Geipel Andreas, Seiz Pia L, Niekamp Hauke, Neumann-Fraune Maria, Zhang Ke, Kaiser Rolf, Protzer Ulrike, Gerlich Wolfram H, Glebe Dieter
Institute of Medical Virology, Justus Liebig University Giessen, National Reference Center for Hepatitis B and D Viruses, Biomedical Research Center Seltersberg, Giessen, Germany.
Antivir Ther. 2015;20(8):779-87. doi: 10.3851/IMP2928. Epub 2015 Jan 5.
Entecavir is an efficient inhibitor of HBV reverse transcriptase (RT) and widely used for therapy of chronic hepatitis B. Entecavir treatment of HBV patients with lamivudine-resistant viral strains, however, often fails, but the mechanism of cross-resistance development is not fully understood.
Using non-linear regression models, dose-response curves of cloned HBV strains from patients pre-treated with RT inhibitors were established in human hepatoma cell lines after transfection with HBV genomes containing HBV polymerase genes from patient isolates. 50% and 90% inhibitory concentrations (IC50 and IC90) and corresponding antiviral resistance factors (RF50 and RF90) were calculated.
The entecavir dose-response curve of lamivudine-resistant HBV RT mutants rtM204 for the replication of HBV decreased less than expected with increasing drug dose. Remarkably, due to the flat dose-response curves, RF90 values against entecavir of samples with rtM204 substitutions were up to 30× higher than their RF50 values.
The unexpectedly high IC90 indicates a strong residual replication capacity of lamivudine-resistant HBV rtM204 variants under entecavir therapy, although IC50 values are initially within the therapeutic range of entecavir. This characteristic favours rapid selection of additional mutants with overt resistance against entecavir. Thus, the current phenotypic resistance assays should include determination of IC90.
恩替卡韦是一种有效的乙肝病毒逆转录酶（RT）抑制剂，广泛用于治疗慢性乙型肝炎。然而，恩替卡韦治疗携带拉米夫定耐药病毒株的乙肝患者时常常失败，但其交叉耐药产生的机制尚未完全明确。
使用非线性回归模型，在用含有来自患者分离株的乙肝病毒聚合酶基因的乙肝病毒基因组转染人肝癌细胞系后，建立来自经RT抑制剂预处理患者的克隆乙肝病毒株的剂量反应曲线。计算50%和90%抑制浓度（IC50和IC90）以及相应的抗病毒耐药因子（RF50和RF90）。
拉米夫定耐药的乙肝病毒RT突变体rtM204的恩替卡韦剂量反应曲线显示，随着药物剂量增加，乙肝病毒复制的下降幅度低于预期。值得注意的是，由于剂量反应曲线平坦，具有rtM204替代的样本对恩替卡韦的RF90值比其RF50值高出多达30倍。
尽管IC50值最初在恩替卡韦治疗范围内，但意外高的IC90表明在恩替卡韦治疗下，拉米夫定耐药的乙肝病毒rtM204变体具有很强的残余复制能力。这一特性有利于快速选择对恩替卡韦具有明显耐药性的其他突变体。因此，当前的表型耐药性检测应包括IC90的测定。
