Institute of Tropical Medicine, Virology Unit, Antwerp, Belgium.
PLoS One. 2013 Jul 17;8(7):e68863. doi: 10.1371/journal.pone.0068863. Print 2013.
Immunogen design for HIV-1 vaccines could be based on epitope identification of naturally occurring neutralizing antibodies in infected patients. A tier 2 neutralizing monoclonal antibody (mAb), HJ16 recognizes a new epitope in the CD4 binding site (CD4bs) region that only partially overlaps with the b12 epitope. We aimed to identify the critical binding site by resistance induction in a sensitive primary CRF02_AG strain. In four independent dose-escalation studies, the N276D mutation was consistently the only alteration found and it was confirmed to be responsible for resistance to HJ16 by site-directed mutagenesis in envelopes (envs) of the homologous CRF02_AG, as well as of a subtype A and a subtype C primary isolate. This mutation removes an N-linked glycosylation site. The effect of N276D was very selective, as it failed to confer resistance to a range of other entry inhibitors. Remarkably, sensitivity to the CD4bs VRC01 and VRC03 mAbs was increased in the N276D mutated viruses. These data indicate that binding of the CD4bs specific HJ16 mAb critically depends on the interaction with the N276-glycan, thus indicating that HJ16 is the first glycan dependent CD4bs-specific mAb.
HIV-1 疫苗的免疫原设计可以基于感染患者体内天然存在的中和抗体的表位鉴定。一种 tier 2 中和单克隆抗体 (mAb)，HJ16 识别 CD4 结合位点 (CD4bs) 区域中的一个新表位，该表位仅部分与 b12 表位重叠。我们旨在通过在敏感的原发性 CRF02_AG 株中诱导耐药性来确定关键结合位点。在四项独立的剂量递增研究中，N276D 突变始终是唯一发现的改变，并且通过对同源 CRF02_AG 包膜（envs）以及亚型 A 和亚型 C 原发性分离物中的突变进行定点诱变，证实其对 HJ16 的耐药性负责。该突变消除了一个 N-连接糖基化位点。N276D 的作用非常具有选择性，因为它未能赋予对一系列其他进入抑制剂的耐药性。值得注意的是，N276D 突变病毒对 CD4bs VRC01 和 VRC03 mAbs 的敏感性增加。这些数据表明，CD4bs 特异性 HJ16 mAb 的结合严重依赖于与 N276-聚糖的相互作用，因此表明 HJ16 是第一个依赖聚糖的 CD4bs 特异性 mAb。
