Inhibition of the binding of HCV serum particles to human hepatocytes by E1E2-specific D32.10 monoclonal antibody

New insights into HCV replication in original cells from Aedes mosquitoes

BACKGROUND

The existing literature about HCV association with, and replication in mosquitoes is extremely poor. To fill this gap, we performed cellular investigations aimed at exploring (i) the capacity of HCV E1E2 glycoproteins to bind on Aedes mosquito cells and (ii) the ability of HCV serum particles (HCVsp) to replicate in these cell lines.

METHODS

First, we used purified E1E2 expressing baculovirus-derived HCV pseudo particles (bacHCVpp) so we could investigate their association with mosquito cell lines from Aedes aegypti (Aag-2) and Aedes albopictus (C6/36). We initiated a series of infections of both mosquito cells (Ae aegypti and Ae albopictus) with the HCVsp (Lat strain - genotype 3) and we observed the evolution dynamics of viral populations within cells over the course of infection via next-generation sequencing (NGS) experiments.

RESULTS

Our binding assays revealed bacHCVpp an association with the mosquito cells, at comparable levels obtained with human hepatocytes (HepaRG cells) used as a control. In our infection experiments, the HCV RNA (+) were detectable by RT-PCR in the cells between 21 and 28 days post-infection (p.i.). In human hepatocytes HepaRG and Ae aegypti insect cells, NGS experiments revealed an increase of global viral diversity with a selection for a quasi-species, suggesting a structuration of the population with elimination of deleterious mutations. The evolutionary pattern in Ae albopictus insect cells is different (stability of viral diversity and polymorphism).

CONCLUSIONS

These results demonstrate for the first time that natural HCV could really replicate within Aedes mosquitoes, a discovery which may have major consequences for public health as well as in vaccine development.

Non-neutralizing epitopes induce robust hepatitis C virus (HCV)-specific antibody-dependent CD56+ natural killer cell responses in chronic HCV-infected patients

Natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (NK-ADCC) is of considerable interest in viral infection. However, little is known about NK-ADCC responses in chronic hepatitis C virus (HCV) infection. In this study, impaired non-specific antibody-dependent CD56⁺ NK cell responses were observed in chronic HCV infection, as shown by decreased degranulation (extracellular CD107a expression) and interferon (IFN)-γ production in response to antibody-bound P815 cells. A peptide pool composed of epitopes recognized by anti-HCV-E1/E2 antibodies could induce pronounced HCV-specific antibody-dependent NK cell responses in sera from approximately half the chronic HCV carriers. Additionally, HCV-specific epitopes with the capacity to induce robust NK-ADCC activity were identified. Five linear NK-ADCC epitopes (aa211-aa217, aa384-aa391, aa464-aa475, aa544-aa551 and aa648-aa659 of the HCV envelope) were identified and do not overlap with putative linear neutralizing epitopes. This study revealed the dysfunctional characteristics of antibody-dependent CD56⁺ NK cell responses in chronic HCV carriers. The key non-neutralizing NK-ADCC epitopes identified in this study may act as new targets for immunological intervention.

Predictors of the therapeutic response in hepatitis C. A 2013 update

Chronic hepatitis C is a major cause of cirrhosis and hepatocellular carcinoma. Current therapy based on pegylated-interferon-α (PEG-IFN) and ribavirin (RBV) combination has limited efficacy and is poorly tolerated. Disease progression is highly variable and pre-therapeutic prediction of response to treatment remains difficult. Although viral kinetics proved most useful to monitor duration of therapy, other predictors would be helpful to identify patients with the best chance of subsequent treatment response prior initiation of antiviral therapy (double or triple therapy). The predictive power of IL28B polymorphism is well-recognized and has become the reference biomarker for clinicians in patients treated with double therapy. The combination of serum IP-10 and IL28B SNPs increases predictive value of treatment response. Recently, anti-E1E2 antibodies appear to closely correlate with therapeutic outcome and predict the complete elimination of HCV. They may represent a new relevant prognostic biomarker of double therapy response. Since the introduction of triple therapy including protease inhibitors (telaprevir/boceprevir), the major priority is to help patients who failed on double therapy, and there is now an urgent need for robust pre-therapeutic predictors of response to better select the patients to treat. Indeed, the relevance of IL28B polymorphism and IP-10 serum concentration are limited in triple therapy. Many new drugs are currently under investigation and there is hope that effective and well-tolerated IFN-free regimens may become a part of future therapy. In this context, this will help to identify the most powerful predictive marker and/or to assess the benefit of anti-E1E2 in decision to treat.

Structural and functional characterization of the single-chain Fv fragment from a unique HCV E1E2-specific monoclonal antibody

The nucleotide sequence of the unique neutralizing monoclonal antibody D32.10 raised against a conserved conformational epitope shared between E1 and E2 on the serum-derived hepatitis C virus (HCV) envelope was determined. Subsequently, the recombinant single-chain Fv fragment (scFv) was cloned and expressed in Escherichia coli, and its molecular characterization was assessed using multi-angle laser light scattering. The scFv mimicked the antibody in binding to the native serum-derived HCV particles from patients, as well as to envelope E1E2 complexes and E1, E2 glycoproteins carrying the viral epitope. The scFv D32.10 competed with the parental IgG for binding to antigen, and therefore could be a promising candidate for therapeutics and diagnostics.

Pretreatment predictive factors for hepatitis C therapy outcome: relevance of anti-E1E2 antibodies compared to IP-10 and IL28B genotypes

BACKGROUND

Unique serum anti-E1E2 antibodies were shown to be associated with spontaneous recovery or predictive of sustained virological response (SVR) in patients with chronic hepatitis C receiving pegylated interferon/ribavirin (PEG-IFN/RBV) therapy. The objectives were to establish the relationship between pretreatment anti-E1E2 titres and HCV RNA kinetics during PEG-IFN/RBV therapy, and to examine whether the combined determination of interleukin (IL)28B rs12979860 and rs8099917, pretreatment inducible protein (IP)-10 levels and/or anti-E1E2 improved the prediction of SVR.

METHODS

Sera from 26 treatment-naive consecutive HCV patients treated with PEG-IFN/RBV for 48 weeks were analysed. Serum anti-E1E2 titres and pretreatment IP-10 levels were measured by enzyme-linked immunosorbent assays. The IL28B variants were determined using genotyping real-time polymerase chain reaction method. Viral decline was measured at weeks (W) 4 and 12 and SVR assessed 6 months after the end of therapy.

RESULTS

Baseline anti-E1E2 titres were correlated with HCV RNA decline at W4 and W12 and were highly predictive of SVR with 100% of patients negative for anti-E1E2 failing to achieve SVR. Receiver operating characteristic curve analyses indicate that the best prediction of SVR (AUC 0.990) was obtained with the combination of anti-E1E2 and IP-10 levels. Predictive values were better than those obtained with IP-10 alone or in combination with IL28B variants.

CONCLUSIONS

Pretreatment serum anti-E1E2 response predicts HCV RNA clearance kinetics and treatment outcome. The combination of anti-E1E2 and IP-10 significantly improved the prediction of treatment response. This warrants further investigation and validation on larger cohorts of patients in the context of new therapeutic strategies.

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.

The HepaRG cell line: a valuable in vitro tool for hepatitis virus infection studies

Hepatitis virus infections, mainly hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, constitute a major problem for public health since they have a worldwide distribution and because they are associated with hepatocellular carcinoma and death. Current anti-HBV vaccines seem to be effective in the majority of people. However, an important issue waiting to be tackled nowadays is how to cure patients with chronic hepatitis B. Moreover, no vaccine is available today for the prevention of HCV infection. Therefore, the use of adequate in vitro infection systems is a prerequisite for the molecular understanding of the infection events of these viruses, which could result in the development of novel powerful therapeutics. In this respect, the HepaRG cell line exhibits a hepatocyte-like morphology and displays drug metabolism capacity similar to that of primary hepatocytes. HepaRG cells have yet been proven to be a useful tool in the study of viral infections, particularly for deciphering the mechanism of HBV entry into hepatocytes.

Long-term propagation of serum hepatitis C virus (HCV) with production of enveloped HCV particles in human HepaRG hepatocytes

HepaRG human liver progenitor cells exhibit morphology and functionality of adult hepatocytes. We investigated the susceptibility of HepaRG hepatocytes to in vitro infection with serum-derived hepatitis C virus (HCV) particles (HCVsp) and the potential neutralizing activity of the E1E2-specific monoclonal antibody (mAb) D32.10. The infection was performed using HCVsp when the cells actively divided at day 3 postplating. HCV RNA, E1E2, and core antigens were quantified in HCV particles recovered from culture supernatants of differentiated cells for up to 66 days. The density distributions of particles were analyzed on iodixanol or sucrose gradients. Electron microscopy (EM) and immune-EM studies were performed for ultrastructural analysis of cells and localization of HCV E1E2 proteins in thin sections. HCV infection of HepaRG cells was documented by increasing production of E1E2-core-RNA(+) HCV particles from day 21 to day 63. Infectious particles sedimented between 1.06 and 1.12 g/mL in iodixanol gradients. E1E2 and core antigens were expressed in 50% of HCV-infected cells at day 31. The D32.10 mAb strongly inhibited HCV RNA production in HepaRG culture supernatants. Infected HepaRG cells frozen at day 56 were reseeded at low density. After only 1-3 subcultures and induction of a cell differentiation process the HepaRG cells produced high titer HCV RNA and thus showed to be sustainably infected. Apolipoprotein B-associated empty E1E2 and complete HCV particles were secreted. Characteristic virus-induced intracellular membrane changes and E1E2 protein-association to vesicles were observed.

CONCLUSION

HepaRG progenitor cells permit HCVsp infection. Differentiated HepaRG cells support long-term production of infectious lipoprotein-associated enveloped HCV particles. The E1E2-specific D32.10 mAb neutralizes the infection and this cellular model could be used as a surrogate infection system for the screening of entry inhibitors.

Association of anti-E1E2 antibodies with spontaneous recovery or sustained viral response to therapy in patients infected with hepatitis C virus

The monoclonal antibody (mAb) D32.10 recognizes a discontinuous epitope encompassing three regions E1 (amino acids 297-306), E2A (amino acids 480-494), and E2B (amino acids 613-621) juxtaposed on the surface of serum-derived hepatitis C virus (HCV) particles (HCVsp). The mAb D32.10 inhibits efficiently and specifically the binding of HCVsp to human hepatocytes. Therefore, we investigated the clinical relevance of anti-E1E2A,B response in the serum of patients infected with HCV. To this end, an enzyme-linked immunosorbent assay (ELISA) using synthetic E1-, E2A-, and E2B-derived peptides was used. The ELISA was validated in terms of sensitivity, specificity, and test efficiency. The detection of the anti-E1E2 D32.10 epitope-binding antibodies during natural HCV infection in more than 300 HCV-positive sera demonstrated significantly (P < 0.001) higher prevalence of these antibodies: (1) in patients who spontaneously cured HCV infection (46 of 52, 88.5%) showing high titers (70% ≥ 1/1000) compared to never-treated patients with chronic hepatitis C (7 of 50, 14%) who actively replicated the virus, and (2) in complete responders (20 of 52, 38.5%) who cleared virus following treatment and achieved a sustained viral response compared to nonresponders (4 of 40, 10%). Serum anti-E1E2 antibodies were monitored before, during, and after the current standard-of-care therapy (pegylated interferon plus ribavirin) in responder and nonresponder patients. Optimal cutoff values were assessed by receiver operating characteristic curve analysis. One month prior to therapy initiation, the threshold of 1131 (optical density × 1000) gave 100% and 86% positive and negative predictive values, respectively, for achieving or not achieving a sustained viral response.

CONCLUSION

The anti-E1E2 D32.10 epitope-binding antibodies are associated with control of HCV infection and may represent a new relevant prognostic marker in serum. This unique D32.10 mAb may also have immunotherapeutic potential.