Dynamic Changes in Ex Vivo T-Cell Function After Viral Clearance in Chronic HCV Infection

Hepatitis C Virus and the Host: A Mutual Endurance Leaving Indelible Scars in the Host's Immunity

Hepatitis C virus (HCV) has spread worldwide, and it is responsible for potentially severe chronic liver disease and primary liver cancer. Chronic infection remains for life if not spontaneously eliminated and viral persistence profoundly impairs the efficiency of the host's immunity. Attempts have been made to develop an effective vaccine, but efficacy trials have met with failure. The availability of highly efficacious direct-acting antivirals (DAA) has created hope for the progressive elimination of chronic HCV infections; however, this approach requires a monumental global effort. HCV elicits a prompt innate immune response in the host, characterized by a robust production of interferon-α (IFN-α), although interference in IFN-α signaling by HCV proteins may curb this effect. The late appearance of largely ineffective neutralizing antibodies and the progressive exhaustion of T cells, particularly CD8 T cells, result in the inability to eradicate the virus in most infected patients. Moreover, an HCV cure resulting from DAA treatment does not completely restore the normal immunologic homeostasis. Here, we discuss the main immunological features of immune responses to HCV and the epigenetic scars that chronic viral persistence leaves behind.

Immune Responses Following Locoregional Treatment for Hepatocellular Carcinoma: Possible Roles of Adjuvant Immunotherapy

Hepatocellular carcinoma (HCC) is a common cause of cancer-related deaths worldwide. Unlike other types of cancer, HCC can be treated with locoregional treatments (LRTs) such as radiofrequency ablation (RFA) or transarterial chemoembolization (TACE). However, recurrences following LRTs are common, and strategies to improve long-term outcomes need to be developed. The exhaustion of anti-tumor immunity in HCC has been well established in many reports and the immunomodulatory effects of LRTs (enhancement of tumor antigen-specific T cell responses after RFA, reduction of effector regulatory T cells after TACE) have also been reported in several previous studies. However, a comprehensive review of previous studies and the possible roles of immunotherapy following LRTs in HCC are not known. In this review, we discuss the immunological evidence of current clinical trials using LRTs and combined immunotherapies, and the possible role of this strategy.

Where to Next? Research Directions after the First Hepatitis C Vaccine Efficacy Trial

Thirty years after its discovery, the hepatitis C virus (HCV) remains a leading cause of liver disease worldwide. Given that many countries continue to experience high rates of transmission despite the availability of potent antiviral therapies, an effective vaccine is seen as critical for the elimination of HCV. The recent failure of the first vaccine efficacy trial for the prevention of chronic HCV confirmed suspicions that this virus will be a challenging vaccine target. Here, we examine the published data from this first efficacy trial along with the earlier clinical and pre-clinical studies of the vaccine candidate and then discuss three key research directions expected to be important in ongoing and future HCV vaccine development. These include the following: 1. design of novel immunogens that generate immune responses to genetically diverse HCV genotypes and subtypes, 2. strategies to elicit broadly neutralizing antibodies against envelope glycoproteins in addition to cytotoxic and helper T cell responses, and 3. consideration of the unique immunological status of individuals most at risk for HCV infection, including those who inject drugs, in vaccine platform development and early immunogenicity trials.

Partial restoration of immune response in Hepatitis C patients after viral clearance by direct-acting antiviral therapy

BACKGROUND & AIMS

HCV CD4+ and CD8+ specific T cells responses are functionally impaired during chronic hepatitis C infection. DAAs therapies eradicate HCV infection in more than 95% of treated patients. However, the impact of HCV elimination on immune responses remain controversial. Here, we aimed to investigate whether HCV cure by DAAs could reverse the impaired immune response to HCV.

METHODS

We analyzed 27 chronic HCV infected patients undergoing DAA treatment in tertiary care hospital, and we determined the phenotypical and functional changes in both HCV CD8+ and CD4+ specific T-cells before and after viral clearance. PD-1, TIM-3 and LAG-3 cell-surface expression was assessed by flow cytometry to determine CD4+ T cell exhaustion. Functional responses to HCV were analyzed by IFN-Ɣ ELISPOT, intracellular cytokine staining (IL-2 and IFN-Ɣ) and CFSE-based proliferation assays.

RESULTS

We observed a significant decrease in the expression of PD-1 in CD4+ T-cells after 12 weeks of viral clearance in non-cirrhotic patients (p = 0.033) and in treatment-naive patients (p = 0.010), indicating a partial CD4 phenotype restoration. IFN-Ɣ and IL-2 cytokines production by HCV-specific CD4+ and CD8+ T cells remained impaired upon HCV eradication. Finally, a significant increase of the proliferation capacity of both HCV CD4+ and CD8+ specific T-cells was observed after HCV elimination by DAAs therapies.

CONCLUSIONS

Our results show that in chronically infected patients HCV elimination by DAA treatment lead to partial reversion of CD4+ T cell exhaustion. Moreover, proliferative capacity of HCV-specific CD4+ and CD8+ T cells is recovered after DAA's therapies.

Immunological Mechanisms for Hepatocellular Carcinoma Risk after Direct-Acting Antiviral Treatment of Hepatitis C Virus Infection

Direct-acting antiviral agents (DAAs) that allow for rapid clearance of hepatitis C virus (HCV) may evoke immunological changes. Some cases of rapid de novo hepatocellular carcinoma (HCC) development or early recurrence of HCC after DAA treatment have been reported. During chronic HCV infection, natural killer (NK) cells exhibited a deviant functional phenotype with decreased production of antiviral cytokines and increased cytotoxicity; however, DAA treatment rapidly decreased their cytotoxic function. Effective DAA therapy also suppressed the intrahepatic activation of macrophages/monocytes. This was followed by a decrease in mucosal-associated invariant T (MAIT) cell cytotoxicity without normalization of cytokine production. Rapid changes in the phenotypes of NK and MAIT cells after DAA treatment may attenuate the cytotoxicity of these cells against cancer cells. Moreover, DAA treatment did not normalize the increased frequencies of regulatory T cells even after clearance of HCV infection. Thus, the persistently increased frequency of regulatory T cells may contribute to a local immunosuppressive milieu and hamper the clearance of cancer cells. This review will focus on recent studies describing the changes in innate and adaptive immune responses after DAA treatment in patients with chronic HCV infection in the context of de novo occurrence or recurrence of HCC.

Th1/Th2 Cells and Associated Cytokines in Acute Hepatitis E and Related Acute Liver Failure

Background and Aims

The involvement of cellular immunity in the development of hepatitis E virus (HEV) infection is rare. We aimed to study the roles of viral load and Th cell responses in acute hepatitis E (AHE) and HEV-related acute liver failure (HEV-ALF).

Methods

We evaluated viral load and Th1/Th2 cytokine levels in 34 patients with HEV infection, including 17 each with AHE or HEV-ALF. Seventeen healthy controls (HCs) were also included who were negative for anti-HEV IgM and IgG.

Results

There was no significant difference in viral load and HEV RNA in the AHE and HEV-ALF groups (both P > 0.05). The Th lymphocyte levels (CD3+, CD4+) in the AHE and HEV-ALF groups were significantly higher than those in the HC group (both P < 0.05), but there was no significant difference between the AHE and HEV-ALF groups (P > 0.05). Both IFN-γ and IL-10 showed gradual upward trend from the HC group to the AHE (both P < 0.01), but IFN-γ showed a sharp downward trend from the AHE group to the HEV-ALF group (P < 0.01) and IL-4 showed gradual upward trend from the AHE group to the HEV-ALF group (P < 0.01).There was no significant difference in Th1 and Th2 cytokines between the HEV RNA(+) group and HEV RNA(-) group (all P > 0.05). Th2 bias was observed from the AHE (ratio = 58.65) to HEV-ALF (ratio = 1.20) groups. The level of IFN-γ was associated with the outcome of HEV-ALF patients.

Conclusions

HEV viral load was not associated with aggravation of AHE, and the HEV-ALF patients showed significant Th2 bias, which may be involved in the aggravation of AHE.

Decrease of T-cells exhaustion markers programmed cell death-1 and T-cell immunoglobulin and mucin domain-containing protein 3 and plasma IL-10 levels after successful treatment of chronic hepatitis C

During chronic hepatitis C virus (HCV) infection, both CD4+ and CD8+ T-cells become functionally exhausted, which is reflected by increased expression of programmed cell death-1 (PD-1) and T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3), and elevated anti-inflammatory interleukin 10 (IL-10) plasma levels. We studied 76 DAA-treated HCV-positive patients and 18 non-infected controls. Flow cytometry measured pretreatment frequencies of CD4+PD-1+, CD4+PD-1+Tim-3+ and CD8+PD-1+Tim-3+ T-cells and IL-10 levels measured by ELISA were significantly higher and CD4+PD-1-Tim-3- and CD8+PD-1-Tim-3- T-cells were significantly lower in patients than in controls. Treatment resulted in significant decrease of CD4+Tim-3+, CD8+Tim-3+, CD4+PD-1+Tim-3+ and CD8+PD-1+Tim-3+ T-cell frequencies as well as IL-10 levels and increase in CD4+PD-1-Tim-3- and CD8+PD-1-Tim-3- T-cells. There were no significant changes in the frequencies of CD4+PD-1+ T-cells, while CD8+PD-1+ T-cells increased. Patients with advanced liver fibrosis had higher PD-1 and lower Tim-3 expression on CD4+T-cells and treatment had little or no effect on the exhaustion markers. HCV-specific CD8+T-cells frequency has declined significantly after treatment, but their PD-1 and Tim-3 expression did not change. Successful treatment of chronic hepatitis C with DAA is associated with reversal of immune exhaustion phenotype, but this effect is absent in patients with advanced liver fibrosis.

Reversal of T Cell Exhaustion in Chronic HCV Infection

The long-term consequences of T cell responses’ impairment in chronic HCV infection are not entirely characterized, although they may be essential in the context of the clinical course of infection, re-infection, treatment-mediated viral clearance and vaccine design. Furthermore, it is unclear whether a complete reinvigoration of HCV-specific T cell response may be feasible. In most studies, attempting to reverse the effects of compromised immune response quality by specific blockades of negative immune regulators, a restoration of functional competence of HCV-specific T cells was shown. This implies that HCV-induced immune dysfunction may be reversible. The advent of highly successful, direct-acting antiviral treatment (DAA) for chronic HCV infection instigated investigation whether the treatment-driven elimination of viral antigens restores T cell function. Most of studies demonstrated that DAA treatment may result in at least partial restoration of T cell immune function. They also suggest that a complete restoration comparable to that seen after spontaneous viral clearance may not be attained, pointing out that long-term antigenic stimulation imprints an irreversible change on the T cell compartment. Understanding the mechanisms of HCV-induced immune dysfunction and barriers to immune restoration following viral clearance is of utmost importance to diminish the possible long-term consequences of chronic HCV infection.

IFNL3-adjuvanted HCV DNA vaccine reduces regulatory T cell frequency and increases virus-specific T cell responses

BACKGROUND & AIMS

Although direct-acting antiviral (DAA) treatment results in a sustained virologic response (SVR) in most patients with chronic HCV infection, they are at risk of re-infection. Moreover, the immune system is not completely normalized even after SVR (e.g. increased regulatory T [Treg] cell frequency). We developed a DNA vaccine, GLS-6150, to prevent re-infection of patients with DAA-induced SVR and evaluated its safety and immunogenicity in individuals with chronic HCV infection.

METHODS

GLS-6150 consists of plasmids encoding HCV non-structural proteins (NS3-NS5A) and adjuvant IFNL3. The vaccine was administered 4 times at 4-weekly intervals to 3 groups (1, 3, or 6 mg/vaccination; n = 6 per group), followed by a 6 mg boost at 24 weeks (n = 14). Peripheral blood T cell responses were evaluated by interferon (IFN)-γ enzyme-linked immunospot assays, intracellular cytokine staining, and major histocompatibility complex class-I (MHC-I) dextramer staining. Treg cell frequency was assessed by flow cytometry.

RESULTS

Severe adverse events or vaccine discontinuation were not reported. The IFN-γ spot-forming cells specific to NS3-NS5A were increased by GLS-6150. Both CD4+ and CD8+ T cells produced multiple cytokines. However, the frequency and phenotype of HCV-specific MHC-I dextramer+CD8+ T cells were not changed. Interestingly, the frequency of Treg cells, particularly activated Treg cells, was decreased by GLS-6150, as expected from previous reports that IFNL3 adjuvants decrease Treg cell frequency. Ex vivo IFN-λ3 treatment reduced Treg frequency in pre-vaccination peripheral blood mononuclear cells. Finally, Treg cell frequency inversely correlated with HCV-specific, IFN-γ-producing T cell responses in the study participants.

CONCLUSIONS

We demonstrate that GLS-6150 decreases Treg cell frequency and enhances HCV-specific T cell responses without significant side effects. A phase I clinical trial of GLS-6150 is currently underway in patients with DAA-induced SVR.

CLINICAL TRIAL NUMBER

NCT02027116.

LAY SUMMARY

Although direct-acting antivirals (DAAs) are successfully used for the treatment of chronic hepatitis C virus (HCV) infection, a prophylactic HCV vaccine needs to be developed, especially for patients who achieve a sustained virologic response. In the current study, we show that a DNA vaccine (GLS-6150) was safe and increased HCV-specific T cell responses. A clinical trial is underway to test this vaccine in patients with a sustained virologic response following DAA therapy.

Chronic Viral Liver Diseases: Approaching the Liver Using T Cell Receptor-Mediated Gene Technologies

Chronic infection with viral hepatitis is a major risk factor for liver injury and hepatocellular carcinoma (HCC). One major contributing factor to the chronicity is the dysfunction of virus-specific T cell immunity. T cells engineered to express virus-specific T cell receptors (TCRs) may be a therapeutic option to improve host antiviral responses and have demonstrated clinical success against virus-associated tumours. This review aims to give an overview of TCRs identified from viral hepatitis research and discuss how translational lessons learned from cancer immunotherapy can be applied to the field. TCR isolation pipelines, liver homing signals, cell type options, as well as safety considerations will be discussed herein.

Reactive Polymer Targeting dsRNA as Universal Virus Detection Platform with Enhanced Sensitivity

Reactive poly(pentafluorophenyl acrylate) (PPFPA)-grafted surfaces offer a versatile platform to immobilize biomolecules. Here, we utilize PPFPA-grafted surface and double-stranded RNA (dsRNA) recognizing J2 antibody to construct a universal virus detection platform with enhanced sensitivity. PPFPA on silicon substrates is prepared, and surface hydrophilicity is modulated by partial substitution of the pentafluorophenyl units with poly(ethylene glycol). Following dsRNA antibody immobilization, the prepared surfaces can distinguish long dsRNAs from single-stranded RNAs of the same length and short dsRNAs. As long dsRNAs are common byproducts of viral transcription/replication, these surfaces can detect the presence of different kinds of viruses without prior knowledge of their genomic sequences. To increase dsRNA detection sensitivity, a two-step method is devised where the captured dsRNAs are visualized with multiple fluorophore-tagged J2 antibodies. We show that the developed platform can differentiate foreign long dsRNAs from cellular dsRNAs and other biomolecules present in the cell lysate. Moreover, when tested against cells infected with hepatitis A or C viruses, both viruses are successfully detected using a single platform. Our study shows that the developed PPFPA platform immobilized with J2 antibody can serve as a primary diagnostic tool to determine the infection status for a wide range of viruses.

The Beginning of Ending Hepatitis C Virus: A Summary of the 26th International Symposium on Hepatitis C Virus and Related Viruses

Hepatitis C virus (HCV) infects ~71 million people worldwide, and 399,000 people die annually due to HCV-related liver cirrhosis and hepatocellular carcinoma. The use of direct-acting antivirals results in a sustained virologic response in >95% of patients with chronic HCV infection. However, several issues remain to be solved to eradicate HCV. At the 26th International Symposium on Hepatitis C Virus and Related Viruses (HCV2019) held in Seoul, South Korea, October 5–8, 2019, virologists, immunologists, and clinical scientists discussed these remaining issues and how we can achieve the elimination of HCV.