Galectin-9 and IL-21 mediate cross-regulation between Th17 and Treg cells during acute hepatitis C

The Multifaceted Roles of Galectins in Host-Virus Interactions: A Comprehensive Overview

Galectins are a family of β-galactosides-binding protein, crucial regulators of host-virus interactions. They achieve this by recognizing specific glycan patterns on viral surfaces or mediating interactions with intracellular viral or host proteins, subsequently influencing the critical phases of the viral life cycle, such as attachment, replication, immune evasion, and reactivation. Furthermore, galectins modulate host immune responses, shaping the progression and outcomes of viral infections. This review comprehensively examines the roles of both endogenous and exogenous galectins in viral infections, noting that only a few galectins, including Galectin-1, -3, -4, -7, -8, and -9, Have been identified as key players in viral infection. Notably, Galectin-1, -3, and -9 play diverse functions in both DNA and RNA viral infection. Emerging evidence highlights the potential of Galectin-4 and -8 as intracellular sensors and modulators of viral pathogenesis. Endogenous galectins, produced by host cells, act through both glycan-dependent and glycan-independent mechanisms, influencing viral processes and immune responses. Exogenous galectins, which are secreted by other cells or administered as recombinant proteins, can either enhance or counteract the actions of endogenous galectins. The functions of galectins are virus-specific and context-dependent, serving as either promoters or inhibitors of viral replication and reactivation. Dysregulation of galectin expression is often linked to disease progression, highlighting their potential as diagnostic and prognostic biomarkers, as well as therapeutic targets. The important and varied roles that galectins play in viral infections are highlighted in this review, which also provides fresh insights into host-pathogen interactions and the development of antiviral tactics.

HIGHLIGHTS

Galectins and Host-Pathogen Interactions: The roles in viral infections

Galectins, a family of carbohydrate-binding proteins, play crucial roles in the host-virus interaction landscape. This review explores the multifaceted contributions of endogenous galectins to various stages of the viral lifecycle, including attachment, replication, assembly, and release of progeny virions. Recent studies have indicated that viral infections can induce the expression and secretion of specific galectins, with elucidated signaling pathways in some cases, enhancing our understanding of their regulatory mechanisms. While many studies have focused on the effects of exogenous recombinant galectins, there is growing interest in the intrinsic functions of endogenous galectins, particularly through genetic alterations in cellular models. This review highlights the need for further research to uncover the complex roles of galectins in modulating viral infections and emphasizes their potential as therapeutic targets in the fight against viral diseases. Understanding these interactions could pave the way for novel strategies to enhance host defense mechanisms and mitigate viral pathogenesis.

Like a Rolling Stone? A Review on Spontaneous Clearance of Hepatitis C Virus Infection

Elimination of hepatitis C virus (HCV) without the need for medical intervention, known as spontaneous clearance (SC), occurs at a significantly lower rate than in the case of hepatitis B virus infection and only in selected individuals, such as reportedly in Keith Richards, a guitarist of The Rolling Stones. The present paper provides an updated narrative review of the research devoted to the phenomenon in order to identify and discuss the demographic, lifestyle-related, clinical, viral genotype-related, and host genetic factors underpinning the SC occurrence. The body of evidence indicates that the likelihood of SC is decreased in older individuals, men, Black people, HIV-coinfected subjects, and intravenous drug and alcohol users. In turn, HBV coinfection and specific polymorphism of the genes encoding interferon lambda 3 (particularly at rs8099917) and interferon lambda 4 (particularly at rs12979860) and HLA genes increase the odds of SC. Numerous other host-specific genetic factors could be implicated in SC, but the evidence is limited only to certain ethnic groups and often does not account for confounding variables. SC of HCV infection is a complex process arising from a combination of various factors, though a genetic component may play a leading role in some cases. Understanding factors influencing the likelihood of this phenomenon justifies better surveillance of high-risk groups, decreasing health inequities in particular ethnic groups, and may guide the development of a prophylactic vaccine, which at present is not available, or novel therapeutic strategies. Further research is needed to elucidate the exact mechanisms underlying SC and to explore potential interventions that could enhance this natural antiviral response.

Update on Hepatitis C Vaccine: Results and Challenges

Therapy against the Hepatitis C virus (HCV) has significantly improved with the introduction of direct-acting antiviral drugs (DAAs), achieving over 95% sustained virological response (SVR). Despite this, the development of an effective anti-HCV vaccine remains a critical challenge due to the low number of patients treated with DAAs and the occurrence of HCV reinfections in high-risk groups. Current vaccine strategies aim to stimulate either B-cell or T-cell responses. Vaccines based on E1 and E2 proteins can elicit broad cross-neutralizing antibodies against all major HCV genotypes, though with varying efficiencies and without full protection against infection. In humans, the neutralizing antibodies induced by such vaccines mainly target the AR3 region, but their levels are generally insufficient for broad neutralization. Various HCV proteins expressed through different viral vectors have been utilized to elicit T cell immune responses, showing sustained expansion of HCV-specific effector memory T cells and improved proliferation and polyfunctionality of memory T cells over time. However, despite these advancements, the frequency and effectiveness of T-cell responses remain limited.

Studying T Cell Responses to Hepatotropic Viruses in the Liver Microenvironment

T cells play an important role in the clearance of hepatotropic viruses but may also cause liver injury and contribute to disease progression in chronic hepatitis B and C virus infections which affect millions of people worldwide. The liver provides a unique microenvironment of immunological tolerance and hepatic immune regulation can modulate the functional properties of T cell subsets and influence the outcome of a virus infection. Extensive research over the last years has advanced our understanding of hepatic conventional CD4+ and CD8+ T cells and unconventional T cell subsets and their functions in the liver environment during acute and chronic viral infections. The recent development of new small animal models and technological advances should further increase our knowledge of hepatic immunological mechanisms. Here we provide an overview of the existing models to study hepatic T cells and review the current knowledge about the distinct roles of heterogeneous T cell populations during acute and chronic viral hepatitis.

Galectins as pivotal components in oncogenesis and immune exclusion in human malignancies

Galectins are galactoside-binding proteins, exerting numerous functions inside and outside the cell, particularly conferring adaptation to stress factors. For most of them, aberrant expression profiles have been reported in the context of cancer. Albeit not being oncogenic drivers, galectins can be harnessed to exacerbate the malignant phenotype. Their impact on disease establishment and progression is not limited to making cancer cells resistant to apoptosis, but is prominent in the context of the tumor microenvironment, where it fosters angiogenesis, immune escape and exclusion. This review focuses mainly on Gal-1, Gal-3 and Gal-9 for which the involvement in cancer biology is best known. It presents the types of galectin dysregulations, attempts to explain the mechanisms behind them and analyzes the different ways in which they favor tumour growth. In an era where tumour resistance to immunotherapy appears as a major challenge, we highlight the crucial immunosuppressive roles of galectins and the potential therapeutic benefits of combinatorial approaches including galectin inhibition.

Secreted filarial nematode galectins modulate host immune cells

Lymphatic filariasis (LF) is a mosquito-borne disease caused by filarial nematodes including Brugia malayi. Over 860 million people worldwide are infected or at risk of infection in 72 endemic countries. The absence of a protective vaccine means that current control strategies rely on mass drug administration programs that utilize inadequate drugs that cannot effectively kill adult parasites, thus established infections are incurable. Progress to address deficiencies in the approach to LF control is hindered by a poor mechanistic understanding of host-parasite interactions, including mechanisms of host immunomodulation by the parasite, a critical adaptation for establishing and maintaining infections. The canonical type 2 host response to helminth infection characterized by anti-inflammatory and regulatory immune phenotypes is modified by filarial nematodes during chronic LF. Current efforts at identifying parasite-derived factors driving this modification focus on parasite excretory-secretory products (ESP), including extracellular vesicles (EVs). We have previously profiled the cargo of B. malayi EVs and identified B. malayi galectin-1 and galectin-2 as among the most abundant EV proteins. In this study we further investigated the function of these proteins. Sequence analysis of the parasite galectins revealed highest homology to mammalian galectin-9 and functional characterization identified similar substrate affinities consistent with this designation. Immunological assays showed that Bma-LEC-2 is a bioactive protein that can polarize macrophages to an alternatively activated phenotype and selectively induce apoptosis in Th1 cells. Our data shows that an abundantly secreted parasite galectin is immunomodulatory and induces phenotypes consistent with the modified type 2 response characteristic of chronic LF infection.

Cancer-inducing niche: the force of chronic inflammation

The growth of cancer tissue is thought to be considered driven by a small subpopulation of cells, so-called cancer stem cells (CSCs). CSCs are located at the apex of a hierarchy in a cancer tissue with self-renewal, differentiation and tumorigenic potential that produce the progeny in the tissue. Although CSCs are generally believed to play a critical role in the growth, metastasis, and recurrence of cancers, the origin of CSCs remains to be reconsidered. We hypothesise that, chronic diseases, including obesity and diabetes, establish the cancer-inducing niche (CIN) that drives the undifferentiated/progenitor cells into CSCs, which then develop malignant tumours in vivo. In this context, a CIN could be traced to chronic inflammation that involves long-lasting tissue damage and repair after being exposed to factors such as cytokines and growth factors. This must be distinguished from the cancer microenvironment, which is responsible for cancer maintenance. The concept of a CIN is most important for cancer prevention as well as cancer therapy.

Expression Level and Significance of Tim-3 in CD4+ T Lymphocytes in Peripheral Blood of Patients with Coronary Heart Disease

OBJECTIVE

To investigate the expression level and significance of T cell immunoglobulin and mucin-domain containing molecules-3 (Tim-3) and interleukin-7 (IL-7) in CD4+ T lymphocytes in peripheral blood of patients with coronary heart disease (CHD).

METHODS

75 patients with CHD treated at our hospital were selected and classified as mild group (25 cases), moderate group (25 cases) and severe group (25 cases), according to the severity of illness. Twenty-five healthy volunteers who underwent a physical examination at our hospital during the same period were selected as the control group. The expression level of Tim-3 in CD4+ T lymphocytes in peripheral blood of patients in four groups was detected by flow cytometry and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The expression level of IL-7 in peripheral blood serum was measured by enzymelinked immunosorbent assay (ELISA). Correlation analyses of Tim-3 and IL-7, Tim-3 and disease severity and IL-7 and disease severity were performed, respectively.

RESULTS

Flow cytometry and qRT-PCR demonstrated that the expression of Tim-3 in CD4+ T lymphocytes in peripheral blood of patients with CHD increased with the aggravation of the disease. ELISA showed that the tendency of IL-7 expression in peripheral blood serum was consistent with the expression of Tim-3, and the expression of Tim-3 had a positive correlation with IL-7. The expression levels of both Tim-3 and IL-7 were positively correlated with the Gensini score.

CONCLUSION

The expression of Tim-3 and IL-7 in peripheral blood of patients with CHD was upregulated and increased with the aggravation of CHD.

Innate and Adaptive Immunopathogeneses in Viral Hepatitis; Crucial Determinants of Hepatocellular Carcinoma

Viral hepatitis B (HBV) and hepatitis C (HCV) infections remain the most common risk factors for the development of hepatocellular carcinoma (HCC), and their heterogeneous distribution influences the global prevalence of this common type of liver cancer. Typical hepatitis infection elicits various immune responses within the liver microenvironment, and viral persistence induces chronic liver inflammation and carcinogenesis. HBV is directly mutagenic but can also cause low-grade liver inflammation characterized by episodes of intermittent high-grade liver inflammation, liver fibrosis, and cirrhosis, which can progress to decompensated liver disease and HCC. Equally, the absence of key innate and adaptive immune responses in chronic HCV infection dampens viral eradication and induces an exhausted and immunosuppressive liver niche that favors HCC development and progression. The objectives of this review are to (i) discuss the epidemiological pattern of HBV and HCV infections, (ii) understand the host immune response to acute and chronic viral hepatitis, and (iii) explore the link between this diseased immune environment and the development and progression of HCC in preclinical models and HCC patients.

In the era of rapid mRNA-based vaccines: Why is there no effective hepatitis C virus vaccine yet?

Hepatitis C virus (HCV) is responsible for no less than 71 million people chronically infected and is one of the most frequent indications for liver transplantation worldwide. Despite direct-acting antiviral therapies fuel optimism in controlling HCV infections, there are several obstacles regarding treatment accessibility and reinfection continues to remain a possibility. Indeed, the majority of new HCV infections in developed countries occur in people who inject drugs and are more plausible to get reinfected. To achieve global epidemic control of this virus the development of an effective prophylactic or therapeutic vaccine becomes a must. The coronavirus disease 19 (COVID-19) pandemic led to auspicious vaccine development against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus, which has renewed interest on fighting HCV epidemic with vaccination. The aim of this review is to highlight the current situation of HCV vaccine candidates designed to prevent and/or to reduce HCV infectious cases and their complications. We will emphasize on some of the crossroads encountered during vaccine development against this insidious virus, together with some key aspects of HCV immunology which have, so far, hampered the progress in this area. The main focus will be on nucleic acid-based as well as recombinant viral vector-based vaccine candidates as the most novel vaccine approaches, some of which have been recently and successfully employed for SARS-CoV-2 vaccines. Finally, some ideas will be presented on which methods to explore for the design of live-attenuated vaccines against HCV.

T cell responses during HBV and HCV infections: similar but not quite the same?

The hepatitis B and C viruses persist by evasion of T cell immunity. Persistence depends upon premature failure of CD4+ T cell help and loss of CD8+ T cell control because of epitope mutational escape and/or functional exhaustion. Powerful new immunological and transcriptomic tools provide insight into the mechanisms of T cell silencing by HBV and HCV. Similarities are apparent, including dysregulated expression of common inhibitory/immune checkpoint receptors and transcription factors. There are also differences. T cell exhaustion is uniform in HCV infection, but varies in HBV infection depending on disease stage and/or protein target. Here, we review recent advances defining similarities and differences in T cell evasion by HBV and HCV, and the potential for reversal following antiviral therapy.

Towards a Systems Immunology Approach to Understanding Correlates of Protective Immunity against HCV

Over the past decade, tremendous progress has been made in systems biology-based approaches to studying immunity to viral infections and responses to vaccines. These approaches that integrate multiple facets of the immune response, including transcriptomics, serology and immune functions, are now being applied to understand correlates of protective immunity against hepatitis C virus (HCV) infection and to inform vaccine development. This review focuses on recent progress in understanding immunity to HCV using systems biology, specifically transcriptomic and epigenetic studies. It also examines proposed strategies moving forward towards an integrated systems immunology approach for predicting and evaluating the efficacy of the next generation of HCV vaccines.

A Tale of Two Viruses: Immunological Insights Into HCV/HIV Coinfection

Nearly 2.3 million individuals worldwide are coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Odds of HCV infection are six times higher in people living with HIV (PLWH) compared to their HIV-negative counterparts, with the highest prevalence among people who inject drugs (PWID) and men who have sex with men (MSM). HIV coinfection has a detrimental impact on the natural history of HCV, including higher rates of HCV persistence following acute infection, higher viral loads, and accelerated progression of liver fibrosis and development of end-stage liver disease compared to HCV monoinfection. Similarly, it has been reported that HCV coinfection impacts HIV disease progression in PLWH receiving anti-retroviral therapies (ART) where HCV coinfection negatively affects the homeostasis of CD4⁺ T cell counts and facilitates HIV replication and viral reservoir persistence. While ART does not cure HIV, direct acting antivirals (DAA) can now achieve HCV cure in nearly 95% of coinfected individuals. However, little is known about how HCV cure and the subsequent resolution of liver inflammation influence systemic immune activation, immune reconstitution and the latent HIV reservoir. In this review, we will summarize the current knowledge regarding the pathogenesis of HIV/HCV coinfection, the effects of HCV coinfection on HIV disease progression in the context of ART, the impact of HIV on HCV-associated liver morbidity, and the consequences of DAA-mediated HCV cure on immune reconstitution and HIV reservoir persistence in coinfected patients.

Chronic Hepatitis C Pathogenesis: Immune Response in the Liver Microenvironment and Peripheral Compartment

Chronic hepatitis C (CHC) pathogenic mechanisms as well as the participation of the immune response in the generation of liver damage are still a topic of interest. Here, we evaluated immune cell populations and cytokines in the liver and peripheral blood (PB) to elucidate their role in CHC pathogenesis. B, CTL, Th, Treg, Th1, Th17, and NK cell localization and frequency were evaluated on liver biopsies by immunohistochemistry, while frequency, differentiation, and functional status on PB were evaluated by flow cytometry. TNF-α, IL-23, IFN-γ, IL-1β, IL-6, IL-8, IL-17A, IL-21, IL-10, and TGF-β expression levels were quantified in fresh liver biopsy by RT-qPCR and in plasma by CBA/ELISA. Liver CTL and Th1 at the lobular area inversely correlated with viral load (r = −0.469, p =0.003 and r = −0.384, p = 0.040). Treg correlated with CTL and Th1 at the lobular area (r = 0.784, p < 0.0001; r = 0.436, p = 0.013). Th17 correlated with hepatic IL-8 (r = 0.52, p < 0.05), and both were higher in advanced fibrosis cases (Th17 p = 0.0312, IL-8 p = 0.009). Hepatic cytokines were higher in severe hepatitis cases (IL-1β p = 0.026, IL-23 p = 0.031, IL-8 p = 0.002, TGF-β, p= 0.037). Peripheral NK (p = 0.008) and NK dim (p = 0.018) were diminished, while NK bright (p = 0.025) was elevated in patients vs. donors. Naïve Th (p = 0.011) and CTL (p = 0.0007) were decreased, while activated Th (p = 0.0007) and CTL (p = 0.0003) were increased. IFN-γ production and degranulation activity in NK and CTL were normal. Peripheral cytokines showed an altered profile vs. donors, particularly elevated IL-6 (p = 0.008) and TGF-β (p = 0.041). Total hepatic CTLs favored damage. Treg could not prevent fibrogenesis triggered by Th17 and IL-8. Peripheral T-lymphocyte differentiation stage shift, elevated cytokine levels and NK-cell count decrease would contribute to global disease.

Follicular helper-T cells restore CD8+-dependent antitumor immunity and anti-PD-L1/PD-1 efficacy

Background

T follicular helper cells (Tfh) are essential to shape B cell response during germinal center formation. Tfh accumulation has been reported in various human cancers, with positive or negative prognostic roles. However, the mechanisms explaining the accumulation of Tfh and their role in cancer remain obscure.

Methods

In vitro differentiated and mouse cell sorted Tfh phenotype was evaluated by flow cytometry and quantitative PCR (qPCR). Antitumor effect of Tfh was evaluated by adoptive transfer in different tumor-bearing mice models. The involvement of immune cells, cytokines and chemokines was evaluated, using depleting antibodies. Chemokines and cytokines expression and production were evaluated by qPCR and ELISA. In human, the impact of immune cells and chemokines on survival was evaluated by analyzing transcriptomic data from public databases and from our own patient cohorts.

Results

In this study, we show that Tfh exert an antitumor immune effect in a CD8⁺-dependent manner. Tfh produce interleukin-21, which sustains proliferation, viability, cytokine production and cytotoxic functions of exhausted T cells. The presence of Tfh is required for efficacy of antiprogrammed cell death ligand-1 therapy. Tfh accumulate in the tumor bed and draining lymph nodes in different mouse cancer models. This recruitment is due to the capacity of transforming growth factor β to drive Chemokine (C-X-C motif) Ligand 13 expression, a chemoattractant of Tfh, by intratumor CD8⁺ T cells. Accumulation of Tfh and exhausted CD8⁺ T cells predicts cancer outcome in various cancer types. In patients treated with anti-programmed cell death-1 mAb, accumulation of Tfh and CD8⁺ at the tumor site is associated with outcome.

Conclusion

This study provides evidence that CD8⁺/Tfh crosstalk is important in shaping antitumor immune response generated by immunotherapy.

Chronic Hepatitis C Virus Infection Modulates the Transcriptional Profiles of CD4+ T Cells

Background

Chronic hepatitis C (CHC) is associated with altered cell-mediated immune response.

Objective

The aim of the study was to characterize functional alterations in CD4⁺ T cell subsets and myeloid-derived suppressor cells (MDSCs) during chronic hepatitis C virus (HCV) infection. Methodology. The expression levels of the lineage-defining transcriptional factors (TFs) T-bet, Gata3, Rorγt, and Foxp3 in circulating CD4⁺ T cells and percentages of MDSCs in peripheral blood were evaluated in 33 patients with CHC, 31 persons, who had spontaneously cleared the HCV infection, and 30 healthy subjects. Analysis. The CD4+ T cells TFs T-bet (T-box expressed in T cells), Foxp3 (Forkhead box P3 transcription factor), Gata3 (Gata-binding protein 3), and Rorγt (retinoic-acid-related orphan receptor gamma) and activation of CD8+ T cells, as well as percentages of MDSCs, were measured by multicolor flow cytometry after intracellular and surface staining of peripheral blood mononuclear cells with fluorescent monoclonal antibodies.

Result

The patients with CHC had significantly lower percentages of CD4⁺ T cells expressing Rorγt and Gata3 and higher percentages of Foxp3-expressing CD4⁺ T cells than healthy controls and persons who spontaneously cleared HCV infection. The ratios of T-bet⁺/Gata3⁺ and Foxp3⁺/Rorγt⁺ CD4⁺ T cells were the highest in the patients with CHC. In the patients with CHC, the percentages of Gata3⁺ and Rorγt⁺ CD4⁺ T cells and the percentages of T-bet⁺ CD4⁺ T cells and CD38⁺/HLA-DR⁺ CD8⁺ T cells demonstrated significant positive correlations. In addition, the percentage of CD38⁺/HLA-DR⁺ CD8⁺ T cells correlated negatively with the percentage of MDSCs.

Conclusion

Chronic HCV infection is associated with downregulation of TFs Gata3 and Rorγt polarizing CD4+ T cells into Th2 and Th17 phenotypes together with upregulation of Foxp3 responsible for induction of regulatory T cells suppressing immune response.

SARS-CoV-2-specific CD8+ T cell responses in convalescent COVID-19 individuals

Characterization of the T cell response in individuals who recover from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is critical to understanding its contribution to protective immunity. A multiplexed peptide-MHC tetramer approach was used to screen 408 SARS-CoV-2 candidate epitopes for CD8+ T cell recognition in a cross-sectional sample of 30 coronavirus disease 2019 convalescent individuals. T cells were evaluated using a 28-marker phenotypic panel, and findings were modelled against time from diagnosis and from humoral and inflammatory responses. There were 132 SARS-CoV-2-specific CD8+ T cell responses detected across 6 different HLAs, corresponding to 52 unique epitope reactivities. CD8+ T cell responses were detected in almost all convalescent individuals and were directed against several structural and nonstructural target epitopes from the entire SARS-CoV-2 proteome. A unique phenotype for SARS-CoV-2-specific T cells was observed that was distinct from other common virus-specific T cells detected in the same cross-sectional sample and characterized by early differentiation kinetics. Modelling demonstrated a coordinated and dynamic immune response characterized by a decrease in inflammation, increase in neutralizing antibody titer, and differentiation of a specific CD8+ T cell response. Overall, T cells exhibited distinct differentiation into stem cell and transitional memory states (subsets), which may be key to developing durable protection.

Gamma-Chain Receptor Cytokines & PD-1 Manipulation to Restore HCV-Specific CD8+ T Cell Response during Chronic Hepatitis C

Hepatitis C virus (HCV)-specific CD8⁺ T cell response is essential in natural HCV infection control, but it becomes exhausted during persistent infection. Nowadays, chronic HCV infection can be resolved by direct acting anti-viral treatment, but there are still some non-responders that could benefit from CD8⁺ T cell response restoration. To become fully reactive, T cell needs the complete release of T cell receptor (TCR) signalling but, during exhaustion this is blocked by the PD-1 effect on CD28 triggering. The T cell pool sensitive to PD-1 modulation is the progenitor subset but not the terminally differentiated effector population. Nevertheless, the blockade of PD-1/PD-L1 checkpoint cannot be always enough to restore this pool. This is due to the HCV ability to impair other co-stimulatory mechanisms and metabolic pathways and to induce a pro-apoptotic state besides the TCR signalling impairment. In this sense, gamma-chain receptor cytokines involved in memory generation and maintenance, such as low-level IL-2, IL-7, IL-15, and IL-21, might carry out a positive effect on metabolic reprogramming, apoptosis blockade and restoration of co-stimulatory signalling. This review sheds light on the role of combinatory immunotherapeutic strategies to restore a reactive anti-HCV T cell response based on the mixture of PD-1 blocking plus IL-2/IL-7/IL-15/IL-21 treatment.

The role of Th17 cells in viral infections

The present review provides an overview of recent advances regarding the function of Th17 cells and their produced cytokines in the progression of viral diseases. Viral infections alone do not lead to virus-induced malignancies, as both genetic and host safety factors are also involved in the occurrence of malignancies. Acquired immune responses, through the differentiation of Th17 cells, form the novel components of the Th17 cell pathway when reacting with viral infections all the way from the beginning to its final stages. As a result, instead of inducing the right immune responses, these events lead to the suppression of the immune system. In fact, the responses from Th17 cells during persistent viral infections causes chronic inflammation through the production of IL-17 and other cytokines which provide a favorable environment for tumor growth and its development. Additionally, during the past decade, these cells have been understood to be involved in tumor progression and metastasis. However, further research is required to understand Th17 cells' immune mechanisms in the vast variety of viral diseases. This review aims to determine the roles and effects of the immune system, especially Th17 cells, in the progression of viral diseases; which can be highly beneficial for the diagnosis and treatment of these infections.

T cell immunity to hepatitis C virus: Lessons for a prophylactic vaccine

There is consensus that HCV-specific T cells play a central role in the outcome (clearance vs. persistence) of acute infection and that they contribute to protection against the establishment of persistence after reinfection. However, these T cells often fail and the virus can persist, largely as a result of T cell exhaustion and the emergence of viral escape mutations. Importantly, HCV cure by direct-acting antivirals does not lead to a complete reversion of T cell exhaustion and thus HCV reinfections can occur. The current lack of detailed knowledge about the immunological determinants of viral clearance, persistence and protective immunity is a major roadblock to the development of a prophylactic T cell vaccine. This minireview highlights the basic concepts of successful T cell immunity, major mechanisms of T cell failure and how our understanding of these concepts can be translated into a prophylactic vaccine.

T-Cell Immunity against the Hepatitis C Virus: A Persistent Research Priority in an Era of Highly Effective Therapy

Approximately 70% of acute hepatitis C virus (HCV) infections become chronic, indicating that the virus is exceptionally well adapted to persist in humans with otherwise normal immune function. Robust, lifelong replication of this small RNA virus does not require a generalized failure of immunity. HCV effectively subverts innate and adaptive host defenses while leaving immunity against other viruses intact. Here, the role of CD4⁺ and CD8⁺ T-cell responses in control of HCV infection and their failure to prevent virus persistence in most individuals are reviewed. Two issues of practical importance remain priorities in an era of highly effective antiviral therapy for chronic hepatitis C. First, the characteristics of successful T-cell responses that promote resolution of HCV infection are considered, as they will underpin development of vaccines that prevent HCV persistence. Second, defects in T-cell immunity that facilitate HCV persistence and whether they are reversed after antiviral cure to provide protection from reinfection are also addressed.

Evaluation of Serum and Gene Expression of Galectin-4, Interleukin-27, and Complement-7 in Hepatitis C Virus-Infected Egyptian Patients

Background

Hepatitis C virus (HCV) is considered a major global public health problem. Recently, there are great advances in HCV therapy, but there are some limitations that are creating an urgent need for assessment of some cytokines that have a potent antiviral effect in the immune system and anti-inflammatory effects to provide a potential novel immunotherapeutic target in HCV infection.

Objective

This study was directed to assess the serum levels and gene expression levels of Galectin-4 (LEG4), Interleukin-27 (IL-27), and Complement-7 (C-7) and their correlation with the viral load in HCV infection. Subjects and Methods. This work was conducted on 80 subjects, Group 1 (n = 40) early detected HCV patients and Group 2 (n = 40) healthy controls. LEG4, IL-27, and C-7 were assessed at the protein levels by ELISA, and their gene expression was assessed by RT-qPCR. The viral load was measured by PCR.

Results

There were significant elevations in the mean levels of gene expression and serum levels of all studied parameters LEG4, IL-27, and C-7 in the HCV group compared to the control group. Significant negative correlations between the viral load and each of the serum proteins and gene expressions of both LEG4 and IL-27 in HCV patients were found. The gene expression levels of LEG4, IL-27, and C-7 were positively correlated with their corresponding serum proteins in HCV patients.

Conclusion

LEG4 and IL-27 showed significant negative correlations with the viral load, which could be an immune response to the control of the extent of hepatic inflammation, thus creating a potential novel immunotherapeutic approach in HCV infection for further studies or therapeutic clinical trials.

IL-21 treatment recovers follicular helper T cells and neutralizing antibody production in respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infections in children under 1 year. RSV vaccines are currently unavailable, and children suffering from multiple reinfections by the same viral strain fail to develop protective responses. Although RSV-specific antibodies can be detected upon infection, these have limited neutralizing capacity. Follicular helper T (Tfh) cells are specialized in providing signals to B cells and help the production and affinity maturation of antibodies, mainly via interleukin (IL) 21 secretion. In this study, we evaluated whether RSV could inhibit Tfh responses. We observed that Tfh cells fail to upregulate IL-21 production upon RSV infection. In the lungs, RSV infection downregulated the expression of IL-21/interleukin-21 receptor (IL-21R) in Tfh cells and upregulated programmed death-ligand 1 (PD-L1) expression in dendritic cells (DCs) and B cells. PD-L1 blockade during infection recovered IL-21R expression in Tfh cells and increased the secretion of IL-21 in a DC-dependent manner. IL-21 treatment decreased RSV viral load and lung inflammation, inducing the formation of tertiary lymphoid organs in the lung. It also decreased regulatory follicular T cells, and increased Tfh cells, B cells, antibody avidity and neutralization capacity, leading to an overall improved anti-RSV humoral response in infected mice. Passive immunization with purified immunoglobulin G from IL-21-treated RSV-infected mice protected against RSV infection. Our results unveil a pathway by which RSV affects Tfh cells by increasing PD-L1 expression on antigen-presenting cells, highlighting the importance of an IL-21-PD-L1 axis for the generation of protective responses to RSV infection.

The role of galectins in virus infection - A systemic literature review

BACKGROUND

Galectins are β-Galactose binding lectins expressed in numerous cells and play multiple roles in various physiological and cellular functions. However, few information is available regarding the role of galectins in virus infections. Here, we conducted a systemic literature review to analyze the role of galectins in human virus infection.

METHODS

This study uses a systematic method to identify and select eligible articles according to the PRISMA guidelines. References were selected from PubMed, Web of Science and Google Scholar database covering publication dated from August 1995 to December 2018.

RESULTS

Results indicate that galectins play multiple roles in regulation of virus infections. Galectin-1 (Gal-1), galectin-3 (Gal-3), galectin-8 (Gal-8), and galectin-9 (Gal-9) were found as the most predominant galectins reported to participate in virus infection. The regulatory function of galectins occurs by extracellularly binding to viral glycosylated envelope proteins, interacting with ligands or receptors on immune cells, or acting intracellularly with viral or cellular components in the cytoplasm. Several galectins express either positive or negative regulatory role, while some had dual regulatory capabilities on virus propagation based on the conditions and their localization. However, limited information about the endogenous function of galectins were found. Therefore, the endogenous effects of galectins in host-virus regulation remains valuable to investigate.

CONCLUSIONS

This study offers information regarding the various roles galectins shown in viral infection and suggest that galectins can potentially be used as viral therapeutic targets or antagonists.

Hepatitis C virus associated hepatocellular carcinoma

Liver cancer is a global problem and hepatocellular carcinoma (HCC) accounts for about 85% of this cancer. In the USA, etiologies and risk factors for HCC include chronic hepatitis C virus (HCV) infection, diabetes, non-alcoholic steatohepatitis (NASH), obesity, excessive alcohol drinking, exposure to tobacco smoke, and genetic factors. Chronic HCV infection appears to be associated with about 30% of HCC. Chronic HCV infection induces multistep changes in liver, involving metabolic disorders, steatosis, cirrhosis and HCC. Liver carcinogenesis requires initiation of neoplastic clones, and progression to clinically diagnose malignancy. Tumor progression associates with profound exhaustion of tumor-antigen-specific CD8⁺T cells, and accumulation of PD-1^hi CD8⁺T cells and Tregs. In this chapter, we provide a brief description of HCV and environmental/genetic factors, immune regulation, and highlight mechanisms of HCV associated HCC. We also underscore HCV treatment and recent paradigm of HCC progression, highlighted the current treatment and potential future therapeutic opportunities.

Immune system control of hepatitis C virus infection

Hepatitis C virus (HCV) remains a global public health problem even though more than 95% of infections can be cured by treatment with direct-acting antiviral agents. Resolution of viremia post antiviral therapy does not lead to protective immunity and therefore reinfections can occur. Immune cell detection of HCV activates signaling pathways that produce interferons and trigger the innate immune response against the virus, preventing HCV replication and spread. Cells in the innate immune system, including natural killer, dendritic, and Kupffer cells, interact with infected hepatocytes and present viral antigens to T and B cells where their effector responses contribute to infection outcome. Despite the immune activation, HCV can evade the host response and establish persistent infection. Plans to understand the correlates of protection and strategies to activate proper innate and adaptive immune responses are needed for development of an effective prophylactic vaccine that stimulates protective immunity and limits HCV transmission.

Lymphocyte Landscape after Chronic Hepatitis C Virus (HCV) Cure: The New Normal

Chronic HCV (CHC) infection is the only chronic viral infection for which curative treatments have been discovered. These direct acting antiviral (DAA) agents target specific steps in the viral replication cycle with remarkable efficacy and result in sustained virologic response (SVR) or cure in high (>95%) proportions of patients. These treatments became available 6–7 years ago and it is estimated that their real impact on HCV related morbidity, including outcomes such as cirrhosis and hepatocellular carcinoma (HCC), will not be known for the next decade or so. The immune system of a chronically infected patient is severely dysregulated and questions remain regarding the immune system’s capacity in limiting liver pathology in a cured individual. Another important consequence of impaired immunity in patients cleared of HCV with DAA will be the inability to generate protective immunity against possible re-infection, necessitating retreatments or developing a prophylactic vaccine. Thus, the impact of viral clearance on restoring immune homeostasis is being investigated by many groups. Among the important questions that need to be answered are how much the immune system normalizes with cure, how long after viral clearance this recalibration occurs, what are the consequences of persisting immune defects for protection from re-infection in vulnerable populations, and does viral clearance reduce liver pathology and the risk of developing hepatocellular carcinoma in individuals cured with these agents. Here, we review the recent literature that describes the defects present in various lymphocyte populations in a CHC patient and their status after viral clearance using DAA treatments.

CD8+ T cell responses in convalescent COVID-19 individuals target epitopes from the entire SARS-CoV-2 proteome and show kinetics of early differentiation

Characterization of the T cell response in individuals who recover from SARS-CoV-2 infection is critical to understanding its contribution to protective immunity. A multiplexed peptide-MHC tetramer approach was used to screen 408 SARS-CoV-2 candidate epitopes for CD8+ T cell recognition in a cross-sectional sample of 30 COVID-19 convalescent individuals. T cells were evaluated using a 28-marker phenotypic panel, and findings were modelled against time from diagnosis, humoral and inflammatory responses. 132 distinct SARS-CoV-2-specific CD8+ T cell epitope responses across six different HLAs were detected, corresponding to 52 unique reactivities. T cell responses were directed against several structural and non-structural virus proteins. Modelling demonstrated a coordinated and dynamic immune response characterized by a decrease in inflammation, increase in neutralizing antibody titer, and differentiation of a specific CD8+ T cell response. Overall, T cells exhibited distinct differentiation into stem-cell and transitional memory states, subsets, which may be key to developing durable protection.

The roles of galectins in hepatic diseases

Hepatic diseases include all diseases that occur in the liver, including hepatitis, cirrhosis, hepatocellular carcinoma, etc. Hepatic diseases worldwide are characterized by high incidences of digestive system diseases, which present with subtle symptoms, are difficult to treat and have high mortality. Galectins are β-galactoside-binding proteins that have been found to be aberrantly expressed during hepatic disease progression. An increasing number of studies have shown that abnormal expression of galectins is extensively involved in hepatic diseases, such as hepatocellular carcinoma (HCC), liver cirrhosis, hepatitis and liver fibrosis. Galectins function as intracellular and extracellular hepatic disease regulators mainly through the binding of their carbohydrate recognition domain to glycoconjugates expressed in hepatocytes. In this review, we summarize current research on the various roles of galectins in cirrhosis, hepatitis, liver fibrosis and HCC, which may provide a preliminary theoretical basis for the exploration of new targets for the treatment of hepatic diseases.

Increased serum levels of galectin-9 in patients with chikungunya fever

Chikungunya fever (CHIKF) is an arboviral disease that has caused an epidemic burst of chronic inflammatory joint disease in Latin America in the last few years. Efforts are being spent in understanding the mechanisms by which it may cause such articular damage and in determining possible biomarkers of the disease. Galectins (GAL) are a family of animal lectins with an affinity for beta-galactosides. They have multiple functions including working as receptors in innate immunity and as a control for inflammatory responses in both innate and adaptive immunity. They regulate functions of immune cells, such as lymphocytes and macrophages, which have a main role in the chikungunya inflammatory process. Galectins are also involved in chronification of viral diseases, participate in the immunopathogenesis of chronic joint diseases such as rheumatoid arthritis, and have a role in inflammation in other arboviral diseases, such as dengue. Thus, we intended to determine the serum levels of galectin-1, -3, -4, -7, and -9 in patients with subacute and chronic articular manifestations of CHIKF and to evaluate their associations with clinical manifestations. We evaluated 44 patients with clinical manifestations of CHIKF and serological confirmation with IgM and/or IgG chikungunya virus (CHIKV) antibodies. Forty-nine age- and gender-matched healthy individuals served as controls. Anti-CHIKV IgM and IgG antibodies and galectins serum levels were measured by ELISA. We found higher levels of GAL-9 (patients median 2192 [1500-2631] pg/mL, controls median 46.88 [46.88-46.88] pg/mL, p < 0.0001) and lower levels of GAL-3 (patients median 235.5 [175.5-351.8] pg/mL, controls median 2236.0 [1256.0-2236.0] pg/mL, p < 0.0001) in patients than in controls. There was no statistical difference in levels of GAL-1, -4 and -7 between patients and control groups. There was no difference in GAL-9 serum levels between patients with subacute or chronic symptoms (median 2148 [1500-2722] pg/mL x 2212 [1844-2500] pg/mL, p = 0.3626). A significant association of GAL-9 with joint stiffness, both in its duration and intensity, was found. These results may reflect the participation of GAL-9 in the immunopathogenesis of the inflammatory process in chikungunya fever, as morning stiffness may reflect the systemic inflammatory process.

Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment

Hepatitis C virus (HCV) infection is the major risk factor for liver cirrhosis and hepatocellular carcinoma (HCC). The mechanisms of HCC initiation, growth, and metastasis appear to be highly complex due to the decade-long interactions between the virus, immune system, and overlapping bystander effects of host metabolic liver disease. The lack of a readily accessible animal model system for HCV is a significant obstacle to understand the mechanisms of viral carcinogenesis. Traditionally, the primary prevention strategy of HCC has been to eliminate infection by antiviral therapy. The success of virus elimination by antiviral treatment is determined by the SVR when the HCV is no longer detectable in serum. Interferon-alpha (IFN-α) and its analogs, pegylated IFN-α (PEG-IFN-α) alone with ribavirin (RBV), have been the primary antiviral treatment of HCV for many years with a low cure rate. The cloning and sequencing of HCV have allowed the development of cell culture models, which accelerated antiviral drug discovery. It resulted in the selection of highly effective direct-acting antiviral (DAA)-based combination therapy that now offers incredible success in curing HCV infection in more than 95% of all patients, including those with cirrhosis. However, several emerging recent publications claim that patients who have liver cirrhosis at the time of DAAs treatment face the risk of HCC occurrence and recurrence after viral cure. This remains a substantial challenge while addressing the long-term benefit of antiviral medicine. The host-related mechanisms that drive the risk of HCC in the absence of the virus are unknown. This review describes the multifaceted mechanisms that create a tumorigenic environment during chronic HCV infection. In addition to the potential oncogenic programming that drives HCC after viral clearance by DAAs, the current status of a biomarker development for early prediction of cirrhosis regression and HCC detection post viral treatment is discussed. Since DAAs treatment does not provide full protection against reinfection or viral transmission to other individuals, the recent studies for a vaccine development are also reviewed.

Hepatitis C virus-specific CD4+ T cell phenotype and function in different infection outcomes

CD4+ T cell failure is a hallmark of chronic hepatitis C virus (HCV) infection. However, the mechanisms underlying the impairment and loss of virus-specific CD4+ T cells in persisting HCV infection remain unclear. Here we examined HCV-specific CD4+ T cells longitudinally during acute infection with different infection outcomes. We found that HCV-specific CD4+ T cells are characterized by expression of a narrower range of T cell inhibitory receptors compared with CD8+ T cells, with initially high expression levels of PD-1 and CTLA-4 that were associated with negative regulation of proliferation in all patients, irrespective of outcome. In addition, HCV-specific CD4+ T cells were phenotypically similar during early resolving and persistent infection and secreted similar levels of cytokines. However, upon viral control, CD4+ T cells quickly downregulated inhibitory receptors and differentiated into long-lived memory cells. In contrast, persisting viremia continued to drive T cell activation and PD-1 and CTLA-4 expression, and blocked T cell differentiation, until the cells quickly disappeared from the circulation. Our data support an important and physiological role for inhibitory receptor-mediated regulation of CD4+ T cells in early HCV infection, irrespective of outcome, with persistent HCV viremia leading to sustained upregulation of PD-1 and CTLA-4.

Circulating T Cells Exhibit Different TIM3/Galectin-9 Expression in Patients with Obesity and Obesity-Related Diabetes

AIMS

Obesity is highly associated with type 2 diabetes mellitus (T2DM). The TIM3/galectin-9 pathway plays an important role in immune tolerance. Herein, we aimed to investigate the expression of TIM3 and galectin-9 in peripheral blood and to evaluate their clinical significance in patients with obesity and obesity-related T2DM.

METHODS

We performed flow cytometry on peripheral blood samples from healthy donors (HC), patients with simple obesity (OB), and patients with obesity comorbid T2DM (OD). The expression of TIM3 on CD3⁺, CD4⁺, and CD8⁺ T cells was determined. The level of galectin-9 in plasma was detected by ELISA.

RESULTS

We demonstrated the enhancement of TIM3 on CD3⁺, CD4⁺, and CD8⁺ T cells in the OB group when compared with healthy controls, while it was decreased significantly in the OD group. The TIM3⁺CD8⁺ T cells of the OB group were positively correlated with risk factors including BMI, body fat rate, and hipline. The concentration of galectin-9 of the OD group in plasma was significantly higher than that of healthy donors and the OB group. Moreover, the level of galectin-9 of the OD group was positively correlated with fasting insulin and C-peptide, which were two clinical features that represented pancreatic islet function in T2DM.

CONCLUSIONS

Our results suggested that TIM3 and galectin-9 may be potential biomarkers related to the pathogenesis of obesity-related T2DM.

An update on potentials and promises of T cell co-signaling molecules in transplantation

The promising outcomes of immune-checkpoint based immunotherapies in cancer have provided a proportional perspective ahead of exploiting similar approaches in allotransplantation. Belatacept (CTLA-4-Ig) is an example of costimulation blockers successfully exploited in renal transplantation. Due to the wide range of regulatory molecules characterized in the past decades, some of these molecules might be candidates as immunomodulators in the case of tolerance induction in transplantation. Although there are numerous attempts on the apprehension of the effects of co-signaling molecules on immune response, the necessity for a better understanding is evident. By increasing the knowledge on the biology of co-signaling pathways, some pitfalls are recognized and improved approaches are proposed. The blockage of CD80/CD28 axis is an instance of evolution toward more efficacy. It is now evident that anti-CD28 antibodies are more effective than CD80 blockers in animal models of transplantation. Other co-signaling axes such as PD-1/PD-L1, CD40/CD154, 2B4/CD48, and others discussed in the present review are examples of critical immunomodulatory molecules in allogeneic transplantation. We review here the outcomes of recent experiences with co-signaling molecules in preclinical studies of solid organ transplantation.

Circulating levels of PD-L1 and Galectin-9 are associated with patient survival in surgically treated Hepatocellular Carcinoma independent of their intra-tumoral expression levels

Tumor expression of immune co-inhibitory ligands, such as PD-L1 and Galectin-9, have potential prognostic value in Hepatocellular Carcinoma (HCC). Circulating levels of these molecules, however, have hardly been studied. This study aims to assess the prognostic significance of circulating PD-L1 and circulating Galectin-9 in patients with resected HCC, and to compare their prognostic significance to the intra-tumoral expression of these same molecules. Archived tissues and stored peripheral blood samples from 81 patients who underwent HCC resection or liver transplantation, with curative intent, were used. Immunohistochemistry was performed to determine intra-tumoral expression of PD-L1 and Galectin-9, while ELISA was used to quantify their respective circulating levels. High circulating PD-L1 (HR 0.12, 95%CI 0.16-0.86, p = 0.011) and high circulating Galectin-9 (HR 0.11, 95%CI 0.15-0.85, p = 0.010) levels were both associated with improved HCC-specific survival. Surprisingly, there was no correlation between circulating levels of PD-L1 and Galectin-9 and their intra-tumoral expression levels. In fact, circulating levels of PD-L1 and Galectin-9 were predictive of HCC-specific survival independently of intra-tumoral levels and baseline clinicopathologic characteristics. Combined analysis of circulating levels and intra-tumoral expression of PD-L1 (HR 0.33, 95%CI 0.16-0.68, p = 0.002) and Galectin-9 (HR 0.27, 95%CI 0.13-0.57, p = 0.001) resulted in more confident prediction of survival. In conclusion, circulating PD-L1 and Galectin-9 levels prognostically differentiate resected HCC patients, independently of their intra-tumoral expression. Combining circulating and intra-tumoral expression levels of PD-L1 or Galectin-9 further improves the prognostic values of these immune biomarkers.

Interleukin-37 Inhibits the Imbalance Between T Helper 17 Cells and Regulatory T Cells in Hand, Foot, and Mouth Disease

The aim of this study was to explore the role of interleukin-37 (IL-37) in imbalance of T helper (Th)17/regulatory T cells (Tregs) in hand, foot, and mouth disease (HFMD). The proportions of CD4⁺ IL-17A⁺ Th17 cells and CD4⁺ CD25⁺Foxp3⁺ Tregs in peripheral blood or peripheral blood mononuclear cells (PBMCs) from HFMD patients and healthy controls were measured by fluorescence activated cell sorter. The level of IL-37, IL-10, IL-17A, IL-23, and transforming growth factor β1 (TGF-β1) in serum or PBMCs of HFMD patients and control subjects were detected using enzyme-linked immunosorbent assay. Results showed that Th17 cells proportion and IL-17A and IL-23 levels were highly increased, whereas Tregs proportion and IL-10 and TGF-β1 levels were significantly decreased in HFMD patients. Moreover, IL-37 stimulation elevated Tregs proportion but reduced Th17 cell proportion in subjects with HFMD. On the contrary, we found methylprednisolone pulse therapy/methylprednisolone combinated with intravenous gamma globulin inhibits Th17/Treg imbalance through upregulation of IL-37 in HFMD. In conclusion, IL-37 inhibits the imbalance of Th17/Tregs in HFMD.

Restoration of HCV-Specific Immune Responses with Antiviral Therapy: A Case for DAA Treatment in Acute HCV Infection

Worldwide, 71 million individuals are chronically infected with Hepatitis C Virus (HCV). Chronic HCV infection can lead to potentially fatal outcomes including liver cirrhosis and hepatocellular carcinoma. HCV-specific immune responses play a major role in viral control and may explain why approximately 20% of infections are spontaneously cleared before the establishment of chronicity. Chronic infection, associated with prolonged antigen exposure, leads to immune exhaustion of HCV-specific T cells. These exhausted T cells are unable to control the viral infection. Before the introduction of direct acting antivirals (DAAs), interferon (IFN)-based therapies demonstrated successful clearance of viral infection in approximately 50% of treated patients. New effective and well-tolerated DAAs lead to a sustained virological response (SVR) in more than 95% of patients regardless of viral genotype. Researchers have investigated whether treatment, and the subsequent elimination of HCV antigen, can reverse this HCV-induced exhausted phenotype. Here we review literature exploring the restoration of HCV-specific immune responses following antiviral therapy, both IFN and DAA-based regimens. IFN treatment during acute HCV infection results in greater immune restoration than IFN treatment of chronically infected patients. Immune restoration data following DAA treatment in chronically HCV infected patients shows varied results but suggests that DAA treatment may lead to partial restoration that could be improved with earlier administration. Future research should investigate immune restoration following DAA therapies administered during acute HCV infection.

Strategies to Circumvent Host Innate Immune Response by Hepatitis C Virus

Innate immune responses generate interferons, proinflammatory cytokines, complement activation, and natural killer (NK) cell response. Ultimately, this leads to the induction of a robust virus-specific adaptive immunity. Although the host innate immune system senses and responds to eliminate virus infection, hepatitis C virus (HCV) evades immune attack and establishes persistent infection within the liver. Spontaneous clearance of HCV infection is associated with a prompt induction of innate immunity generated in an infected host. In this review, we have highlighted the current knowledge of our understanding of host⁻HCV interactions, especially for endogenous interferon production, proinflammatory response, NK cell response, and complement activation, which may impair the generation of a strong adaptive immune response for establishment of chronicity. The information may provide novel strategies in augmenting therapeutic intervention against HCV.

Vaccination to prevent T cell subversion can protect against persistent hepacivirus infection

Efforts to develop an effective vaccine against the hepatitis C virus (HCV; human hepacivirus) have been stymied by a lack of small animal models. Here, we describe an experimental rat model of chronic HCV-related hepacivirus infection and its response to T cell immunization. Immune-competent rats challenged with a rodent hepacivirus (RHV) develop chronic viremia characterized by expansion of non-functional CD8⁺ T cells. Single-dose vaccination with a recombinant adenovirus vector expressing hepacivirus non-structural proteins induces effective immunity in majority of rats. Resolution of infection coincides with a vigorous recall of intrahepatic cellular responses. Host selection of viral CD8 escape variants can subvert vaccine-conferred immunity. Transient depletion of CD8⁺ cells from vaccinated rats prolongs infection, while CD4⁺ cell depletion results in chronic viremia. These results provide direct evidence that co-operation between CD4⁺ and CD8⁺ T cells is important for hepacivirus immunity, and that subversion of responses can be prevented by prophylactic vaccination.

Development of a HCV vaccine is hampered by a lack of appropriate small animal models. Here, Hartlage et al. describe a rat model of hepacivirus persistence and show that persistence can be prevented by vaccination with viral non-structural proteins.

Hepatitis C Virus Manipulates Humans as its Favorite Host for a Long-Term Relationship

Chronic hepatitis C virus (HCV) infection-associated liver disease is a global health problem. HCV often causes silent disease, and eventually progresses to end-stage liver disease. HCV infects hepatocytes; however, initial manifestation of liver disease is mostly displayed in hepatic stellate cells (HSCs), causing fibrosis/cirrhosis, and is believed to occur from inflammation in the liver. It remains unclear why HCV is not spontaneously cleared from infected liver in the majority of individuals and develops chronic infection with progressive liver disease. Direct-acting antivirals (DAAs) show excellent results in controlling viremia, although beneficial consequence in advanced liver disease remains to be understood. In this review, we highlight the current knowledge that has contributed to our understanding of the role of HCV in inflammation, immune evasion, metabolic disorders, liver pathogeneses, and efforts in vaccine development.

Dual effect of T helper cell 17 (Th17) and regulatory T cell (Treg) in liver pathological process: From occurrence to end stage of disease

Liver disease is a complicated pathological status with acute or chronic progressions, causing a series of damages to liver and massive burden to public health and society. Th17 and Treg, two subsets of CD4⁺ T helper cells, seem to keep a subtle balance in the maintenance of organic immune homeostasis including liver. The dysfunction of Th17/Treg balance in liver has been proved associated with hepatic injury and disease. Herein, we summarized the research advance of Th17 and Treg cells in different phenotypes of liver diseases in the past decade. It is known to all that hepatic diseases start from stimulations or infections like virus, autoimmune, alcohol and so on in the early stage, which would cause inflammation. With the disease consistently existed, severe outcomes like cirrhosis and hepatocellular carcinoma appear finally. In conclusion, it is found that Th17 and Treg cells serve as an important role in the immune response imbalance of liver diseases from the beginning to the end stage. However, the effect of these two subsets of CD4⁺ T helper cells is not a stereotype. Pathological role which exacerbates the disease and protective character which inhibits damage to liver are co-existed in the effect of Th17 and Treg cells. Still, more studies should be carried out to enrich the understandings of liver disease and Th17/Treg immune balance in the future.

Gal power: the diverse roles of galectins in regulating viral infections

Viruses, as a class of pathogenic microbe, remain a significant health burden globally. Viral infections result in significant morbidity and mortality annually and many remain in need of novel vaccine and anti-viral strategies. The development of effective novel anti-viral therapeutics, in particular, requires detailed understanding of the mechanism of viral infection, and the host response, including the innate and adaptive arms of the immune system. In recent years, the role of glycans and lectins in pathogen-host interactions has become an increasingly relevant issue. This review focuses on the interactions between a specific lectin family, galectins, and the broad range of viral infections in which they play a role. Discussed are the diverse activities that galectins play in interacting directly with virions or the cells they infect, to promote or inhibit viral infection. In addition we describe how galectin expression is regulated both transcriptionally and post-transcriptionally by viral infections. We also compare the contribution of known galectin-mediated immune modulation, across a range of innate and adaptive immune anti-viral responses, to the outcome of viral infections.

Influence of hepatitis C virus eradication with direct-acting antivirals on the gut microbiota in patients with cirrhosis

BACKGROUND

The cure of hepatitis C virus (HCV) infection may contribute to the reduction of liver fibrosis progression and potentially influence the gut-liver axis.

AIM

To investigate the influence of HCV infection eradication with direct-acting antivirals (DAAs) on the gut microbiota composition as well as on intestinal and systemic inflammatory parameters in patients with cirrhosis.

METHODS

Consecutive patients with HCV-related cirrhosis receiving DAA treatment were included. The gut microbiota composition, intestinal permeability, and inflammation were assessed before treatment and after 1 year. Clinical outcomes such as episodes of decompensation and markers of liver fibrosis were evaluated over a 2-year follow-up period.

RESULTS

The gut microbiota alpha diversity in cirrhotic patients, which was lower than that in healthy subjects, was significantly improved by the cure of HCV infection and a shift in the overall gut microbiota composition was observed compared to baseline. The abundance of potentially pathogenic bacteria (Enterobacteriaceae, Enterococcus, and Staphylococcus) was decreased after treatment. The gut microbiota composition was associated with the inflammatory profile and markers of liver fibrosis. Although a significant reduction in the serum levels of cytokines and chemokines was observed post-DAA treatment, measures of intestinal permeability and inflammation remained unchanged.

CONCLUSIONS

Cure of HCV infection with DAAs in patients with cirrhosis is associated with a modification of the gut microbiota, which correlates with fibrosis and inflammation but does not improve intestinal barrier function.

Reactivation of latent HIV-1 in vitro using an ethanolic extract from Euphorbia umbellata (Euphorbiaceae) latex

Euphorbia umbellata (E. umbellata) belongs to Euphorbiaceae family, popularly known as Janauba, and its latex contains a combination of phorbol esters with biological activities described to different cellular protein kinase C (PKC) isoforms. Here, we identified deoxi-phorbol esters present in E. umbellata latex alcoholic extract that are able to increase HIV transcription and reactivate virus from latency models. This activity is probably mediated by NF-kB activation followed by nuclear translocation and binding to the HIV LTR promoter. In addition, E. umbellata latex extract induced the production of pro inflammatory cytokines in vitro in human PBMC cultures. This latex extract also activates latent virus in human PBMCs isolated from HIV positive patients as well as latent SIV in non-human primate primary CD4+ T lymphocytes. Together, these results indicate that the phorbol esters present in E. umbellata latex are promising candidate compounds for future clinical trials for shock and kill therapies to promote HIV cure and eradication.

HCV-Specific T Cell Responses During and After Chronic HCV Infection

Hepatitis C virus (HCV)-specific T cell responses are closely linked to the clinical course of infection. While T cell responses in self-limiting infection are typically broad and multi-specific, they display several distinct features of functional impairment in the chronic phase. Moreover, HCV readily adapts to immune pressure by developing escape mutations within epitopes targeted by T cells. Much of our current knowledge on HCV-specific T cell responses has been gathered under the assumption that this might eventually pave the way for a therapeutic vaccine. However, with the development of highly efficient direct acting antivirals (DAAs), there is less interest in the development of a therapeutic vaccine for HCV and the scope of T cell research has shifted. Indeed, the possibility to rapidly eradicate an antigen that has persisted over years or decades, and has led to T cell exhaustion and dysfunction, provides the unique opportunity to study potential T cell recovery after antigen cessation in a human in vivo setting. Findings from such studies not only improve our basic understanding of T cell immunity but may also advance immunotherapeutic approaches in cancer or chronic hepatitis B and D infection. Moreover, in order to edge closer to the WHO goal of HCV elimination by 2030, a prophylactic vaccine is clearly required. Thus, in this review, we will summarize our current knowledge on HCV-specific T cell responses and also provide an outlook on the open questions that require answers in this field.

Modulation of the Immune System in Chronic Hepatitis C and During Antiviral Interferon-Free Therapy

The treatment of patients with chronic hepatitis C virus (HCV) infection has changed tremendously over the past 2 years, with an increasing variety of all-oral direct-acting antiviral (DAA) treatment regimens available for different HCV genotypes and distinct clinical settings. These treatments have significantly improved safety in patients with advanced liver disease compared with interferon (IFN)-based regimens. HCV modifies the human immune system to escape immunosurveillance via several mechanisms. One of the basic mechanisms of HCV is the ability to “switch” the immune response by reducing the activity of cells responsible for the elimination of virus-infected cells. IFN-free DAA treatment regimens provide a unique opportunity to assess the effect of HCV elimination on the immune system. Abrupt changes in the immune system can in some cases be responsible for two alarming processes: viral reactivation in patients with chronic hepatitis B and recurrence of hepatocellular carcinoma in patients with previous successful cancer treatment.

Dynamics of helper CD4 T cells during acute and stable allergic asthma

Asthma comprises heterogeneous clinical subtypes driven by diverse pathophysiological mechanisms. We characterized the modulation of the inflammatory environment with the phenotype, gene expression, and function of helper CD4 T cells among acutely exacerbated and stable asthma patients. Systemic Th2 immune deviation (IgE and Th2 cytokines) and inflammation (IL-6, CRP) were associated with increased Th17 cells during acute asthma. Th2/Th17 cell differentiation during acute asthma was regulated by the enhanced expression of transcription factors (c-MAF, IRF-4). The development of pathogenic Th2 cells during acute asthma was characterized by the secretion of inflammatory cytokines coupled with Th2 molecules and PPARγ expression. The acquisition of CD15S, CD39, CD101, and CCR4 contributed to the increased heterogeneity of Regulatory T cells during asthma. Two clusters were derived from above cytokines, CD4 T cell phenotypes, and clinical data. Cluster 1, characterized by high eosinophils, Th2 and ILC2 frequencies, and higher exacerbation rates, may represent Th2-high subtype. Cluster 2 represents a more complex subtype; it is constituted by higher neutrophils or Th17 frequencies, higher inhaled corticosteroids dose and poor asthma control. In conclusion, we characterized systematically and longitudinally Th2-high and non-Th2 asthma subtypes and the heterogeneity of CD4 T cells in stable and acute asthma.

Type 3 cytokines IL-17A and IL-22 drive TGF-β-dependent liver fibrosis

Inflammatory immune cells can modulate activation of hepatic stellate cells (HSCs) and progression of liver fibrosis. Type 3 inflammation characterized by production of interleukin-17A (IL-17) and IL-22 by innate and adaptive immune cells is implicated in many inflammatory conditions of the gut and can be counteracted by regulatory T cells (Tregs), but its contribution to liver fibrosis is still poorly understood. Here, we evaluated the contribution of type 3 inflammation in liver fibrosis using clinical liver biopsies, in vitro stimulation of primary HSCs, and in vivo mouse models. We report dysregulated type 3 responses in fibrotic lesions with increased IL-17+CD4+/FOXP3hiCD4+ ratio and increased IL-17 and IL-22 production in advanced liver fibrosis. Neutrophils and mast cells were the main sources of IL-17 in situ in humans. In addition, we demonstrate a new profibrotic function of IL-22 through enhancement of transforming growth factor-β signaling in HSCs in a p38 mitogen-activated protein kinase-dependent manner. In vivo, IL-22RA1 knockout mice exhibited reduced fibrosis in response to thioacetamide and carbon tetrachloride. Blocking either IL-22 or IL-17 production using aryl hydrocarbon receptor or RAR-related orphan receptor gamma-t antagonists resulted in reduced fibrosis. Together, these data have identified a pathogenic role for type 3 immune response mediated by IL-22 in driving liver fibrosis during chronic liver injury.