Hypervariable Region 1 Differentially Impacts Viability of Hepatitis C Virus Strains of Genotypes 1 to 6 and Impairs Virus Neutralization

Abstract

Hypervariable region 1 (HVR1) of hepatitis C virus (HCV) E2 envelope glycoprotein has been implicated in virus neutralization and persistence. We deleted HVR1 from JFH1-based HCV recombinants expressing Core/E1/E2/p7/NS2 of genotypes 1 to 6, previously found to grow efficiently in human hepatoma Huh7.5 cells. The 2a ⌬HVR1 , 5a ⌬HVR1 , and 6a ⌬HVR1 Core-NS2 recombinants retained viability in Huh7.5 cells, whereas 1a ⌬HVR1 , 1b ⌬HVR1 , 2b ⌬HVR1 , 3a ⌬HVR1 , and 4a ⌬HVR1 recombinants were severely attenuated. However, except for recombinant 4a ⌬HVR1 , viruses eventually spread, and reverse genetics studies revealed adaptive envelope mutations that rescued the infectivity of 1a ⌬HVR1 , 1b ⌬HVR1 , 2b ⌬HVR1 , and 3a ⌬HVR1 recombinants. Thus, HVR1 might have distinct functional roles for different HCV isolates. Ultracentrifugation studies showed that deletion of HVR1 did not alter HCV RNA density distribution, whereas infectious particle density changed from a range of 1.0 to 1.1 g/ml to a single peak at ϳ1.1 g/ml, suggesting that HVR1 was critical for low-density HCV particle infectivity. Using chronic-phase HCV patient sera, we found three distinct neutralization profiles for the original viruses with these genotypes. In contrast, all HVR1-deleted viruses were highly sensitive with similar neutralization profiles. In vivo relevance for the role of HVR1 in protecting HCV from neutralization was demonstrated by ex vivo neutralization of 2a and 2a ⌬HVR1 produced in human liver chimeric mice. Due to the high density and neutralization susceptibility of HVR1-deleted viruses, we investigated whether a correlation existed between density and neutralization susceptibility for the original viruses with genotypes 1 to 6. Only the 2a virus displayed such a correlation. Our findings indicate that HVR1 of HCV shields important conserved neutralization epitopes with implications for viral persistence, immunotherapy, and vaccine development.

Characterization of Hepatitis C Virus Particle Subpopulations Reveals Multiple Usage of the Scavenger Receptor BI for Entry Steps

“…We found that whereas supernatant levels of HCV RNA and core protein were similar for HVR1-mutant and parental HCVcc (Fig. 2, A and B, left panels), either HVR1 modification had effects on HCVcc infectivity with a reduction of 40-fold for ⌬HVR1-HCVcc, consistently with previous reports (14,81), and 3-fold for L399R-HCVcc (Fig. 2C, left panel).…”

Immunoglobulin with High-Titer In Vitro Cross-Neutralizing Hepatitis C Virus Antibodies Passively Protects Chimpanzees from Homologous, but Not Heterologous, Challenge

“…This supports the observation that polyclonal antibodies given postchallenge could control HCV infection only temporarily in the chimpanzee model (41). The infused NAbs might have prevented infection with heterologous 6a virus, and this was the strain previously found to be most efficiently neutralized in HCVcc assays (19,42).…”

Hepatitis C virus entry into the hepatocyte

“…Although they have an attenuated phenotype, most viruses lacking HVR1 remain infectious [14]. Furthermore, it has been proposed that this region obstructs the viral CD81 binding site as well as conserved neutralizing epitopes [14,15], potentially playing a role in some aspects of HCV immune evasion.…”