Additional Glycosylation Within a Specific Hypervariable Region of Subtype 3a of Hepatitis C Virus Protects Against Virus Neutralization

Background. The envelope glycoprotein E2 of hepatitis C virus (HCV) contains several hypervariable regions. Interestingly, 2 regions of intragenotypic hypervariability within E2 have been described as being specific to HCV subtype 3a. Based on their amino acid position in E2, they were named HVR495 and HVR575. Here, we further investigated these regions in order to better understand their role in HCV infection. Methods. Sequences of HCV envelope glycoproteins from Pakistani patients infected with subtype 3a were cloned and compared with other subtype 3a sequences. The entry functions and the sensitivity to antibody neutralization of selected HCV glycoprotein sequences were tested in the HCV pseudotyped particles (HCVpp) system. In addition, the cell-cultured HCV system (HCVcc) was also used to confirm some of the data obtained with the HCVpp system. Results. We observed interesting new features within HVR495 and HVR575 for several subtype 3a isolates. Indeed, changes in glycosylation sites were observed with the appearance of a new glycosylation site within HVR495. Importantly, HCVpp and HCVcc that contained this new HVR495 glycosylation site were less sensitive to antibody neutralization. Conclusions. We identified a new glycosylation site within the HVR495 region of HCV subtype 3a that has a protective effect against antibody neutralization.