Svarovskaia Evguenia S, Feng Joy Y, Margot Nicolas A, Myrick Florence, Goodman Derrick, Ly John K, White Kirsten L, Kutty Nilima, Wang Ruth, Borroto-Esoda Katyna, Miller Michael D
Gilead Sciences, Inc, 4 University Place, 4611 University Drive, Durham, NC 27707, USA.
J Acquir Immune Defic Syndr. 2008 Aug 1;48(4):428-36. doi: 10.1097/QAI.0b013e31817bbe93.
The K65R mutation in human immunodeficiency virus type 1 reverse transcriptase can be selected by abacavir, didanosine, tenofovir, and stavudine in vivo resulting in reduced susceptibility to these drugs and decreased viral replication capacity. In clinical isolates, K65R is frequently accompanied by the A62V and S68G reverse transcriptase mutations.
The role of A62V and S68G in combination with K65R was investigated using phenotypic, viral growth competition, pre-steady-state kinetic, and excision analyses.
Addition of A62V and S68G to K65R caused no significant change in human immunodeficiency virus type 1 resistance to abacavir, didanosine, tenofovir, or stavudine but partially restored the replication defect of virus containing K65R. The triple mutant K65R+A62V+S68G still showed some replication defect compared with wild-type virus. Pre-steady-state kinetic analysis demonstrated that K65R resulted in a decreased rate of incorporation (kpol) for all natural dNTPs, which were partially restored to wild-type levels by addition of A62V and S68G. When added to K65R and S68G, the A62V mutation seemed to restore adenosine triphosphate-mediated excision of tenofovir to wild-type levels.
A62V and S68G serve as partial compensatory mutations for the K65R mutation in reverse transcriptase by improving the viral replication capacity, which is likely due to increased incorporation efficiency of the natural substrates.
1型人类免疫缺陷病毒逆转录酶中的K65R突变可在体内被阿巴卡韦、去羟肌苷、替诺福韦和司他夫定选择出来，导致对这些药物的敏感性降低以及病毒复制能力下降。在临床分离株中，K65R常常伴有A62V和S68G逆转录酶突变。
使用表型、病毒生长竞争、前稳态动力学和切除分析研究A62V和S68G与K65R组合的作用。
在K65R中添加A62V和S68G对1型人类免疫缺陷病毒对阿巴卡韦、去羟肌苷、替诺福韦或司他夫定的耐药性没有显著影响，但部分恢复了含有K65R病毒的复制缺陷。与野生型病毒相比，三重突变体K65R+A62V+S68G仍表现出一些复制缺陷。前稳态动力学分析表明，K65R导致所有天然脱氧核苷三磷酸的掺入率（kpol）降低，添加A62V和S68G后，其部分恢复到野生型水平。当添加到K65R和S68G中时，A62V突变似乎将三磷酸腺苷介导的替诺福韦切除恢复到野生型水平。
A62V和S68G通过提高病毒复制能力作为逆转录酶中K65R突变的部分补偿性突变，这可能是由于天然底物的掺入效率增加所致。
