AIDS Institute; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
PLoS One. 2012;7(9):e44241. doi: 10.1371/journal.pone.0044241. Epub 2012 Sep 10.
Identification of broadly cross-reactive HIV-1-neutralizing antibodies (bnAbs) may assist vaccine immunogen design. Here we report a novel human monoclonal antibody (mAb), designated m43, which co-targets the gp120 and gp41 subunits of the HIV-1 envelope glycoprotein (Env). M43 bound to recombinant gp140 s from various primary isolates, to membrane-associated Envs on transfected cells and HIV-1 infected cells, as well as to recombinant gp120 s and gp41 fusion intermediate structures containing N-trimer structure, but did not bind to denatured recombinant gp140 s and the CD4 binding site (CD4bs) mutant, gp120 D368R, suggesting that the m43 epitope is conformational and overlaps the CD4bs on gp120 and the N-trimer structure on gp41. M43 neutralized 34% of the HIV-1 primary isolates from different clades and all the SHIVs tested in assays based on infection of peripheral blood mononuclear cells (PBMCs) by replication-competent virus, but was less potent in cell line-based pseudovirus assays. In contrast to CD4, m43 did not induce Env conformational changes upon binding leading to exposure of the coreceptor binding site, enhanced binding of mAbs 2F5 and 4E10 specific for the membrane proximal external region (MPER) of gp41 Envs, or increased gp120 shedding. The overall modest neutralization activity of m43 is likely due to the limited binding of m43 to functional Envs which could be increased by antibody engineering if needed. M43 may represent a new class of bnAbs targeting conformational epitopes overlapping structures on both gp120 and gp41. Its novel epitope and possibly new mechanism(s) of neutralization could helpdesign improved vaccine immunogens and candidate therapeutics.
鉴定广泛交叉中和的 HIV-1 中和抗体（bnAbs）可能有助于疫苗免疫原设计。在此，我们报告了一种新型人源单克隆抗体（mAb），命名为 m43，其可同时靶向 HIV-1 包膜糖蛋白（Env）的 gp120 和 gp41 亚基。m43 结合了来自各种原始分离株的重组 gp140s、转染细胞和感染 HIV-1 的细胞上的膜相关 Env、以及含有 N-三聚体结构的重组 gp120s 和 gp41 融合中间结构，但不结合变性重组 gp140s 和 CD4 结合位点（CD4bs）突变体 gp120 D368R，表明 m43 表位是构象性的，与 gp120 上的 CD4bs 和 gp41 上的 N-三聚体结构重叠。m43 中和了来自不同分支的 34%的 HIV-1 原始分离株，以及在基于外周血单核细胞（PBMC）感染的复制型病毒的测定中所有测试的 SHIV，但其在基于细胞系的假病毒测定中的效力较低。与 CD4 不同，m43 结合后不会诱导 Env 构象变化，导致核心受体结合位点暴露，增强了针对 gp41 Env 膜近端外部区域（MPER）的 mAbs 2F5 和 4E10 的结合，或增加 gp120 的脱落。m43 的总体中和活性较弱可能是由于 m43 与功能性 Env 的结合有限，如果需要，可以通过抗体工程增加 m43 的结合。m43 可能代表一种新型的 bnAbs，其针对的构象表位与 gp120 和 gp41 上的结构重叠。其新型表位和可能的新中和机制（多个）有助于设计改进的疫苗免疫原和候选治疗药物。
