Structural flexibility at a major conserved antibody target on hepatitis C virus E2 antigen
Structural flexibility at a major conserved antibody target on hepatitis C virus E2 antigen
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DOI：
10.1073/pnas.1609780113
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发表时间：
2016-11-08
影响因子：
11.1
通讯作者：
Law, Mansun
中科院分区：
文献类型：
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作者：
Kong, Leopold;Lee, David E.;Law, Mansun
丙型肝炎病毒（HCV）是肝脏疾病的主要原因，影响超过2%的世界人口。HCV包膜糖蛋白E1和E2介导病毒进入，其中E2是中和抗体应答的主要靶标。E2的结构研究已经产生了疫苗设计的模板，包括保守的CD 81受体结合位点（CD 81 bs），这是广泛中和抗体（bNAb）的关键靶点。不幸的是，用重组E2和E1 E2免疫很少产生足够水平的bNAb用于保护。为了理解引发针对CD 81 bs的bNAb应答的挑战，我们通过电子显微镜（EM）、氢-氘交换（HDX）、分子动力学（MD）和量热法研究了E2 CD 81 bs。通过EM，我们观察到HCV 1，一种识别CD 81 bs的N-末端区域的bNAb，从多个角度结合可溶性E2核心构建体，表明CD 81 bs的组分是柔性的。多个E2构建体的HDX一致地表明整个CD 81 bs相对于E2蛋白的其余部分是柔性的，这通过MD模拟进一步证实。然而，E2具有84.8摄氏度的高熔化温度，这更类似于来自嗜热生物的蛋白质。因此，重组E2总体上是一种高度稳定的蛋白质，但具有异常灵活的CD 81 bs。这种灵活性可能会促进诱导非中和抗体的bNAbs E2 CD 81 bs，强调了必要性，硬化这一抗原区域作为合理的疫苗设计的目标。
Hepatitis C virus (HCV) is a major cause of liver disease, affecting over 2% of the world's population. The HCV envelope glycoproteins E1 and E2 mediate viral entry, with E2 being the main target of neutralizing antibody responses. Structural investigations of E2 have produced templates for vaccine design, including the conserved CD81 receptor-binding site (CD81bs) that is a key target of broadly neutralizing antibodies (bNAbs). Unfortunately, immunization with recombinant E2 and E1E2 rarely elicits sufficient levels of bNAbs for protection. To understand the challenges for eliciting bNAb responses against the CD81bs, we investigated the E2 CD81bs by electron microscopy (EM), hydrogen-deuterium exchange (HDX), molecular dynamics (MD), and calorimetry. By EM, we observed that HCV1, a bNAb recognizing the N-terminal region of the CD81bs, bound a soluble E2 core construct from multiple angles of approach, suggesting components of the CD81bs are flexible. HDX of multiple E2 constructs consistently indicated the entire CD81bs was flexible relative to the rest of the E2 protein, which was further confirmed by MD simulations. However, E2 has a high melting temperature of 84.8 degrees C, which is more akin to proteins from thermophilic organisms. Thus, recombinant E2 is a highly stable protein overall, but with an exceptionally flexible CD81bs. Such flexibility may promote induction of nonneutralizing antibodies over bNAbs to E2 CD81bs, underscoring the necessity of rigidifying this antigenic region as a target for rational vaccine design.