An estimated number of 71 million people are living with chronic hepatitis C virus (HCV) infection worldwide and 400,000 annual deaths are related to the infection. HCV entry into the hepatocytes is complex and involves several host factors. The tetraspanin human CD81 (hCD81) is one of the four essential entry factors and is composed of one large extracellular loop, one small extracellular loop, four transmembrane domains, one intracellular loop and two intracellular tails. The large extracellular loop interacts with the E2 glycoprotein of HCV. Regions outside the large extracellular loop (backbone) of hCD81 have a critical role in post-binding entry steps and determine susceptibility of hepatocytes to HCV. Here, we investigated the effect of five non-synonymous single-nucleotide variants in the backbone of hCD81 on HCV susceptibility. We generated cell lines that stably express the hCD81 variants and infected the cells using HCV pseudoparticles and cell culture-derived HCV. Our results show that all the tested hCD81 variants support HCV pseudoparticle entry with similar efficiency as wild-type hCD81. In contrast, variants A54V, V211M and M220I are less supportive to cell culture-derived HCV infection. This altered susceptibility is HCV genotype dependent and specifically affected the cell entry step. Our findings identify three hCD81 genetic variants that are impaired in their function as HCV host factors for specific viral genotypes. This study provides additional evidence that genetic host variation contributes to inter-individual differences in HCV infection and outcome.

中文翻译：

---

人 CD81 中的单核苷酸变异影响丙型肝炎病毒对肝癌细胞的感染。

据估计，全球有 7100 万人患有慢性丙型肝炎病毒 (HCV) 感染，每年有 40 万人死于该感染。HCV 进入肝细胞的过程很复杂，涉及多种宿主因素。四跨膜蛋白人CD81（hCD81）是四种必需进入因子之一，由1个大细胞外环、1个小细胞外环、4个跨膜结构域、1个细胞内环和2个细胞内尾部组成。大的细胞外环与 HCV 的 E2 糖蛋白相互作用。hCD81 的大细胞外环（骨架）之外的区域在结合后进入步骤中发挥着关键作用，并决定肝细胞对 HCV 的易感性。在这里，我们研究了 hCD81 主链中的五个非同义单核苷酸变异对 HCV 易感性的影响。我们生成了稳定表达 hCD81 变体的细胞系，并使用 HCV 假颗粒和细胞培养物衍生的 HCV 感染细胞。我们的结果表明，所有测试的 hCD81 变体都支持 HCV 伪粒子进入，其效率与野生型 hCD81 相似。相比之下，变体 A54V、V211M 和 M220I 对细胞培养源性 HCV 感染的支持作用较小。这种改变的易感性依赖于 HCV 基因型，并且特别影响细胞进入步骤。我们的研究结果确定了三种 hCD81 遗传变异体，它们作为特定病毒基因型的 HCV 宿主因子的功能受损。这项研究提供了额外的证据，证明宿主遗传变异导致 HCV 感染和结果的个体间差异。