Programmed death-1/programmed death-L1 signaling pathway and its blockade in hepatitis C virus immunotherapy

Immune checkpoint inhibitors and SARS-CoV2 infection

Infection with severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) triggers coronavirus disease 2019 (COVID-19), which predominantly targets the respiratory tract. SARS-CoV-2 infection, especially severe COVID-19, is associated with dysregulated immune responses against the virus, including exaggerated inflammatory responses known as the cytokine storm, together with lymphocyte and NK cell dysfunction known as immune cell exhaustion. Overexpression of negative immune checkpoints such as PD-1 and CTLA-4 plays a considerable role in the dysfunction of immune cells upon SARS-CoV-2 infection. Blockade of these checkpoints has been suggested to improve the clinical outcome of COVID-19 patients by promoting potent immune responses against the virus. In the current review, we provide an overview of the potential of checkpoint inhibitors to induce potent immune responses against SARS-CoV-2 and improving the clinical outcome of severe COVID-19 patients.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.

What role does PDL1 play in EMT changes in tumors and fibrosis?

Epithelial-mesenchymal transformation (EMT) plays a pivotal role in embryonic development, tissue fibrosis, repair, and tumor invasiveness. Emerging studies have highlighted the close association between EMT and immune checkpoint molecules, particularly programmed cell death ligand 1 (PDL1). PDL1 exerts its influence on EMT through bidirectional regulation. EMT-associated factors, such as YB1, enhance PDL1 expression by directly binding to its promoter. Conversely, PDL1 signaling triggers downstream pathways like PI3K/AKT and MAPK, promoting EMT and facilitating cancer cell migration and invasion. Targeting PDL1 holds promise as a therapeutic strategy for EMT-related diseases, including cancer and fibrosis. Indeed, PDL1 inhibitors, such as pembrolizumab and nivolumab, have shown promising results in clinical trials for various cancers. Recent research has also indicated their potential benefit in fibrosis treatment in reducing fibroblast activation and extracellular matrix deposition, thereby addressing fibrosis. In this review, we examine the multifaceted role of PDL1 in immunomodulation, growth, and fibrosis promotion. We discuss the challenges, mechanisms, and clinical observations related to PDL1, including the limitations of the PD1/PDL1 axis in treatment and PD1-independent intrinsic PDL1 signaling. Our study highlights the dynamic changes in PDL1 expression during the EMT process across various tumor types. Through interplay between PDL1 and EMT, we uncover co-directional alterations, regulatory pathways, and diverse changes resulting from PDL1 intervention in oncology. Additionally, our findings emphasize the dual role of PDL1 in promoting fibrosis and modulating immune responses across multiple diseases, with potential implications for therapeutic approaches. We particularly investigate the therapeutic potential of targeting PDL1 in type II EMT fibrosis: strike balance between fibrosis modulation and immune response regulation. This analysis provides valuable insights into the multifaceted functions of PDL1 and contributes to our understanding of its complex mechanisms and therapeutic implications.

Immunotherapy in cancer patients with chronic hepatitis C viral infection

Disease management in challenging patient population with cancer and concomitant serious conditions presents an unmet clinical need. The major gap is the lack of data from properly designed trials that could support clinical decisions. Despite many advances in the fields of oncology, immunology, and infectious diseases, chronic viral infections in cancer patients remain to some extent terra incognita. Therefore, many patients lose the opportunity to receive the most advanced therapy, and physicians are compelled to make treatment decisions without sufficient evidence. In this review, we discuss the utility of immunotherapy in patients with chronic hepatitis C viral infection. Limited data from several studies and case reports support the hypothesis that immune checkpoint inhibitors can be used safely and effectively in this patient population. Available results warrant further investigation of immunotherapy in infected patients. Taking into account the current state of our knowledge, expanding clinical trial eligibility should be considered by investigators and sponsors to allow patient access to novel therapies and better matching of clinical research to the real-world population.

Hepatitis Viruses Control Host Immune Responses by Modifying the Exosomal Biogenesis Pathway and Cargo

The development of smart immune evasion mechanisms is crucial for the establishment of acute and chronic viral hepatitis. Hepatitis is a major health problem worldwide arising from different causes, such as pathogens, metabolic disorders, and xenotoxins, with the five hepatitis viruses A, B, C, D, and E (HAV, HBV, HCV, HDV, and HEV) representing the majority of the cases. Most of the hepatitis viruses are considered enveloped. Recently, it was reported that the non-enveloped HAV and HEV are, in reality, quasi-enveloped viruses exploiting exosomal-like biogenesis mechanisms for budding. Regardless, all hepatitis viruses use exosomes to egress, regulate, and eventually escape from the host immune system, revealing another key function of exosomes apart from their recognised role in intercellular communication. This review will discuss how the hepatitis viruses exploit exosome biogenesis and transport capacity to establish successful infection and spread. Then, we will outline the contribution of exosomes in viral persistence and liver disease progression.

Nivolumab and anti-HCV activity, a case report

Exhaustion of antigen-specific T-cells in order to escape immune destruction is frequently seen in chronic viral infection and different types of cancer. Blockade of overexpressed negative co-stimulatory pathways, a process known as immune checkpoint modulation, is a promising novel therapy that could improve the treatment of liver diseases with features of T cell exhaustion. We present a case of a 54-year-old hepatitis C virus (HCV) positive patient with an acute flare of hepatitis during nivolumab treatment for a stage IV lung carcinoma, an anti-programmed death-1 (PD-1) immunotherapy. Retrospective testing of HCV RNA documented infection more than 6 months ago. Nivolumab treatment was associated with an alanine aminotransferase (ALT) flare reaching a peak value of 663 U/L, along with bilirubin levels of 0.74 mg/dL and no signs of coagulopathy. The assumption of a nivolumab-associated autoimmune hepatitis led to the interruption of the immune checkpoint inhibitor treatment. However, a subsequent 1-log decrease of HCV RNA load was noticed, which raised the possibility of an immune reconstitution against the HCV-infected hepatocytes with cell lysis. Liver biopsy specimen demonstrated no evidence for autoimmune liver disease or fibrosis. Clinical evolution was favorable and serum transaminases returned to normal levels and HCV RNA load increased to baseline values following nivolumab cessation. The current case suggests an anti-HCV activity of anti-PD-1 treatment in the setting of concomitant HCV viremia and lung carcinoma.

PD-1 Blockade Restores the Proliferation of Peripheral Blood Lymphocyte and Inhibits Lymphocyte Apoptosis in a BALB/c Mouse Model of CP BVDV Acute Infection

Acute infection of bovine viral diarrhea virus (BVDV) is associated with immune dysfunction and can cause peripheral blood lymphopenia and lymphocyte apoptosis. Our previous study has confirmed that programmed death-1 (PD-1) blockade inhibits peripheral blood lymphocytes (PBL) apoptosis and restores proliferation and anti-viral immune functions of lymphocytes after BVDV infection in vitro. However, the situation in vivo remains to be further studied and confirmed. Therefore, in this study, we established a BALB/c mouse model of acute BVDV infection with cytopathic (CP) BVDV (strain NADL) and non-cytopathic (NCP) BVDV (strain NY-1). Then, we examined the mRNA and protein levels of PD-1 and programmed death-ligand 1 (PD-L1) in peripheral blood mononuclear cells (PBMC) from BVDV-infected mice and analyzed the effects of PD-1 blockade on the proportions of CD3+, CD4+, and CD8+ T cell subsets, the apoptosis and proliferation of PBL, and the production of IL-2 and IFN-γ. We found that leukopenia, lymphocytopenia, and thrombocytopenia were developed in both CP and NCP BVDV-infected mice at day 7 of post-infection. The mRNA and protein expression of PD-1 and PD-L1 were significantly upregulated in CP and NCP BVDV-infected mice. Moreover, PD-1/PD-L1 upregulation was accompanied by leukopenia and lymphopenia. Additionally, PD-1 blockade inhibited PBL apoptosis and virus replication, restored the proportions of CD3+, CD4+, and CD8+ T cell subsets, and increased IFN-γ production and p-ERK expression in BVDV-infected mice. However, blocking PD-1 did not significantly affect PBL proliferation and IL-2 production in NCP BVDV-infected mice. Our findings further confirmed the immunomodulatory role of PD-1 in peripheral blood lymphocytopenia in vivo and provided a scientific basis for exploring the molecular mechanism of immune dysfunction caused by acute BVDV infection.

Downregulation of the PD-1/PD-Ls pathway in peripheral cells correlates with asbestosis severity

Background

Asbestosis and silicosis are characterized by diffuse or nodular interstitial lung fibrosis resulting from exposure to asbestos or silica dust, respectively. This study was designed to detect programmed cell death protein (PD-1)/programmed death ligands (PD-Ls) expression in patients with asbestosis and silicosis and to explore the possible clinical significance of PD-1/PD-Ls expression in patients with the two diseases.

Methods

Thirty patients with asbestosis, 23 patients with silicosis and 25 healthy controls were consecutively recruited and provided informed consent to participate in the study. Clinical data were collected from patients’ clinical charts. PD-1/PD-Ls expression in peripheral blood (PB) was detected using flow cytometry.

Results

PD-1 was expressed at significantly lower levels on CD4⁺ or CD8⁺ peripheral T cells from patients with asbestosis and silicosis than on cells from healthy controls. Similarly, significantly lower PD-L1 and PD-L2 expression was detected on CD14⁺ monocytes from patients with asbestosis and silicosis than on cells from healthy controls. In addition, no significant differences in PD-1, PD-L1 and PD-L2 expression were observed between the asbestosis and silicosis groups. Moreover, the proportions of PD-1⁺ CD4⁺ T cells and PD-1⁺ CD8⁺ T cells in patients with asbestosis were positively correlated with the percentage of forced vital capacity predicted.

Conclusions

Decreased PD-1 expression on CD4⁺ T or CD8⁺ T cells in PB was positively correlated with the asbestosis severity, implying that pulmonary fibrosis development in patients with asbestosis was positively correlated with the downregulation of the PD-1/PD-Ls pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01531-5.

Safety and efficacy of immune checkpoint inhibitors in non-small-cell lung cancer: focus on challenging populations

In recent years, immune-checkpoint inhibitors (ICIs) have represented one of the major breakthroughs in advanced non-small cell lung cancer treatment scenario. However, enrollment in registering clinical trials is usually restricted, since frail patients (i.e., elderly, individuals with poor performance status and/or active brain metastases), as well as patients with chronic infections or who take concurrent medications, such as steroids, are routinely excluded. Thus, safety and efficacy of ICIs for these subgroups have not been adequately assessed in clinical trials, although these populations often occur in clinical practice. We reviewed the available data regarding the use of ICIs in these 'special' populations, including a focus on the issues raised by the administration of immunotherapy in lung cancer patients infected with Sars-Cov-2.

Immune Checkpoints in Viral Infections

As evidence has mounted that virus-infected cells, such as cancer cells, negatively regulate the function of T-cells via immune checkpoints, it has become increasingly clear that viral infections similarly exploit immune checkpoints as an immune system escape mechanism. Although immune checkpoint therapy has been successfully used in cancer treatment, numerous studies have suggested that such therapy may also be highly relevant for treating viral infection, especially chronic viral infections. However, it has not yet been applied in this manner. Here, we reviewed recent findings regarding immune checkpoints in viral infections, including COVID-19, and discussed the role of immune checkpoints in different viral infections, as well as the potential for applying immune checkpoint blockades as antiviral therapy.

Programmed death-1 expression and regulatory T cells increase in the Intestinal mucosa of cytomegalovirus colitis in patients with HIV/AIDS

BACKGROUND

Cytomegalovirus (CMV) is among the most common opportunistic infections identified in patients with HIV/AIDS. CMV often targets the colon in such patients. However, the role of regulatory T cells (T_regs) and Programmed death-1 (PD-1) in intestinal CMV infection is unclear. In this study, we evaluate the expression of programmed death -1 (PD-1) and its association with regulatory T cells (T_regs) in patients with HIV/AIDS having CMV colitis.

METHODS

CMV was detected in the intestinal mucosal biopsy samples via nucleic acid in situ hybridization. PD-1, CD4, CD8, and T_reg-specific marker as well as the winged-helix transcription factor and forkhead box P3 (FoxP3) were detected by immunohistochemical methods.

RESULTS

Intestinal CMV diease was identified in 20 out of 195 patients with HIV/AIDS enrolled in our study. CMV was diagnosed microscopically by the presence of giant cell inclusion bodies in epithelial cells, histiocytes, and fibroblasts. Levels of immunoreactive PD-1 detected in mucosal biopsies from patients with HIV/AIDS having CMV colitis were significantly higher than CMV-negative control group (p = 0.023). FoxP3⁺ cells were detected in the CMV colitis group slight more than that in the control group. CD4⁺ T lymphocyte counts in the peripheral blood and intestinal mucosal biopsies from CMV colitis group were all notably decreased compared with those with control group (p < 0.001 for both). PD-1 had a significant negative correlation with CD4 counts in intestinal mucosa (p = 0.016). CD8⁺T lymphocyte counts in peripheral blood and intestinal mucosa were slightly lower than those in the control group, although the differences were not statistically significant.

CONCLUSIONS

CMV colitis with HIV/AIDS is associated with significant changes in T lymphocyte populations. These findings may have important implications for disease pathogenesis and progression.

Checkpoint inhibitors for the treatment of JC virus-related progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a frequently fatal brain infection caused by the JC polyomavirus (JCV). PML occurs in people with impaired cellular immunity, and the only effective treatment is restoration of immune function. Infection in immunocompromised hosts is often associated with immune exhaustion, which is mediated by inhibitory cell surface receptors known as immune checkpoints, leading to loss of T cell effector function. Blockade of immune checkpoints can reinvigorate host responses to fight infection. Recently, there have been several reports of checkpoint blockade to treat PML in patients in whom immune reconstitution is otherwise not possible, with some evidence for positive response. Larger studies are needed to better understand efficacy of checkpoint blockade in PML and factors that determine response.

Nivolumab in patients with metastatic renal cell carcinoma and chronic hepatitis C virus infection

BACKGROUND

Hepatitis C virus (HCV) interferes with activation of innate and adaptive immune responses. Theoretically, the efficacy and toxicity of immune checkpoint inhibitors in cancer patients infected with HCV may differ. Nevertheless, HCV was an exclusion criterion in most checkpoint inhibitor trials. We evaluated the efficacy and safety of nivolumab in metastatic renal cell carcinoma (mRCC) patients with or without chronic HCV infection.

METHODS

In a matched cohort study, data were collected from 174 patients, retrospectively. All patients had clear-cell mRCC, chronic HCV infection (case study group), no evidence of other malignancy or cirrhosis, and had received nivolumab (3 mg/kg every 2 weeks) until disease progression or unacceptable toxicity. Quantitation of HCV RNA in plasma samples was performed before and during treatment with nivolumab with the automated HCV test (Hoffmann-La Roche, Switzerland). The primary endpoint was overall survival (OS). Secondary endpoints included progression-free survival (PFS), objective response rate (ORR), and rate of grade 3-4 adverse events in study and control cohorts.

RESULTS

A total of 44 matched patients were included. Groups were well balanced. HCV-infected patients had significantly longer OS and PFS. Median OS was 27.5 (95% CI 25.3-29.7) and 21.7 (20.3-23.1) in study and control groups, respectively (P = 0.005). Median PFS was 7.5 (5.7-9.3) and 4.9 (4-5.8) (P = 0.013). Despite no differences in ORR between groups (27% vs. 23%, P = 0.7), patients with HCV had significantly more durable responses (P = 0.01). Nivolumab was well tolerated in all HCV-positive patients. No unexpected toxicity was observed. Assessment of viral load during nivolumab therapy was available in 14 of 22 (64%) patients with HCV. Nivolumab did not significantly impact HCV concentration (mean change 210 IU/ml, P = 0.82) in the absence of antiviral therapy.

CONCLUSIONS

The efficacy and safety profiles observed in this study support the administration of nivolumab in mRCC patients infected with HCV and warrant further investigation.

PD-L1/PD-1 axis as a potent therapeutic target in breast cancer

Although both the incidence and the mortality rate of breast cancer is rising, there is no potent and practical option for the treatment of these patients, particularly in advanced stages. One of the most critical challenges for treatment is the presence of complicated and extensive tumor escape mechanisms in the tumor microenvironment. Immune checkpoint molecules are of the main immunosuppressive mechanisms used by cancerous cells to block anti-cancer immune responses. Among these molecules, PD-1 (Programmed cell death) and PD-L1 (programmed cell death-ligand 1) have been considered as worthy therapeutic targets for breast cancer therapy. In this review, we intend to discuss the immunobiology and signaling of the PD-1/PD-L1 axis and highlight its importance as a worthy therapeutic target in breast cancer. We believe that the prognostic value of PD-L1 depends on the breast cancer subtype. Moreover, the combination of PD-1/PD-L1 targeting with immune-stimulating vaccines can be considered as an effective therapeutic strategy in breast cancer.

Nivolumab treatment in advanced lung cancer patient with chronic active hepatitis C and systemic lupus erythematosus

The proportion of cancer patients candidate to receive immune checkpoint inhibitors (ICI) as part of the therapeutic approach is increasing in all settings, from the early to the advanced stage of disease. The management of ICI in special populations of patients with viral hepatitis or autoimmune disease still lacks strong evidence-based recommendations. Patients having one of these two clinical conditions are generally excluded from clinical trials testing immunotherapic compounds. We present the experience of a patient with heavily pretreated advanced non-small-cell lung cancer affected by both chronic active hepatitis C and systemic lupus erythematosus, treated with nivolumab. We give a report of long-term efficacy and safety data, and we provide an insight on this important topic.

Seluang Fish (Rasbora Spp.) Oil Decreases Inflammatory Cytokines Via Increasing Vitamin D Level in Systemic Lupus Erythematosus

BACKGROUND

Systemic Lupus Erythematosus (SLE) is an autoimmune disorder mediated by inflammatory cytokines. Decreasing vitamin D levels is a common feature in SLE patients. Vitamin D has the capacity in suppressing inflammatory cascade. Seluang fish (Rasbora spp.) contained a high level of vitamin D with the potential as a new therapeutic modality.

AIM

This study aimed to assess the efficacy of Seluang fish oil against proinflammatory cytokines, vitamin D levels, and clinical conditions of SLE.

METHODS

A randomised, double-blind, clinical trial study design was conducted. The subjects were 16 SLE subjects treated with 500uL Seluang fish oil capsules and 16 SLE subjects with placebo capsules. Measurement of vitamin D, IL-1, IL-6 and IL-17 levels were performed with ELISA. Clinical assessment of SLE was performed with MEX-SLEDAI. Bivariate analysis, T-test, was performed. Data were presented in the form of mean ± SD.

RESULTS

The administration of Seluang fish oil was clinically able to show efficacy assessed by the MEX SLEDAI score. Significant results were also shown by increased vitamin D levels and reduced levels of IL-1, IL-6 and IL-17, in Seluang fish oil group.

CONCLUSION

Seluang fish oil possessed the efficacy of reducing the inflammatory response in SLE patients by increasing serum vitamin D levels.

PD-1 blockade inhibits lymphocyte apoptosis and restores proliferation and anti-viral immune functions of lymphocyte after CP and NCP BVDV infection in vitro

Bovine viral diarrhea virus (BVDV) is an important virus that can cause extensive economic losses in both dairy and beef industry worldwide. Acute infection with BVDV results in peripheral blood lymphopenia, apoptosis and immunosuppression. Up-regulated programmed death-1 (PD-1) expression induces functional exhaustion of lymphocytes, inhibition of proliferation and apoptosis of lymphocytes during acute and chronic viral infections, such as HIV and HCV. However, there are no reports showing the role of PD-1 in peripheral blood lymphopenia, apoptosis and immunosuppression after acute BVDV infection. Accordingly, we measured the mRNA and protein expression of PD-1 and programmed death-ligand 1 (PD-L1) in peripheral blood mononuclear cells (PBMCs) infected with BVDV, and analyzed the effects of PD-1 blockade on immune-associated function and activity in peripheral blood lymphocytes (PBLs). The results showed that both cytopathic (CP) BVDV (strain NADL) and non-cytopathic (NCP) BVDV (strain KD) infection stimulated the mRNA and protein expression of PD-1 and PD-L1 significantly. The upregulation of PD-1/PD-L1 was accompanied by the decreased PBLs proliferation and increased apoptosis. Additionally, PD-1 blockade restored proliferation, inhibited apoptosis, increased IFN-γ production and decreased BVDV load. Remarkably, the PD-1/PD-L1 interaction has a more substantial effect on the immunoregulation of inhibiting proliferation induced by CP BVDV infection. Our findings confirm that PD-1 plays a vital role in peripheral blood lymphopenia and apoptosis caused by acute BVDV infection, and provide new insights into exploring the immunopathological mechanisms of BVDV or other members of the Flaviviridae family, and a potential therapeutic strategy to control BVDV infection.

Drug response to PD-1/PD-L1 blockade: based on biomarkers

In recent years, immunotherapies targeting programmed death-1 (PD-1)/programmed death ligand 1 (PD-L1) have provided great hopes for patients with cancer. A successful anti-PD-1/PD-L1 therapy includes not only the elimination of immunosuppressive tumor cells but also the rejuvenation of exhausted T cells. Nevertheless, the efficacy of therapy is still low, so that biomarker-driven therapy has attracted more and more attention to identify patients who are likely to benefit from therapy and to reduce unnecessary disease progression. While many studies have focused on characteristics of tumor biopsies, biomarkers linked to T cell exhaustion and rejuvenation have just become new hot spots in drug response studies. However, no biomarker is perfect in drug response prediction currently, so there is an urgent need for other biomarkers to compensate for the deficiency. In this review, we summarize some approved and candidate biomarkers predictive of drug response before and during PD-1/PD-L1 blockade, including those characterizing responsive or suppressive tumor cells and those evaluating the T cell rejuvenation. Overall, we set up a comprehensive network of biomarkers of tumor characteristics and T cell rejuvenation, predicting drug response before and during anti-PD-1/PD-L1 therapies.

Model of the adaptive immune response system against HCV infection reveals potential immunomodulatory agents for combination therapy

A regulated immune system employs multiple cell types, diverse variety of cytokines and interacting signalling networks against infections. Systems biology offers a promising solution to model and simulate such large populations of interacting components of immune systems holistically. This study focuses on the distinct components of the adaptive immune system and analysis, both individually and in association with HCV infection. The effective and failed adaptive immune response models have been developed followed by interventions/perturbations of various treatment strategies to get better assessment of the treatment responses under varying stimuli. Based on the model predictions, the NK cells, T regulatory cells, IL-10, IL-21, IL-12, IL-2 entities are found to be the most critical determinants of treatment response. The proposed potential immunomodulatory therapeutic interventions include IL-21 treatment, blocking of inhibitory receptors on T-cells and exogenous anti-IL-10 antibody treatment. The relative results showed that these interventions have differential effect on the expression levels of cellular and cytokines entities of the immune response. Notably, IL-21 enhances the expression of NK cells, Cytotoxic T lymphocytes and CD4+ T cells and hence restore the host immune potential. The models presented here provide a starting point for cost-effective analysis and more comprehensive modeling of biological phenomenon.

Immunomodulatory effects of Tim-3 and PD-1 on chronic hepatitis B virus infection

In patients with chronic hepatitis B virus (HBV) infection, the immune cells are dysfunctional, and the immune function cannot work normally. T-cell immunoglobulin mucin-3 (Tim-3) and programmed death receptor-1 (PD-1) are overexpressed on the surface of immune cells, such as cluster of differentiation (CD)4+, CD8+ T-lymphocytes, and natural killer (NK) cells. Many studies indicate that this phenomenon is closely related to the persistence, occurrence, development, and prognosis of HBV. Tim-3 and PD-1 may be used as new immune targets for the treatment of chronic hepatitis B.

Salmonella enterica Serovar Typhimurium Increases Functional PD-L1 Synergistically with Gamma Interferon in Intestinal Epithelial Cells via Salmonella Pathogenicity Island 2

Nontyphoidal serovars of Salmonella enterica are pathogenic bacteria that are common causes of food poisoning. Whereas Salmonella mechanisms of host cell invasion, inflammation, and pathogenesis are mostly well established, a new possible mechanism of immune evasion is being uncovered. Programmed death ligand 1 (PD-L1) is an immunosuppressive membrane protein that binds to activated T cells via their PD-1 receptor and thereby halts their activation. PD-L1 expression plays an essential role in the immunological tolerance of self-antigens but is also exploited for immune evasion by pathogen-infected cells and cancer cells. Here, we show for the first time that Salmonella infection of intestinal epithelial cells causes the induction of PD-L1. The increased expression of PD-L1 through Salmonella infection was seen in both human and rat intestinal epithelial cell lines. We determined that cellular invasion by the bacteria is necessary for PD-L1 induction, potentially indicating that Salmonella strains are delivering mediators from inside the host cell that trigger the increased PD-L1 expression. Using knockout mutants, we determined that this effect largely originates from the Salmonella pathogenicity island 2. We also show for the first time in any cell type that Salmonella combined with gamma interferon (IFN-γ) causes a synergistic induction of PD-L1. Finally, we show that Salmonella plus IFN-γ induction of PD-L1 decreased the cytokine production of activated T cells. Understanding Salmonella immune evasion strategies could generate new therapeutic targets and help to manipulate PD-L1 expression in other diseases.

Intrahepatic Vγ9Vδ2 T-cells from HCV-infected patients show an exhausted phenotype but can inhibit HCV replication

Hepatitis C virus (HCV) persistence results from inefficiencies of both innate and adaptive immune responses to eradicate the infection. A functional impairment of circulating Vγ9Vδ2 T-cells was described but few data are available on Vγ9Vδ2 T-cells in the liver that, however, represents the battlefield in the HCV/host interaction. Aim of this work was to compare circulating and intrahepatic Vγ9Vδ2 T-cells in chronic HCV-infected patients (HCV^pos) and in HCV-negative (HCV^neg) subjects. Phenotypic and functional analysis was performed by flow cytometry. Anti-HCV activity was analyzed by using an in vitro autologous liver culture system. Independently from HCV infection, the liver was enriched of Vγ9Vδ2 T-cells expressing an effector/activated phenotype. In contrast, an enrichment of PD-1 expressing Vγ9Vδ2 T-cells was observed both in the peripheral blood and in the liver of HCV^pos patients, probably due to a persistent antigenic stimulation. Moreover, a lower frequency of IFN-γ producing Vγ9Vδ2 T-cells was observed in the liver of HCV^pos patients, suggesting a functional impairment in the cytokine production in HCV^pos liver. Despite this hypo-responsiveness, intrahepatic Vγ9Vδ2 T-cells are able to exert an anti-HCV activity after specific stimulation. Altogether, our data show that HCV infection induced a dysregulation of intrahepatic Vγ9Vδ2 T cells that maintain their anti-HCV activity after specific stimulation. A study aimed to evaluate the mechanisms of the antiviral activity may be useful to identify new pathways able to improve Vγ9Vδ2 T-cells intrahepatic function during HCV infection.

Chronic Exposure to Malaria Is Associated with Inhibitory and Activation Markers on Atypical Memory B Cells and Marginal Zone-Like B Cells

In persistent infections that are accompanied by chronic immune activation, such as human immunodeficiency virus, hepatitis C virus, and malaria, there is an increased frequency of a phenotypically distinct subset of memory B cells lacking the classic memory marker CD27 and showing a reduced capacity to produce antibodies. However, critical knowledge gaps remain on specific B cell changes and immune adaptation in chronic infections. We hypothesized that expansion of atypical memory B cells (aMBCs) and reduction of activated peripheral marginal zone (MZ)-like B cells in constantly exposed individuals might be accompanied by phenotypic changes that would confer a tolerogenic profile, helping to establish tolerance to infections. To better understand malaria-associated phenotypic abnormalities on B cells, we analyzed peripheral blood mononuclear cells from 55 pregnant women living in a malaria-endemic area of Papua Nueva Guinea and 9 Spanish malaria-naïve individuals using four 11-color flow cytometry panels. We assessed the expression of markers of B cell specificity (IgG and IgM), activation (CD40, CD80, CD86, b220, TACI, and CD150), inhibition (PD1, CD95, and CD71), and migration (CCR3, CXCR3, and CD62l). We found higher frequencies of active and resting aMBC and marked reduction of MZ-like B cells, although changes in absolute cell counts could not be assessed. Highly exposed women had higher PD1⁺-, CD95⁺-, CD40⁺-, CD71⁺-, and CD80⁺-activated aMBC frequencies than non-exposed subjects. Malaria exposure increased frequencies of b220 and proapoptotic markers PD1 and CD95, and decreased expression of the activation marker TACI on MZ-like B cells. The increased frequencies of inhibitory and apoptotic markers on activated aMBCs and MZ-like B cells in malaria-exposed adults suggest an immune-homeostatic mechanism for maintaining B cell development and function while simultaneously downregulating hyperreactive B cells. This mechanism would keep the B cell activation threshold high enough to control infection but impaired enough to tolerate it, preventing systemic inflammation.

IFN-α-based treatment of patients with chronic HCV show increased levels of cells with myeloid-derived suppressor cell phenotype and of IDO and NOS

INTRODUCTION

Hepatitis C virus (HCV) infection causes chronic hepatitis, which is often associated with suppressed anti-HCV immune responses. We have recently reported accumulation of myeloid-derived suppressor cells (MDSCs) and suppressed immunity in cancer patients.

AIM

The main aim of this study was to determine whether chronic HCV patients harbor high of MDSCs in general and in nonresponders to IFN-based therapy in particular as well as to analyze the immune suppressive molecules.

METHODS

Peripheral blood samples withdrawn from 154 patients with chronic HCV infection and were categorized into responders and nonresponders based on viral titer upon IFN-α treatment.

RESULTS

The relative and absolute numbers of MDSCs defined as Lin^-/HLA-DR^-/CD33⁺/CD11b⁺ increased in all HCV patients, where they were higher in nonresponders than in responders. Additionally, the levels of MDSCs after 4-6 months of treatment in responders were lower than during the course of treatment. The responders also showed higher levels of IL-2 coincided with increased numbers of dendritic cells (DCs), CD4⁺ and CD8⁺ T cells. The levels of total NOS and IDO were also higher in nonresponders as compared to responders and healthy controls, while the expression levels of CD3ζ was lower in responders as compared to nonresponders and healthy volunteers.

CONCLUSION

Chronic HCV patients harbor high numbers of MDSCs, which are higher in nonresponders than in responders. The higher numbers of MDSCs associated with increases in the suppressing factors.

Immune checkpoints and their inhibition in cancer and infectious diseases

The development of chronic infections and cancer is facilitated by a variety of immune subversion mechanisms, such as the production of anti-inflammatory cytokines, induction of regulatory T (Treg) cells, and expression of immune checkpoint molecules, including CTLA-4 and PD-1. CTLA-4, expressed on T cells, interacts with CD80/CD86, thereby limiting T-cell activation and leading to anergy. PD-1 is predominantly expressed on T cells and its interaction with PD-L1 and PD-L2 expressed on antigen-presenting cells (APCs) and tumors sends a negative signal to T cells, which can lead to T-cell exhaustion. Given their role in suppressing effector T-cell responses, immune checkpoints are being targeted for the treatment of cancer. Indeed, antibodies binding to CTLA-4, PD-1, or PD-L1 have shown remarkable efficacy, especially in combination therapies, for a number of cancers and have been licensed for the treatment of melanoma, nonsmall cell lung cancer, and renal and bladder cancers. Moreover, immune checkpoint inhibitors have been shown to enhance ex vivo effector T-cell responses from patients with chronic viral, bacterial, or parasitic infection, including HIV, tuberculosis, and malaria. Although the data from clinical trials in infectious diseases are still sparse, these inhibitors have great potential for treating chronic infections, especially when combined with therapeutic vaccines.

Increase of Soluble Programmed Cell Death Ligand 1 in Patients with Chronic Hepatitis C

Objectives: To determine whether the soluble programmed cell death ligand 1 (sPD-L1) levels in patients with chronic hepatitis C (CHC) are associated with the clinical features of the disease and the efficacy of treatment, including interferon (IFN)-α. Methods: We investigated the sPD-L1 levels in the sera of 80 genotype 1b Japanese patients with CHC who underwent 12 weeks of telaprevir (TVR)- or simeprevir (SMV)-based triple therapy followed by 12 weeks of dual therapy with pegylated IFN-α plus ribavirin. Serum was also obtained from 22 patients with chronic hepatitis B (CHB) and from 10 healthy donors (HC). The sPD-L1 levels were measured using an ELISA kit. In addition, we examined the PD-L1 expression on the cell surface of immortalized hepatocytes (HPT1) after incubation with cytokines, including IFN-γ. Results: The pretreatment serum sPD-L1 levels were significantly increased in patients with CHC (median 109.3 pg/ml, range 23.1-402.3) compared with patients with CHB (69.2 pg/ml, 15.5-144.8; P <0.001) and HC (100.3 pg/ml, 40.1-166.6; P = 0.039). No significant differences in the sustained virological response (SVR) rates were found between the TVR- (85.0%, n=40) and SMV-treated (80.0%, n=40) groups, and the pretreatment levels of serum sPD-L1 were not significantly different between patients who achieved SVR (105.0 pg/ml, 23.1-402.3) and non-SVR patients (133.5 pg/ml, 39.9-187.2; P = 0.391). The pretreatment level of sPD-L1 was positively correlated with the alanine aminotransferase and alpha-fetoprotein levels (R² = 0.082, P = 0.016, and R² = 0.149, P = 0.002, respectively). Although immortalized hepatocytes do not express PD-L1, we confirmed that PD-L1 expression was induced after stimulation with IFN-γ. Conclusions: In this study, we first found that sPD-L1 was increased in patients with CHC. Our results indicate that the level of serum sPD-L1 might be associated with the progression of CHC and the generation of hepatocellular carcinoma.

PD-L1 is a critical mediator of regulatory B cells and T cells in invasive breast cancer

Regulatory T cells (Tregs), a key mediator in regulating anti-tumor immune suppression, tumor immune escape, metastasis and relapse, are considered an important therapeutic target in immunotherapy of human cancers. In the present investigation, elevated CD19⁺ CD24⁺ CD38⁺ regulatory B cells (Bregs) were observed in PBMCs of invasive carcinoma of breast (IBCa) patients compared with that in patients with fibroadenoma (FIBma) or healthy individuals, and the positive correlation existed between Bregs and CD4⁺ CD25⁺ CD127⁻ Tregs (r = 0.316, P = 0.001). We found that PD-L1 expression was higher on Bregs in IBCa patients compared with patients with FIBma or healthy individuals (P < 0.05, respectively), and that a tight correlation exists between CD19⁺ CD24⁺ CD38⁺ PD-L1⁺ Bregs and CD19⁺ CD24⁺ CD38⁺ Bregs (r = 0.267, P = 0.007), poor TNM phases and up-regulated expression of PD-L1 on Bregs. The pattern of PD-1 expression on CD4⁺ T cells indicated that high level of PD-1^hi expressed on CD4⁺ CD25⁺ CD127⁺ effector T cells (P < 0.001). More importantly, the presence of PD-L1 on Bregs was positively correlated with Tregs (r = 0.299, P = 0.003), but negatively correlated with PD-1^hi effector T cells (r = −0.22, P = 0.031). Together, results of the present study indicated that PD-L1 is an important molecule on Bregs, mediated the generation of Tregs in IBCa.

PD-1 Antibody Monotherapy for Malignant Melanoma: A Systematic Review and Meta-Analysis

Antibodies targeting programmed death 1 (PD-1) help prevent tumor cells from escaping immune-mediated destruction. We conducted this systematic review and meta-analysis to gain insight into the efficacy of PD-1 antibodies for the treatment of melanoma. Five trials involving 2,828 adult patients were included in this meta-analysis. In patients with previously untreated or refractory melanoma, treatment with PD-1 antibodies significantly improved the six-month progression-free survival (PFS) (HR 0.55, 95% CI 0.50-0.60, P<0.00001) and the overall response rate (OR 3.89, 95% CI 3.12-4.83, P<0.00001). This meta-analysis indicated that anti-PD-1 treatment might provide a significant survival benefit in patients with melanoma. In addition, we found that patients treated with nivolumab reported significantly fewer treatment-related adverse events (OR 0.74, 95% CI 0.57-0.97, P = 0.03) than those treated with other agents, but there was a dose-dependent increase in the frequency of adverse events in patients treated with pembrolizumab.