic inflammation may increase the risk of gastric atrophy and adenocarcinoma. We studied the association of the response of IgG1 and IgG2 antibodies to H. pylori with grade of gastric chronic inflammation and atrophy in a population with a high prevalence of H. pylori, and compared these data with the data obtained from the study of gastric cancer patients, as well as with the data for CagA positivity. Altogether, 114 persons from two adult population samples from Estonia and 45 consecutive gastric cancer patients were studied. All patients were positive for the H. pylori antibody determined by ELISA. Adenocarcinoma was classified histologically according to the Laurén's system. The response of the IgG subclasses to H. pylori (acid glycine-extracted whole cell proteins) was determined by ELISA and the results were compared with the ELISA results for the recombinant fragment of the CagA protein. Helicobacter pylori IgG level was lower in atrophic gastritis compared with nonatrophic gastritis (chronic inflammation) (p=0.001). In the group of cancer patients, the response of IgG and IgG1 was lower compared with both gastritis groups (p=0.01 and p=0.0002 for IgG, and p=0.001 and p=0.0005 for IgG1). IgG2 was lower for gastric cancer localized in the corpus (p=0.03). In conclusion, atrophic gastritis and gastric cancer were associated with a significant decline in IgG and IgG1 response to H. pylori compared with nonatrophic gastritis. Higher value of CagA antibodies was seen in gastric cancer and in gastric atrophy compared with nonatrophic gastritis; in gastric cancer patients, IgG1 response to H. pylori was correlated with CagA status.

The role of type-specific antibodies in colonization and infection by Helicobacter pylori

PURPOSE OF REVIEW

Helicobacter pylori is a Gram-negative spiral bacterium that colonizes the stomach of humans, causing gastritis, peptic ulcer disease, or gastric cancer. H. pylori infection accounts for a high percentage of mortality and morbidity rates in developing as well as developed countries. H. pylori bacteria reside in the mucus layer covering the gastric epithelium, and therefore the type of protective measures that could confer resistance appear to be limited. Although H. pylori infection stimulates strong local and systemic specific IgA and IgG antibody production, the influence of antibodies on bacterial colonization and gastric inflammation is still controversial.

RECENT FINDINGS

Recent studies in experimental animal models have indicated a non-essential role of specific antibodies for host resistance against H. pylori infection. Recent data show that protection is mediated by T cells, CD4 T helper type 1 cells, in particular. Antibodies are not only dispensable for protection, but they impair both the elimination of bacteria and the development of gastritis. This effect appears to be IgA-dependent and is not a function of specific IgM or IgG antibodies.

SUMMARY

This review highlights the recent advances in our understanding of how antibodies may influence the development of gastric inflammation and bacterial colonization. Such information can significantly increase our basic knowledge of immune regulation and protection against H. pylori infection, but can also indicate new strategies for vaccine development.

Effect of sucralfate on antibiotic therapy for Helicobacter pylori infection in mice

It has been documented that sucralfate, a basic aluminum salt, enhances the efficacies of antibiotics against Helicobacter pylori, resulting in eradication rates comparable to those associated with the use of proton pump inhibitors. However, its mechanism of action remains unclear. The aim of the present study was to investigate sucralfate's ability to complement antibiotic treatment of H. pylori infection in vivo. Four weeks following induced H. pylori infection, clarithromycin (CAM) and amoxicillin (AMPC) were administered orally to C57BL/6 mice for 5 days, both with and without sucralfate or lansoprazole. When sucralfate was concurrently given with CAM and AMPC at the maximum noninhibitory doses for the treatment of H. pylori infection, the bacterial clearance rates were comparable to those achieved by treatment with lansoprazole plus those antibiotics. The results of pharmacokinetic studies showed that lansoprazole delayed gastric clearance and accelerated the absorption of CAM, whereas sucralfate suppressed both gastric clearance and absorption. AMPC was undetectable in all samples. Scanning electron microscopy with a microscope to which a energy dispersive spectrometer was attached revealed that aluminum-containing aggregated substances coated the mucosa surrounding H. pylori in mice receiving sucralfate plus antibiotics, whereas the gastric surface and pits where H. pylori had attached were clearly visible in mice receiving lansoprazole plus antibiotics. The addition of sucralfate to the antibiotic suspension resulted in a more viscous mixture that bound to the H. pylori-infected mucosa and that inhibited the loss of CAM bioavailability in the acidic environment. Sucralfate delays gastric clearance of CAM and physically captures H. pylori through the creation of an adherent mucus, which leads to bacterial clearance.

Inflammation, immunity and vaccines for Helicobacter pylori

Helicobacter pylori causes chronic gastritis in the human stomach, yet only a minority of infected individuals develop peptic ulcer disease, atrophic gastritis, or gastric malignancies. The severity, progression, and consequences of H. pylori infection have been shown to depend on the host genetic background, and in particular on gene polymorphisms affecting the host immune response. Numerous studies published last year brought new information on the mechanisms by which the host genetic make-up modifies the inflammatory and immune responses to H. pylori and the induction of tissue damage secondary to the infection. Novel insights on the regulatory role of H. pylori on the adaptive T-cell response and on its consequences for the persistence of the infection and for the development of vaccines are discussed.