Vaccine-elicited primate antibodies use a distinct approach to the HIV-1 primary receptor binding site informing vaccine redesign
Vaccine-elicited primate antibodies use a distinct approach to the HIV-1 primary receptor binding site informing vaccine redesign
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DOI：
10.1073/pnas.1319512111
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发表时间：
2014-02-18
影响因子：
11.1
通讯作者：
Wyatt, Richard T.
中科院分区：
文献类型：
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作者：
Tran, Karen;Poulsen, Christian;Wyatt, Richard T.
HIV-1的中和需要Ab接近功能性包膜糖蛋白（Env）尖峰。我们最近报道了从可溶性Env三聚体免疫的恒河猴中分离出以前未识别的疫苗诱导的CD4结合位点（CD4bs）定向单克隆抗体，表明该区域在亚单位疫苗接种背景下具有免疫原性。为了阐明三聚体诱导的单抗与gp120的相互作用以及它们与HIV-1初级分离刺突的相互作用不足，我们结晶了两个单抗GE136和GE148的Fab片段。对它们的互补性决定区域进行丙氨酸扫描，加上对gp120上的表位进行表位扫描，发现Ab/gp120界面上可能存在接触残基。GE136和GE148 fab与gp120对接，再加上这些非广泛中和的单克隆抗体（non-bNAbs）与gp120单体结合的EM重建，以及EM对有序三聚体的建模，表明相对于CD4bs导向的bNAbs VRC01和PGV04使用的更侧向的相互作用模式，Ab通过垂直的接触角度接近CD4bs。将结构拟合到可用的冷冻电镜天然刺突密度中表明，这两种疫苗诱导的单克隆抗体与顶部可变区刺突帽发生冲突，而单克隆抗体则在这个四级屏蔽下有效地接触到原代HIV分离物上的CD4bs。这些结果为目前疫苗诱导的cd4bs定向抗体观察到的有限中和广度提供了结构基础，并强调需要更好的有序三聚体免疫原。因此，本文的分析为指导HIV-1疫苗免疫原的重新设计提供了有价值的信息。
HIV-1 neutralization requires Ab accessibility to the functional envelope glycoprotein (Env) spike. We recently reported the isolation of previously unidentified vaccine-elicited, CD4 binding site (CD4bs)-directed mAbs from rhesus macaques immunized with soluble Env trimers, indicating that this region is immunogenic in the context of subunit vaccination. To elucidate the interaction of the trimer-elicited mAbs with gp120 and their insufficient interaction with the HIV-1 primary isolate spike, we crystallized the Fab fragments of two mAbs, GE136 and GE148. Alanine scanning of their complementarity-determining regions, coupled with epitope scanning of their epitopes on gp120, revealed putative contact residues at the Ab/gp120 interface. Docking of the GE136 and GE148 Fabs to gp120, coupled with EM reconstructions of these nonbroadly neutralizing mAbs (non-bNAbs) binding to gp120 monomers and EM modeling to well-ordered trimers, suggested Ab approach to the CD4bs by a vertical angle of access relative to the more lateral mode of interaction used by the CD4bs-directed bNAbs VRC01 and PGV04. Fitting the structures into the available cryo-EM native spike density indicated clashes between these two vaccine-elicited mAbs and the topside variable region spike cap, whereas the bNAbs duck under this quaternary shield to access the CD4bs effectively on primary HIV isolates. These results provide a structural basis for the limited neutralizing breadth observed by current vaccine-induced, CD4bs-directed Abs and highlight the need for better ordered trimer immunogens. The analysis presented here therefore provides valuable information to guide HIV-1 vaccine immunogen redesign.