Increased hepatitis C virus (HCV)-specific CD4+CD25+ regulatory T lymphocytes and reduced HCV-specific CD4+ T cell response in HCV-infected patients with normal versus abnormal alanine aminotransferase levels

Interaction of peripheral CD4+CD25+CD127− Tregs with prolactin in HCV hepatocellular carcinoma: oncogenic or immunogenic mechanisms

Background and objective

There is little and conflicting data about the peripheral CD4+CD25+CD127− Tregs in patients with hepatocellular carcinoma (HCC) of various etiologies. The expressed membrane-bound transforming growth factor (mTGF-β1) on these Tregs is a marker of their suppressive function. Prolactin suppresses Tregs function in healthy subjects but enhances local Tregs in breast cancer. Our study is the first to assess the frequency and function of CD4+CD25+CD127−Tregs and their association with clinicopathological features and staging in HCV-related HCC and to determine whether prolactin acts as an oncogenic growth factor or participates in the regulation of the immune response mediated by peripheral Tregs. In patients with HCV- elated HCC, HCV-cirrhotic patients, and healthy subjects, we measured the frequency of peripheral traditional CD4+ CD25+ Tregs and well-characterized CD4+CD25+CD127−Tregs and their mTGF-β1 using flow cytometric analysis and measured serum prolactin level.

Results

The frequency of CD4+ CD25+ and CD4+CD25+CD127− Tregs was comparable between HCC and cirrhotic patients and healthy subjects. Serum prolactin and mTGF-β1 on traditional and CD4+CD25+CD127− Tregs were significantly higher in HCC and cirrhotic patients than healthy subjects with an insignificant difference between HCC and cirrhotic patients. Roc curve analysis revealed that cutoff value for mTGF-β1 on Tregs ≥ 13.5% is a good specific (87%) but low sensitive (54%) test in discriminating HCC patients from healthy subjects. The frequency of Tregs and mTGF-β1 were not correlated to clinicopathological characteristics or staging of HCC. Prolactin was higher in the multifocal lesions and negatively correlated to expressed mTGFβ1. The expressed mTGF-β1 was positively correlated with hemoglobin and alanine transaminase. The traditional Tregs was positively correlated with hemoglobin and albumin.

Conclusion

mTGFβ1, as a marker for suppressive function of peripheral CD4 + CD25 + CD127-Tregs, has a diagnostic role in discriminating HCV-related HCC patient from healthy subjects, unfortunately not from HCV-related cirrhotic patients. Serum prolactin has an oncogenic role as it is correlated to multiple focal lesions. It also impedes the suppressive function of peripheral Tregs as an immunogenic role. mTGF-β1 is related to hemoglobin and hepatic inflammation.

Potential roles of core and core+1 proteins during the chronic phase of hepatitis C virus infection

The HCV Core protein is a multifunctional protein that interacts with many viral and cellular proteins. In addition to the encapsidation of the viral genome, it can disturb various cellular pathways and impede antiviral cellular responses such as interferon (IFN) production. The Core protein can also disrupt the functions of immune cells against HCV. The Core protein helps viral infection persistency by interfering with apoptosis. The Core+1 protein plays a significant role in inducing chronic HCV infection through diverse mechanisms. We review some of the mechanisms by which Core and Core+1 proteins facilitate HCV infection to chronic infection. These proteins could be considered for designing more sufficient treatments and effective vaccines against HCV.

Crosstalk of Microorganisms and Immune Responses in Autoimmune Neuroinflammation: A Focus on Regulatory T Cells

Regulatory T cells (Tregs) are the major determinant of peripheral immune tolerance. Many Treg subsets have been described, however thymus-derived and peripherally induced Tregs remain the most important subpopulations. In multiple sclerosis, a prototypical autoimmune disorder of the central nervous system, Treg dysfunction is a pathogenic hallmark. In contrast, induction of Treg proliferation and enhancement of their function are central immune evasion mechanisms of infectious pathogens. In accordance, Treg expansion is compartmentalized to tissues with high viral replication and prolonged in chronic infections. In friend retrovirus infection, Treg expansion is mainly based on excessive interleukin-2 production by infected effector T cells. Moreover, pathogens seem also to enhance Treg functions as shown in human immunodeficiency virus infection, where Tregs express higher levels of effector molecules such as cytotoxic T-lymphocyte-associated protein 4, CD39 and cAMP and show increased suppressive capacity. Thus, insights into the molecular mechanisms by which intracellular pathogens alter Treg functions might aid to find new therapeutic approaches to target central nervous system autoimmunity. In this review, we summarize the current knowledge of the role of pathogens for Treg function in the context of autoimmune neuroinflammation. We discuss the mechanistic implications for future therapies and provide an outlook for new research directions.

Influence of everolimus-based treatment on circulating regulatory T cells after liver transplantation: Comparative study with tacrolimus-based therapy

Liver transplantation remains the only treatment for terminal liver diseases. However, immunosuppressive drugs required for allograft acceptance are toxic and may be responsible for severe side effects. Modulating the immune system to induce tolerance is a promising approach to reduce immunosuppressive regimen. More particularly, promoting natural CD4⁺ CD25⁺ FoxP3⁺ Tregs could be crucial in achieving tolerance. Contrary to calcineurin inhibitors, reports indicate that mTOR inhibitors may have a positive impact on Tregs. Here we present the first randomized prospective clinical study where Tregs levels from liver transplanted patients receiving either tacrolimus or everolimus were monitored for 6 months, starting from the day of transplantation. A total of 30 patients from four centers were monitored. Blood samples were obtained at day 0, day 14, one month, three months and six months post-transplantation. Flow-cytometry immunophenotyping of Tregs (CD4⁺ CD25⁺ CD127^- FoxP3⁺) and functional assays with Tregs were performed to assess their immunosuppressive capacity. Levels of Tregs were significantly reduced after one month of standard tacrolimus-based immunosuppressive regimen (p<0.05). Four months after conversion, levels of Tregs from patients treated with everolimus was significantly higher than patients under tacrolimus (p<0.02). Functional assays demonstrated that Tregs conserved their capacity to suppress the proliferation of activated PBMC.

Effects of Pegylated Interferon Alpha and Ribavirin (pegIFN-α/RBV) Therapeutic Approach on Regulatory T Cells in HCV-Monoinfected and HCV/HIV-Coinfected Patients

Approximately 25% of HIV-infected patients are co-infected with HCV. Notably, the burden of HCV infection (e.g., viral persistence, viral load, or HCV-related liver symptoms) is more pronounced in the presence of HIV co-infection. However, to date, the underlying immune mechanisms accounting for accelerated disease progression in HIV/HCV-coinfected individuals have not been described in sufficient detail. We hypothesized that regulatory T cells (Treg) bearing potent immunosuppressive capacities could not only play a substantial role in the pathogenesis of HCV/HIV coinfection but also modulate the response to the standard anti-viral therapy.

MATERIALS AND METHODS

To this end, we studied alterations in frequencies of Treg cells in correlation with other Treg-related and virus-related parameters in both HCV and HCV/HIV-infected patients subjected to standard pegIFN-α/RBV therapy.

RESULTS

Notably, we found that pegIFN-α/RBV therapy significantly increased levels of Treg cells in HCV-infected but not in HIV/HCV-coinfected individuals. Furthermore, HIV/HCV-coinfection was demonstrated to inhibit expansion of regulatory T cells during anti-viral treatment; thus, it might probably be responsible for viral persistence and HCV-related liver damage.

CONCLUSIONS

Therapy with pegIFN-α/RBV demonstrated a significant effect on regulatory T cells in the course of HIV and/or HCV infection indicating a crucial role in the anti-viral immune response.

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.

Immunological Dynamics Associated with Direct-Acting Antiviral Therapies in Naive and Experimented HCV Chronic-Infected Patients

The therapeutic strategies used in the treatment of hepatitis C are essentially based on the combination of direct-acting antiviral agents (DAAs). This therapy has been shown to be very effective in relation to patient adherence to treatment and has shown high rates of sustained virological response (SVR). However, the immunological dynamics of patients infected with HCV is poorly understood. This fact led us to investigate the immune system of naive and experienced patients, who we followed before the therapy and three months after the end of treatment. In this study, 35 naive and experienced Brazilian patients with chronic hepatitis C and 50 healthy donors (HD group) were studied. The analysis of the soluble immunological biomarkers was performed using the flow cytometry methodology. The SVR rate was >90% among the 35 patients. Before treatment, correlations in the naive HCV group demonstrated a mix of inflammatory response occurring with moderate correlations between chemokines, inflammatory cytokines, and Th2 profile, with a strong regulation between IL-10 and IL-17A. On the other hand, experienced patients demonstrated a poor interaction between cytokines, chemokines, and cells with a strong correlation between IL-10, IL-6, CXCL-10, and CD8⁺ besides the interactions between IFN-γ and IL-4. Furthermore, naive and experienced patients seem to have a distinct soluble biomarker profile; therefore, a long-term follow-up is needed to evaluate patients treated with DAAs.

Reparative T lymphocytes in organ injury

Acute organ injuries such as acute cerebrovascular accidents, myocardial infarction, acute kidney injury, acute lung injury, and others are among the leading causes of death worldwide. Dysregulated or insufficient organ repair mechanisms limit restoration of homeostasis and contribute to chronic organ failure. Studies reveal that both humans and mice harness potent non-stem cells that are capable of directly or indirectly promoting tissue repair. Specific populations of T lymphocytes have emerged as important reparative cells with context-specific actions. These T cells can resolve inflammation and secrete reparative cytokines and growth factors as well as interact with other immune and stromal cells to promote the complex and active process of tissue repair. This Review focuses on the major populations of T lymphocytes known to mediate tissue repair, their reparative mechanisms, and the diseases in which they have been implicated. Elucidating and harnessing the mechanisms that promote the reparative functions of these T cells could greatly improve organ dysfunction after acute injury.

The -3279C>A and -924A>G polymorphisms in the FOXP3 Gene Are Associated With Viral Load and Liver Enzyme Levels in Patients With Chronic Viral Liver Diseases

The transcription factor FOXP3 is an essential marker of the development and activation of regulatory T cells (Tregs), which are cells specialized in the regulation and normal tolerance of the immune response. In the context of chronic viral liver diseases, Tregs participate in the maintenance of infections by promoting histopathological control and favor the immune escape of viral agents by suppressing the antiviral response. Single nucleotide polymorphisms (SNPs) may influence the function of FOXP3 in a number of pathological conditions. The present study sought to evaluate the influence of SNPs in the FOXP3 gene promoter region in patients with chronic viral liver diseases. Three SNPs (−3279C>A, −2383C>T, and −924A>G) were analyzed in groups of patients with chronic hepatitis C (CHC), active chronic hepatitis B (CHB-A), inactive chronic hepatitis B (CHB-I), and a healthy control group (CG) using real-time PCR. The frequencies of the polymorphic variants were compared between groups and correlated with liver histopathological characteristics and enzyme levels [i.e., alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT)] obtained via biopsy and from the clinical records of the participating patients, respectively. For the −2338C>T SNP, no significant differences were found in the frequencies of variants between groups or in the histological findings. Significant associations between the polymorphisms and the CHB-I group were not established. The −3279C>A SNP was associated with altered viral loads (log₁₀) and GGT levels in CHC patients with advanced stages of inflammatory activity and liver fibrosis. The −924A>G SNP was associated with altered viral loads (log₁₀) and liver enzyme levels among CHB-A patients with milder inflammation and fibrosis. However, the frequencies of the −3279C>A and −924A>G polymorphisms were not directly associated with the histopathological profiles of the analyzed patients. These polymorphic variants may influence hepatic function in patients with chronic viral liver diseases but are not directly associated with the establishment of the degree of inflammatory activity and liver fibrosis.

Different core-specific T cell subsets are expanded in chronic hepatitis C with advanced liver disease

Chronic hepatitis C (CHC) is frequently related to liver fibrosis, and several studies have suggested that the immunological activity of HCV antigens contributes to hepatic damage. In the present study, among structural and non-structural HCV antigens, elevatedIL-1β, IL-6, IL-17 levels were secreted by PBMC cultures obtained from CHC patients following stimulation with core antigen. Moreover, the percentage of core-specific IL-6⁺IL-17⁺(CD4⁺ and CD8⁺) T cells was significantly higher in patients with worsehepatic lesions, determined on the Metavir scale. When compared with healthy subjects, the percentage of circulating Treg cells was elevated in CHC patients, mainly among those with advanced liver fibrosis. Nevertheless, in this last group of patients, the proportion of CD39⁺ Treg subsets was very low. Finally, the percentage of senescent (CD57⁺ CD28^-) and exhausted (PD-1⁺CD28⁺) core-specific T cells in CHC patients was also found to be a result of fibrotic hepatic status. In summary, imbalances between different core-specific T cell subsets are associated with liver fibrosis severity.

According to Hepatitis C Virus (HCV) Infection Stage, Interleukin-7 Plus 4-1BB Triggering Alone or Combined with PD-1 Blockade Increases TRAF1low HCV-Specific CD8+ Cell Reactivity

Hepatitis C virus (HCV)-specific CD8⁺ T cells suffer a progressive exhaustion during persistent infection (PI) with HCV. This process could involve the positive immune checkpoint 4-1BB/4-1BBL through the loss of its signal transducer, TRAF1. To address this issue, peripheral HCV-specific CD8⁺ T cells (pentamer-positive [pentamer⁺]/CD8⁺ T cells) from patients with PI and resolved infection (RI) after treatment were studied. The duration of HCV infection and the liver fibrosis progression rate inversely correlated with the likelihood of detection of peripheral pentamer⁺/CD8⁺ cells. In PI, pentamer⁺/CD8⁺ cells had impaired antigen-specific reactivity that worsened when these cells were not detectable ex vivo Short/midduration PI was characterized by detectable peripheral PD-1⁺ CD127^low TRAF1^low cells. After triggering of T cell receptors (TCR), the TRAF1 level positively correlated with the levels of CD127, Mcl-1, and CD107a expression and proliferation intensity but negatively with PD-1 expression, linking TRAF1^low to exhaustion. In vitro treatment with interleukin-7 (IL-7) upregulated TRAF1 expression, while treatment with transforming growth factor-β1 (TGF-β1) did the opposite, suggesting that the IL-7/TGF-β1 balance, besides TCR stimulation, could be involved in TRAF1 regulation. In fact, the serum TGF-β1 concentration was higher in patients with PI than in patients with RI, and it negatively correlated with TRAF1 expression. In line with IL-7 increasing the level of TRAF1 expression, IL-7 plus 4-1BBL treatment in vitro enhanced T cell reactivity in patients with short/midduration infection. However, in patients with long-lasting PI, anti-PD-L1, in addition to the combination of IL-7 and 4-1BBL, was necessary to reestablish T cell proliferation in individuals with slowly progressing liver fibrosis (slow fibrosers) but had no effect in rapid fibrosers. In conclusion, a peripheral hyporeactive TRAF1^low HCV-specific CD8⁺ T cell response, restorable by IL-7 plus 4-1BBL treatment, characterizes short/midduration PI. In long-lasting disease, HCV-specific CD8⁺ T cells are rarely detectable ex vivo, but treatment with IL-7, 4-1BBL, and anti-PD-L1 recovers their reactivity in vitro in slow fibrosers.IMPORTANCE Hepatitis C virus (HCV) infects 71 million people worldwide. Two-thirds develop a chronic disease that can lead to cirrhosis and hepatocellular carcinoma. Direct-acting antivirals clear the infection, but there are still patients who relapse. In these cases, additional immunotherapy could play a vital role. A successful anti-HCV immune response depends on virus-specific CD8⁺ T cells. During chronic infection, these cells are functionally impaired, which could be due to the failure of costimulation. This study describes exhausted specific T cells, characterized by low levels of expression of the signal transducer TRAF1 of the positive costimulatory pathway 4-1BB/4-1BBL. IL-7 upregulated TRAF1 expression and improved T cell reactivity in patients with short/midduration disease, while in patients with long-lasting infection, it was also necessary to block the negative PD-1/PD-L1 checkpoint. When the results are taken together, this work supports novel ways of restoring the specific CD8⁺ T cell response, shedding light on the importance of TRAF1 signaling. This could be a promising target for future immunotherapy.

Capturing the systemic immune signature of a norovirus infection: an n-of-1 case study within a clinical trial

Background: The infection of a participant with norovirus during the adaptive study of interleukin-2 dose on regulatory T cells in type 1 diabetes (DILT1D) allowed a detailed insight into the cellular and cytokine immune responses to this prevalent gastrointestinal pathogen.

Methods:  Serial blood, serum and peripheral blood mononuclear cell (PBMC) samples were collected pre-, and post-development of the infection. To differentiate between the immune response to norovirus and to control for the administration of a single dose of aldesleukin (recombinant interleukin-2, rIL-2) alone, samples from five non-infected participants administered similar doses were analysed in parallel.

Results: Norovirus infection was self-limited and resolved within 24 hours, with the subsequent development of anti-norovirus antibodies. Serum pro- and anti-inflammatory cytokine levels, including IL-10, peaked during the symptomatic period of infection, coincident with increased frequencies of monocytes and neutrophils. At the same time, the frequency of regulatory CD4 ⁺ T cell (Treg), effector T cell (Teff) CD4 ⁺ and CD8 ⁺ subsets were dynamically reduced, rebounding to baseline levels or above at the next sampling point 24 hours later.  NK cells and NKT cells transiently increased CD69 expression and classical monocytes expressed increased levels of CD40, HLA-DR and SIGLEC-1, biomarkers of an interferon response. We also observed activation and mobilisation of Teffs, where increased frequencies of CD69 ⁺ and Ki-67 ⁺ effector memory Teffs were followed by the emergence of memory CD8 ⁺ Teff expressing the mucosal tissue homing markers CD103 and β7 integrin. Treg responses were coincident with the innate cell, Teff and cytokine response. Key Treg molecules FOXP3, CTLA-4, and CD25 were upregulated following infection, alongside an increase in frequency of Tregs with the capacity to home to tissues.

Conclusions:  The results illustrate the innate, adaptive and counter-regulatory immune responses to norovirus infection. Low-dose IL-2 administration induces many of the Treg responses observed during infection.

Capturing the systemic immune signature of a norovirus infection: an n-of-1 case study within a clinical trial

BACKGROUND

The infection of a participant with norovirus during the adaptive study of interleukin-2 dose on regulatory T cells in type 1 diabetes (DILT1D) allowed a detailed insight into the cellular and cytokine immune responses to this prevalent gastrointestinal pathogen.

METHODS

Serial blood, serum and peripheral blood mononuclear cell (PBMC) samples were collected pre-, and post-development of the infection. To differentiate between the immune response to norovirus and to control for the administration of a single dose of aldesleukin (recombinant interleukin-2, rIL-2) alone, samples from five non-infected participants administered similar doses were analysed in parallel.

RESULTS

Norovirus infection was self-limited and resolved within 24 hours, with the subsequent development of anti-norovirus antibodies. Serum pro- and anti-inflammatory cytokine levels, including IL-10, peaked during the symptomatic period of infection, coincident with increased frequencies of monocytes and neutrophils. At the same time, the frequency of regulatory CD4 ⁺ T cell (Treg), effector T cell (Teff) CD4 ⁺ and CD8 ⁺ subsets were dynamically reduced, rebounding to baseline levels or above at the next sampling point 24 hours later.  NK cells and NKT cells transiently increased CD69 expression and classical monocytes expressed increased levels of CD40, HLA-DR and SIGLEC-1, biomarkers of an interferon response. We also observed activation and mobilisation of Teffs, where increased frequencies of CD69 ⁺ and Ki-67 ⁺ effector memory Teffs were followed by the emergence of memory CD8 ⁺ Teff expressing the mucosal tissue homing markers CD103 and β7 integrin. Treg responses were coincident with the innate cell, Teff and cytokine response. Key Treg molecules FOXP3, CTLA-4, and CD25 were upregulated following infection, alongside an increase in frequency of Tregs with the capacity to home to tissues.

CONCLUSIONS

The results illustrate the innate, adaptive and counter-regulatory immune responses to norovirus infection. Low-dose IL-2 administration induces many of the Treg responses observed during infection.

Capturing the systemic immune signature of a norovirus infection: an n-of-1 case study within a clinical trial

Background: The infection of a participant with norovirus during the adaptive study of interleukin-2 dose on regulatory T cells in type 1 diabetes (DILT1D) allowed a detailed insight into the cellular and cytokine immune responses to this prevalent gastrointestinal pathogen. Methods: Serial blood, serum and peripheral blood mononuclear cell (PBMC) samples were collected pre-, and post-development of the infection. To differentiate between the immune response to norovirus and to control for the administration of a single dose of aldesleukin (recombinant interleukin-2, rIL-2) alone, samples from five non-infected participants administered similar doses were analysed in parallel. Results: Norovirus infection was self-limited and resolved within 24 hours, with the subsequent development of anti-norovirus antibodies. Serum pro- and anti-inflammatory cytokine levels, including IL-10, peaked during the symptomatic period of infection, coincident with increased frequencies of monocytes and neutrophils. At the same time, the frequency of regulatory CD4+ T cell (Treg), effector T cell (Teff) CD4+ and CD8+ subsets were dynamically reduced, rebounding to baseline levels or above at the next sampling point 24 hours later.  NK cells and NKT cells transiently increased CD69 expression and classical monocytes expressed increased levels of CD40, HLA-DR and SIGLEC-1, biomarkers of an interferon response. We also observed activation and mobilisation of Teffs, where increased frequencies of CD69+ and Ki-67+ effector memory Teffs were followed by the emergence of memory CD8+ Teff expressing the mucosal tissue homing markers CD103 and β7 integrin. Treg responses were coincident with the innate cell, Teff and cytokine response. Key Treg molecules FOXP3, CTLA-4, and CD25 were upregulated following infection, alongside an increase in frequency of Tregs with the capacity to home to tissues. Conclusions: The results illustrate the innate, adaptive and counter-regulatory immune responses to norovirus infection. Low-dose IL-2 administration induces many of the Treg responses observed during infection.

Direct-Acting Antiviral Therapy Restores Immune Tolerance to Patients With Hepatitis C Virus-Induced Cryoglobulinemia Vasculitis

BACKGROUND & AIMS

Interferon-free direct-acting antiviral (DAA) therapies are effective in patients with hepatitis C virus-induced cryoglobulinemia vasculitis (HCV-CV). We analyzed blood samples from patients with HCV-CV before and after DAA therapy to determine mechanisms of these drugs and their effects on cellular immunity.

METHODS

We performed a prospective study of 27 consecutive patients with HCV-CV (median age, 59 y) treated with DAA therapy (21 patients received sofosbuvir plus ribavirin for 24 weeks, 4 patients received sofosbuvir plus daclatasvir for 12 weeks, and 2 patients received sofosbuvir plus simeprevir for 12 weeks) in Paris, France. Blood samples were collected from these patients before and after DAA therapy, and also from 12 healthy donors and 12 individuals with HCV infection without CV. HCV load, cryoglobulins, and cytokines were quantified by flow cytometry, cytokine multiplex assays, and enzyme-linked immunosorbent assay.

RESULTS

Twenty-four patients (88.9%) had a complete clinical response of CV to DAA therapy at week 24, defined by improvement of all the affected organs and the absence of relapse. Compared with healthy donors and patients with HCV infection without CV, patients with HCV-CV, before DAA therapy, had a lower percentage of CD4+CD25hiFoxP3+ regulatory T cells (P < .01), but higher proportions of IgM+CD21-/low memory B cells (P < .05), CD4+IFNγ+ cells (P < .01), CD4+IL17A+ cells (P < .01), and CD4+CXCR5+interleukin 21+ follicular T-helper (Tfh) cells (P < .01). In patients with HCV-CV, there was a negative correlation between numbers of IgM+CD21-/low memory B cells and T-regulatory cells (P = .03), and positive correlations with numbers of Tfh cells (P = .03) and serum levels of cryoglobulin (P = .01). DAA therapy increased patients' numbers of T-regulatory cells (1.5% ± 0.18% before therapy vs 2.1% ± 0.18% after therapy), decreased percentages of IgM+CD21-/low memory B cells (35.7% ± 6.1% before therapy vs 14.9% ± 3.8% after therapy), and decreased numbers of Tfh cells (12% ± 1.3% before therapy vs 8% ± 0.9% after therapy). Expression levels of B lymphocyte stimulator receptor 3 and programmed cell death 1 on B cells increased in patients with HCV-CV after DAA-based therapy (mean fluorescence units, 37 ± 2.4 before therapy vs 47 ± 2.6 after therapy, P < .01; and 29 ± 7.3 before therapy vs 48 ± 9.3 after therapy, P < .05, respectively).

CONCLUSIONS

In a prospective clinical trial of patients with HCV-CV, DAA-based therapy restored disturbances in peripheral B- and T-cell homeostasis.

Regulatory T Cell and Forkhead Box Protein 3 as Modulators of Immune Homeostasis

The transcription factor forkhead box protein 3 (FOXP3) is an essential molecular marker of regulatory T cell (Treg) development in different microenvironments. Tregs are cells specialized in the suppression of inadequate immune responses and the maintenance of homeostatic tolerance. Studies have addressed and elucidated the role played by FOXP3 and Treg in countless autoimmune and infectious diseases as well as in more specific cases, such as cancer. Within this context, the present article reviews aspects of the immunoregulatory profile of FOXP3 and Treg in the management of immune homeostasis, including issues relating to pathology as well as immune tolerance.

Hepatitis B reactivation during or after direct acting antiviral therapy - implication for susceptible individuals

INTRODUCTION

The FDA issued a warning following 24 cases of HBV reactivation during DAA therapy for HCV, including individuals with inactive, occult and past HBV infection. Clinical presentations ranged from asymptomatic fluctuations in HBV DNA to fulminant hepatic failure, liver transplantation and death. The mechanism is unknown. Areas covered: HCV/HBV coinfection is common, particularly in regions endemic for HBV. HCV and HBV utilize host factors to support replication; both viruses evade/impair host immunity. Clinical presentations of HBV reactivation during DAAs are summarized. Other causes of HBV reactivation are revisited and recent data regarding HBV reactivation are presented. Expert opinion: HBV reactivation during DAAs for HCV occurs, with life-threatening consequences in some individuals. The risk of HBV reactivation is observed in all HBV stages. The rapid removal of HCV likely alters and liberates host-viral ± viral-viral interactions that lead to increased HBV replication. As immune reconstitution occurs with HCV removal, host recognition of HBV DNA likely ensues followed by vigorous host immune responses leading to liver injury (HBV flare). These cases highlight the importance of HBV testing prior to initiating DAA therapy, the need for close monitoring of HBV during therapy and timely administration of anti-HBV therapy to prevent serious sequelae.

Immune modulation by the hepatitis C virus core protein

Hepatitis C virus (HCV) infection is currently the most important cause of chronic viral hepatitis in the world and one of the most frequent indications for liver transplantation. HCV uses different strategies to evade the innate and adaptive immune response, and this evasion plays a key role in determining viral persistence. Several HCV viral proteins have been described as immune modulators. In this review, we will focus on the effect of HCV nucleocapsid core protein in the function of immune cells and its correlation with the findings observed in HCV chronically infected patients. Effects on immune cell function related to both extracellular and intracellular HCV core localization will be considered. This review provides an updated perspective on the mechanisms involved in HCV evasion related to one single HCV protein, which could become a key tool in the development of new antiviral strategies able to control and/or eradicate HCV infection.

Regulatory T Cells in Hepatitis B and C Virus Infections

Hepatitis B virus (HBV) and hepatitis C virus (HCV) are hepatotropic viruses that establish chronic persistent infection by effectively escaping the host immune response and can cause immune-mediated liver injury. It has recently become apparent that regulatory T (Treg) cells, specifically CD4+CD25+Foxp3+ Treg cells, modulate viral diseases by suppressing antiviral immune responses and regulating inflammatory host injury. The roles of Treg cells in HBV and HCV infections range from suppressing antiviral T cell responses to protecting the liver from immune-mediated damage. This review describes Treg cells and subpopulations and focuses on the roles of these cells in HBV and HCV infections.

A Mouse Model of Chronic West Nile Virus Disease

Infection with West Nile virus (WNV) leads to a range of disease outcomes, including chronic infection, though lack of a robust mouse model of chronic WNV infection has precluded identification of the immune events contributing to persistent infection. Using the Collaborative Cross, a population of recombinant inbred mouse strains with high levels of standing genetic variation, we have identified a mouse model of persistent WNV disease, with persistence of viral loads within the brain. Compared to lines exhibiting no disease or marked disease, the F1 cross CC(032x013)F1 displays a strong immunoregulatory signature upon infection that correlates with restraint of the WNV-directed cytolytic response. We hypothesize that this regulatory T cell response sufficiently restrains the immune response such that a chronic infection can be maintained in the CNS. Use of this new mouse model of chronic neuroinvasive virus will be critical in developing improved strategies to prevent prolonged disease in humans.

Association between IL28B rs12979860 single nucleotide polymorphism and the frequency of colonic Treg in chronically HCV-infected patients

The IL28B gene is associated with spontaneous or treatment-induced HCV viral clearance. However, the mechanism by which the IL28B single nucleotide polymorphism (SNP) affects the extra-hepatic HCV immune responses and its relationship to HCV pathogenesis have not been thoroughly investigated. To examine the mechanism by which IL28B affects HCV clearance. Forty Egyptian patients with chronic HCV infection receiving an Interferon/ribavirin treatment regimen were enrolled into this study. There were two groups: non-responders (NR; n = 20) and sustained virologic responders (SVR; n = 20). The initial plasma HCV viral loads prior to treatment and IL28B genotypes were determined by quantitative RT-PCR and sequencing, respectively. Liver biopsies were examined to determine the inflammatory score and the stage of fibrosis. Colonic regulatory T cell (Treg) frequency was estimated by immunohistochemistry. No significant association between IL28B genotypes and response to therapy was identified, despite an odds ratio of 3.4 to have the TT genotype in NR compared to SVR (95 % confidence interval 0.3-35.3, p = 0.3). Patients with the TT-IL28Brs12979860 genotype (unfavorable genotype) have significantly higher frequencies of colonic Treg compared to the CT (p = 0.04) and CC (p = 0.03) genotypes. The frequency of colonic Treg cells in HCV-infected patients had a strong association with the IL-28B genotype and may have a significant impact on HCV clearance.

Intrahepatic mRNA Expression of FAS, FASL, and FOXP3 Genes Is Associated with the Pathophysiology of Chronic HCV Infection

This study aimed to evaluate the relative mRNA expression of Fas receptor (FAS), Fas ligand (FASL), and forkhead box protein 3 (FOXP3) in liver biopsy specimens obtained from patients with viral and non-viral chronic hepatitis and correlate their expression with the fibrosis stage. A total of 51 liver biopsy specimens obtained from HBV (n = 6), HCV (n = 28), and non-viral hepatic disease (NVHD) (n = 9) patients and from individuals with normal liver histology (n = 8) (control—CT) were analyzed. Quantifications of the target genes were assessed using qPCR, and liver biopsies according to the METAVIR classification. The mRNA expression levels of FAS and FASL were lower in the CT group compared to the groups of patients. The increase in the mRNA expression of FAS and FASL was correlated with higher levels of inflammation and disease progression, followed by a decline in tissues with cirrhosis, and it was also associated with increased levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Higher mRNA expression of FOXP3 was observed in the HCV and NVHD groups, with the peak observed among patients with cirrhosis. The increased FOXP3 mRNA expression was positively correlated with increased FAS and FASL mRNA expression and the AST and ALT levels in all patients. Conclusions: These results suggest that regardless of the cause, the course of chronic liver disease may be modulated by the analyzed genes and correlated with an increase in regulatory T cells during the liver damage followed by hepatocyte destruction by Fas/FasL system and subsequent non specific lymphocytic infiltrate accumulation.

Dynamic changes in CD45RA(-)Foxp3(high) regulatory T-cells in chronic hepatitis C patients during antiviral therapy

OBJECTIVES

CD4(+)Foxp3(+) regulatory T-cells (Treg) are known to accumulate under certain pathological conditions. This study was conducted to evaluate the characteristics of and dynamic changes in Treg cells in chronic hepatitis C (CHC) patients during antiviral therapy.

METHODS

One hundred and forty-five subjects were enrolled in this study, including 105 CHC patients and 40 healthy donors. The phenotypes and functions of Treg cells were analyzed by flow cytometry.

RESULTS

A significant elevation in Treg cells was observed in the peripheral blood of CHC patients compared with healthy donors. Interestingly, compared with non-suppressive Treg (non-Treg) and resting Treg (rTreg) cells, activated Treg (aTreg) cells expressed higher levels of ectonucleotidase, CD39, and CD73. After treatment with interferon alpha (IFN-α) and ribavirin (RBV) in vitro, the frequencies of total Treg cells and aTreg cells in peripheral blood mononuclear cells (PBMC), as well as the levels of transforming growth factor beta (TGF-β) secreted by aTreg and non-Treg cells, were significantly decreased. Importantly, it was found that levels of aTreg cells in patients with a sustained virological response (SVR) were lower than in relapsed patients, suggesting that a high frequency of aTreg cells might be associated with a poor clinical outcome in HCV infection.

CONCLUSION

These results demonstrate a decreasing trend in aTreg cells, which express higher levels of CD39, CD73, and TGF-β, in SVR patients during antiviral therapy.

Cellular immune response to hepatitis-C-virus in subjects without viremia or seroconversion: is it important?

Hepatitis C Virus (HCV) causes chronic infection and represents a global health burden. To date, there is no licensed vaccine for HCV. The high viral replication rate and the existence of several HCV genotypes and quasispecies hamper the development of an effective universal vaccine. In this regard, the current HCV vaccine candidates show genotype-specific protection or narrow cross reactivity against other genotypes. Importantly, HCV spontaneous clearance occurs in 15-50 % of infected subjects, indicating that natural resistance to chronic infection exists. This phenomenon was demonstrated among humans and chimpanzees and continues to motivate researchers attempting to develop an effective HCV vaccine. However, what constitutes a protective immune response or correlate of protection against HCV infection is still vague. Additionally, the mechanisms behind successful HCV clearance suggest the coordination of several arms of the immune system, with cell-mediated immunity (CMI) playing a crucial role in this process. By contrast, although neutralizing antibodies have been identified, they are isolate-specific and poorly correlate with viral clearance. Antigen-specific CD4 T cells, instead, correlate with transient decline in HCV viremia and long-lasting control of the infection. Unfortunately, HCV has been very successful in evading host immune mechanisms, leading to complications such as liver fibrosis, cirrhosis and hepatocellular carcinoma. Interestingly, CMI to HCV antigens were shown among exposed individuals without viremia or seroconversion, suggesting the clearance of prior HCV infection(s). These individuals include family members living with HCV-infected subjects, healthcare workers, IV drug users, and sexual contacts. The correlates of protection could be closely monitored among these individuals. This review provides a summary of HCV-specific immune responses in general and of CMI in particular in these cohorts. The importance of these CMI responses are discussed.

Immunopathogenesis of Hepatitis C Virus Infection

Despite advances in therapy, hepatitis C virus infection remains a major global health issue with 3 to 4 million incident cases and 170 million prevalent chronic infections. Complex, partially understood, host-virus interactions determine whether an acute infection with hepatitis C resolves, as occurs in approximately 30% of cases, or generates a persistent hepatic infection, as occurs in the remainder. Once chronic infection is established, the velocity of hepatocyte injury and resultant fibrosis is significantly modulated by immunologic as well as environmental factors. Immunomodulation has been the backbone of antiviral therapy despite poor understanding of its mechanism of action.

Role of regulatory T-cells during hepatitis C infection: From the acute phase to post-transplantation recurrence

Hepatitis C viral infection persists and becomes chronic in a majority of affected individuals. Numerous factors have been described to explain how the virus manages to escape the host immune system. One important escape mechanism is the increase in regulatory T cells induced by the virus. In this review, we will focus on the status of regulatory T cells throughout the natural history of hepatitis C infection and after liver transplantation. The molecular mechanisms involved in increasing the number of regulatory T cells are also discussed, as are data regarding the impact of regulatory T-cells on hepatic fibrosis in the context of hepatitis C viral infection.

Association of colonic regulatory T cells with hepatitis C virus pathogenesis and liver pathology

BACKGROUND AND AIM

Forkhead box protein P3 (FoxP3)(+) regulatory T (Treg ) cells play a fundamental role in maintaining the balance between the tissue-damaging and protective immune response to chronic hepatitis C (CHC) infection. Herein, we investigated the frequency of Treg cells in the colon and their potential relationship to the various CHC outcomes and hepatic histopathology.

METHODS

Colonic biopsies were collected from three groups with CHC: treatment naïve (TN; n = 20), non-responders (NR; n = 20), sustained virologic response (SVR; n = 20), and a fourth healthy control group (n = 10). The plasma viral loads and cytokines levels were determined by quantitative real-time polymerase chain reaction, and ELISA, respectively. Liver biopsies were examined to assess inflammatory score and fibrosis stage. Colonic Treg frequency was estimated by immunohistochemistry using confocal microscopy.

RESULTS

A significant increase in the frequency of colonic Treg was found in TN, and NR groups compared with the control and SVR group. The frequency of colonic Treg , plasma interleukin (IL)-10 and IL-4 levels were significantly positively correlated with viral load and negatively correlated with METAVIR inflammatory score, and fibrosis stages.

CONCLUSION

Colonic Treg cells are negatively correlated with liver inflammation and hepatitis C virus (HCV) viral load, which suggests a strong linkage between gut-derived Treg cell populations and HCV infection.

Virus-Specific Cellular Response in Hepatitis C Virus Infection

Studies performed on chimpanzees and humans have revealed that strong, multispecific and sustained CD4(+) and CD8(+) T cell immune responses is a major determinant of hepatitis C virus (HCV) clearance. However, spontaneous elimination of the virus occurs in minority of infected individuals and cellular response directed against HCV antigens is not persistent in individuals with chronic infection. This review presents characteristics of the HCV-specific T cell response in patients with different clinical course of infection, including acute and chronic infection, persons who spontaneously eliminated HCV and non-infected subjects exposed to HCV. Detection of HCV-specific response, especially in non-infected subjects exposed to HCV, may be indicative of HCV prevalence in population and rate of spontaneous viral clearance. Understanding the mechanisms and role of HCV-specific cellular immune response would contribute to better understanding of HCV epidemiology, immunopathogenesis and may help to design an effective vaccine.

Is toxoplasmosis a potential risk factor for liver cirrhosis?

OBJECTIVE

To document Toxoplasma gondii (T. gondii) antibody status in patients with liver disease, blood samples were taken from 180 hepatic patients and 180 healthy controls.

METHODS

Toxoplasma IgG antibody was detected using enzyme-linked immunosorbent assay and histopathological assessment of liver biopsy METAVIR score was applied.

RESULTS

Anti-T. gondii IgG antibodies were found in 32.8% of patients and in 22.2% of controls (P = 0.02). Toxoplasma seropositivity was significantly associated with lymphadenopathy, history of blood transfusion and reflex impairment in patients. Chronic hepatitis C virus (HCV) and chronic HCV-related cirrhosis groups compared to chronic HBV and chronic HBV-related cirrhosis groups expressed significantly higher prevalence of T. gondii seropositivity (odds ratio (OR) = 4; 95% confidence interval (CI): 1.3-12.6; P = 0.013, OR = 4.8; 95% CI: 1.5-14.9; P = 0.006, respectively). Within the chronic HCV group, T. gondii seropositivity significantly associated disease evolution as regards to METAVIR histopathological system for fibrosis and inflammation (OR = 19.4; 95% CI: 2.3-165.2; P = 0.0008, OR = 0.29; 95% CI: 0.1-0.8; P = 0.01, respectively). Albumin, international normalized ratio (INR) and platelets count were the laboratory parameters significantly altered in Toxoplasma-positive chronic HCV patients (P = 0.001, 0.03, 0.04, respectively). Child-Pugh scoring for cirrhosis in chronic HCV group placed the majority of seropositive patient in class C with significant statistical difference compared to Child A reference group (OR = 0.08; 95% CI: 0.01-0.5; P = 0.003).

CONCLUSIONS

Toxoplasma seropositivity was high in patients with cirrhosis and associated higher grades of inflammation and necrosis signifying disease evolution, suggesting that cirrhotic patients may thus form a risk group for toxoplasmosis.

The Immune Fulcrum: Regulatory T Cells Tip the Balance Between Pro- and Anti-inflammatory Outcomes upon Infection

Regulatory T cells (Tregs) are indispensable for immune homeostasis and the prevention of autoimmunity. In the context of infectious diseases, Tregs are multidimensional. Here, we describe how they may potentiate effector responses by assisting in recruitment of T cells into the infection site to resolve infection, facilitate accelerated antigen-specific memory responses, limit pathology, and contribute to disease resolution and healing, to the great benefit of the host. We also explore the villainous functions of Tregs during infection by reviewing several diseases in which the depletion or reduction in Treg frequency allows for better generation of effector memory, and results in acute resolution of infection, as opposed to chronicity or severe long-term outcomes. We describe findings generated using mouse models of infection as well as experiments performed using human cells and tissues. We propose that Tregs represent an immunologic fulcrum, promoting both pathogen clearance and damage control by preventing excessive destruction of infected tissues though unchecked immune responses.

Effect of Salmonella infection on cecal tonsil regulatory T cell properties in chickens

Two studies were conducted to study regulatory T cell [Treg (CD4⁺CD25⁺)] properties during the establishment of a persistent intestinal infection in broiler chickens. Four-day-old broiler chicks were orally gavaged with 5 × 10⁶ CFU/mL Salmonella enteritidis (S. enteritidis) or sterile PBS (control). Samples were collected at 4, 7, 10, and 14 d postinfection. There was a significant (P < 0.05) increase in the number of CD4⁺CD25⁺ cells by d 4 postinfection that increased steadily throughout the course of the 14-d infection, whereas the number of CD4⁺CD25⁺ cells in the noninfected controls remained steady throughout the study. CD4⁺CD25⁺ cells from cecal tonsils of S. enteritidis-infected birds had a higher (P < 0.05) IL-10 mRNA content than CD4⁺CD25⁺ cells from the noninfected controls at all time-points studied. The amount of IL-2 mRNA content in the cecal tonsil CD4⁺CD25⁻ cells from the infected birds did not differ (P > 0.05) when compared to that of noninfected control birds. At a lower effector/responder cell ratio of 0.25:1, CD4⁺CD25⁺ cells from cecal tonsils of Salmonella-infected birds suppressed T cell proliferation at d 7 and 14 post-S. enteritidis infection, while CD4⁺CD25⁺ cells from noninfected control groups did not suppress T cell proliferation. In the second studu, 1-day-old chickens were orally gavaged with PBS (control) or 1.25 × 10⁸ CFU/bird S. enteritidis. At 7 and 21 d post-Salmonella infection, CD25⁺ cells collected from cecal tonsils of S. enteritidis-infected birds and restimulated in vitro with Salmonella antigen had higher (P < 0.05) IL-10 mRNA content compared to those in the control group. Spleen CD4⁺CD25⁺, CD4⁺, and CD8⁺ cell percentage did not differ (P > 0.05) between the Salmonella-infected and control birds. In conclusion, a persistent intestinal S. enteritidis infection increased the Treg percentage, suppressive properties, and IL-10 mRNA amounts in the cecal tonsils of broiler birds.

STIM1 controls T cell-mediated immune regulation and inflammation in chronic infection

Chronic infections induce a complex immune response that controls pathogen replication, but also causes pathology due to sustained inflammation. Ca2+ influx mediates T cell function and immunity to infection, and patients with inherited mutations in the gene encoding the Ca2+ channel ORAI1 or its activator stromal interaction molecule 1 (STIM1) are immunodeficient and prone to chronic infection by various pathogens, including Mycobacterium tuberculosis (Mtb). Here, we demonstrate that STIM1 is required for T cell-mediated immune regulation during chronic Mtb infection. Compared with WT animals, mice with T cell-specific Stim1 deletion died prematurely during the chronic phase of infection and had increased bacterial burdens and severe pulmonary inflammation, with increased myeloid and lymphoid cell infiltration. Although STIM1-deficient T cells exhibited markedly reduced IFN-γ production during the early phase of Mtb infection, bacterial growth was not immediately exacerbated. During the chronic phase, however, STIM1-deficient T cells displayed enhanced IFN-γ production in response to elevated levels of IL-12 and IL-18. The lack of STIM1 in T cells was associated with impaired activation-induced cell death upon repeated TCR engagement and pulmonary lymphocytosis and hyperinflammation in Mtb-infected mice. Chronically Mtb-infected, STIM1-deficient mice had reduced levels of inducible regulatory T cells (iTregs) due to a T cell-intrinsic requirement for STIM1 in iTreg differentiation and excessive production of IFN-γ and IL-12, which suppress iTreg differentiation and maintenance. Thus, STIM1 controls multiple aspects of T cell-mediated immune regulation to limit injurious inflammation during chronic infection.

F protein increases CD4+CD25+ T cell population in patients with chronic hepatitis C

HCV is a global health problem with an estimated 230 million chronically infected people worldwide. It has been reported that a 17-kd protein translated from core-encoding genomic region can contribute to immune-mediated mechanisms associated with the development of the chronic disease. Also, Treg cells can be contributed to an inadequate response against the viruses, leading to chronic infection. Here we evaluated the ability of protein F to modulate the frequency of CD4+CD25+FoxP3+T and IL-10+T cells in patients with chronic HCV infection. F gene was amplified and cloned in the expression vector. The protein was purified and used for stimulation of PBMCs in the HCV chronic patients and the control groups. The frequency of CD4+CD25+FoxP3+ T cell-like populations and IL-10-producing CD4+CD25+ T cells was assessed in the HCV-infected patients and in the healthy controls by flow cytometry, which showed an increase of both CD4+CD25+FoxP3+ T cell-like population and IL-10-producing CD4+CD25+ T cells in the HCV-infected patients positive for anti-F antibody. Our results suggest the potential involvement of F and core antigens in increasing the frequency of CD4+CD25+FoxP3+ T cell-like population and IL-10-producing CD4+CD25+ T cells which may be associated with HCV-persistent infection.

Schistosome infection aggravates HCV-related liver disease and induces changes in the regulatory T-cell phenotype

Schistosome infections are renowned for their ability to induce regulatory networks such as regulatory T cells (Treg) that control immune responses against homologous and heterologous antigens such as allergies. However, in the case of co-infections with hepatitis C virus (HCV), schistosomes accentuate disease progression and we hypothesized that expanding schistosome-induced Treg populations change their phenotype and could thereby suppress beneficial anti-HCV responses. We therefore analysed effector T cells and n/iTreg subsets applying the markers Granzyme B (GrzB) and Helios in Egyptian cohorts of HCV mono-infected (HCV), schistosome-co-infected (Sm/HCV) and infection-free individuals. Interestingly, viral load and liver transaminases were significantly elevated in Sm/HCV individuals when compared to HCV patients. Moreover, overall Treg frequencies and Helios(pos) Treg were not elevated in Sm/HCV individuals, but frequencies of GrzB(+) Treg were significantly increased. Simultaneously, GrzB(+) CD8(+) T cells were not suppressed in co-infected individuals. This study demonstrates that in Sm/HCV co-infected cohorts, liver disease is aggravated with enhanced virus replication and Treg do not expand but rather change their phenotype with GrzB possibly being a more reliable marker than Helios for iTreg. Therefore, curing concurrent schistosome disease could be an important prerequisite for successful HCV treatment as co-infected individuals respond poorly to interferon therapy.

Indoleamine 2,3-dioxygenase expression and activity in patients with hepatitis C virus-induced liver cirrhosis

Indoleamine 2,3-dioxygenase (IDO) is an immunoregulatory enzyme. It plays a key role in various malignancies, infection and autoimmune diseases. IDO induces immunosuppression through the depletion of tryptophan and its downstream metabolites. Hepatitis C virus (HCV) has infected more than 12 million individuals in Pakistan. The aim of the present study was to assess the expression and activity of IDO in HCV-infected patients. The functional enzymatic activity of IDO was measured by colorimetric assay. Serum samples from 100 HCV-infected patients were taken to examine IDO activity and samples from 100 healthy volunteers were used as controls. Liver sections from patients with HCV (n=35) and healthy controls (n=5) were used for immunohistochemical studies. Immunohistochemical analysis revealed that IDO was overexpressed in 28 of 35 (80%) cirrhotic liver samples, whereas 5 of 35 (14.2%) cases presented moderate and 2 of 35 (5.7%) cases presented mild expression of IDO. The enzymatic activity of IDO was significantly higher in the serum samples of HCV-infected patients as compared with those in the control. These data indicate that the expression of IDO correlated with the pathogenesis of disease. In summary, it is suggested that the high expression of IDO in the progressively cirrhotic livers of HCV-infected patients might contribute to the development of hepatocellular carcinoma. IDO may characterize a novel therapeutic target against HCV.

Control of the inflammatory response mechanisms mediated by natural and induced regulatory T-cells in HCV-, HTLV-1-, and EBV-associated cancers

Virus infections are involved in chronic inflammation and, in some cases, cancer development. Although a viral infection activates the immune system's response that eradicates the pathogen mainly through inflammatory mechanisms, it is now recognized that this inflammatory condition is also favorable to the development of tumors. Indeed, it is well described that viruses, such as hepatitis C virus (HCV), Epstein Barr virus (EBV), human papillomavirus (HPV) or human T-cell lymphotropic virus type-1 (HTLV-1), are important risk factors for tumor malignancies. The inflammatory response is a fundamental immune mechanism which involves several molecular and cellular components consisting of cytokines and chemokines that are released by various proinflammatory cells. In parallel to this process, some endogenous recruited components release anti-inflammatory mediators to restore homeostasis. The development of tools and strategies using viruses to hijack the immune response is mostly linked to the presence of regulatory T-cells (Treg) that can inhibit inflammation and antiviral responses of other effector cells. In this review, we will focus on current understanding of the role of natural and induced Treg in the control and the resolution of inflammatory response in HCV-, HTLV-1-, and EBV-associated cancers.

Regulatory T-cell homeostasis: steady-state maintenance and modulation during inflammation

Regulatory T (Treg) cells play a vital role in the prevention of autoimmunity and the maintenance of self-tolerance, but these cells also have an active role in inhibiting immune responses during viral, bacterial, and parasitic infections. Although excessive Treg activity can lead to immunodeficiency, chronic infection, and cancer, too little Treg activity results in autoimmunity and immunopathology and impairs the quality of pathogen-specific responses. Recent studies have helped define the homeostatic mechanisms that support the diverse pool of peripheral Treg cells under steady-state conditions and delineate how the abundance and function of Treg cells changes during inflammation. These findings are highly relevant for developing effective strategies to manipulate Treg cell activity to promote allograft tolerance and treat autoimmunity, chronic infection, and cancer.

Smarter vaccine design will circumvent regulatory T cell-mediated evasion in chronic HIV and HCV infection

Despite years of research, vaccines against HIV and HCV are not yet available, due largely to effective viral immunoevasive mechanisms. A novel escape mechanism observed in viruses that cause chronic infection is suppression of viral-specific effector CD4(+) and CD8(+) T cells by stimulating regulatory T cells (Tregs) educated on host sequences during tolerance induction. Viral class II MHC epitopes that share a T cell receptor (TCR)-face with host epitopes may activate Tregs capable of suppressing protective responses. We designed an immunoinformatic algorithm, JanusMatrix, to identify such epitopes and discovered that among human-host viruses, chronic viruses appear more human-like than viruses that cause acute infection. Furthermore, an HCV epitope that activates Tregs in chronically infected patients, but not clearers, shares a TCR-face with numerous human sequences. To boost weak CD4(+) T cell responses associated with persistent infection, vaccines for HIV and HCV must circumvent potential Treg activation that can handicap efficacy. Epitope-driven approaches to vaccine design that involve careful consideration of the T cell subsets primed during immunization will advance HIV and HCV vaccine development.

Contradictory immune response in post liver transplantation hepatitis B and C

Hepatitis B and C often progress to decompensated liver cirrhosis requiring orthotopic liver transplantation (OLT). After OLT, hepatitis B recurrence is clinically controlled with a combination of hepatitis B immunoglobulin (HBIG) and nucleos(t)ide analogues. Another approach is to induce self-producing anti-hepatitis B virus (HBV) antibodies using a HBV envelope antigen vaccine. Patients who had not been HBV carriers such as acutely infected liver failure or who received liver from HBV self-limited donor are good candidate. For chronic HBV carrier patients, a successful response can only be achieved in selected patients such as those treated with experimentally reduced immunosuppression protocols or received an anti-HBV adaptive memory carrying donor liver. Hepatitis C virus (HCV) reinfects transplanted livers at a rate of >90%. HCV reinfected patients show different severities of hepatitis, from mild and slowly progressing to severe and rapidly progressing, possibly resulting from different adaptive immune responses. More than half the patients require interferon treatment, although the success rate is low and carries risks for leukocytopenia and rejection. Managing the immune response has an important role in controlling recurrent hepatitis C. This study aimed to review the adaptive immune response in post-OLT hepatitis B and C.

Frequency of regulatory T-cell and hepatitis C viral antigen-specific immune response in recurrent hepatitis C after liver transplantation

INTRODUCTION

Regulatory T (Treg) and type 1 regulatory T (Tr1) cells facilitate hepatitis C virus (HCV) recurrence after orthotopic liver transplantation (OLT). However, their frequencies and effects on HCV-specific immune responses have not been well investigated.

METHODS

We determined Treg and Tr1 frequencies in OLT patients with hepatitis C and assessed their associations with HCV-specific T cell responses. These patients comprised the following groups: an early post-transplantation group (n=14); an OLT-chronic active hepatitis C group (n=14) with active hepatitis C (alanine aminotransferase of>upper limit of normal/positive for HCV-RNA); an OLT-persistently normal alanine aminotransferase group (n=12) without active hepatitis C (not interferon/positive for HCV-RNA); and an OLT-sustained viral response group (n=6) with sustained viral responses using interferon treatment (negative for HCV-RNA). The frequencies of HCV-specific CD4+ T cells that secreted interferon-γ were determined by enzyme-linked immunosorbent spot assay (except for the OLT early group).

RESULTS

Treg and Tr1 frequencies were low during the early post-transplantation period. OLT patients with sustained viral responses had lower Treg frequencies than those with chronic hepatitis C, whereas Tr1 frequencies were significantly reduced in OLT patients with persistently normal alanine aminotransferase levels compared to those with chronic hepatitis C (p<0.05). Treg frequencies positively correlated with HCV NS3 antigen-specific interferon-γ responses, which corresponded to HCV clearance.

CONCLUSIONS

Increased Treg frequencies and reduced HCV-NS3 antigen-specific responses recovered after viral eradication in post-OLT chronic hepatitis C patients. Reduced Tr1 frequencies were associated with hepatitis activity control, which may facilitate controlling chronic hepatitis C in patients after OLT.

Distinct and complementary roles for Aspergillus fumigatus-specific Tr1 and Foxp3+ regulatory T cells in humans and mice

Unlike induced Foxp3⁺ regulatory T cells (Foxp3⁺ iT_reg) that have been shown to play an essential role in the development of protective immunity to the ubiquitous mold Aspergillus fumigatus, type-(1)-regulatory T cells (Tr1) cells have, thus far, not been implicated in this process. Here, we evaluated the role of Tr1 cells specific for an epitope derived from the cell wall glucanase Crf-1 of A. fumigatus (Crf-1/p41) in antifungal immunity. We identified Crf-1/p41-specific latent-associated peptide⁺ Tr1 cells in healthy humans and mice after vaccination with Crf-1/p41+zymosan. These cells produced high amounts of interleukin (IL)-10 and suppressed the expansion of antigen-specific T cells in vitro and in vivo. In mice, in vivo differentiation of Tr1 cells was dependent on the presence of the aryl hydrocarbon receptor, c-Maf and IL-27. Moreover, in comparison to Tr1 cells, Foxp3⁺ iT_reg that recognize the same epitope were induced in an interferon gamma-type inflammatory environment and more potently suppressed innate immune cell activities. Overall, our data show that Tr1 cells are involved in the maintenance of antifungal immune homeostasis, and most likely play a distinct, yet complementary, role compared with Foxp3⁺ iT_reg.

Hepatic immune regulation and its involvement in viral hepatitis infection

The liver has unique immune regulatory functions that promote the induction of tolerance rather than responses to antigens encountered locally. These functions are mediated by local expression of coinhibitory receptors and immunosuppressive mediators that help prevent overwhelming tissue damage. Over the years, we have gained more insight into the local regulatory cues that determine the functional complexity of immune responses regulated locally in the liver. Both the unique hepatic microenvironment and the particular liver sinusoidal cell populations, in addition to hepatocytes, actively modulate immune responses locally in the liver and thereby determine the outcome of hepatic immune responses. This is of high biological and clinical relevance in hepatitis B virus and hepatitis C virus infections, which can cause acute and persistent infections associated with chronic inflammation in humans that eventually progress to cirrhosis and hepatocellular carcinoma. Here, we review current knowledge about the balance between immunity and tolerance in the liver and how this may affect our understanding of the determinants of hepatitis B virus and hepatitis C virus clearance, persistence, and virus-induced liver disease.

Type I interferons directly inhibit regulatory T cells to allow optimal antiviral T cell responses during acute LCMV infection

Inhibition of T reg cells by type I IFNs is necessary for the generation of optimal antiviral T cell responses during acute LCMV infection.

Regulatory T (T reg) cells play an essential role in preventing autoimmunity but can also impair clearance of foreign pathogens. Paradoxically, signals known to promote T reg cell function are abundant during infection and could inappropriately enhance T reg cell activity. How T reg cell function is restrained during infection to allow the generation of effective antiviral responses remains largely unclear. We demonstrate that the potent antiviral type I interferons (IFNs) directly inhibit co-stimulation–dependent T reg cell activation and proliferation, both in vitro and in vivo during acute infection with lymphocytic choriomeningitis virus (LCMV). Loss of the type I IFN receptor specifically in T reg cells results in functional impairment of virus-specific CD8⁺ and CD4⁺ T cells and inefficient viral clearance. Together, these data demonstrate that inhibition of T reg cells by IFNs is necessary for the generation of optimal antiviral T cell responses during acute LCMV infection.

CD4+ primary T cells expressing HCV-core protein upregulate Foxp3 and IL-10, suppressing CD4 and CD8 T cells

Adaptive T cell responses are critical for controlling HCV infection. While there is clinical evidence of a relevant role for regulatory T cells in chronic HCV-infected patients, based on their increased number and function; mechanisms underlying such a phenomena are still poorly understood. Accumulating evidence suggests that proteins from Hepatitis C virus can suppress host immune responses. We and others have shown that HCV is present in CD4+ lymphocytes from chronically infected patients and that HCV-core protein induces a state of unresponsiveness in the CD4+ tumor cell line Jurkat. Here we show that CD4+ primary T cells lentivirally transduced with HCV-core, not only acquire an anergic phenotype but also inhibit IL-2 production and proliferation of bystander CD4+ or CD8+ T cells in response to anti-CD3 plus anti-CD28 stimulation. Core-transduced CD4+ T cells show a phenotype characterized by an increased basal secretion of the regulatory cytokine IL-10, a decreased IFN-γ production upon stimulation, as well as expression of regulatory T cell markers, CTLA-4, and Foxp3. A significant induction of CD4+CD25+CD127(low)PD-1(high)TIM-3(high) regulatory T cells with an exhausted phenotype was also observed. Moreover, CCR7 expression decreased in HCV-core expressing CD4+ T cells explaining their sequestration in inflamed tissues such as the infected liver. This work provides a new perspective on de novo generation of regulatory CD4+ T cells in the periphery, induced by the expression of a single viral protein.

HCV-specific immune responses induced by CIGB-230 in combination with IFN-α plus ribavirin

AIM: To analyze hepatitis C virus (HCV)-specific immune responses in chronically infected patients under triple therapy with interferon-α (IFN-α) plus ribavirin and CIGB-230.

METHODS: CIGB-230 was administered in different schedules with respect to IFN-α plus ribavirin therapy. Paired serum and peripheral blood mononuclear cells (PBMC) samples from baseline and end of treatment were analyzed. The HCV-specific humoral response was tested by enzyme-linked immunosorbent assay, neutralizing antibodies were evaluated by cell culture HCV neutralization assays, PBMC proliferation was assayed by carboxyfluorescein succinimidyl ester staining and IFN-γ secretion was assessed by enzyme-linked immunospot. Data on virological and histological response and their association with immune variables are also provided.

RESULTS: From week 12 to week 48, all groups of patients showed a significant reduction in mean leukocyte counts. Statistically significant reductions in antibody titers were frequent, but only individuals immunized with CIGB-230 as early add-on treatment sustained the core-IgG response, and the neutralizing antibody response was enhanced only in patients receiving CIGB-230. Cell-mediated immune responses also tended to decline, but significant reductions in IFN-γ secretion and total absence of core-specific lymphoproliferation were exclusive of the control group. Only CIGB-230-immunized individuals showed de novo induced lymphoproliferative responses against the structural antigens. Importantly, it was demonstrated that the quality of the CIGB-230-induced immune response depended on the number of doses and timing of administration in relation to the antiviral therapy. Specifically, the administration of 6 doses of CIGB-230 as late add-on to therapy increased the neutralizing antibody activity and the de novo core-specific IFN-γ secretion, both of which were associated with the sustained virological response.

CONCLUSION: CIGB-230, combined with IFN-α-based therapy, modifies the immune response in chronic patients. The study provides evidence for the design of more effective therapeutic vaccine interventions against HCV.

An insight into the diagnosis and pathogenesis of hepatitis C virus infection

This review focuses on research findings in the area of diagnosis and pathogenesis of hepatitis C virus (HCV) infection over the last few decades. The information based on published literature provides an update on these two aspects of HCV. HCV infection, previously called blood transmitted non-A, non-B infection, is prevalent globally and poses a serious public health problem worldwide. The diagnosis of HCV infection has evolved from serodetection of non-specific and low avidity anti-HCV antibodies to detection of viral nucleic acid in serum using the polymerase chain reaction (PCR) technique. Current PCR assays detect viral nucleic acid with high accuracy and the exact copy number of viral particles. Moreover, multiplex assays using real-time PCR are available for identification of HCV-genotypes and their isotypes. In contrast to previous methods, the newly developed assays are not only fast and economic, but also resolve the problem of the window period as well as differentiate present from past infection. HCV is a non-cytopathic virus, thus, its pathogenesis is regulated by host immunity and metabolic changes including oxidative stress, insulin resistance and hepatic steatosis. Both innate and adaptive immunity play an important role in HCV pathogenesis. Cytotoxic lymphocytes demonstrate crucial activity during viral eradication or viral persistence and are influenced by viral proteins, HCV-quasispecies and several metabolic factors regulating liver metabolism. HCV pathogenesis is a very complex phenomenon and requires further study to determine the other factors involved.

Intrahepatic IL-8 producing Foxp3⁺CD4⁺ regulatory T cells and fibrogenesis in chronic hepatitis C

BACKGROUND & AIMS

Regulatory CD4(+) T cells (Tregs) are considered to affect outcomes of HCV infection, because they increase in number during chronic hepatitis C and can suppress T-cell functions.

METHODS

Using microarray analysis, in situ immunofluorescence, ELISA, and flowcytometry, we characterised functional differentiation and localisation of adaptive Tregs in patients with chronic hepatitis C.

RESULTS

We found substantial upregulation of IL-8 in Foxp3(+)CD4(+) Tregs from chronic hepatitis C. Activated GARP-positive IL-8(+) Tregs were particularly enriched in livers of patients with chronic hepatitis C in close proximity to areas of fibrosis and their numbers were correlated with the stage of fibrosis. Moreover, Tregs induced upregulation of profibrogenic markers TIMP1, MMP2, TGF-beta1, alpha-SMA, collagen, and CCL2 in primary human hepatic stellate cells (HSC). HSC activation, but not Treg suppressor function, was blocked by adding a neutralizing IL-8 antibody.

CONCLUSIONS

Our studies identified Foxp3(+)CD4(+) Tregs as an additional intrahepatic source of IL-8 in chronic hepatitis C acting on HSC. Thus, Foxp3(+)CD4(+) Tregs in chronic hepatitis C have acquired differentiation as regulators of fibrogenesis in addition to suppressing local immune responses.

CD4+ T-cell engagement by both wild-type and variant HCV peptides modulates the conversion of viral clearing helper T cells to Tregs

AIM

To determine whether modulation of T-cell responses by naturally occurring viral variants caused an increase in numbers of Tregs in HCV-infected patients.

PATIENTS MATERIALS & METHODS

Human peripheral blood mononuclear cells, having proliferative responses to a wild-type HCV-specific CD4⁺ T-cell epitope, were used to quantify, via proliferative assays, flow cytometry and class II tetramers, the effects of naturally occurring viral variants arising in the immunodominant epitope.

RESULTS

In combination, the wild-type and variant peptides led to enhanced suppression of an anti-HCV T-cell response. The variant had a lower avidity for the wild-type-specific CD4⁺ T cell. Variant-stimulated CD4⁺ T cells had increased Foxp3, compared with wild-type-stimulated cells.

CONCLUSION

A stable viral variant from a chronic HCV subject was able to induce Tregs in multiple individuals that responded to the wild-type HCV-specific CD4⁺ T-cell epitope.

Role of T cell immunity in hepatitis C virus infections

Chronic infections with the hepatitis C virus (HCV) are a major global health issue. Viral replication is restricted to hepatocytes, and occurs for decades at high replication rates. Over the last decade, it became accepted that HCV-specific CD4(+) and CD8(+) T cells are crucial for protective immunity to HCV. However, a characteristic feature of persistent HCV infection is the dysfunctional T cell response, and over recent years enormous progress has been made in understanding the mechanisms that dampen the antiviral T cell responses in blood and liver of chronic HCV patients and also impact disease progression.

Anti-inflammatory cytokines, pro-fibrogenic chemokines and persistence of acute HCV infection

Chemokines and cytokines play a vital role in directing and regulating immune responses to viral infections. Persistent hepatitis C virus (HCV) infection is characterized by the loss of anti-HCV cellular immune responses, while control of HCV infection is associated with maintenance of anti-HCV cellular immune responses. To determine whether plasma concentrations of 19 chemokines and cytokines controlling T-cell trafficking and function differed based on infection outcome, we compared them in at-risk subjects followed prospectively for HCV infection. Levels were compared over time in subjects who controlled HCV infection (Clearance) and subjects who developed persistent HCV infection (Persistence) at two time points during acute infection: (i) first viraemic sample (initial viraemia) and (ii) last viraemic sample in Clearance subjects and time-matched samples in Persistence subjects. At initial viraemia, increased pro-inflammatory tumour necrosis factor α (TNFα) plasma concentrations were observed in the Clearance group, while the plasma levels of anti-inflammatory interleukin (IL)-2, IL-10 and IL-13 were higher in the Persistence group. IL-13 was positively correlated with IL-2 and IL-10 at initial viraemia in the Persistence group. At the time of last viraemia, plasma levels of eotaxin, macrophage chemoattractant protein-4 (MCP-4), IL-5 and IL-10 were higher in the Persistence group and IL-10 and IL-5 levels were positively correlated. Collectively, these results suggest that the development of persistent infection is associated with an anti-inflammatory and pro-fibrogenic chemokine and cytokine profile that is evident at the onset of infection and maintained throughout acute infection.