Gutfreund K S, Williams M, George R, Bain V G, Ma M M, Yoshida E M, Villeneuve J P, Fischer K P, Tyrrel D L
Department of Medicine, University of Alberta, Edmonton, Canada.
J Hepatol. 2000 Sep;33(3):469-75. doi: 10.1016/s0168-8278(00)80284-6.
BACKGROUND/AIMS: Hepatitis B mutant strains of virus emerging during treatment with the nucleoside analog lamivudine are being increasingly recognized. In the majority of lamivudine-resistant isolates the mutations have been reported to occur within the YMDD motif of the viral polymerase, either as a single mutation M552I or as M552V concomitant with L528M. We analyzed the time course and genetic succession pattern during the emergence of lamivudine resistance.
Seven patients with breakthrough viremia in the setting of chronic hepatitis (n=5) or recurrent HBV after liver transplantation (n=2) were investigated. Pre- and post-breakthrough serum samples were evaluated by single- or second-round PCR amplification and sequencing analysis.
Genotypic succession of the virus populations was observed to occur from M552I to M552I/L528M (n=2) and from L528M to M552V/L528M (n=1). The double mutations M552I/L528M (n=4) or M552V/L528M (n=2) were found in six out of seven patients, and represented the stable virus populations throughout the follow-up period. Breakthrough viremia was not associated with the single L528M mutation. The mean duration of uninterrupted treatment with lamivudine until breakthrough was 422 days (range 182-642) and was longer in the setting of chronic hepatitis B than in recurrent hepatitis B after liver transplantation. HBV DNA levels after breakthrough were lower than pretreatment levels in the majority of patients with chronic hepatitis but higher after liver transplantation.
Our observations show that the virus populations conferring resistance to lamivudine can evolve from single to double mutations at amino acid 552 and 528 of the HBV polymerase, and that M552I/ L528M or M552V/L528M seem to be the predominant mutations arising during long-term antiviral therapy with lamivudine.
背景/目的：在核苷类似物拉米夫定治疗期间出现的乙型肝炎病毒突变株越来越受到关注。据报道，在大多数对拉米夫定耐药的分离株中，突变发生在病毒聚合酶的YMDD基序内，要么是单一突变M552I，要么是与L528M同时出现的M552V。我们分析了拉米夫定耐药出现过程中的时间进程和基因演变模式。
对7例慢性肝炎（n = 5）或肝移植后复发性HBV（n = 2）出现突破性病毒血症的患者进行了研究。通过单轮或二轮PCR扩增及测序分析对突破前和突破后的血清样本进行评估。
观察到病毒群体的基因型演变从M552I到M552I/L528M（n = 2）以及从L528M到M552V/L528M（n = 1）。在7例患者中的6例中发现了双突变M552I/L528M（n = 4）或M552V/L528M（n = 2），并且在整个随访期间代表稳定的病毒群体。突破性病毒血症与单一L528M突变无关。拉米夫定持续治疗直至突破的平均时间为422天（范围182 - 642天），在慢性乙型肝炎患者中比肝移植后复发性乙型肝炎患者更长。大多数慢性肝炎患者突破后的HBV DNA水平低于治疗前水平，但肝移植后则更高。
我们的观察结果表明，对拉米夫定耐药的病毒群体可从乙型肝炎病毒聚合酶第552和528位氨基酸的单突变演变为双突变，并且M552I/L528M或M552V/L528M似乎是拉米夫定长期抗病毒治疗期间出现的主要突变。
