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Characterization of antibody-mediated neutralization directed against the hypervariable region 1 of hepatitis C virus E2 glycoprotein.

ABSTRACT: The hypervariable region 1 (HVR1) comprising the first 27 aa of E2 glycoprotein is a target for neutralizing antibodies against hepatitis C virus (HCV), but the mechanisms of this neutralization in the cell-culture-infectious genotype 2a strain JFH1 HCV virus (HCVcc) system are unknown. Two rabbit polyclonal sera, R1020 and R140, recognizing the HVR1 of the genotype 1a isolates H77c and Glasgow (Gla), respectively, and a Gla HVR1-specific mouse mAb AP213 have been described previously. However, attempts to generate of antibodies to the JFH1 HVR1 were unsuccessful. Therefore, this study produced chimeric JFH1 HCVcc viruses harbouring the H77c or Gla HVR1 to assess the reactivity of antibodies to this region and their effects on virus infectivity. The inter-genotypic HVR1 swap did not significantly affect virus infectivity. The genotype 1a HVR1-specific antibodies neutralized chimeric viruses in an isolate-dependent manner, underlining the role of HVR1 in HCV infection. The neutralizing antibodies reacted mainly with the C-terminal portion of HVR1, and detailed mapping identified A17, F20 and Q21 in the Gla HVR1 sequence and T21 (and possibly L20) in the corresponding H77c sequence as key epitope residues for AP213 and R140, and R1020, respectively. Importantly, none of the antibodies inhibited in vitro binding of viral envelope glycoproteins to the best-characterized HCV receptor, CD81, or to the glycosaminoglycan attachment factors. However, the HVR1 antibodies were capable of post-attachment neutralization. Overall, this study emphasizes the role of HVR1 in HCVcc entry and provides new tools to study this region further in the context of complete virions.

SUBMITTER: Vieyres G

PROVIDER: S-EPMC3081231 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Characterization of antibody-mediated neutralization directed against the hypervariable region 1 of hepatitis C virus E2 glycoprotein.

Vieyres Gabrielle G Dubuisson Jean J Patel Arvind H AH

The Journal of general virology 20101117 Pt 3

The hypervariable region 1 (HVR1) comprising the first 27 aa of E2 glycoprotein is a target for neutralizing antibodies against hepatitis C virus (HCV), but the mechanisms of this neutralization in the cell-culture-infectious genotype 2a strain JFH1 HCV virus (HCVcc) system are unknown. Two rabbit polyclonal sera, R1020 and R140, recognizing the HVR1 of the genotype 1a isolates H77c and Glasgow (Gla), respectively, and a Gla HVR1-specific mouse mAb AP213 have been described previously. However, ...[more]

PMID: 21084495

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Project description:Hepatitis C virus (HCV) envelope glycoproteins E1 and E2 form a heterodimer and mediate receptor interactions and viral fusion. Both E1 and E2 are targets of the neutralizing antibody (NAb) response and are candidates for the production of vaccines that generate humoral immunity. Previous studies demonstrated that N-terminal hypervariable region 1 (HVR1) can modulate the neutralization potential of monoclonal antibodies (MAbs), but no information is available on the influence of HVR2 or the intergenotypic variable region (igVR) on antigenicity. In this study, we examined how the variable regions influence the antigenicity of the receptor binding domain of E2 spanning HCV polyprotein residues 384 to 661 (E2661) using a panel of MAbs raised against E2661 and E2661 lacking HVR1, HVR2, and the igVR (?123) and well-characterized MAbs isolated from infected humans. We show for a subset of both neutralizing and nonneutralizing MAbs that all three variable regions decrease the ability of MAbs to bind E2661 and reduce the ability of MAbs to inhibit E2-CD81 interactions. In addition, we describe a new MAb directed toward the region spanning residues 411 to 428 of E2 (MAb24) that demonstrates broad neutralization against all 7 genotypes of HCV. The ability of MAb24 to inhibit E2-CD81 interactions is strongly influenced by the three variable regions. Our data suggest that HVR1, HVR2, and the igVR modulate exposure of epitopes on the core domain of E2 and their ability to prevent E2-CD81 interactions. These studies suggest that the function of HVR2 and the igVR is to modulate antibody recognition of glycoprotein E2 and may contribute to immune evasion.This study reveals conformational and antigenic differences between the ?123 and intact E2661 glycoproteins and provides new structural and functional data about the three variable regions and their role in occluding neutralizing and nonneutralizing epitopes on the E2 core domain. The variable regions may therefore function to reduce the ability of HCV to elicit NAbs directed toward the conserved core domain. Future studies aimed at generating a three-dimensional structure for intact E2 containing HVR1, and the adjoining NAb epitope at residues 412 to 428, together with HVR2, will reveal how the variable regions modulate antigenic structure.

Project description:An effective vaccine for hepatitis C virus (HCV) is a major unmet need, and it requires an antigen that elicits immune responses to key conserved epitopes. Based on structures of antibodies targeting HCV envelope glycoprotein E2, we designed immunogens to modulate the structure and dynamics of E2 and favor induction of broadly neutralizing antibodies (bNAbs) in the context of a vaccine. These designs include a point mutation in a key conserved antigenic site to stabilize its conformation, as well as redesigns of an immunogenic region to add a new N-glycosylation site and mask it from antibody binding. Designs were experimentally characterized for binding to a panel of human monoclonal antibodies (HMAbs) and the coreceptor CD81 to confirm preservation of epitope structure and preferred antigenicity profile. Selected E2 designs were tested for immunogenicity in mice, with and without hypervariable region 1, which is an immunogenic region associated with viral escape. One of these designs showed improvement in polyclonal immune serum binding to HCV pseudoparticles and neutralization of isolates associated with antibody resistance. These results indicate that antigen optimization through structure-based design of the envelope glycoproteins is a promising route to an effective vaccine for HCV.IMPORTANCE Hepatitis C virus infects approximately 1% of the world's population, and no vaccine is currently available. Due to the high variability of HCV and its ability to actively escape the immune response, a goal of HCV vaccine design is to induce neutralizing antibodies that target conserved epitopes. Here, we performed structure-based design of several epitopes of the HCV E2 envelope glycoprotein to engineer its antigenic properties. Designs were tested in vitro and in vivo, demonstrating alteration of the E2 antigenic profile in several cases, and one design led to improvement of cross-neutralization of heterologous viruses. This represents a proof of concept that rational engineering of HCV envelope glycoproteins can be used to modulate E2 antigenicity and optimize a vaccine for this challenging viral target.

Project description:Current evidence supports a protective role for virus-neutralizing antibodies in immunity against hepatitis C virus (HCV) infection. Many cross-neutralizing monoclonal antibodies have been identified. These antibodies have been shown to provide protection or to clear infection in animal models. Previous clinical trials have shown that a gpE1/gpE2 vaccine can induce antibodies that neutralize the in vitro infectivity of all the major cell culture-derived HCV (HCVcc) genotypes around the world. However, cross-neutralization appeared to favor certain genotypes, with significant but lower neutralization against others. HCV may employ epitope masking to avoid antibody-mediated neutralization. Hypervariable region 1 (HVR1) at the amino terminus of glycoprotein E2 has been shown to restrict access to many neutralizing antibodies. Consistent with this, other groups have reported that recombinant viruses lacking HVR1 are hypersensitive to neutralization. It has been proposed that gpE1/gpE2 lacking this domain could be a better vaccine antigen to induce broadly neutralizing antibodies. In this study, we examined the immunogenicity of recombinant gpE1/gpE2 lacking HVR1 (ΔHVR1). Our results indicate that wild-type (WT) and ΔHVR1 gpE1/gpE2 antigens induced antibodies targeting many well-characterized cross-genotype-neutralizing epitopes. However, while the WT gpE1/gpE2 vaccine can induce cross-genotype protection against various genotypes of HCVcc and/or HCV-pseudotyped virus (HCVpp), antisera from ΔHVR1 gpE1/gpE2-immunized animals exhibited either reduced homologous neutralization activity compared to that of the WT or heterologous neutralization activity similar to that of the WT. These data suggest that ΔHVR1 gpE1/gpE2 is not a superior vaccine antigen. Based on previously reported chimpanzee protection data using WT gpE1/gpE2 and our current findings, we are preparing a combination vaccine including wild-type recombinant gpE1/gpE2 for clinical testing in the future.IMPORTANCE An HCV vaccine is an unmet medical need. Current evidence suggests that neutralizing antibodies play an important role in virus clearance, along with cellular immune responses. Previous clinical data showed that gpE1/gpE2 can effectively induce cross-neutralizing antibodies, although they favor certain genotypes. HCV employs HVR1 within gpE2 to evade host immune control. It has been hypothesized that the removal of this domain would improve the production of cross-neutralizing antibodies. In this study, we compared the immunogenicities of WT and ΔHVR1 gpE1/gpE2 antigens as vaccine candidates. Our results indicate that the ΔHVR1 gpE1/gpE2 antigen confers no advantages in the neutralization of HCV compared with the WT antigen. Previously, we showed that this WT antigen remains the only vaccine candidate to protect chimpanzees from chronic infection, contains multiple cross-neutralizing epitopes, and is well tolerated and immunogenic in humans. The current data support the further clinical development of this vaccine antigen component.

Dataset Information

Characterization of antibody-mediated neutralization directed against the hypervariable region 1 of hepatitis C virus E2 glycoprotein.

Publications

Characterization of antibody-mediated neutralization directed against the hypervariable region 1 of hepatitis C virus E2 glycoprotein.

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