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.
Highlights
Hepatitis C virus (HCV) is a major cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma
Neutralizing antibodies to hypervariable region 1 (HVR1) of HCV E2 glycoprotein specific (Fig. 1)
Here we found that the AP213 and R140 antibodies neutralized the infectivity of HCV pseudoparticle (HCVpp) incorporating H77c E1E2 with Gla HVR1
Summary
Hepatitis C virus (HCV) is a major cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. A common feature of RNA viruses, is a major hindrance in developing effective treatments or vaccines to fight HCV. HCV isolates are classified into seven distinct genotypes differing at the nucleotide level by around 30 % and each divided into numerous subtypes. Within a single individual, the virus exists as a constantly evolving quasispecies (Bukh et al, 1995; Pawlotsky, 2003; Simmonds, 1995). HCV, a member of the family Flaviviridae, has a positivesense RNA encoding a polyprotein, which is cleaved by cellular and viral proteases into structural and non-structural proteins (reviewed by Moradpour et al, 2007).
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