Department of Pathology, Stanford University School of Medicine, Stanford, California, USA.
J Virol. 2013 Jan;87(1):37-51. doi: 10.1128/JVI.01941-12. Epub 2012 Oct 24.
A challenge for hepatitis C virus (HCV) vaccine development is defining conserved epitopes that induce protective antibodies against this highly diverse virus. An envelope glycoprotein (E2) segment located at amino acids (aa) 412 to 423 contains highly conserved neutralizing epitopes. While polyclonal antibodies to aa 412 to 423 from HCV-infected individuals confirmed broad neutralization, conflicting findings have been reported on polyclonal antibodies to an adjacent region, aa 434 to 446, that may or may not interfere with neutralization by antibodies to aa 412 to 423. To define the interplay between these antibodies, we isolated human monoclonal antibodies (HMAbs) to aa 412 to 423, designated HC33-related HMAbs (HC33 HMAbs), and characterized their interactions with other HMAbs to aa 434 to 446. A subset of the HC33 HMAbs neutralized genotype 1 to 6 infectious cell culture-derived HCV virions (HCVcc) with various activities. Although nonneutralizing HC33 HMAbs were isolated, they had lower binding affinities than neutralizing HC33 HMAbs. These antibodies could be converted to neutralizing antibodies by affinity maturation. Unidirectional competition for binding to E2 was observed between HC33 HMAbs and HMAbs to aa 434 to 446. When HMAbs to aa 434 to 446, which mediated neutralization, were combined with neutralizing HC33 HMAbs, biphasic patterns in neutralization were observed. A modest degree of antagonism was observed at lower concentrations, and a modest degree of synergism was observed at higher concentrations. However, the overall effect was additive neutralization. A similar pattern was observed when these antibodies were combined to block E2 binding to the HCV coreceptor, CD81. These findings demonstrate that both of these E2 regions participate in epitopes mediating virus neutralization and that the antibodies to aa 412 to 423 and aa 434 to 446 do not hinder their respective virus-neutralizing activities.
丙型肝炎病毒 (HCV) 疫苗开发面临的一个挑战是确定诱导针对这种高度多样化病毒的保护性抗体的保守表位。位于氨基酸 (aa) 412 至 423 的包膜糖蛋白 (E2) 片段包含高度保守的中和表位。虽然来自 HCV 感染个体的 aa 412 至 423 的多克隆抗体证实了广泛的中和作用，但对 aa 434 至 446 附近区域的多克隆抗体的发现却存在冲突，这些抗体可能会或可能不会干扰对 aa 412 至 423 的抗体的中和作用。为了确定这些抗体之间的相互作用，我们分离了针对 aa 412 至 423 的人源单克隆抗体 (HMAb)，命名为 HC33 相关 HMAb (HC33 HMAb)，并对其与针对 aa 434 至 446 的其他 HMAb 的相互作用进行了表征。一组 HC33 HMAb 可中和基因型 1 至 6 的感染性细胞培养衍生的 HCV 病毒粒子 (HCVcc)，具有不同的活性。虽然分离出了非中和性的 HC33 HMAb，但它们的结合亲和力低于中和性的 HC33 HMAb。这些抗体可以通过亲和力成熟转化为中和抗体。观察到 HC33 HMAb 和针对 aa 434 至 446 的 HMAb 之间存在单向竞争结合 E2。当针对 aa 434 至 446 的介导中和作用的 HMAb 与中和性的 HC33 HMAb 结合时，观察到中和的双相模式。在较低浓度下观察到适度的拮抗作用，在较高浓度下观察到适度的协同作用。然而，总体效果是相加性的中和。当这些抗体结合以阻断 E2 与 HCV 核心受体 CD81 的结合时，观察到类似的模式。这些发现表明这两个 E2 区域都参与了介导病毒中和的表位，并且针对 aa 412 至 423 和 aa 434 至 446 的抗体不会阻碍其各自的病毒中和活性。
