Dynamics Of Lamivudine-resistant Hepatitis B Virus In Patients With Entecavir Rescue Therapy

Objective:To investigate the dynamics of lamivudine-resistant hepatitis B virus inpatients during entecavir rescue therapy.Methods:1、Serum samples were taken at eight different time points(0、24、48、72、96、120、144、168weeks, respectively) in twenty-onelamivudine-resistant patients during entecavir rescue therapy.2、The HBV DNA polymerase gene was amplified at five different timepoints(0、24、48、96、144weeks, respectively)by nested polymerase chainreaction.3、The HBV DNA polymerase gene was cloned and sequenced at fivedifferent time points(0、24、48、96、144weeks, respectively)to analyzethe amino acid substitutions within HBV DNA polymerase gene anddistribution of virus quasispecies.Results:After21lamivudine-resistant patients were switched to ETV rescue therapy, LMV resistant strains were detected in all patients and they showedthree different evolutionary patterns of HBV quasispecies.1、Four patients (A, B, C and D) showed a reversion to WT HBVpopulation at codon204and180and three patients (A, B and D) achievedcomplete virologic response, which meant an ideal HBV DNA level (lessthan300copies/ml) at the end of follow up.2、Five patients (E, F, G, H and I) developed entecavir genotypicresistance, with a prior occurrence of lamivudine-resistant mutationL180M±M204V/I.3、Twelve patients showed dominance of lamivudine-resistant mutantswithout ETV genotypic resistance throughout the whole period and fivepatients achieved complete virologic response at the end of the follow up.4、The average HBV DNA level was significantly lower in four patients(A, B, C and D) with a reversion to WT HBV population than in thosewithout at the end of follow up(P<0.05). The average HBV DNA level wassignificantly higher in five patients (E, F, G, H and I) with ETV genotypicresistance than in those without at the end of follow up(P<0.05).Conclusions:1、 Reversion to WT HBV population is a real phenomenon inlamivudine resistant patients during ETV rescue therapy, which is afavorable indicator for good response at the end of follow up.2、Lamivudine resistant patients without ETV genotypic resistance during ETV rescue therapy will still achieve a good response at the end offollow up.3、Persistent selection of LMV resistant mutants is related with theconsequent ETV genotypic resistance in LMV resistant patients withlong-term ETV administration.