From the Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers (Amsterdam UMC), Location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
Pepscan Therapeutics BV, Zuidersluisweg 2, 8243 RC Lelystad, The Netherlands.
J Biol Chem. 2019 Apr 12;294(15):5736-5746. doi: 10.1074/jbc.RA119.007360. Epub 2019 Jan 29.
HIV-1 entry into cells is mediated by the envelope glycoprotein (Env) and represents an attractive target for therapeutic intervention. Two drugs that inhibit HIV entry are approved for clinical use: the membrane fusion-inhibitor T20 (Fuzeon, enfuvirtide) and the C-C chemokine receptor type 5 (CCR5) blocker maraviroc (Selzentry). Another class of entry inhibitors supposedly target the fusion peptide (FP) and are termed anchor inhibitors. These include the VIRIP peptide and VIRIP derivatives such as VIR165, VIR353, and VIR576. Here, we investigated the mechanism of inhibition by VIR165. We show that substitutions within the FP modulate sensitivity to VIR165, consistent with the FP being the drug target. Our results also revealed that VIR165 acts during an intermediate post-CD4-binding entry step that is overlapping but not identical to the step inhibited by fusion inhibitors such as T20. We found that some but not all resistance mutations to heptad repeat 2 (HR2)-targeting fusion inhibitors can provide cross-resistance to VIR165. In contrast, resistance mutations in the HR1-binding site for the fusion inhibitors did not cause cross-resistance to VIR165. However, Env with mutations located outside this binding site and thought to affect fusion kinetics, exhibited decreased sensitivity to VIR165. Although we found a strong correlation between Env stability and resistance to HR2-based fusion inhibitors, such correlation was not observed for Env stability and VIR165 resistance. We conclude that VIRIP analogs target the FP during an intermediate, post-CD4-binding entry step that overlaps with but is distinct from the step(s) inhibited by HR2-based fusion inhibitors.
HIV-1 进入细胞是由包膜糖蛋白（Env）介导的，这是治疗干预的一个有吸引力的靶点。两种抑制 HIV 进入的药物已被批准用于临床使用：膜融合抑制剂 T20（Fuzeon，恩夫韦肽）和 C-C 趋化因子受体 5（CCR5）阻断剂马拉韦罗（Selzentry）。另一类据称针对融合肽（FP）的进入抑制剂被称为锚定抑制剂。其中包括 VIRIP 肽和 VIRIP 衍生物，如 VIR165、VIR353 和 VIR576。在这里，我们研究了 VIR165 的抑制机制。我们表明，FP 内的取代会调节对 VIR165 的敏感性，这与 FP 是药物靶标一致。我们的结果还表明，VIR165 在 CD4 结合后进入的一个中间步骤中发挥作用，该步骤与 T20 等融合抑制剂所抑制的步骤重叠但不完全相同。我们发现，一些但不是所有针对七肽重复 2（HR2）靶向融合抑制剂的耐药突变可提供对 VIR165 的交叉耐药性。相比之下，融合抑制剂 HR1 结合位点的耐药突变不会导致对 VIR165 的交叉耐药性。然而，Env 中的突变位于该结合位点之外，并且被认为会影响融合动力学，对 VIR165 的敏感性降低。尽管我们发现 Env 稳定性与基于 HR2 的融合抑制剂的耐药性之间存在很强的相关性，但这种相关性在 Env 稳定性与 VIR165 耐药性之间并不存在。我们得出结论，VIRIP 类似物在 CD4 结合后进入的一个中间步骤中靶向 FP，该步骤与基于 HR2 的融合抑制剂所抑制的步骤重叠但不同。
