Labrosse B, Treboute C, Alizon M
INSERM U.332, Institut Cochin de Génétique Moléculaire, 75014 Paris, France.
J Virol. 2000 Mar;74(5):2142-50. doi: 10.1128/jvi.74.5.2142-2150.2000.
The triterpene RPR103611 is an efficient inhibitor of membrane fusion mediated by the envelope proteins (Env, gp120-gp41) of CXCR4-dependent (X4) human immunodeficiency virus type 1 (HIV-1) strains, such as HIV-1(LAI) (LAI). Other X4 strains, such as HIV-1(NDK) (NDK), and CCR5-dependent (R5) HIV-1 strains, such as HIV-1(ADA) (ADA), were totally resistant to RPR103611. Analysis of chimeric LAI-NDK Env proteins identified a fragment of the NDK gp41 ectodomain determining drug resistance. A single difference at position 91, leucine in LAI and histidine in NDK, apparently accounted for their sensitivity or resistance to RPR103611. We had previously identified a mutation of isoleucine 84 to serine in a drug escape LAI variant. Both I84 and L91 are located in the "loop region" of gp41 separating the proximal and distal helix domains. Nonpolar residues in this region therefore appear to be important for the antiviral activity of RPR103611 and are possibly part of its target. However, another mechanism had to be envisaged to explain the drug resistance of ADA, since its gp41 loop region was almost identical to that of LAI. Fusion mediated by chimeric Env consisting of LAI gp120 and ADA gp41, or the reciprocal construct, was fully blocked by RPR103611. The gp120-gp41 complex of R5 strains is stable, relative to that of X4 strains, and this stability could play a role in their drug resistance. Indeed, when the postbinding steps of ADA infection were performed under mildly acidic conditions (pH 6.5 or 6.0), a treatment expected to favor dissociation of gp120, we achieved almost complete neutralization by RPR103611. The drug resistance of NDK was partially overcome by preincubating virus with soluble CD4, a gp120 ligand inducing conformational changes in the Env complex. The antiviral efficacy of RPR103611 therefore depends on the sequence of the gp41 loop and the stability of the gp120-gp41 complex, which could limit the accessibility of this target.
三萜类化合物RPR103611是一种有效的膜融合抑制剂，可抑制依赖CXCR4的1型人类免疫缺陷病毒（HIV-1）毒株（如HIV-1(LAI)）的包膜蛋白（Env，gp120-gp41）介导的膜融合。其他X4毒株，如HIV-1(NDK)，以及依赖CCR5的HIV-1毒株，如HIV-1(ADA)，对RPR103611完全耐药。对嵌合的LAI-NDK Env蛋白的分析确定了NDK gp41胞外域中决定耐药性的一个片段。LAI的第91位是亮氨酸，NDK的第91位是组氨酸，这一单一差异显然导致了它们对RPR103611的敏感或耐药。我们之前在一个耐药的LAI变异体中鉴定出异亮氨酸84突变为丝氨酸。I84和L91都位于gp41的“环区”，该区域分隔近端和远端螺旋结构域。因此，该区域的非极性残基似乎对RPR103611的抗病毒活性很重要，并且可能是其靶点的一部分。然而，必须设想另一种机制来解释ADA的耐药性，因为其gp41环区与LAI的几乎相同。由LAI gp120和ADA gp41组成的嵌合Env介导的融合，或反向构建体介导的融合，均被RPR103611完全阻断。相对于X4毒株，R5毒株的gp120-gp41复合物更稳定，这种稳定性可能在其耐药性中起作用。事实上，当在轻度酸性条件（pH 6.5或6.0）下进行ADA感染的结合后步骤时（这种处理预期有利于gp120的解离），我们通过RPR103611实现了几乎完全的中和。通过将病毒与可溶性CD4预孵育，部分克服了NDK的耐药性，可溶性CD4是一种可诱导Env复合物构象变化的gp120配体。因此，RPR103611的抗病毒效力取决于gp41环的序列以及gp120-gp41复合物的稳定性，这可能会限制该靶点的可及性。
