Early and late changes in natural killer cells in response to ledipasvir/sofosbuvir treatment

Unmet needs in the post-direct-acting antivirals era: The risk and molecular mechanisms of hepatocellular carcinoma after hepatitis C virus eradication

Hepatitis C virus (HCV) infection is one of the major etiologies of hepatocellular carcinoma (HCC) with approximately 30% of HCC being due to HCV infection worldwide. HCV eradication by antivirals greatly reduces the risk of HCC; nevertheless, HCC remains to occur in chronic hepatitis C (CHC) patients who have achieved a sustained virological response (SVR). The proportion of post-SVR HCC among newly diagnosed HCC patients is increasing in the direct-acting antiviral (DAA) era and might be due to preexisting inflammatory and fibrotic liver backgrounds, immune dysregulation between host and virus interactions, as well as host epigenetic scars, genetic predispositions and alternations. By means of applying surrogate markers and adopting risk stratification, HCC surveillance should be consistently performed in high-risk populations. In this review, we discuss the possible molecular mechanism, risk factors, and HCC surveillance strategy for HCC development after HCV eradication in CHC patients.

Sofosbuvir (+) daclatasvir (+) ribavirin in Egyptian patients with hepatitis C virus: Therapeutic outcomes and the prognostic role of natural killer cells

BACKGROUND

One of the prominent causes of chronic liver disease worldwide is the hepatitis C virus (HCV). HCV believed that innate immunity contributes to a sustained virological response (SVR) to the treatment of Sofosbuvir (SOF) (+) Daclatasvir (DCV) (+) Ribavirin (RBV). This study aimed to evaluate the impact of SOF (+) DCV (+) RBV therapy and persistent HCV infection on the subset of natural killer cells (NK) in HCV genotype four patients from Egypt.

MATERIALS AND METHODS

One hundred and ten patients with persistent HCV infections requiring SOF (+) DCV (+) RBV therapy were grouped, and a flow cytometry (FCM) study of the NK cell subset in peripheral blood was performed. The assessment was performed before and after three and/or six months of the cessation of viral suppression therapy when a patient had a long-term viral response (SVR). One hundred and ten volunteers from the National Liver Institute's (NLI) blood bank were selected as controls.

RESULTS

Patients with chronic HCV infection before therapy had considerably lower CD16+ and CD3- CD56+ cells than controls. Their levels increase during SOF (+) DCV (+) RBV therapy. In patients with SVR during treatment, CD16+ and CD3- CD56+ cells increased significantly compared to those who did not get SVR. Furthermore, CD56+ cells were significantly higher in patients with persistent infection before treatment than controls but diminished with the response to treatment.

CONCLUSION

NK cell activation following SOF (+) DCV (+) RBV therapy and polarization to cytotoxicity occurred early in HCV antiviral therapy and was elevated in the respondents. Our data illustrated that establishing an inhibitory cytotoxic NK profile is related to therapeutic outcomes.

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.

Proteomics reveals a global phenotypic shift of NK cells in HCV patients treated with direct-acting antivirals

Chronic hepatitis C virus (HCV) infections compromise natural killer (NK)-cell immunity. Direct-acting antivirals (DAA) effectively eliminate HCV, but the long-term effects on NK cells in cured patients are debated. We conducted a proteomic study on CD56+ NK cells of chronic HCV-infected patients before and 1 year after DAA therapy. Donor-variation was observed in NK-cell proteomes of HCV-infected patients, with 46 dysregulated proteins restored after DAA therapy. However, 30% of the CD56+ NK-cell proteome remained altered 1 year post-therapy, indicating a phenotypic shift with low donor-variation. NK cells from virus-negative cured patients exhibited global regulation of RNA-processing and pathways related to "stimuli response", "chemokine signaling", and "cytotoxicity regulation". Proteomics identified downregulation of vesicle transport components (CD107a, COPI/II complexes) and altered receptor expression profiles, indicating an inhibited NK-cell phenotype. Yet, activated NK cells from HCV patients before and after therapy effectively upregulated IFN-γ and recruited CD107a. Conversely, reduced surface expression levels of Tim-3 and 2B4 were observed before and after therapy. In conclusion, this study reveals long-term effects on the CD56+ NK-cell compartment in convalescent HCV patients 1 year after therapy, with limited abundance of vesicle transport complexes and surface receptors, associated with a responsive NK-cell phenotype.

Chronic HCV infection promotes cytotoxicity in antigen-specific CD8+ T cells regardless of virus specificity

Introduction

Despite advancements in hepatitis C virus (HCV) infection treatment, HCV still represents a significant public health burden. Besides progressive hepatic damage, viral persistence has lasting effects on innate and adaptive immune responses. Lack of a complete understanding of the factors driving an effective HCV response contributes to the failure to develop a vaccine for prevention. This study advances the existing knowledge on HCV-specific CD8+ T cells and describes the impact of current or past HCV infection on CD8+ T cells specific for other viruses.

Methods

We used barcoded-dextramers to identify and sort CD8+ T cells specific for HCV, cytomegalovirus, and influenza, and characterized them using single-cell RNA sequencing technology. Our cohort included chronic (cHCV), spontaneously resolved (rHCV), and subjects undergoing direct-acting antiviral (DAA) therapy.

Results

We show that HCV-specific CD8+ T cells have cytotoxic features in patients with cHCV, which is progressively reduced with DAA therapy and persists 12 weeks after treatment completion. We also observe a shift in the CD8+ T cell phenotype on DAA treatment, with decreased effector memory and exhausted cell signatures. In rHCV, we also detected a smaller proportion of effector memory cells compared to cHCV. The proportion of CD8+ exhausted T cells in cHCV and rHCV subjects was comparable. Moreover, we also observed that non-HCV virus-specific CD8+ T cells exhibit robust cytotoxic traits during cHCV infection.

Discussion

Altogether, our findings suggest that cHCV infection promotes cytotoxicity in CD8+ T cells regardless of virus specificity. The immunological changes caused by cHCV infection in CD8+ T cells may contribute to worsening the ongoing hepatic damage caused by HCV infection or exacerbate the immune response to possible co-infections. Our data provide a resource to groups exploring the underlying mechanisms of HCV-specific T cell spontaneous and treatment-induced resolution to inform the development of effective vaccines against HCV infection.

CD4/CD8 Ratio could be predictor of burden hepatocellular carcinoma in Egyptian chronic hepatitis C after combined sofosbuvir and daclatasvir therapy

Background

During the first years of the use of direct acting Hepatitis C antiviral drugs (DAAS), several studies reported a possible correlation between this new era of treatment and an increased risk of Hepatocellular carcinoma (HCC). Its development could possibly be favored by the changes in the immunological milieu and the different cellular behavior after eradication of HCV infection with them. For this reason, this study aimed to address the immunological effect of DAAS.

Subject & methods

Prospective paired -sample design, carried out on 90 naïve chronically infected HCV patients before and after receiving a combination therapy of sofosbuvir; at a dose of 400 mg once daily and daclatasvir; at a dose of 60 mg once daily for 12 weeks and follow up for one year. immunological tests including: total T cell count, T helper cell count, T cytotoxic cell count and natural killer cell count in peripheral blood through (CD3, CD3/CD4, CD3/CD8 and CD56 respectively) by Fluorochrome monoclonal antibodies labelled with specific dyes through Multiparameter, FACSCanto ™ II flow cytometer (Becton Dickinson, USA).

Result

Concerning the immunological changes, total T cells (CD3+), Natural killer cells showed non-significant decrease at end of therapy while significant decrease in T helper cells (CD3+CD4+) T cytotoxic cells (CD3+CD8+) compared to pre-treatment value. Long follow up revealed 26.6% developed focal HCC, in more addition, multivariate analysis show CD4/CD8 ratio could be predictor as well as sex for early development of HCC after combined DAAS therapy.

Conclusion

HCV treatment by DAAS produces significant decrease in T helper, T cytotoxic cells in CHC patients at the end of therapy. 26.6% developed focal HCC with independent CD4/CD8 predictor for burden malignancy. Further large extended population study is needed for clarify this concern.

Direct-acting Antiviral-induced Transient Recovery of NK Cells in Early-stage Treatment of Chronic Hepatitis C Patients

BACKGROUND AND AIMS

The rapid clearance of hepatitis C virus induced by direct-acting antivirals (DAAs) affects natural killer (NK) cells, but the reported results are not consistent, and the relative mechanism was unclear. This study focused on the dynamic changes of NK cells during and after DAA treatment and analyzed the reasons.

METHODS

Peripheral blood from 35 chronic hepatitis C patients who were treated with DAAs were collected at baseline and weeks 1, 2, 4, 12, and post-treatment week-12. The frequency, subset, and phenotype of NK cells were assayed by flow cytometry. Lactate dehydrogenase assays were used to evaluate the cytotoxicity of NK cells. Cytokine concentrations were measured with Luminex kits.

RESULTS

All patients achieved a sustained viral response (SVR), and the NK cell frequencies were not changed significantly during DAA therapy. However, the cytotoxicity of NK cells recovered significantly early in week 1, and then continuously decreased below normal levels. The changes of genotypes including NKp30⁺, NKp46⁺, and NKG2A⁺ NK cells were parallel to NK function. The subset of CD56^dim NK cells continuously increased and did not return to normal even at 12 weeks after treatment. Interleukin (IL)-2, IL10, IL15, interferon-gamma, and tumor necrosis factor-alpha all increased after week 4, peaked at the end of therapy, and then exhibited varying degrees of reduction with time.

CONCLUSIONS

DAA treatment led to transient functional recovery of NK cells in the early stage of treatment, and then continuously decreased to below normal levels. Alterations of NK subsets, phenotypes, and the microenvironment may be involved in the changes.

Metabolic dysfunction and cancer in HCV: Shared pathways and mutual interactions

HCV hijacks many host metabolic processes in an effort to aid viral replication. The resulting hepatic metabolic dysfunction underpins many of the hepatic and extrahepatic manifestations of chronic hepatitis C (CHC). However, the natural history of CHC is also substantially influenced by the host metabolic status: obesity, insulin resistance and hepatic steatosis are major determinants of CHC progression toward hepatocellular carcinoma (HCC). Direct-acting antivirals (DAAs) have transformed the treatment and natural history of CHC. While DAA therapy effectively eradicates the virus, the long-lasting overlapping metabolic disease can persist, especially in the presence of obesity, increasing the risk of liver disease progression. This review covers the mechanisms by which HCV tunes hepatic and systemic metabolism, highlighting how systemic metabolic disturbance, lipotoxicity and chronic inflammation favour disease progression and a precancerous niche. We also highlight the therapeutic implications of sustained metabolic dysfunction following sustained virologic response as well as considerations for patients who develop HCC on the background of metabolic dysfunction.

Single-cell transcriptomic analyses of T cells in chronic HCV-infected patients dominated by DAA-induced interferon signaling changes

Chronic infection with HCV is manifested by dysregulation of innate immune responses and impaired T cell function at multiple levels. These changes may impact susceptibility to other infections, responsiveness to antiviral therapies, vaccine responsiveness, and development of complications such as hepatocellular carcinoma. Highly effective direct-acting antiviral (DAA) therapy has revolutionized the management of chronic HCV, with expected cure rates exceeding 95%. DAA treatment represents a unique opportunity to investigate to what extent elimination of viral replication and chronic antigen stimulation can restore immunologic phenotype. In this study we interrogated the global transcriptional profile of isolated peripheral blood T cells before, during and after IFN-free DAA therapy using single-cell mRNA sequencing. Our results demonstrate that T cells mapped at single-cell resolution have dramatic transcriptomic changes early after initiation of DAA and many of these changes are sustained after completion of DAA therapy. Specifically, we see a significant reduction in transcripts associated with innate immune activation and interferon signaling such as ISG15, ISG20, IFIT3, OAS and MX1 in many different T cell subsets. Furthermore, we find an early upregulation of a gene involved in suppression of immune activation, DUSP1, in circulating T cells. Conclusion: This study provides the first in-depth transcriptomic analysis at the single-cell level of patients undergoing DAA therapy, demonstrating that IFN-free antiviral therapy in chronic HCV infection induces hitherto unrecognized shifts in innate immune and interferon signaling within T cell populations early, during, and long-term after treatment. The present study provides a rich data source to explore the effects of DAA treatment on bulk T cells.

Hepatitis C Virus Relapse After Ultrashort Direct-Acting Antiviral Therapy Associates With Expression of Genes Involved With Natural Killer-Cell and CD8+ T-Cell Function

To identify immunologic correlates of hepatitis C virus (HCV) relapse after direct-acting antiviral (DAA) therapy, we quantified select immune transcripts in whole blood from noncirrhotic HCV subjects treated with 4-6 weeks of DAAs. We identified specific markers of natural killer-cell and CD8+ T-cell function (GZMB, PRF1, NKp46) with higher expression in subjects who relapsed. These findings suggest a role for host immunity in HCV eradication with ultrashort DAA therapy. We quantified whole blood immune transcripts in noncirrhotic HCV subjects treated with shortcourse antiviral therapy. Markers of natural killer-cell and CD8+ T-cell function had higher expression in virologic relapsers, suggesting a role for host immunity in HCV eradication.

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.

Adaptive Natural Killer Cell Functional Recovery in Hepatitis C Virus Cured Patients

BACKGROUND AND AIMS

Current evidence suggests that dysfunctional natural killer (NK) cell responses during hepatitis C virus (HCV) infection can be restored after viral eradication with direct acting antivirals (DAAs). However, the fate of the recently described adaptive NK cell population, endowed with increased ability to mediate antibody-dependent cell-mediated cytotoxicity (ADCC), during HCV infection is poorly defined, while no study has explored the effects of DAAs on this NK subset.

APPROACH AND RESULTS

We performed multicolor flow cytometry to investigate CD57⁺ FcεRIγ^neg adaptive and FcεRIγ^pos conventional NK cell phenotype and function before and after DAA treatment in 59 patients chronically infected with HCV, 39 with advanced liver fibrosis, and 20 with mild-moderate liver fibrosis. Moreover, bulk NK cell phenotype and function were analyzed after cytokine activation following contact with K562 target cells. The proportion of FcεRIγ^neg NK cells in patients with HCV was associated with increased HCV load at baseline, and it was significantly reduced after treatment. Patients with an advanced fibrosis stage displayed increased NK cell activation and exhaustion markers that normalized after therapy. Of note, adaptive NK cells from patients with HCV were characterized by increased programmed death receptor 1 expression and reduced ADCC activity at baseline. DAA treatment restored ADCC ability and reduced programmed death receptor 1 expression.

CONCLUSIONS

HCV profoundly affects the frequency, phenotype, and function of adaptive NK cells. DAA therapy restores a normal adaptive NK phenotype and enhances interferon-gamma production by this cell subset.

Ribavirin Improves NK Cell IFNγ Response During Sofosbuvir-based DAA Therapy in CV-infected Liver Transplant Recipients

BACKGROUND

Chronic hepatitis C virus (HCV) infection is characterized by activation of natural killer (NK) cells. Here, we asked whether HCV-elimination by sofosbuvir-based direct-acting antivirals (DAAs) and addition of RBV improves NK cell function in liver transplant (LTx) recipients.

METHODS

We analyzed NK cell degranulation and IFNγ-response along with STAT-1 and STAT-4 phosphorylation in 29 HCV-infected LTx-recipients and 17 HCV-infected patients during DAA-treatment.

RESULTS

Compared to uninfected LTx-recipients, NK cells from HCV-infected LTx-recipients were polarized towards cytotoxicity with increased CD107a-degranulation (10.1% vs 14.6%; P=0.0263) and reduced capacity to produce IFNγ (43.0% vs 26.7%; P=0.0002). The altered phenotype of NK cells in HCV-infected LTx-recipients was accompanied by increased STAT-1 (44.6% vs 87.4%; P<0.0001) and STAT-1 phosphorylation (0.7% vs 8.9%; P=0.0005) compared to pSTAT-4 IFNα-induction (29.9% vs 17.6%; P=0.0014). Successful DAA-therapy did not affect CD107a-degranulation, but decreased STAT-1. RBV cotreatment with DAA-therapy for HCV increased CD56Bright NK cell IFNγ-responses in LTx-recipients (70.9% vs 89.2%; P=0.002) and this correlated to an increase in the inducibility of pSTAT-4 (MFI 157 vs 173; P=0.0002).

CONCLUSION

RBV cotreatment of HCV-infection improved pSTAT4-dependent IFNγ-production in NK cells. This is relevant especially for immunocompromised patients such as LTx-recipients or patients with end-stage liver disease.

Peripheral blood correlates of virologic relapse after Sofosbuvir and Ribavirin treatment of Genotype-1 HCV infection

Background

Treatment of chronic hepatitis C virus infection with direct acting antiviral therapy results in viral elimination in over 90% of cases. The duration of treatment required to achieve cure differs between individuals and relapse can occur. We asked whether cellular and transcriptional profiling of peripheral blood collected during treatment could identify biomarkers predictive of treatment outcome.

Methods

We analyzed peripheral blood collected during treatment of genotype 1 HCV with 24 weeks of sofosbuvir and weight-based or low dose ribavirin in a trial in which 29% of patients relapsed. Changes in host immunity during treatment were assessed by flow cytometry and whole blood gene expression profiling. Differences in expression of immune-relevant transcripts based on treatment outcome were analyzed using the Nanostring Human Immunology V2 panel.

Results

Multiple cellular populations changed during treatment, but pre-treatment neutrophil counts were lower and natural post-treatment killer cell counts were higher in patients who relapsed. Pre-treatment expression of genes associated with interferon-signaling, T-cell dysfunction, and T-cell co-stimulation differed by treatment outcome. We identified a pre- and post-treatment gene expression signature with high predictive capacity for distinguishing treatment outcome, but neither signature was sufficiently robust to suggest viability for clinical use.

Conclusions

Patients who relapse after hepatitis C virus therapy differ immunologically from non-relapsers based on expression of transcripts related to interferon signaling and T-cell dysfunction, as well as by peripheral neutrophil and NK-cell concentrations. These data provide insight into the host immunologic basis of relapse after DAA therapy for HCV and suggests mechanisms which may be relevant for understanding outcomes with currently approved regimens.

The impact of cytokine change after hepatitis C virus clearance by direct antiviral agents on the risk of hepatocellular carcinoma

BACKGROUND/PURPOSE

De novo and early recurrent hepatocellular carcinoma (HCC) have been observed in clinical practice after direct antiviral agents (DAA) treatment. The study aims to investigate the change of cytokines and growth factors after hepatitis C virus (HCV) clearance by DAAs and their impact on the risk of HCC development.

METHODS

The chronic hepatitis C (CHC) patients with or without HCC who received DAA treatment were prospectively enrolled. The cytokines and growth factors were measured using Bio-Plex Pro™ Human Cytokine 27-plex Assay before and 12 weeks off DAA treatment.

RESULTS

A total of 37 patients were enrolled for final analysis. There were 11 males (29.7%) and 26 females (70.3%). The mean age was 67.39 ± 10.48 years. 11 (29.7%) patients were HCV-related HCC patients. The HCV genotype included genotype 2 in 26 patients and genotype 1b in 10 patients, and genotype 6 in 1. Among them, 35 (94.6%) patients achieved sustained virologic response (SVR). Two patients with HCC failed to DAA treatment. In HCV-related HCC patients, serum IP-10 level significantly declined after HCV clearance, but no difference in five growth factors including G-CSF, GM-CSF, basic FGF, PDGF-BB, and VEGF. Several cytokines including IP-10 significantly declined after HCV clearance in CHC patients.

CONCLUSION

This study showed only serum IP-10 level, a risk factor of HCC, was significantly declined after HCV clearance and no change in the markers of growth factors in HCV-related HCC patients, suggesting no promotion of HCC using DAA treatment for HCV-related HCC patients.

Reversal of Immunity After Clearance of Chronic HCV Infection-All Reset?

Chronic viral infections cause deterioration of our immune system. However, since persistent infections rarely can be eliminated, the reinvigoration capacity of an exhausted immune system has remained largely elusive. Chronic hepatitis C virus (HCV) infection can since some years be effectively cured with novel direct acting antiviral agents. Thus, it is now possible to study reversal of immunity in patients that are cured from a long-lasting chronic infection. We here highlight recent developments in the analysis of various immune cell populations during and after clearance of HCV infection. Surprisingly, whereas reinvigoration of certain immune traits clearly can be seen, many features of immune exhaustion persist over time after viral elimination. Thus, a long-term chronic insult might result in irreversible damage to our immune system. This will be important to consider in therapeutic vaccination efforts against chronic infection and in the development of immunotherapy based strategies against cancer.

Control of HCV Infection by Natural Killer Cells and Macrophages

Host defense against invading pathogens within the liver is dominated by innate immunity. Natural killer (NK) cells have been implicated at all stages of hepatitis C virus (HCV) infection, from providing innate protection to contributing to treatment-induced clearance. Decreased NK cell levels, altered NK cell subset distribution, activation marker expression, and functional polarization toward a cytolytic phenotype are hallmarks of chronic HCV infection. Interferon α (IFN-α) is a potent activator of NK cells; therefore, it is not surprising that NK cell activation has been identified as a key factor associated with sustained virological response (SVR) to IFN-α-based therapies. Understanding the role of NK cells, macrophages, and other innate immune cells post-SVR remains paramount for prevention of disease pathogenesis and progression. Novel strategies to treat liver disease may be aimed at targeting these cells.

Hepatitis C Virus (HCV) Eradication With Interferon-Free Direct-Acting Antiviral-Based Therapy Results in KLRG1+ HCV-Specific Memory Natural Killer Cells

Direct acting antiviral therapies rapidly clear chronic hepatitis C virus (HCV) infection and restore natural killer (NK) cell function. We investigated NK-cell memory formation following HCV clearance by examining NK-cell phenotype and responses from control and chronic HCV patients before and after therapy following sustained virologic response at 12 weeks post therapy (SVR12). NK-cell phenotype at SVR12 differed significantly from paired pretreatment samples, with an increase in maturation markers CD16, CD57, and KLRG1. HCV patients possessed stronger cytotoxic responses against HCV-infected cells as compared to healthy controls; a response that further increased following SVR12. The antigen-specific response was mediated by KLRG1+ NK cells, as demonstrated by increased degranulation and proliferation in response to HCV antigen only. Our data suggest that KLRG1+ HCV-specific memory NK cells develop following viral infection, providing insight into their role in HCV clearance and relevance with regard to vaccine design.

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

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

Immunomodulation of the Natural Killer Cell Phenotype and Response during HCV Infection

Hepatitis C virus (HCV) infection develops into chronic hepatitis in over two-thirds of acute infections. While current treatments with direct-acting antivirals (DAAs) achieve HCV eradication in >95% of cases, no vaccine is available and re-infection can readily occur. Natural killer (NK) cells represent a key cellular component of the innate immune system, participating in early defence against infectious diseases, viruses, and cancers. When acute infection becomes chronic, however, NK cell function is altered. This has been well studied in the context of HCV, where changes in frequency and distribution of NK cell populations have been reported. While activating receptors are downregulated on NK cells in both acute and chronic infection, NK cell inhibiting receptors are upregulated in chronic HCV infection, leading to altered NK cell responsiveness. Furthermore, chronic activation of NK cells following HCV infection contributes to liver inflammation and disease progression through enhanced cytotoxicity. Consequently, the NK immune response is a double-edged sword that is a significant component of the innate immune antiviral response, but persistent activation can drive tissue damage during chronic infection. This review will summarise the role of NK cells in HCV infection, and the changes that occur during HCV therapy.

Cirrhosis Hampers Early and Rapid Normalization of Natural Killer Cell Phenotype and Function in Hepatitis C Patients Undergoing Interferon-Free Therapy

Background: Chronic hepatitis C virus (HCV) infection impairs natural killer (NK) cell phenotype and function. Whether restoration of NK cells occurs after successful interferon (IFN)-free therapies remains a controversial issue. Aim: To analyze how HCV-related liver cirrhosis impacts changes in NK cells prior and post-IFN-free therapies. Methods: NK cell analysis by multicolor flow cytometry was performed in HCV-infected patients with (n = 17) and without (n = 14) cirrhosis at baseline, week 4 during therapy, and weeks 12 and 48 after the end of therapy (FU12 and FU48, respectively). Non-HCV cirrhotic patients (n = 12) and healthy individuals (n = 12) served as controls. Results: At baseline, HCV cirrhotic patients presented an altered distribution of NK subsets (CD56dim and CD56bright) with higher expression of NKp46, HLA-DR, NKp30, KIR2DL2/L3, NKG2A, and CD85j receptors compared to healthy controls. All frequencies normalized by FU48, except for CD85j+ cells. Likewise, substantial alterations were detected in NK cell function assessed by (i) signal transducer and activator of transcription 1 (STAT1) and phosphorylated levels of STAT1 and STAT4, (ii) degranulation (CD107a), (iii) cytotoxicity [tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)], and (iv) cytokine production [IFN-γ and tumor necrosis factor-α (TNF-α)]. Of note, NK cell function at FU48 remained partially impaired. In contrast, non-cirrhotics showed normal baseline frequencies of HLA-DR-, NKG2A-, and CD85j-expressing NK cells. Importantly, altered baseline frequencies of NK cell subsets and NKp46+ CD56dim cells, as well as NK cell function, were rapidly and completely restored. Conclusions: NK cell phenotype alterations persist after HCV eradication in cirrhotic patients, while their function is only partially restored, compromising immune restoration and immunosurveillance.

Elimination of hepatitis C virus has limited impact on the functional and mitochondrial impairment of HCV-specific CD8+ T cell responses

BACKGROUND & AIMS

Hepatitis C virus (HCV)-specific CD8+ T cells are functionally impaired in chronic hepatitis C. Even though HCV can now be rapidly and sustainably cleared from chronically infected patients, the repercussions of HCV clearance on virus-specific CD8+ T cells remain elusive. Here, we aimed to investigate if HCV clearance by direct-acting antivirals (DAAs) could restore the functionality of exhausted HCV-specific CD8+ T cell responses.

METHODS

HCV-specific CD8+ T cells in peripheral blood were obtained from 40 patients with chronic HCV infection, during and 6 months following IFN-free DAA therapy. These cells were analyzed for comprehensive phenotypes, proliferation, cytokine production, mitochondrial fitness and response to immune-checkpoint blockade.

RESULTS

We show that, unlike activation markers that decreased, surface expression of multiple co-regulatory receptors on exhausted HCV-specific CD8+ T cells remained unaltered after clearance of HCV. Likewise, cytokine production by HCV-specific CD8+ T cells remained impaired following HCV clearance. The proliferative capacity of HCV multimer-specific CD8+ T cells was not restored in the majority of patients. Enhanced in vitro proliferative expansion of HCV-specific CD8+ T cells during HCV clearance was more likely in women, patients with low liver stiffness and low alanine aminotransferase levels in our cohort. Interestingly, HCV-specific CD8+ T cells that did not proliferate following HCV clearance could preferentially re-invigorate their proliferative capacity upon in vitro immune-checkpoint inhibition. Moreover, altered mitochondrial dysfunction exhibited by exhausted HCV-specific CD8+ T cells could not be normalized after HCV clearance.

CONCLUSION

Taken together, our data implies that exhausted HCV-specific CD8+ T cells remain functionally and metabolically impaired at multiple levels following HCV clearance in most patients with chronic hepatitis C. Our results might have implications in cases of re-infection with HCV and for HCV vaccine development.

LAY SUMMARY

Direct-acting antiviral therapy results in cure of hepatitis C virus (HCV) in almost all treated patients. However, the impacts of HCV cure on immune responses remain controversial. Whether immune responses to HCV recover is important in cases of re-exposure, or for the resolution of extrahepatic manifestations. The main finding of our study was that HCV-specific T cells remain functionally impaired despite HCV clearance. This finding could explain the fact that HCV cure does not lead to protective immunity and that re-infections have frequently been observed.

Observed Changes in Natural Killer and T cell Phenotypes with Evaluation of Immune Outcome in a Longitudinal Cohort Following Sofosbuvir-Based Therapy for Chronic Hepatitis C Infection

Background

Chronic hepatitis C virus (HCV) infection diminishes immune function through cell exhaustion and repertoire alteration. Direct acting antiviral (DAA)-based therapy can restore immune cell subset function and reduce exhaustion states. However, the extent of immune modulation following DAA-based therapy and the role that clinical and demographic factors play remain unknown.

Methods

We examined natural killer (NK) cell, CD4⁺, and CD8⁺ T cell subsets along with activation and exhaustion phenotypes across an observational study of sofosbuvir-based treatment for chronic HCV infection. Additionally, we examined the ability of clinical variables and duration of infection to predict 12 weeks of sustained virologic response (SVR12) immune marker outcomes.

Results

We show that sofosbuvir-based therapy restores NK cell subset distributions and reduces chronic activation by SVR12. Likewise, T cell subsets, including HCV-specific CD8⁺ T cells, show reductions in chronic exhaustion markers by SVR12. Immunosuppressive CD4⁺ regulatory T cells decrease at 4-weeks treatment and SVR12. We observe the magnitude and direction of change in immune marker values from pretreatment to SVR12 varies greatly among participants. Although we observed associations between the estimated date of infection, HCV diagnosis date, and extent of immune marker outcome at SVR12, our regression analyses did not indicate any factors as strong SVR12 outcome predictors.

Conclusion

Our study lends further evidence of immune changes following sofosbuvir-based therapy. Further investigation beyond SVR12 and into factors that may predict posttreatment outcome is warranted.

Hepatitis C virus-associated hepatocellular carcinoma after sustained virologic response

The introduction of a direct-acting antiviral (DAA) for patients with hepatitis C virus (HCV) infection, could lead to higher sustained virologic response (SVR) rates with fewer adverse events, and it could shorten the treatment duration relative to the interferon era. Although most recent clinical studies have demonstrated that the occurrence rates of hepatocellular carcinoma (HCC) are decreased by SVR with both interferon-based and interferon-free-regimens, there are several reports about the unexpected observation of high rates of early tumor occurrence and recurrence in patients with HCV-related HCC undergoing interferon-free therapy despite SVR. Several mechanisms of HCC occurrence and rapid immunological changes, including cytokines and chemokines during and after DAA treatment, have also been reported. We focused on the possibilities that HCC occurs or recurs during and after DAA treatment, based on the reported clinical and basic studies. Further studies and observations will be needed to determine the short-term and long-term effects on hepatocarcinogenesis caused by the eradication of HCV with DAAs. New serum biomarkers and a follow-up system for HCV-patients with SVR should be established.