Background and Aims: Chronic hepatitis C virus (HCV) infection afflicts around 50 million people globally, causing ~250,000 deaths yearly. An effective vaccine needs to overcome high viral diversity and HCV’s ability to evade neutralizing antibodies (NAbs). Rapid antigenic drift in the N-terminal motif of envelope protein E2, named hypervariable region 1 (HVR1), is critically involved in NAb evasion via an incompletely understood mechanism involving viral entry factors. The canonical length of HVR1 is 27 amino acids, but insertions of 2-4 amino acids was described in patients infected with genotype 1b. We aimed at determining whether HVR1 insertions may be underreported due to extreme HVR1 variability. Approach and Results: We observed a 0.7% HVR1 insertion prevalence in routine NGS patient contigs. Thus, we performed direct sequence analysis of E1E2 sequences from 131 HCV infected patients. Interestingly, we observed that 3% of patients harbored viruses (genotype 1a, 2b, 3a) with dominant HVR1 insertions. Insertion of longer non-canonical HVR1s into HCV cell culture recombinants frequently caused loss of fitness. However, culture-viable viruses with HVR1 insertions were fully viable in vivo. Interestingly, in adapted genotype 1b recombinants with HVR1 insertions, we found internal HVR1 deletions, that increased antibody sensitivity, which surprisingly correlated more with reduced LDLr than reduced SR-BI dependency, indicating a role of LDLr in NAb evasion. Conversely, HVR1 insertions had no effect on receptor dependency, however, they modulated epitope-specific NAb sensitivity. Conclusions: HVR1 insertion prevalence and NAb sensitivity modulation indicate they represent a mechanism by which HCV evades emerging NAbs during infection.

中文翻译：

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丙型肝炎病毒高变区 1 插入的患病率及其在抗体逃避中的作用


背景和目的：慢性丙型肝炎病毒 （HCV） 感染全球约有 5000 万人，每年造成 ~250,000 人死亡。有效的疫苗需要克服高病毒多样性和 HCV 逃避中和抗体 （NAb） 的能力。包膜蛋白 E2 的 N 末端基序（称为高变区 1 （HVR1））的快速抗原漂移通过涉及病毒进入因子的不完全了解的机制与 NAb 逃避密切相关。HVR1 的规范长度为 27 个氨基酸，但在感染基因型 1b 的患者中描述了 2-4 个氨基酸的插入。我们旨在确定 HVR1 插入是否可能因 HVR1 的极端变异性而被低估。方法和结果： 我们在常规 NGS 患者重叠群中观察到 0.7% 的 HVR1 插入患病率。因此，我们对 131 例 HCV 感染患者的 E1E2 序列进行了直接序列分析。有趣的是，我们观察到 3% 的患者携带病毒 （基因型 1a 、 2b 、 3a） 且 HVR1 插入占主导地位。将较长的非经典 HVR1 插入 HCV 细胞培养重组体中经常会导致适应性丧失。然而，插入 HVR1 的培养活病毒在体内是完全活的。有趣的是，在具有 HVR1 插入的适应基因型 1b 重组体中，我们发现了内部 HVR1 缺失，这增加了抗体敏感性，令人惊讶的是，这与降低的 LDLr 相关程度高于减少的 SR-BI 依赖性，表明 LDLr 在 NAb 逃避中的作用。相反，HVR1 插入对受体依赖性没有影响，但是，它们调节表位特异性 NAb 敏感性。结论： HVR1 插入流行率和 NAb 敏感性调节表明它们代表了 HCV 在感染过程中逃避新出现的 NAb 的机制。