Hepatitis C virus kinetics by administration of pegylated interferon-α in human and chimeric mice carrying human hepatocytes with variants of the IL28B gene

Hepatocyte Intrinsic Innate Antiviral Immunity against Hepatitis Delta Virus Infection: The Voices of Bona Fide Human Hepatocytes

The pathogenesis of viral infection is attributed to two folds: intrinsic cell death pathway activation due to the viral cytopathic effect, and immune-mediated extrinsic cellular injuries. The immune system, encompassing both innate and adaptive immunity, therefore acts as a double-edged sword in viral infection. Insufficient potency permits pathogens to establish lifelong persistent infection and its consequences, while excessive activation leads to organ damage beyond its mission to control viral pathogens. The innate immune response serves as the front line of defense against viral infection, which is triggered through the recognition of viral products, referred to as pathogen-associated molecular patterns (PAMPs), by host cell pattern recognition receptors (PRRs). The PRRs-PAMPs interaction results in the induction of interferon-stimulated genes (ISGs) in infected cells, as well as the secretion of interferons (IFNs), to establish a tissue-wide antiviral state in an autocrine and paracrine manner. Cumulative evidence suggests significant variability in the expression patterns of PRRs, the induction potency of ISGs and IFNs, and the IFN response across different cell types and species. Hence, in our understanding of viral hepatitis pathogenesis, insights gained through hepatoma cell lines or murine-based experimental systems are uncertain in precisely recapitulating the innate antiviral response of genuine human hepatocytes. Accordingly, this review article aims to extract and summarize evidence made possible with bona fide human hepatocytes-based study tools, along with their clinical relevance and implications, as well as to identify the remaining gaps in knowledge for future investigations.

HCV treatment outcome depends on SNPs of IFNL3-Gene polymorphisms (rs12979860) and cirrhotic changes in liver parenchyma

The allelic discrimination of IFNL3-(rs12979860 C > T) polymorphism reveals ambiguous associations with the effectiveness of oral HCV treatment. Solitary intra peripheral-blood-mononuclear-cells (PBMCs) HCV-RNA antisense-strands are independently detected in naïve and experienced cases regardless of viremia or hepatic-parenchymal alterations. We examined the frequencies of IFNL3-genetic variants with chronic-HCV-induced liver changes during the sustained virologic response (SVR) by evaluating the PBMCs- HCV-PCR after oral antiviral therapy. Methods: Twelve weeks after finishing oral antiviral therapy, the effects of IFNL3-genetic variants were evaluated in three groups of patients: Group-I (n = 25) showed HCV-RNA negativity in both serum and PBMCs-, group II (n = 52) showed positivity of HCV-RNA in PBMCs, and group-III (n = 25) had positive HCV-RNA in serum. The genetic variants of the IFNL3-gene were estimated for all the enrolled cases and correlated with their hepatic image changes. Results: IFNL3-(rs12979860) genotyping in post-direct acting antivirals (DAAs) SVR and HCV-relapse revealed: a) high frequency of CC-genotype and C-allele in group I compared to group II (P < 0.005) and group III(P ≤ 0.05) when hepatic-parenchyma looks normal by ultrasound b) frequent CT-genotype and T-allele in group II compared with I(P < 0.01) and III(P < 0.05) when liver tissues are bright (early cirrhotic-changes) c) frequent TT-genotype and T-allele in group III relative to I (P < 0.05) and II (P ≤ 0.08) when liver-tissues appear coarse by ultrasound. Conclusion: Outcomes of HCV treatment depend on host IFNL3-gene polymorphism and hepatic-parenchymal changes. A high frequency of wild-CC-genotype and C-allele is observed in patients with normal hepatic parenchyma and that achieved SVR. Solitary relapse in PBMCs occurs on increasing CT-genotype frequency when liver tissues are bright. Serologic relapse is detected when TT-genotype and T-allele are dominant in association with the cirrhotic liver. Therefore, IFNL3-gene-SNP analysis as a genetic predictor in relation to ultra-sonographic hepatic-parenchymal changes could be valuable for selecting the patients with the highest priority for treatment.

Cell-cycle-gated feedback control mediates desensitization to interferon stimulation

Cells use molecular circuits to interpret and respond to extracellular cues, such as hormones and cytokines, which are often released in a temporally varying fashion. In this study, we combine microfluidics, time-lapse microscopy, and computational modeling to investigate how the type I interferon (IFN)-responsive regulatory network operates in single human cells to process repetitive IFN stimulation. We found that IFN-α pretreatments lead to opposite effects, priming versus desensitization, depending on input durations. These effects are governed by a regulatory network composed of a fast-acting positive feedback loop and a delayed negative feedback loop, mediated by upregulation of ubiquitin-specific peptidase 18 (USP18). We further revealed that USP18 upregulation can only be initiated at the G1/early S phases of cell cycle upon the treatment onset, resulting in heterogeneous and delayed induction kinetics in single cells. This cell cycle gating provides a temporal compartmentalization of feedback loops, enabling duration-dependent desensitization to repetitive stimulations.

Interferon-alpha treatment rapidly clears Hepatitis E virus infection in humanized mice

Antiviral treatment options for chronic Hepatitis E Virus (HEV) infections are limited and immunological determinants of viral persistence remain largely unexplored. We studied the antiviral potency of pegylated interferon-α (pegIFNα) against HEV infections in humanized mice and modelled intrahepatic interferon stimulated gene (ISG) responses. Human gene expression levels in humanized mouse livers were analyzed by qPCR and Nanostring. Human CXCL10 was measured in mouse serum. HEV genotype 3 (gt3) infections were cleared from liver and feces within 8 pegIFNα doses in all mice and relapsed after a single pegIFNα injection in only half of treated animals. Rapid viral clearance by pegIFNα was confirmed in HEV gt1, but not in Hepatitis B Virus infected animals. No ISG induction was observed in untreated HEV gt3 and gt1 infected humanized livers compared to control chimeric mice, irrespective of the human hepatocyte donor, viral isolate or HEV infection duration. Human specific ISG transcript levels in mouse liver increased significantly after pegIFNα treatment and induced high circulating human CXCL10 in mouse serum. In conclusion, HEV gt1 and gt3 infections do not elicit innate intrahepatic immune responses and remain highly sensitive to pegIFNα in immunocompromised humanized mice.

Haem oxygenase-1 polymorphisms can affect HCV replication and treatment responses with different efficacy in humanized mice

BACKGROUND & AIMS

Enhancement of host anti-oxidant enzymes, such as haemoxygenase-1, may attenuate virus-mediated hepatocyte injury, while the induction of HO-1 by cobalt-protoporphyrin-IX (CoPP) administration, as the application of its haem degradation product biliverdin (BV), was shown to hinder HCV replication in vitro. In addition, (GT)_n -repeats length in the polymorphic region of the HO-1 promoter may affect HO-1 expression and responsiveness to infection and disease severity. Aim of this study was to investigate the antiviral and hepatoprotective effects of CoPP-mediated HO-1 induction, alone or in combination with interferon alpha (peg-IFNα), in HCV-infected mice harbouring hepatocytes from donors with different HO-1-promoter polymorphisms.

METHODS

Upon establishment of HCV infection, CoPP, BV and peg-IFNα were given alone or in combination. Viraemia changes and intrahepatic human gene expression were determined by qRT-PCR and immunohistochemistry.

RESULTS

CoPP administration increased human HO-1 expression and significantly reduced viraemia, although changes correlated with promoter length (Δ0.5log and Δ2log reduction with medium- and short-polymorphism respectively). Polymorphisms did not influence BV-mediated antiviral effects (Δ1log). Notably, HO-1 induction attenuated basal HCV-driven enhancement of interferon genes and pro-inflammatory cytokines, both in cells with short- or medium-polymorphisms. Moreover, simultaneous administration of CoPP and peg-IFNα reduced viraemia even stronger (median 3log), whereas 1log viraemia reduction was determined in mice receiving peg-IFNα monotherapy.

CONCLUSIONS

Although the protective function of HO-1 could be elicited in vivo with both host polymorphisms, the strength of HO-1 induction and suppression of HCV occurred in a polymorphism-dependent manner, indicating that host-genetic determinants may affect disease progression and infection outcome.

IFN-λ3, not IFN-λ4, likely mediates IFNL3-IFNL4 haplotype-dependent hepatic inflammation and fibrosis

Genetic variation in the IFNL3-IFNL4 (interferon-λ3-interferon-λ4) region is associated with hepatic inflammation and fibrosis. Whether IFN-λ3 or IFN-λ4 protein drives this association is not known. We demonstrate that hepatic inflammation, fibrosis stage, fibrosis progression rate, hepatic infiltration of immune cells, IFN-λ3 expression, and serum sCD163 levels (a marker of activated macrophages) are greater in individuals with the IFNL3-IFNL4 risk haplotype that does not produce IFN-λ4, but produces IFN-λ3. No difference in these features was observed according to genotype at rs117648444, which encodes a substitution at position 70 of the IFN-λ4 protein and reduces IFN-λ4 activity, or between patients encoding functionally defective IFN-λ4 (IFN-λ4-Ser70) and those encoding fully active IFN-λ4-Pro70. The two proposed functional variants (rs368234815 and rs4803217) were not superior to the discovery SNP rs12979860 with respect to liver inflammation or fibrosis phenotype. IFN-λ3 rather than IFN-λ4 likely mediates IFNL3-IFNL4 haplotype-dependent hepatic inflammation and fibrosis.

IL28B genotype is associated with cirrhosis or transition to cirrhosis in treatment-naive patients with chronic HCV genotype 1 infection: the international observational Gen-C study

Background and purpose

Contradictory data exist on the association between host interleukin-28B (IL28B) rs12979860 genotype and liver fibrosis in patients with chronic hepatitis C (CHC). This large, international, observational study (NCT01675427/MV25600) investigated relationships between IL28B rs12979860 genotype and liver fibrosis stage in CHC patients.

Methods

A total of 3003 adult, treatment-naive CHC patients were enrolled into the study. Patients made one study visit to provide a blood sample for genotyping; other data were obtained from medical records.

Results

2916 patients comprised the analysis population; the majority were enrolled in Europe (n = 2119), were Caucasian (n = 2582) and had hepatitis C virus (HCV) genotype (G)1 infection (n = 1702) (G2 = 323, G3 = 574, G4 = 260). Distribution of IL28B genotypes varied according to region of enrolment, patient ethnicity and HCV genotype. A significant association was observed between increasing number of IL28B T alleles and the prevalence of cirrhosis/transition to cirrhosis (based on biopsy or non-invasive assessments) in G1-infected patients (CC = 22.2% [111/499], CT = 27.5% [255/928], TT = 32.3% [87/269]; p = 0.0018). The association was significant in the large subgroup of European Caucasian G1 patients (n = 1245) but not in the smaller Asian (n = 25), Latin American (n = 137) or Middle Eastern (n = 289) G1 subgroups. IL28B genotype was not associated with liver fibrosis stage in patients with HCV G2, G3 or G4 infection.

Conclusion

This large, international study found that IL28B rs12979860 genotype is significantly associated with liver fibrosis stage in CHC patients with HCV G1 infection. This association was evident in European Caucasians but not in G1-infected patients from Asia, Latin America or the Middle East.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-3663-6) contains supplementary material, which is available to authorized users.

Organ system view of the hepatic innate immunity in HCV infection

An orchestration of innate and adaptive immunity determines the infection outcome and whether the host achieves clearance or allows the pathogen to establish persistent infection. The robust activation of the innate immune response plays the most critical role in both limiting viral replication and halting the spread of the pathogen immediately after infection. The magnitude of innate immune activation is coupled with the efficient mounting of the adaptive immunity. Although immunity against HCV infection is known to be inadequate as most cases transitions to chronicity, approximately 25% of acute infection cases result in spontaneous clearance. The exact immune mechanisms that govern the infection outcome remain largely unknown; recent discoveries suggest that the innate immune system facilitates this event. Both infected hepatocytes and local innate immune cells trigger the front line defense program of the liver as well as the recruitment of diverse adaptive immune cells to the site of infection. Although hepatocyte is the target of HCV infection, nearly all cell types that exist in the liver are involved in the innate defense and contribute to the pathophysiology of hepatic inflammation. The main focus of this comprehensive review is to discuss the current knowledge on how each hepatic cell type contributes to the organ system level innate immunity against HCV infection as well as interplays with the viral evasion program. Furthermore, this review article also aims to synchronize the observations from both molecular biological studies and clinical studies with the ultimate goal of improving our understanding of HCV mediated hepatitis. J. Med. Virol. 88:2025-2037, 2016. © 2016 Wiley Periodicals, Inc.

Intrinsic Viral Factors Are the Dominant Determinants of the Hepatitis C Virus Response to Interferon Alpha Treatment in Chimeric Mice

BACKGROUND

Hepatitis C virus infection is a global health problem. New direct-acting antiviral agents have been recently approved. However, due to their high cost and some genotypes remaining difficult to treat, interferon-based therapy with pegylated interferon and ribavirin likely may remain a component of hepatitis C virus treatment for some patients. Unfortunately, pegylated interferon / ribavirin treatment achieved favorable outcomes in less than 50% of patients. Factors determining the outcome to pegylated interferon/ribavirin include both host and viral factors. It has been a major challenge to separate the host and viral factors in most in vivo systems.

AIMS & METHODS

We used two hepatitis C virus strains from patients with different interferon-sensitivities and three hepatocyte donors, each with distinct interleukin 28B and interferon lambda 4 single nucleotide polymorphisms to investigate the contributions of viral and host factors to the response of hepatitis C virus to interferon treatment in chimeric mice.

RESULTS AND CONCLUSIONS

We found that viral factors were the dominant factors in determining the interferon treatment outcomes in chimeric mice. Host factors, such as pre-treatment liver interferon-stimulated gene expression and single nucleotide polymorphisms near interleukin 28B and interferon lambda 4 coding regions, were less important determinants of the response to interferon in the chimeric mice than they were in patients. Our results also suggest that a complete immune system as seen in patients may be required for host factors such as single nucleotide polymorphisms near interleukin 28B/interferon lambda 4 and pre-treatment liver interferon-stimulated gene upregulation to have an effect on the interferon response.

Assessment of interleukin 28B genotype as a predictor of response to combined therapy with pegylated interferon plus ribavirin in HCV infected Egyptian patients

BACKGROUND AND AIM

Single nucleotide polymorphisms (SNPs) of interleukin 28B (IL28B) gene is associated with spontaneous clearance and variable response to combined therapy with pegylated interferon (PEG-IFN) and ribavirin (RBV) in chronic hepatitis C virus (HCV) infected patients. This study aimed at assessing the value of IL28B rs8099917 gene polymorphism in predicting sustained virological response (SVR) among HCV infected Egyptian patients treated with PEG-IFN and RBV.

METHODS

Our study was conducted on 153 chronic HCV infected patients treated with PEG-IFN and RBV. Genotyping of rs8099917 near the IL-28B gene was performed by Real Time PCR using Taq-Man probe assay.

RESULTS

The overall SVR was achieved in 49.6% of patients. Patients with TT genotype showed significantly higher SVR rate than minor allele (TG/GG) carriers (74% vs. 26%, P=0.004). Logistic regression analysis revealed that TT carriers had 2.8 higher chance for SVR achievement than G allele carriers TG/GG (OR=2.8, 95% CI=1.4-5.6, P=0.004). Younger age, male sex and low activity grading were significant predictors of SVR (P=0.003, P=<0.001 and P<0.001 respectively). High pretreatment AST levels and advanced liver fibrosis were negative predictors of SVR (P=0.04 and P<0.001 respectively).

CONCLUSION

IL28B genotype is a significant pre-treatment predictor of response to PEG-IFN/RBV in HCV infected Egyptian patients.

Sustained Virologic Response to a Dual Peginterferon alfa-2a and Ribavirin in Treating Chronic hepatitis C Infection: A Retrospective Cohort Study

In Myanmar, hepatitis C virus (HCV) infection prevalence is 2%. A combination therapy of pegylated interferon alfa-2a and ribavirin (PEG-IFNa/RBV) is a standard treatment, but the effect of this antiviral therapy needs evaluation as to determine the efficacy and safety of dual PEG-IFNa/RBV therapy in treating patients infected with HCV in Myanmar.This was a retrospective analysis of data from a single clinic exclusively for gastrointestinal diseases in Yangon, Myanmar. We assessed treatment responses at the defined time points and stratified by genotypes of HCV. We also determined incidences of adverse events (AEs). We investigated independent predictors of sustained virologic response (SVR) in the participants.A total of 362 HCV-infected cases were included in this study. The majority were females (51.7%) with mean age of 47.12 years (±11.6) and noncirrhosis patients (82%). Rapid virologic response (RVR), early virologic response (EVR), end of treatment response (ETR), and SVR 24 weeks after completion of the dual treatment were 50.3% (178/362), 88% (314/357), 80.1% (286/357), and 85.6% (167/195), respectively. The most frequently reported AEs were nausea/anorexia (72.8%) and flu-like symptoms (62.4%). In multivariate analysis, 4 factors were independently associated with SVR; SVR to genotype 3 (odds ratio [OR] 2.4, 95% CI: 1.24-4.62), EVR (OR 0.54, 95% CI: 0.3-0.95), and duration of treatment (OR 1.52, 95% CI: 1.18-1.98). Study limitations were acknowledged.The efficacy and safety of the dual therapy in treating HCV-infected patient in Myanmar was acceptable. We recommend a prospective randomized control trial looking at duration of therapy and rates of achieving SVR, which could significantly impact the care of HCV-infected patients in Myanmar and perhaps other countries as well.

Advances in experimental systems to study hepatitis C virus in vitro and in vivo

Hepatitis C virus (HCV) represents a global health concern affecting over 185 million people worldwide. Chronic HCV infection causes liver fibrosis and cirrhosis and is the leading indication for liver transplantation. Recent advances in the field of direct-acting antiviral drugs (DAAs) promise a cure for HCV in over 90% of cases that will get access to these expensive treatments. Nevertheless, the lack of a protective vaccine and likely emergence of drug-resistant viral variants call for further studies of HCV biology. With chimpanzees being for a long time the only non-human in vivo model of HCV infection, strong efforts were put into establishing in vitro experimental systems. The initial models only enabled to study specific aspects of the HCV life cycle, such as viral replication with the subgenomic replicon and entry using HCV pseudotyped particles (HCVpp). Subsequent development of protocols to grow infectious HCV particles in cell-culture (HCVcc) ignited investigations on the full cycle of HCV infection and the virus-host interactions required for virus propagation. More recently, small animal models permissive to HCV were generated that allowed in vivo testing of novel antiviral therapies as well as vaccine candidates. This review provides an overview of the currently available in vitro and in vivo experimental systems to study HCV biology. Particular emphasis is given to how these model systems furthered our understanding of virus-host interactions, viral pathogenesis and immunological responses to HCV infection, as well as drug and vaccine development.

Influence of genes suppressing interferon effects in peripheral blood mononuclear cells during triple antiviral therapy for chronic hepatitis C

The levels of expression of interferon-stimulated genes (ISGs) in liver are associated with response to treatment with pegylated interferon (PEG-IFN) plus ribavirin (RBV). However, associations between the responses of ISGs to IFN-based therapy and treatment efficacy or interleukin-28B (IL28B) genotype have not yet been determined. Therefore, we investigated the early responses of ISGs and interferon-lambdas (IFN-λs) in peripheral blood mononuclear cells (PBMCs) during PEG-IFN/RBV plus NS3/4 protease inhibitor (PI) therapy. We prospectively enrolled 50 chronic hepatitis C patients with HCV genotype 1, and collected PBMCs at baseline, 8 and 24 h after the initial administration of PEG-IFN/RBV/PI. Levels of mRNAs for selected ISGs and IFN-λs were evaluated by real-time PCR. All 31 patients with a favorable IL28B genotype and 13 of 19 with an unfavorable genotype achieved sustained virological responses (SVR). Levels of mRNA for A20, SOCS1, and SOCS3, known to suppress antiviral activity by interfering with the IFN signaling pathway, as well as IRF1 were significantly higher at 8 h in patients with an unfavorable IL28B genotype than in those with a favorable one (P = 0.007, 0.026, 0.0004, 0.0006, respectively), especially in the non-SVR group. Particularly, the fold-change of IRF1 at 8 h relative to baseline was significantly higher in non-SVR than in SVR cases with an unfavorable IL28B genotype (P = 0.035). In conclusion, levels of several mRNAs of genes suppressing antiviral activity in PBMCs during PEG-IFN/RBV/PI differed according to IL28B genotypes, paralleling treatment efficacy.

Immune cell responses are not required to induce substantial hepatitis B virus antigen decline during pegylated interferon-alpha administration

BACKGROUND & AIMS

Pegylated interferon-alpha (PegIFNα) remains an attractive treatment option for chronic hepatitis B virus (HBV) infection because it induces higher rates of antigen loss and seroconversion than treatment with polymerase inhibitors. Although early HBsAg decline is recognised as the best predictor of sustained response to IFN-based therapy, it is unclear whether immune cell functions are required to induce significant antigenemia reduction in the first weeks of treatment. Aim of the study was to investigate whether PegIFNα can induce sustained human hepatocyte responsiveness and substantial loss of circulating and intrahepatic viral antigen loads in a system lacking immune cell functions.

METHODS

HBV-infected humanized uPA/SCID mice received either PegIFNα, entecavir (ETV), or both agents in combination. Serological and intrahepatic changes were determined by qRT-PCR and immunohistochemistry and compared to untreated mice.

RESULTS

After 4 weeks of treatment, median viremia reduction was greater in mice treated with ETV (either with or without PegIFNα) than with PegIFNα. In contrast, levels of circulating HBeAg, HBsAg, and intrahepatic HBcAg were significantly reduced (p = 0.03) only in mice receiving PegIFNα alone or in combination, as compared to mice receiving ETV monotherapy. Progressive antigen reduction was also demonstrated in mice receiving PegIFNα for 12 weeks (HBeAg = Δ1log; HBsAg = Δ1.4log; p < 0.0001). Notably, repeated administrations of the longer-active PegIFNα could breach the impairment of HBV-infected hepatocyte responsiveness and induce sustained enhancement of human interferon stimulated genes (ISG).

CONCLUSIONS

The antiviral effects of PegIFNα exerted on the human hepatocytes can induce sustained responsiveness and trigger substantial HBV antigen decline without claiming the involvement of immune cell responses.

Role of IL28B for chronic hepatitis C treatment toward personalized medicine

Genome-wide association studies recently revealed that certain interleukin-28B (IL28B) polymorphisms are strongly associated with responses to pegylated interferon (PEG-IFN) and ribavirin (RBV) therapy in patients chronically infected with hepatitis C virus (HCV) genotype 1, as well as with spontaneous clearance of HCV. Subsequent reports revealed that IL28B genotypes also affect treatment efficacy in chronic infection with other HCV genotypes. Furthermore, there have been several reports that implicate IL28B genotypes in inflammatory status, progression of fibrosis and adverse clinical outcomes in chronic hepatitis C (CHC). Therapy of CHC recently entered a new era with the deployment of direct-acting antivirals. These include nonstructural 3/4A protease inhibitors which have shown promise in combination with PEG-IFN/RBV in several clinical trials. IFN-free therapy is expected to be useful especially in IFN-resistant patients and may become the standard of care in the future. Several clinical trials have revealed an association between IL28B genotype and treatment efficacy in triple therapy or IFN-free regimens. On the other hand the mechanism of the effect of IL28B on HCV infection has not yet been elucidated. Recently, it was shown that the polymorphism of IFN-lambda 4 (IFNL4) is in high linkage disequilibrium with that of near IL28B, and more strongly associated with spontaneous or treatment-induced HCV clearance than IL28B genotypes, especially in individuals of African ancestry. This finding provides new insights into the genetic regulation of HCV clearance and its clinical management. IL28B genotyping will be also useful for personalized CHC treatment in the forthcoming era of direct-acting antivirals.

Hepatitis C virus infection and related liver disease: the quest for the best animal model

Hepatitis C virus (HCV) is a major cause of cirrhosis and hepatocellular carcinoma (HCC) making the virus the most common cause of liver failure and transplantation. HCV is estimated to chronically affect 130 million individuals and to lead to more than 350,000 deaths per year worldwide. A vaccine is currently not available. The recently developed direct acting antivirals (DAAs) have markedly increased the efficacy of the standard of care but are not efficient enough to completely cure all chronically infected patients and their toxicity limits their use in patients with advanced liver disease, co-morbidity or transplant recipients. Because of the host restriction, which is limited to humans and non-human primates, in vivo study of HCV infection has been hampered since its discovery more than 20 years ago. The chimpanzee remains the most physiological model to study the innate and adaptive immune responses, but its use is ethically difficult and is now very restricted and regulated. The development of a small animal model that allows robust HCV infection has been achieved using chimeric liver immunodeficient mice, which are therefore not suitable for studying the adaptive immune responses. Nevertheless, these models allowed to go deeply in the comprehension of virus-host interactions and to assess different therapeutic approaches. The immunocompetent mouse models that were recently established by genetic humanization have shown an interesting improvement concerning the study of the immune responses but are still limited by the absence of the complete robust life cycle of the virus. In this review, we will focus on the relevant available animal models of HCV infection and their usefulness for deciphering the HCV life cycle and virus-induced liver disease, as well as for the development and evaluation of new therapeutics. We will also discuss the perspectives on future immunocompetent mouse models and the hurdles to their development.

Determination of the human antibody response to the neutralization epitopes encompassing amino acids 313-327 and 432-443 of hepatitis C virus E1E2 glycoproteins

It has been reported that monoclonal antibodies (MAbs) to the E1E2 glycoproteins may have the potential to prevent hepatitis C virus (HCV) infection. The protective epitopes targeted by these MAbs have been mapped to the regionsencompassing amino acids 313–327 and 432–443. In this study, we synthesized these two peptides and tested the reactivity of serum samples from 336 patients, 210 of whichwere from Chronic Hepatitis C (CHC) patients infected with diverse HCV genotypes.The remaining 126 samples were isolated from patients who had spontaneously clearedHCV infection.In the chronic HCV-infected group (CHC group), the prevalence of human serum antibodies reactive to epitopes 313–327 and 432–443was 24.29%(51 of 210) and4.76%(10 of 210),respectively. In thespontaneousclearance group (SC group),the prevalence was 0.79%(1 of 126) and 12.70%(16 of 126), respectively.The positive serum samples that contained antibodies reactive to epitope 313–327 neutralizedHCV pseudoparticles (HCVpp) bearing the envelope glycoproteins of genotypes 1a or 1b and/or 4, but genotypes 2a, 3a, 5 and 6 were not neutralized. The neutralizing activity of these serum samples could not be inhibited by peptide 313–327. Six samples (SC17, SC38, SC86, SC92, CHC75 and CHC198) containing antibodies reactive to epitope 432–443 had cross-genotype neutralizing activities. Theneutralizing activityof SC38, SC86, SC92 and CHC75waspartiallyinhibited by peptide 432–443. However,the neutralizing activity of sample SC17 for genotype 4HCVpp and sample CHC198 for genotype 1b HCVppwere notinhibited by the peptide.This study identifies the neutralizing ability of endogenous anti-HCV antibodies and warrants the exploration of antibodies reactive to epitope432–443as sources for future antibody therapies.