Department of Surgery, Duke University Medical Center, Durham, NC, United States of America.
Fred Hutchinson Cancer Research Center, Department of Global Health, Seattle, WA, United States of America.
PLoS Pathog. 2018 Nov 5;14(11):e1007431. doi: 10.1371/journal.ppat.1007431. eCollection 2018 Nov.
Broadly neutralizing antibody (bnAb) induction is a high priority for effective HIV-1 vaccination. VRC01-class bnAbs that target the CD4 binding site (CD4bs) of trimeric HIV-1 envelope (Env) glycoprotein spikes are particularly attractive to elicit because of their extraordinary breadth and potency of neutralization in vitro and their ability to protect against infection in animal models. Glycans bordering the CD4bs impede the binding of germline-reverted forms of VRC01-class bnAbs and therefore constitute a barrier to early events in initiating the correct antibody lineages. Deleting a subset of these glycans permits Env antigen binding but not virus neutralization, suggesting that additional barriers impede germline-reverted VRC01-class antibody binding to functional Env trimers. We investigated the requirements for functional Env trimer engagement of VRC01-class naïve B cell receptors by using virus neutralization and germline-reverted antibodies as surrogates for the interaction. Targeted deletion of a subset of N-glycans bordering the CD4bs, combined with Man5 enrichment of remaining N-linked glycans that are otherwise processed into larger complex-type glycans, rendered HIV-1 426c Env-pseudotyped virus (subtype C, transmitted/founder) highly susceptible to neutralization by near germline forms of VRC01-class bnAbs. Neither glycan modification alone rendered the virus susceptible to neutralization. The potency of neutralization in some cases rivaled the potency of mature VRC01 against wildtype viruses. Neutralization by the germline-reverted antibodies was abrogated by the known VRC01 resistance mutation, D279K. These findings improve our understanding of the restrictions imposed by glycans in eliciting VRC01-class bnAbs and enable a neutralization-based strategy to monitor vaccine-elicited early precursors of this class of bnAbs.
广泛中和抗体(bnAb)的诱导是 HIV-1 有效疫苗接种的首要任务。靶向三聚体 HIV-1 包膜(Env)糖蛋白刺突的 CD4 结合位点(CD4bs)的 VRC01 类 bnAb 因其在体外具有非凡的中和广度和效力,以及在动物模型中能够预防感染而特别具有吸引力。CD4bs 周围的聚糖阻碍了 VRC01 类 bnAb 种系回复形式的结合,因此构成了启动正确抗体谱系的早期事件的障碍。删除这些聚糖的一部分允许 Env 抗原结合,但不允许病毒中和,这表明存在其他障碍阻碍了种系回复的 VRC01 类抗体与功能性 Env 三聚体的结合。我们通过使用病毒中和和种系回复抗体作为相互作用的替代物,研究了 VRC01 类 naïve B 细胞受体与功能性 Env 三聚体结合的要求。靶向删除 CD4bs 周围的一组 N-聚糖,同时富集其余的 N-连接聚糖,使其成为更大的复杂型聚糖,使得 HIV-1 426c Env 假型病毒(亚型 C,传播/创始)高度易受 VRC01 类 bnAb 的近种系形式的中和。单独的聚糖修饰都不能使病毒易受中和。在某些情况下,中和的效力与成熟的 VRC01 对野生型病毒的效力相当。种系回复抗体的中和作用被已知的 VRC01 抗性突变 D279K 所阻断。这些发现提高了我们对糖基在诱导 VRC01 类 bnAb 中所施加的限制的理解,并使基于中和的策略能够监测该类 bnAb 的疫苗诱导的早期前体。
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