Low rate of YMDD motif mutations in polymerase gene of hepatitis B virus in chronically infected patients not treated with lamivudine

Background Lamivudine is used for the treatment of chronic hepatitis B (CH-B), and exhibits excellent antiviral activity. However, longterm administration increases the likelihood of the emergence of resistant viruses, with an accompanying relapse of hepatitis. However, recent studies have reported lamivudine-resistant viruses in patients with CH-B before such treatment. The aim of this study was to investigate whether YMDD mutants occur in nature.Methods The existence of lamivudine-resistant viruses was examined in 20 asymptomatic carriers of hepatitis B virus (ASC), 10 patients who lost hepatitis B surface antigen (HBsAg) during follow-up and in 20 lamivudine-treated patients with and without breakthrough hepatitis. Both polymerase chain reaction (PCR) restriction fragment length polymorphism and SMITEST hepatitis B virus (HBV)-YMDD mutation detection methods were used to detect resistant viruses.Results No YMDD mutants were detected in the sera of the 20 ASC at the initial and final medical examinations, nor were YMDD mutants detected in sera collected at the initial medical examination, about 6 months before, or immediately after the loss of HBsAg in the 10 patients. In the 20 patients treated with lamivudine, YMDD mutants were not detected in any of them before treatment, whereas mutants were detected in the sera of 10 patients during treatment.Conclusions Our results suggest that lamivudine-resistant YMDD mutant viruses were present in a few patients with HBV infection who before they have been treated with lamivudine.     

Early detection and quantification of lamivudine-resistant hepatitis B virus mutants by fluorescent biprobe hybridization assay in lamivudine-treated patients

Background Long-term lamivudine treatment induces the emergence of lamivudine-resistant hepatitis B virus (HBV). The objective of this study was to develop a fluorescent biprobe hybridization (FBH) assay for the detection and quantification of HBV mutants in the clinical course of lamivudine-treated patients and to evaluate its clinical usefulness. Methods We developed an FBH assay to detect mutations in the HBV DNA polymerase gene. The assay's detection sensitivity was determined using a dilution series of wild-type/mutant plasmid DNA. Blood samples obtained from 27 lamivudine-treated patients were analyzed. Results Mutant DNA levels as low as 10% of total HBV DNA were detected (sensitivity = 100%, specificity = 80%). HBV mutants were detected in five of the 27 patients during an average follow-up of 20 months after lamivudine administration. In one of the five patients, the YIDD mutant was detected at the initiation of lamivudine treatment, while the remaining four patients were identified as having YIDD mutants within 3 months after beginning lamivudine administration. Of the five patients with an HBV mutant, four developed breakthrough hepatitis more than 10 months after the detection of HBV mutants, following the reappearance or a re-increase of HBV DNA, characterized by a predominance of the mutant. The YIDD mutant was detected in one patient, even when the titer of the serum HBV DNA was below the detection limit of commercially available quantitative polymerase chain reaction. Conclusions The FBH assay is an efficient method for detecting and quantifying HBV mutants, as early as 3 months after lamivudine administration.     

188例慢性乙型肝炎患者拉米夫定治疗不同阶段耐药突变的分析

目的定量分析拉米夫定治疗不同时期耐药突变的变化规律,为及时调整治疗方案提供依据。方法将接受拉米夫定治疗的188例患者根据治疗时间进行分组,采用实时荧光PCR方法定量检测各组患者血清HBV DNA水平和酪氨酸-甲硫氨酸-天冬氨酸-天冬氨酸(YMDD)变异。结果拉米夫定治疗后血清HBV DNA水平>104cop ies/m l的患者中,治疗时间少于6个月者6例,其中1例发生突变;6个月~12个月者26例,其中14例发生突变;12个月~24个月者38例,其中26例发生突变;24~36个月者38例,全部出现YMDD变异。各组之间YMDD变异发生率比较差异有显著性(P<0.05)。结论对拉米夫定治疗6个月以上而没有达到病毒学完全应答的患者进行YMDD变异检测,有助于及时调整治疗方案。     

Detection of YMDD motif mutations in some lamivudine-untreated asymptomatic hepatitis B virus carriers

BACKGROUND/AIM: It is well documented that long-term lamivudine treatment induces emergence of lamivudine-resistant hepatitis B virus (HBV), namely, YMDD motif mutation in some patients chronically infected with HBV. We previously reported that there were no YMDD mutant viruses in patients with chronic hepatitis B who were not treated with lamivudine. In this series, we examined mutations in the YMDD motif gene in asymptomatic carriers who maintained normal ALT values for 1 year or more. METHODS: Serum samples obtained from 18 patients chronically infected with HBV who consulted our university were used. None of these patients had any experience of using antiviral agents. For detection of mutant viruses, a kit developed in our laboratory was used. RESULTS: Mutations were detected in five of 18 samples: YMDD+YIDD in three samples and YMDD+YVDD+YIDD in two samples. All of these five samples were positive for anit-HBe. In five samples in which mutations were observed, sequencing was carried out following subcloning. CONCLUSION: The present study demonstrates that YMDD mutant viruses are present in lamivudine-untreated asymptomatic hepatitis B virus carriers as well.     

Detection of YMDD mutant using a novel sensitive method in chronic liver disease type B patients before and during lamivudine treatment

BACKGROUND/AIMS: The emergence of lamivudine-resistant hepatitis B virus (HBV) was reported in patients with prolonged lamivudine administration. There was no report of the existence of tyrosine-methionine-aspartate-aspartate (YMDD) mutant in non-lamivudine treated chronic hepatitis B patients. In the present study, we developed a sensitive assay and applied it to the detection of YMDD mutant.METHODS: We developed peptide nucleic acid (PNA) mediated polymerase chain reaction clamping for detecting mutations in a YMDD motif of the hepatitis B virus DNA polymerase gene. We studied YMDD mutants in a patient with HBV DNA breakthrough longitudinally and in non-lamivudine treated patients (36 patients).RESULTS: We could detect as little as 0.01-0.001% of mutant viruses coexisting in 10(5)-10(9) copies of wild-type viruses using this assay. YMDD mutant was detected 7 months before clinical breakthrough, which was 6 months earlier than using the conventional restriction fragment length polymorphism assay. YMDD mutants were also detected in four of 18 anti-HBe antibody positive untreated chronic hepatitis type B: YMDD+tyrosine-valine-aspartate-aspartate (YVDD) in two patients and YMDD+tyrosine-isoleucine-aspartate-aspartate (YIDD) in two patients, however, none in HBe antigen positive patients.CONCLUSIONS: We developed a highly sensitive assay for detecting YMDD mutants. This is an effective procedure for monitoring patients during or before lamivudine treatment and can provide more insights into the therapeutic strategies for chronic hepatitis B patients.     

不同实验方法在监测拉米夫定耐药突变中的应用价值

目的 通过对三种检测乙型肝炎病毒(HBV)YMDD突变方法的比较,评价其在监测拉米夫定抗HBV治疗中发生耐药突变的价值。方法 用熔解曲线法、聚合酶链反应微板核酸杂交-酶联免疫吸附法(PCRmnh-ELISA)和错配聚合酶链反应限制性片段长度多态性分析法(mPCR-RFLP)对拉米夫定治疗过程中出现HBV DNA由阴转阳的44例慢性乙型肝炎患者的血清进行YMDD突变检测,比较它们的敏感性,并与直接测序法比较它们的特异性。结果 mPCR-RFLP法、PCRmnh-ELISA法和熔解曲线法检出HBV DNA的灵敏度分别为10~4、10~5和10~6拷贝/ml。44例患者血清中,用mPCR-RFLP法检出26例为YMDD突变株,18例为野生株。在26例突变株中,熔解曲线法检出16例,PCRmnh-ELISA法检出18例;而在18例野生株中,熔解曲线法检出2例突变株,PCRmnh-ELISA法检出13例突变株。将上述三种方法检测结果不一致的16例标本进行测序,mPCR-RFLP法、熔解曲线法和PCRmnh-ELISA与测序的符合率分别为93.8%(15/16)、43.8%(7/16)、18.8%(3/16),差异有极显著性(x~2=18.7,P<0.01)。结论 mPCR-RFLP法检测YMDD突变株具有较好的可靠性,是监测拉米夫定耐药株的一种非常有效的方法;熔解曲线法和PCRmnh-ELISA法需要进一步完善以提高敏感性和特异性。     

Hepatitis B virus genotypes and lamivudine resistance mutations in Jordan

AIM：To investigate and identify prevalent hepatitis B virus（HBV） genotypes and to explore lamivudine-resistant mutations among treated and untreated patients in Jordan.METHODS：A total of 107 cases with chronic hepatitis B were recruited from different medical centers in Jordan.Serological tests were preformed for all cases using a microparticle enzyme immunoassay.HBV Genotyping was performed for 70 cases using Line probe genotyping assay.The YMDD mutations were explored for 20 cases（4 were lamivudine naive） using the INNO-LiPA HBV DR assay.RESULTS：Genotype D was the only detected genotype.A total of 6 YMDD mutations were detected in 5 treated patients（31%） while one mutation was detected in the naive patients.Seventeen percent of cases were positive for HBeAg and had statistically significant higher levels of serum aminotransferases.CONCLUSION：HBV genotype D appears to be the only circulating type in Jordanian patients.The YMDD mutations were detected in 31% of lamivudine-treated cases with similar patterns to those found in the literature.We also found a relatively low prevalence of HBeAg expression among examined cases（17%）.Awareness of these serologic,genotypic and resistance patterns might help in the formulation of management plans and for predicting clinical outcomes.Further larger scale studies are needed to confirm our results and to examine possible associations among clinical,serologic,and genetic patterns of HBV infections in Jordan.     

Activity of adefovir dipivoxil against all patterns of lamivudine-resistant hepatitis B viruses in patients

One hundred and thirty-one post-liver transplantation patients with chronic hepatitis B and failing lamivudine therapy with detectable serum hepatitis B virus (HBV) deoxyribonucleic acid by hybridization assays or > or =1 x 10(6) copies/mL by polymerase chain reaction, and elevated alanine transaminase levels despite continuous lamivudine, were enrolled in an open-label study of adefovir dipivoxil. The B and C domains of HBV polymerase were sequenced for baseline samples to determine the presence of lamivudine resistance mutations. The results showed that 98% of the samples had tyrosine-methionine-aspartate-aspartate (YMDD) mutations, indicating a strong correlation between the above clinical definition of lamivudine treatment failure and the presence of YMDD mutations. In addition to the rtM204V/I and the rtL180M mutations, the mutation rtV173L was identified in 19% of patients. Four major patterns of lamivudine-resistant HBV were identified: rtL180M + rtM204V (60%), rtV173L + rtL180M + rtM204V (19%), rtM204I (9%) and rtL180M + rtM204I (9%). Treatment with adefovir dipivoxil showed similar antiviral efficacy in patients with lamivudine-resistant virus from all four patterns.     

Quantitation of hepatitis B lamivudine resistant mutants by real-time amplification refractory mutation system PCR

BACKGROUND/AIMS: Lamivudine is an antiviral drug that is used to treat hepatitis B virus (HBV) infection. Long-term therapy does not completely suppress viral replication, and resistant mutants emerge. Resistance is mediated by changes in the tyrosine-methionine-apartate-aspartate (YMDD) motif in the catalytic site of the HBV polymerase gene. We describe a method to detect and quantify mutant viral populations using amplification refractory mutation system (ARMS) PCR. METHODS: We developed a real-time ARMS-PCR to detect point mutations in the polymerase gene. Using real-time PCR (LightCycler) with a ResonSense probe, PCRs were performed using clones of the HBV polymerase gene containing the different YMDD mutations. Dilution series of the templates were made and tested against each of the primer pairs. This method was applied to quantify mutant virus in patient serum samples. RESULTS: As little as 0.01% mutant DNA in 10(5)-10(9) copies wild-type DNA were detected. The method is more sensitive than amplicon sequencing, which is the current method of mutant determination in the YMDD motif. CONCLUSIONS: This study demonstrates a rapid, highly sensitive and reproducible method of quantifying mutant HBV virus in lamivudine treated patients. It can be used to monitor patients before and during lamivudine therapy.     

乙型肝炎病毒YMDD联合前C变异及其临床意义

目的：研究拉米夫定治疗过程中乙型肝炎病毒（HBV）前C区，P区YMDD基序变异及其对疗效的影响。方法：对5例拉米夫定（100mg/d)治疗过程中HBeAg血清转换而HBV DNA仍阳性的慢性乙型肝炎患者，采用聚合酶链反应（PCR）产物直接测序方法分析HBV前C、P区的基因序列，结果：5例患者前C区均发现有G1896A变异，其中3例HBeAg血清转换前未发现此变异，2例已有此变异，同时5例患者在拉米夫定治疗后检测出YMDD变异，变异类型均为M5521，其中有1例在出现M5521变异40周后变为M552V变异，有2例M5521联合L528M变异，5例患者中有1例治疗无反应，另4例在治疗过程中HBV DNA突发，结论：拉米夫定治疗过程中YMDD变异的出现可导致HBV DNA突发，而前C区G1896A变异可致HBeAgbe阴转，因此在治疗过程中出现HBeAg血清转换后需结合HBV DNA检测，排除前C区变异的可能。     

Selection of hepatitis B virus polymerase mutants with enhanced replication by lamivudine treatment after liver transplantation

BACKGROUND & AIMS: Lamivudine has become a main therapeutic option for treating hepatitis B virus (HBV) infection. Although drug resistance develops, the clinical course after selection of antiviral-resistant HBV mutants seems to be benign. However, we observed a severe clinical course of hepatitis B infection in several liver transplant recipients after the emergence of lamivudine resistance. This was associated with high viral load in the blood. METHODS: In this report, we characterize the molecular mechanisms underlying drug-dependent enhanced replication of particular lamivudine-resistant HBV mutants selected in these patients, which were associated with sudden onset of liver failure. RESULTS: The clinical course was characterized by a sudden rise in serum bilirubin, prothrombin time, and transaminase. HBV sequence analysis of these patients revealed both mutations in the "a-determinant" of the envelope and the YMDD (tyrosine, methionine, aspartate, aspartate) motif (domain C) of the polymerase protein. Transfection experiments with replication competent vectors indicated that the "a-determinant" changes were not associated with resistance, whereas mutations in the YMDD motif conferred resistance to lamivudine. More importantly, combinations of mutations in the "a-determinant" and the YMDD motif in patients with a severe hepatitis were not only resistant to lamivudine treatment, but showed enhanced replication in vitro in the presence of lamivudine. This observation was confirmed in separate laboratories. CONCLUSIONS: Severe and fatal hepatitis B infection can occur during lamivudine therapy and may be associated with certain HBV mutants selected during sequential nucleoside and HBIg treatment. The lamivudine-enhanced replication shown by these mutants suggests that continuation of therapy with lamivudine could be deleterious in some patients.     

基因芯片监测拉米夫定致乙型肝炎病毒耐药突变的临床研究

目的 研究基因芯片技术在监测拉米夫定致乙型肝炎病毒(HBV)耐药突变中的临床意义。方法应用前瞻性方法,对20例经拉米夫定治疗和10例未治疗的乙型肝炎患者观察18个月,以聚合酶链反应扩增血清HBV,应用已研发的4位点拉米夫定耐药检测芯片监测YMDD相关突变。结果 基因芯片技术监测能有效分辨野生型和突变型HBV。HBV的耐药突变随用药时间延长,突变率显著增加(x~2=6.6 9,P<0.01),突变类型以M539V L515M为主,次之为M539I。HBV在YMDD突变后,继续应用拉米夫定对突变型病毒无效。结论 在应用拉米夫定时需要定期检测YMDD突变,常规的HBV DNA定性技术与基因芯片相比,可能会出现结论偏差,后者是最好的方法之一。出现耐药突变后,继续使用拉米夫定对耐药株无效,应停用或更换其它治疗方案。     

Entecavir for treatment of lamivudine-refractory, HBeAg-positive chronic hepatitis B

BACKGROUND & AIMS: Lamivudine treatment is associated with frequent development of resistant hepatitis B virus (HBV) and loss of treatment benefit. In preclinical and phase II studies, entecavir demonstrated potent antiviral activity against lamivudine-resistant HBV. METHODS: In this phase III, double-blind trial, hepatitis B e antigen-positive patients who were refractory to lamivudine therapy (persistent viremia or documented YMDD mutations while receiving lamivudine) were randomized to switch to entecavir 1 mg daily (n = 141) or continue lamivudine 100 mg daily (n = 145) for a minimum of 52 weeks. Two coprimary end points were assessed at 48 weeks: histologic improvement and a composite end point (HBV branched DNA <0.7 MEq/mL and alanine aminotransferase [ALT] <1.25 times the upper limit of normal). RESULTS: Histologic improvement occurred in 55% (68/124) of entecavir-treated vs 28% (32/116) of lamivudine-treated patients (P < .0001). More patients on entecavir than lamivudine achieved the composite end point: 55% (77/141) vs 4% (6/145), respectively (P < .0001). Mean change from baseline in HBV DNA was -5.11 log(10) copies/mL for entecavir-treated patients and -0.48 log(10) copies/mL for lamivudine-treated patients (P < .0001). Virologic rebound because of entecavir resistance substitutions occurred in 2 of 141 of entecavir-treated patients, and genotypic evidence of resistance was detected in 10 patients. The safety profile of entecavir was comparable to lamivudine with fewer ALT flares on treatment. CONCLUSIONS: In patients with lamivudine-refractory chronic hepatitis B, switching to entecavir provides superior histologic improvement, viral load reduction, and ALT normalization compared with continuing lamivudine, with a comparable adverse event profile.     

阿德福韦酯治疗YMDD变异慢性乙型肝炎患者96周疗效观察

目的观察阿德福韦酯联合拉米夫定治疗酪氨酸-蛋氨酸-天门冬氨酸-天门冬氨酸（YMDD）变异感染慢性乙型肝炎患者的疗效。方法选择56例在拉米夫定治疗后发生YMDD变异的慢性乙型肝炎患者,随机分为治疗组28例,给予阿德福韦酯联合拉米夫定治疗;对照组开始治疗与治疗组相同,但在12周后停用拉米夫定,继续服用阿德福韦酯治疗,观察96周的疗效。结果在治疗96周时,两组ALT和HBV DNA水平均显著下降;治疗组HBV DNA转阴率为96.4%,对照组为75.0%（P〈0.05）;治疗组ALT复常率为96.4%,对照组为85.7%（P〉0.05）;两组均未发现与药物相关的不良反应发生。结论阿德福韦酯联合拉米夫定治疗YMDD变异的慢性乙型肝炎患者疗效优于单用阿德福韦酯治疗。     

Long-term follow-up of chronic hepatitis B after the emergence of mutations in the hepatitis B virus polymerase region

Treatment of chronic hepatitis B has been greatly improved by the use of lamivudine, but mutations occur in the polymerase region of hepatitis B virus (HBV) and lamivudine-resistant mutants frequently develop. The emergence of lamivudine-resistant strains of HBV is a problem for treating chronic hepatitis B using lamivudine. We observed biochemical and virological changes in 15 patients with chronic hepatitis B for a median period of 29 months (range: 4-42 months) after the emergence of lamivudine-resistant mutants of HBV. Patterns of mutation of the polymerase gene were examined by sequencing the LLAQ motif in domain B and the YMDD motif in domain C. Exacerbation of liver dysfunction occurred in 14 (93.3%) of the 15 patients at a median of 4 months after the emergence of mutations. However, exacerbation of liver dysfunction was observed only in four patients (26.7%) at the time of appearance of the first mutations and in 80.0% of the patients at the time of appearance of the second mutations. Increase in serum alanine aminotransferase (ALT) levels was significantly greater at the time of appearance of second mutations (P = 0.0096). In most cases, wild-type HBV was mutated with the substitution of only rtM204I at first, and rtL180M/M204I mutations and then rtL180M/M204V mutations subsequently appeared. Further mutations of the polymerase region caused clinical deterioration. Thus as mutations emerge in the polymerase region, the clinical outcome deteriorates. Thus, monitoring the patterns of mutation of the polymerase gene is useful when using lamivudine for treating HBV.     

Evolution of multi-drug resistant hepatitis B virus during sequential therapy

Multi-drug resistant hepatitis B virus (HBV) has been reported in hepatitis B patients who received sequential antiviral therapy. In vitro studies showed that HBV constructs with mutations resistant to lamivudine and adefovir have marked reduction in sensitivity to combination of lamivudine and adefovir, whereas constructs with mutations resistant to either drug remain sensitive to the other drug. We conducted this study to determine whether mutations conferring resistance to multiple antiviral agents co-locate on the same HBV genome in vivo and to describe the evolution of these mutations. Sera from six patients who had been found to have multi-drug resistant HBV mutations to lamivudine+adefovir, lamivudine+hepatitis B immunoglobulin (HBIG), or lamivudine+entecavir on direct sequencing were cloned after nested polymerase chain reaction (PCR). Analysis of 215 clones from 11 samples with multi-drug resistant mutations on direct sequencing showed that 183 (85%) clones had mutations to both therapies on the same genome; 31 clones had lamivudine-resistant mutants only. Clonal analysis of serial samples from three patients showed progressive evolution from all clones with lamivudine-resistant HBV mutations only to mixtures of clones that have multi-drug resistant mutations and clones that have lamivudine-resistant HBV mutations only, and ultimately all clones having multi-drug resistant HBV mutations. In conclusion, mutations conferring resistance to multiple antiviral agents co-locate on the same viral genome, suggesting that combination therapy directed against mutants resistant to each treatment may not be adequate in suppressing multi-drug resistant HBV. De novo combination therapy may prevent the emergence of multi-drug resistant mutants.     

Emergence of YMDD motif mutant of hepatitis B virus during short-term lamivudine therapy in South Korea

BACKGROUND/AIMS: The emergence of a YMDD mutant resistant to lamivudine therapy has been reported in patients with hepatitis B treated with long-term lamivudine therapy. However, it is not well known whether the YMDD mutant could be detected early in lamivudine therapy in hepatitis B virus (HBV) endemic areas. The aim of this study was to investigate the emergence of the YMDD mutant during short-term lamivudine therapy in South Korea. METHODS: We prospectively investigated the emergence of the YMDD mutant by the nested PCR assay using restriction fragment length polymorphism in 28 patients with chronic hepatitis B who were treated with 100 mg of lamivudine daily for 12 weeks. RESULTS: The YMDD mutant was detected in 17 (60.7%) out of 28 patients at week 12, and the only type of mutation found was the YIDD mutation. When we carried out the nested PCR serially in five patients, YIDD mutants were detected as early as 2 weeks by the nested PCR assay. The nested PCR results were in concordance with DNA sequencing in one patient's serial samples. CONCLUSIONS: YMDD mutants in HBV were detected within a few weeks during lamivudine therapy in South Korea, which suggests that the YMDD mutant may exist even before lamivudine therapy in HBV endemic areas.     

Long-term follow-up of patients with anti-HBe/HBV DNA-positive chronic hepatitis B treated for 12 months with lamivudine

BACKGROUND/AIMS: Interferon alpha provides benefit in only a limited number of patients with chronic anti-HBe-positive hepatitis B. The aim of this study was to verify the long-term efficacy of lamivudine treatment of these patients and the incidence of lamivudine-resistant hepatitis B virus mutants. METHODS: Fifteen consecutive patients with chronic anti-HBe-positive hepatitis B were treated with lamivudine 100 mg once daily for 52 weeks. Levels of alanine aminotransferase, HBV DNA, hepatitis B surface antigen, and IgM antibodies to hepatitis B core antigen were monitored during therapy and 12-month follow up. The polymerase gene was amplified by polymerase chain reaction and the region coding for YMDD amino acid motif was directly sequenced. RESULTS: Only 2/15 patients (13%) had a sustained virological and biochemical response and improved histologically. Eleven out of 15 (74%) showed inhibition of viral replication and normalization of alanine aminotransferase levels during lamivudine treatment but relapsed 1-12 months after terminating therapy. In the two remaining patients (13%), HBV DNA initially became negative but reappeared in the serum after 24 weeks, and in both patients the emergence of YMDD mutants was demonstrated. CONCLUSIONS: Our data confirm the antiviral efficacy of lamivudine in anti-HBe-positive patients, but response to a 1-year course was only transient as the majority of patients relapsed after therapy withdrawal. The lack of a sustained effect and the emergence of lamivudine-resistant mutants suggest that therapy for chronic hepatitis B should be based on a combination of several therapeutic agents.     

乙型肝炎病毒YMDD及e抗原相关多重变异及其临床意义

目的 研究拉米夫定治疗慢性乙型肝炎期间HBVYMDD基序、影响HBeAg分泌的多重变异情况与临床的关系。方法 采用基因芯片技术对拉米夫定治疗9～30个月的慢性乙型肝炎患者进行YMDD基序、G1896A、A1814C、A1762T和G1764A(BCP双突变)单碱基变异检测。结果 102例慢性乙型肝炎患者拉米夫定平均治疗18个月时,22例发生YMDD变异,其中8例发生多重变异,包括G1896A3例、A1814C2例、G1896A A1814C、BCP双突变、BCP双突变 G1896A多重变异各1例,单纯YMDD变异和前5例联合变异均为HBeAg阳性,而后3例多重变异则为HBeAg阴性,其中1例多重变异继续治疗3个月后转变为单纯YMDD野生株阳性,同时伴有HBeAg的复阳。结论 拉米夫定治疗过程中存在YMDD及HBeAg相关多重变异的优势病毒株可能是HBVDNA复阳、同时伴有HBeAg阴转的原因之一,拉米夫定治疗过程中,HBeAg阴性时应监测其可能的相关变异。