Ou Wu, Lu Ning, Yu Sloane S, Silver Jonathan
Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Building 4, Room 336, Bethesda, MD 20892, USA.
J Virol. 2006 Mar;80(5):2539-47. doi: 10.1128/JVI.80.5.2539-2547.2006.
The membrane-proximal region of the human immunodeficiency virus type 1 (HIV-1) transmembrane protein (TM) is critical for envelope (Env)-mediated membrane fusion and contains the target for broadly reactive neutralizing antibody 2F5. It has been proposed that 2F5 neutralization might involve interaction of its long, hydrophobic, complementarity-determining region (CDR) H3, with adjacent viral membrane. Using Moloney murine leukemia virus (MLV) as a tool, we examined the effect of epitope position on 2F5 neutralization. When the 2F5 epitope was inserted in the proline-rich region of MLV Env surface protein (SU), 2F5 blocked cell fusion and virus infection, whereas MLV with a hemagglutinin (HA) epitope at the same position was not neutralized by anti-HA, even though the antibodies bound their respective Envs on the surface of infected cells and viruses equally well. When the 2F5 epitope was inserted in the MLV Env TM at a position comparable to its natural position in HIV-1 TM, 2F5 antibody blocked Env-mediated cell fusion. Epitope position had subtle effects on neutralization by 2F5: the antibody concentration for 50% inhibition of cell fusion was more than 10-fold lower when the 2F5 epitope was in SU than in TM, and inhibition was less complete at high concentrations of antibody; we discuss possible explanations for these effects of epitope position. Since membrane proximity was not required for neutralization by 2F5 antibody, we speculate that the CDR H3 of 2F5 contributes to neutralization by destabilizing an adjacent protein rather than by inserting into an adjacent membrane.
人类免疫缺陷病毒1型（HIV-1）跨膜蛋白（TM）的膜近端区域对于包膜（Env）介导的膜融合至关重要，并且包含广泛反应性中和抗体2F5的靶点。有人提出，2F5的中和作用可能涉及其长的、疏水的互补决定区（CDR）H3与相邻病毒膜的相互作用。我们使用莫洛尼鼠白血病病毒（MLV）作为工具，研究了表位位置对2F5中和作用的影响。当2F5表位插入到MLV包膜表面蛋白（SU）富含脯氨酸的区域时，2F5阻断细胞融合和病毒感染，而在相同位置带有血凝素（HA）表位的MLV则不被抗HA中和，尽管这些抗体在感染细胞和病毒表面与各自的Env结合得同样好。当2F5表位插入到MLV Env TM中与其在HIV-1 TM中的天然位置相当的位置时，2F抗体阻断Env介导的细胞融合。表位位置对2F5的中和作用有微妙影响：当2F5表位在SU中时，50%抑制细胞融合的抗体浓度比在TM中低10倍以上，并且在高浓度抗体时抑制作用不太完全；我们讨论了表位位置这些影响的可能解释。由于2F5抗体中和不需要膜接近，我们推测2F5的CDR H3通过使相邻蛋白不稳定而不是通过插入相邻膜来促进中和作用。
