Study for mechanism of drug-resistance of hepatitis B virus against anti-viral therapy for patients with chronic hepatitis B virus infection

乙肝病毒是慢性肝炎、肝硬变、肝细胞癌等慢性肝病的主要病因之一。乙肝病毒感染通常在一生中慢性持续，并且不是自我限制的。因此，通过抗病毒治疗控制和抑制病毒复制和肝损伤具有重要意义。近年来，作为一种抑制病毒复制的核苷酸类似物，拉米夫定被广泛应用于慢性乙型肝炎患者，该药具有很强的抗病毒活性，但有三分之一的患者在治疗过程中病毒逐年突破。因此，研究在抗病毒治疗过程中产生耐药的机制是非常重要的。我们调查了在拉米夫定治疗过程中出现病毒突破的患者的背景及其病毒DNA序列。与治疗效果良好相关的因素是ALT升高和HBeAg阴性状态。而与耐药相关的因素仅为HBV型。因此，我们将研究逆转录酶突变与乙肝病毒基因分型的关系。在逆转录酶区域，不同的HBV型间核苷酸序列存在一定的异质性。热点突变与各基因异质性之间的关系十分重要。利用载体系统构建的在Huh7细胞中重组的复制模型，结合各基因型的HBV全基因组序列，将进一步探讨耐药机制。此外，其他核苷酸类似物，如阿德福韦或恩替卡韦，也应该用同样的方法进行研究。

Hepatitis B virus (HBV) is one of the major cause of chronic liver diseases, such as chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. HBV infection usually continues chronically, in life-time and is not self-limited. Thus, it is important to control and suppress the viral replication and liver damage by anti-viral therapy. Recently, lamivudine, which is one of the nucleotide analogue suppressing viral replication, is widely used for patients with chronic hepatitis B. This drug has very strong anti-viral activity against HBV, however one thirds of patients treated with this drug show viral breakthrough during therapy year by year. So, it is very important to investigate the mechanism of developing drug-resistance during anti-viral therapy.We investigated the background of the patients and their viral DNA sequences in patients who developed viral breakthrough during lamivudine therapy. The factors which are related with favorable response to the therapy were higher ALT levels and negative-HBeAg status. In contrast, the factors which associated with drug-resistance were only HBV genotype. So, we are going to study the relation between the reversetranscriptase mutations and HBV genotypes. In the reversetranscriptase region, there are some heterogeneities of nucleotide sequences among different HBV genotypes. The relation is important between hot spot mutations and heterogeneities of each genotype. Using the replication model which is constructed by vector system in Huh7 cells recombined with full-genomic sequences of HBV of each genotype, the mechanism of drug-resistance will be further investigated. In addition, the other nucleotide analogues, like adefovir or entecavir, should be also investigated in the same method.