Chinnadurai Raghavan, Rajan Devi, Münch Jan, Kirchhoff Frank
Institute for Virology, University Clinic, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
J Virol. 2007 Jun;81(12):6563-72. doi: 10.1128/JVI.02546-06. Epub 2007 Apr 11.
Human immunodeficiency virus type 1 (HIV-1) fusion inhibitors blocking viral entry by binding the gp41 heptad repeat 1 (HR1) region offer great promise for antiretroviral therapy, and the first of these inhibitors, T20 (Fuzeon; enfuvirtide), is successfully used in the clinic. It has been reported previously that changes in the 3-amino-acid GIV motif at positions 36 to 38 of gp41 HR1 mediate resistance to T20 but usually not to second-version fusion inhibitors, such as T1249, which target an overlapping but distinct region in HR1 including a conserved hydrophobic pocket (HP). Based on the common lack of cross-resistance and the difficulty of selecting T1249-resistant HIV-1 variants, it has been suggested that the determinants of resistance to first- and second-version fusion inhibitors may be different. To further assess HIV-1 resistance to fusion inhibitors and to analyze where changes in HR1 are tolerated, we randomized 16 codons in the HR1 region, including those making contact with HR2 codons and/or encoding residues in the GIV motif and the HP. We found that changes only at positions 37I, 38V, and 40Q near the N terminus of HR1 were tolerated. The propagation of randomly gp41-mutated HIV-1 variants in the presence of T1249 allowed the effective selection of highly resistant forms, all containing changes in the IV residues. Overall, the extent of T1249 resistance was inversely correlated to viral fitness and cytopathicity. Notably, one HIV-1 mutant showing approximately 10-fold-reduced susceptibility to T1249 inhibition replicated with wild type-like kinetics and caused substantial CD4+-T-cell depletion in ex vivo-infected human lymphoid tissue in the presence and absence of an inhibitor. Taken together, our results show that the GIV motif also plays a key role in resistance to second-version fusion inhibitors and suggest that some resistant HIV-1 variants may be pathogenic in vivo.
1型人类免疫缺陷病毒（HIV-1）融合抑制剂通过结合gp41七肽重复序列1（HR1）区域来阻断病毒进入，为抗逆转录病毒疗法带来了巨大希望，其中第一种抑制剂T20（福泽昂；恩夫韦肽）已成功应用于临床。此前有报道称，gp41 HR1第36至38位的3个氨基酸组成的GIV基序发生变化会介导对T20的耐药性，但通常不会介导对第二代融合抑制剂的耐药性，比如T1249，它靶向HR1中一个重叠但不同的区域，该区域包括一个保守的疏水口袋（HP）。基于普遍缺乏交叉耐药性以及难以筛选出对T1249耐药的HIV-1变体，有人提出对第一代和第二代融合抑制剂的耐药决定因素可能不同。为了进一步评估HIV-1对融合抑制剂的耐药性，并分析HR1中哪些位置的变化是可耐受的，我们对HR1区域的16个密码子进行了随机化处理，包括那些与HR2密码子接触和/或编码GIV基序及疏水口袋中残基的密码子。我们发现，只有HR1 N端附近的37I、38V和40Q位置的变化是可耐受的。在T1249存在的情况下，随机发生gp41突变的HIV-1变体的增殖使得能够有效筛选出高度耐药的形式，所有这些形式都包含IV残基的变化。总体而言，T1249耐药程度与病毒适应性和细胞病变性呈负相关。值得注意的是，一种对T1249抑制的敏感性降低约10倍的HIV-1突变体，在有或没有抑制剂的情况下，都以类似野生型的动力学进行复制，并在体外感染的人淋巴组织中导致大量CD4+ T细胞耗竭。综上所述，我们的结果表明GIV基序在对第二代融合抑制剂的耐药性中也起关键作用，并表明一些耐药的HIV-1变体在体内可能具有致病性。
