Ly John K, Margot Nicolas A, MacArthur Holly L, Hung Magdeleine, Miller Michael D, White Kirsten L
Gilead Sciences, Inc, Foster City, CA, USA.
Antivir Chem Chemother. 2007;18(6):307-16. doi: 10.1177/095632020701800603.
The HIV-1 reverse transcriptase (RT) resistance mutations K65R and M184V occur individually and in combination, and can contribute to decreased treatment responses in patients. In order to understand how these mutations interact with one another to confer drug resistance, the susceptibilities and underlying resistance mechanisms of these mutants to nucleoside RT inhibitors (NRTIs) were determined. Virus carrying K65R have reduced susceptibility to most NRTIs, but retain full susceptibility to zidovudine (AZT). M184V mutants have reduced susceptibility to lamivudine (3TC), emtricitabine (FTC) and didanosine (ddl), and contribute to reduced susceptibility to abacavir; however, they remain fully susceptible to tenofovir (TFV), AZT and stavudine (d4T). In cell culture, the K65R+M184V virus showed slightly increased susceptibility to TFV, AZT and d4T compared with K65R alone, but showed further decreases in susceptibility to 3TC, FTC, ddl and abacavir. There are two major biochemical mechanisms of resistance: altered NRTI binding/incorporation and altered NRTI excision after incorporation. For most NRTIs, the primary mechanism of resistance by K65R, M184V and K65R+M184V mutant RTs is to disrupt the NRTI-binding/incorporation steps. In the case of AZT, however, decreased binding/incorporation by K65R and K65R+M184V was counteracted by decreased AZT excision resulting in wild-type susceptibility. For TFV, decreased excision by K65R and K65R+M184V may partially counteract the K65R-driven decrease in incorporation relative to wild-type resulting in only low levels of TFV resistance. The K65R-mediated effect on decreasing NRTI excision was stronger than for M184V. These studies show that both mechanisms of resistance (binding/incorporation and excision) must be considered when defining resistance mechanisms.
人类免疫缺陷病毒1型（HIV-1）逆转录酶（RT）的耐药性突变K65R和M184V可单独出现或同时出现，并可能导致患者治疗反应降低。为了解这些突变如何相互作用以产生耐药性，我们测定了这些突变体对核苷类逆转录酶抑制剂（NRTIs）的敏感性及潜在耐药机制。携带K65R的病毒对大多数NRTIs的敏感性降低，但对齐多夫定（AZT）仍保持完全敏感性。M184V突变体对拉米夫定（3TC）、恩曲他滨（FTC）和去羟肌苷（ddl）的敏感性降低，并导致对阿巴卡韦的敏感性降低；然而，它们对替诺福韦（TFV）、AZT和司他夫定（d4T）仍保持完全敏感性。在细胞培养中，与单独的K65R相比，K65R+M184V病毒对TFV、AZT和d4T的敏感性略有增加，但对3TC、FTC、ddl和阿巴卡韦的敏感性进一步降低。耐药性主要有两种生化机制：NRTI结合/掺入改变和掺入后NRTI切除改变。对于大多数NRTIs，K65R、M184V和K65R+M184V突变体RT产生耐药性的主要机制是破坏NRTI结合/掺入步骤。然而，对于AZT，K65R和K65R+M184V导致的结合/掺入减少被AZT切除减少所抵消，从而产生野生型敏感性。对于TFV，K65R和K65R+M_{184}V导致的切除减少可能部分抵消K65R相对于野生型驱动的掺入减少，从而仅产生低水平的TFV耐药性。K65R介导的降低NRTI切除的作用比M184V更强。这些研究表明，在定义耐药机制时，必须同时考虑两种耐药机制（结合/掺入和切除）。
