El-Diwany Ramy, Cohen Valerie J, Mankowski Madeleine C, Wasilewski Lisa N, Brady Jillian K, Snider Anna E, Osburn William O, Murrell Ben, Ray Stuart C, Bailey Justin R
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
Department of Medicine, University of California, San Diego, La Jolla, California, United States of America.
PLoS Pathog. 2017 Feb 24;13(2):e1006235. doi: 10.1371/journal.ppat.1006235. eCollection 2017 Feb.
Broadly-neutralizing monoclonal antibodies (bNAbs) may guide vaccine development for highly variable viruses including hepatitis C virus (HCV), since they target conserved viral epitopes that could serve as vaccine antigens. However, HCV resistance to bNAbs could reduce the efficacy of a vaccine. HC33.4 and AR4A are two of the most potent anti-HCV human bNAbs characterized to date, binding to highly conserved epitopes near the amino- and carboxy-terminus of HCV envelope (E2) protein, respectively. Given their distinct epitopes, it was surprising that these bNAbs showed similar neutralization profiles across a panel of natural HCV isolates, suggesting that some viral polymorphisms may confer resistance to both bNAbs. To investigate this resistance, we developed a large, diverse panel of natural HCV envelope variants and a novel computational method to identify bNAb resistance polymorphisms in envelope proteins (E1 and E2). By measuring neutralization of a panel of HCV pseudoparticles by 10 μg/mL of each bNAb, we identified E1E2 variants with resistance to one or both bNAbs, despite 100% conservation of the AR4A binding epitope across the panel. We discovered polymorphisms outside of either binding epitope that modulate resistance to both bNAbs by altering E2 binding to the HCV co-receptor, scavenger receptor B1 (SR-B1). This study is focused on a mode of neutralization escape not addressed by conventional analysis of epitope conservation, highlighting the contribution of extra-epitopic polymorphisms to bNAb resistance and presenting a novel mechanism by which HCV might persist even in the face of an antibody response targeting multiple conserved epitopes.
广泛中和单克隆抗体（bNAbs）可能会为包括丙型肝炎病毒（HCV）在内的高变异性病毒的疫苗开发提供指导，因为它们靶向可作为疫苗抗原的保守病毒表位。然而，HCV对bNAbs的抗性可能会降低疫苗的效力。HC33.4和AR4A是迄今为止鉴定出的两种最有效的抗HCV人bNAbs，分别与HCV包膜（E2）蛋白氨基和羧基末端附近的高度保守表位结合。鉴于它们不同的表位，令人惊讶的是，这些bNAbs在一组天然HCV分离株中表现出相似的中和谱，这表明一些病毒多态性可能使两种bNAbs都产生抗性。为了研究这种抗性，我们构建了一个庞大且多样的天然HCV包膜变体库以及一种新的计算方法，以鉴定包膜蛋白（E1和E2）中的bNAb抗性多态性。通过用10μg/mL的每种bNAb检测一组HCV假颗粒的中和情况，我们鉴定出了对一种或两种bNAbs具有抗性的E1E2变体，尽管该变体库中AR4A结合表位的保守性为100%。我们发现，在任一结合表位之外的多态性通过改变E2与HCV共受体清道夫受体B1（SR-B1）的结合来调节对两种bNAbs的抗性。本研究聚焦于一种传统表位保守性分析未涉及的中和逃逸模式，突出了表位外多态性对bNAb抗性的作用，并提出了一种新机制，即即便面对靶向多个保守表位的抗体应答，HCV仍可能持续存在。
