Berkower Ira, Patel Chiraag, Ni Yisheng, Virnik Konstantin, Xiang Zhexin, Spadaccini Angelo
Laboratory of Immunoregulation, DVP, Office of Vaccine Research and Review, Center for Biologics, FDA, Bldg 29, Room 523, NIH Campus, Bethesda, MD 20892, USA.
Virology. 2008 Aug 1;377(2):330-8. doi: 10.1016/j.virol.2008.03.040. Epub 2008 Jun 2.
Different isolates of HIV-1 are known to vary in antibody binding and sensitivity to neutralization. In response to selective pressure, the virus may conceal important neutralizing determinants, such as the CD4 binding site on gp120, through steric hindrance or conformational masking. The 3D structure of gp120 shows five loop structures that surround the CD4 binding site (CD4BS) and may restrict antibody access to the site. We have generated gp120 mutants lacking each of these loops and characterized them with a panel of monoclonal antibodies, including b12 and F105. A targeted deletion in the beta20-beta21 loop resulted in gp120 with enhanced binding of both monoclonals. Enhancement of b12 binding suggests reduced steric hindrance, since the antibody is relatively insensitive to conformation. Enhanced binding of F105, which depends strongly on the protein conformation, suggests that the mutation may allow gp120 to move more freely into the liganded form. The same viral strategies that limit antibody binding may also inhibit antibody induction. Modified forms of gp120, in which the CD4 binding site is more exposed and accessible to antibodies, could provide novel immunogens for eliciting antibodies to this broadly shared neutralizing determinant.
已知HIV-1的不同分离株在抗体结合和对中和的敏感性方面存在差异。在选择性压力的作用下，病毒可能通过空间位阻或构象掩盖来隐藏重要的中和决定簇，例如gp120上的CD4结合位点。gp120的三维结构显示有五个环绕CD4结合位点（CD4BS）的环结构，可能会限制抗体接近该位点。我们构建了缺失这些环中每一个的gp120突变体，并用一组单克隆抗体（包括b12和F105）对其进行了表征。β20-β21环中的靶向缺失导致gp120与两种单克隆抗体的结合增强。b12结合增强表明空间位阻降低，因为该抗体对构象相对不敏感。强烈依赖蛋白质构象的F105结合增强表明，该突变可能使gp120更自由地转变为配体形式。限制抗体结合的相同病毒策略也可能抑制抗体诱导。修饰后的gp120形式，其中CD4结合位点对抗体更暴露且可接近，可为引发针对这种广泛共享的中和决定簇的抗体提供新型免疫原。
