Callens Nathalie, Ciczora Yann, Bartosch Birke, Vu-Dac Ngoc, Cosset François-Loïc, Pawlotsky Jean-Michel, Penin François, Dubuisson Jean
Unité Hépatite C, CNRS-UPR2511, Institut de Biologie de Lille, 1 rue Calmette, BP447, 59021 Lille cedex, France.
J Virol. 2005 Dec;79(24):15331-41. doi: 10.1128/JVI.79.24.15331-15341.2005.
The N terminus of hepatitis C virus (HCV) envelope glycoprotein E2 contains a hypervariable region (HVR1) which has been proposed to play a role in viral entry. Despite strong amino acid variability, HVR1 is globally basic, with basic residues located at specific sequence positions. Here we show by analyzing a large number of HVR1 sequences that the frequency of basic residues at each position is genotype dependent. We also used retroviral pseudotyped particles (HCVpp) harboring genotype 1a envelope glycoproteins to study the role of HVR1 basic residues in entry. Interestingly, HCVpp infectivity globally increased with the number of basic residues in HVR1. However, a shift in position of some charged residues also modulated HCVpp infectivity. In the absence of basic residues, infectivity was reduced to the same level as that of a mutant deleted of HVR1. We also analyzed the effect of these mutations on interactions with some potential HCV receptors. Recognition of CD81 was not affected by changes in the number of charged residues, and we did not find a role for heparan sulfates in HCVpp entry. The involvement of the scavenger receptor class B type I (SR-BI) was indirectly analyzed by measuring the enhancement of infectivity of the mutants in the presence of the natural ligand of SR-BI, high-density lipoproteins (HDL). However, no correlation between the number of basic residues within HVR1 and HDL enhancement effect was observed. Despite the lack of evidence of the involvement of known potential receptors, our results demonstrate that the presence of basic residues in HVR1 facilitates virus entry.
丙型肝炎病毒（HCV）包膜糖蛋白E2的N端包含一个高变区（HVR1），该区域被认为在病毒进入过程中发挥作用。尽管氨基酸变异性很强，但HVR1总体呈碱性，碱性残基位于特定的序列位置。在这里，我们通过分析大量HVR1序列表明，每个位置碱性残基的频率取决于基因型。我们还使用携带1a基因型包膜糖蛋白的逆转录病毒假型颗粒（HCVpp）来研究HVR1碱性残基在病毒进入中的作用。有趣的是，HCVpp的感染性总体上随着HVR1中碱性残基数量的增加而增加。然而，一些带电荷残基位置的改变也会调节HCVpp的感染性。在没有碱性残基的情况下，感染性降低到与缺失HVR1的突变体相同的水平。我们还分析了这些突变对与一些潜在HCV受体相互作用的影响。CD81的识别不受带电荷残基数量变化的影响，并且我们没有发现硫酸乙酰肝素在HCVpp进入中的作用。通过测量在SR-BI的天然配体高密度脂蛋白（HDL）存在下突变体感染性的增强，间接分析了B类I型清道夫受体（SR-BI）的参与情况。然而，未观察到HVR1内碱性残基数量与HDL增强效应之间的相关性。尽管缺乏已知潜在受体参与的证据，但我们的结果表明HVR1中碱性残基的存在促进了病毒进入。
