Overlapping gene mutations of hepatitis B virus in a chronic hepatitis B patient with hepatitis B surface antigen loss during lamivudine therapy

Disappearance of hepatitis B surface antigens (HBsAg) in chronic hepatitis B usually indicates clearance of hepatitis B virus (HBV) infection. However, false HBsAg negativity with mutations in pre-S2 and 'a' determinant has been reported. It is also known that YMDD mutations decrease the production of HBV and escape detection of serum HBsAg. Here, we report overlapping gene mutations in a patient with HBsAg loss during the lamivudine therapy. After 36 months of lamivudine therapy in a 44-yrold Korean chronic hepatitis B patient, serum HBsAg turned negative while HBV DNA remained positive by a DNA probe method. Nucleotide sequence of serum HBV DNA was compared with the HBV genotype C subtype adr registered in NCBI AF 286594. Deletion of nucleotides 23 to 55 (amino acids 12 to 22) was identified in the pre-S2 region. Sequencing of the 'a' determinant revealed amino acid substitutions as I126S, T131N, M133T, and S136Y. Methionine of rtM204 in the P gene was substituted for isoleucine indicating YIDD mutation (rtM204I). We identified a HBV mutant composed of pre-S2 deletions and 'a' determinant substitutions with YMDD mutation. Our result suggests that false HBsAg negativity can be induced by combination of overlapping gene mutations during the lamivudine therapy.     

Direct detection of lamivudine-resistant hepatitis B virus mutants by a multiplex PCR using dual-priming oligonucleotide primers

Mutations in the YMDD motif of the hepatitis B virus (HBV) polymerase gene increase lamivudine resistance of HBV, highlighting the clinical importance of accurate and sensitive detection of HBV mutants. Using dual-priming oligonucleotide primer technology, an assay that can detect mutations at codons 180 (L528M) and 204 (YVDD, YIDD, and YSDD) by a single-step multiplex PCR was developed. This Seeplex Lami-DR assay was sufficiently sensitive to detect 10(3)HBV/ml and was able to detect minor mutants comprising as little as 2% of the viral population. Mutants were detected in 57 of 65 serum samples (88%) from patients with chronic hepatitis B who had been treated with lamivudine (median, 32 months; range, 1-83 months). The agreement with direct sequencing was only 38.5% (25/65). Discrepancies between these methods resulted from detection of additional mutants by the Seeplex Lami-DR assay, as confirmed by a novel verification analysis. This assay is not only highly accurate and sensitive, but is also simple and cost-effective, requiring no expensive probes, laborious sequencing procedures, or digestion with restriction enzymes. Accordingly, the Seeplex HBV Lami-DR assay should be considered as a first-line, cost-effective tool for detecting viral mutations in patients with chronic hepatitis B receiving lamivudine therapy.     

Evolution of viral load and changes of polymerase and precore/core promoter sequences in lamivudine-resistant hepatitis B virus during adefovir therapy

Adefovir dipivoxil (ADV) has demonstrated clinical activity against both wild-type and lamivudine-resistant hepatitis B virus (HBV). We analyzed the evolution of viral load and the changes of polymerase and precore/core promoter sequences in lamivudine-resistant virus during ADV therapy. The authors studied 14 patients who had breakthrough hepatitis after lamivudine therapy. Serial sera were obtained prior to adefovir administration and at 3, 6 and 12 months after ADV therapy. Nucleotide sequences of polymerase and the precore/core promoter from the hepatitis B virus were analyzed. The median serum HBV DNA decrease with adefovir treatment was 4.35 log(10) copies/mL at 12 months. Tyrosine-methionine-aspartate-aspartate (YMDD) mutants were found in 12 patients among the 14 patients with lamivudine resistance. The YMDD mutant viruses reversed to the wild-type in 6 patients out of the 12 patients after 3-6 months of ADV after discontinuing lamivudine therapy. In the analysis of the nucleotide sequences of the precore/core promoter gene, core promoter mutants in 12 patients were replaced by wild-type virus in three patients (25%), while precore mutants in four patients were replaced by the wild-type in three patients (75%). The results demonstrate the patterns of polymerase and precore/core promoter mutations in lamivudine-resistant hepatitis B viruses and the reversion from the mutant to the wild-type in some patients. In addition, despite several mutations in the polymerase during ADV therapy, ADV effectively suppressed HBV replication without the emergence of resistant viral mutants.     

Prevalence and profile of mutations associated with lamivudine therapy in Indian patients with chronic hepatitis B in the surface and polymerase genes of hepatitis B virus

Lamivudine results in the selection of resistant hepatitis B virus (HBV) variants. Because the surface gene of HBV overlaps completely the polymerase gene, the incidence and profile of surface and polymerase gene mutations were investigated prospectively in chronic HBV patients who were on lamivudine therapy. Twenty-six patients with chronic liver disease confirmed histologically were included in this study. Extracted HBV DNA from sera samples were subjected to PCR amplification for the mutation prone regions of the surface and polymerase genes of the HBV genome. The emergence of mutant forms and biochemical derangements were studied carefully during the course of the therapy. In six of 26 (23%) patients, mutations emerged on lamivudine therapy. YM552I/VDD resistant mutants were observed in one (6%) and five (29%) patients at Month 12 and 18, respectively, out of 17 patients, who had completed more than 9 months of therapy. The mean time of emergence of resistance was 16.4 +/- 6.8 months. In three of the five patients, emergence of YM552I/VDD mutation was accompanied with a rise in HBV DNA levels. In two patients, mutations were noticed at the end of the viral breakthrough; when the DNA level went down to undetectable levels (<0.5 pg/mL). In two patients, normal ALT levels were found at the time of emergence of the YMDD mutation. YM552I/VDD mutations were observed in 43% of HBeAg positive and 20% of anti-HBe positive patients (P = ns). Although the 'a'-determinant region was found to be unaffected; in one patient, a novel pattern due to emergence of YIDD mutant was observed; the corresponding aa in the S-ORF turned to a stop codon. In summary, the frequency of emergence of YM552I/VDD mutations was 29% at Month 18 in the Indian patients. The presence of normal ALT and low levels of HBV DNA do not exclude the existence of resistant mutants. Novel mutations in the S-ORF, which lead to premature surface gene termination might affect the production of HBsAg and need further study.     

SNaPshot技术检测乙型肝炎病毒基因组P基因区单核苷酸多态性的研究

目的　建立SNaPshot技术对乙型肝炎病毒(HBV)基因组P基因区单核苷酸多态性(SNP)的分析。方法　针对HBVYMDD变异位置的上、下游设计引物,用PCR方法进行DNA扩增,产物直接测序或克隆测序。再针对变异位点74 1A G变异型(YVDD)和74 3G T变异型(YIDD)的紧邻上游设计高度特异的SNaPshot检测引物,用不同荧光标记的ddNTP对PCR产物进行一步延伸,然后置于310型DNA测序仪上观察荧光信号,可直观的检测上述两位点的单核苷酸多态性。结果　在拉米夫定治疗的慢性乙型肝炎患者中,经测序证实P基因区不仅存在74 1、74 3位点的变异,还存在5 14C A、5 2 3C A、5 6 2T A、6 6 7C A等位点的变异。对已证实P基因区变异的13例患者血清用SNaPshot技术检测YMDD结果与测序结果完全相同,显示SNaPshot技术高度的特异性。结论　SNaPshot技术检测HBV基因组SNPs具有快速、简便、准确特异的特点,还检测到野生株和变异株的混合存在。     

PCR-RFLP结合克隆测序监测乙肝病毒拉米夫定耐药突变株的产生

目的 建立PCR结合酶切的方法监测慢性乙型肝炎患者体内拉米夫定耐药突变株的产生,并与PCR产物克隆后测序相结合。了解此方法的可靠性和可行性,同时用此方法筛查50例应用拉米夫定治疗的慢性乙型肝炎患者中耐药株的发生情况。方法 拉米夫定治疗的慢性乙型肝炎患者50例,治疗时间9个月-24个月,设计错配PCR结合限制性片段长度多态性方法,快速检测患者体内乙型肝炎病毒（HBV）酪氨酸-蛋氨酸-天门冬氨酸-天门冬氨酸（Tyrosine-Methionine-Aspartic acid-Aspartic acid,YMDD)变异株的发生情况,对筛检耐药株阳性的标本应用PCR产物克隆后测序加以证实。结果 在50例服用拉米夫定患者中发现9斧正患者在用药超过9个月时出现拉米夫定耐药突变株（YMDD变异株）,其中YIDD变异5例,YVDD变异4例,后者有3例合并有1526M突变。结论 本方法在检测YMDD变异方面具人快速简便的特点,经克隆后测序证实,具有较好的可靠性。     

Virological and biochemical relapse according to YMDD motif mutant type during long-term lamivudine monotherapy

Whether the type of lamivudine-resistant virus in hepatitis B virus (HBV) influences the clinical outcome, it is not completely understood. We evaluated the serial changes in YMDD motif mutant in 60 Japanese genotype C-HBV patients who received long-term lamivudine monotherapy. YIDD or YVDD alone tended to stop shifting to the mixed type (YVDD and YIDD) within 12 months after the detection of mutant virus. Hence, the characteristics, virological relapse (DNA breakthrough) and biochemical relapse (breakthrough hepatitis) of 49 patients, who could be classified into three types (continuous YVDD, continuous YIDD, and the mixed type), were investigated. YVDD and YIDD type tended to have the opposite background with regard to age, histology, and viral load. The mixed and YIDD types tended to have similar backgrounds, except for viral load. In the mixed type, both the HBeAg-positive rate and viral load as risk factors for emergence of the mutant tended to be high. Mutant virus, DNA breakthrough and breakthrough hepatitis emerged significantly earlier in the mixed type than the two other types. The incidence of severe breakthrough hepatitis accompanied by icteric flare-up tended to be higher in the mixed type than the other types. Our results suggest that the YMDD motif mutant type might emerge from different backgrounds and modulate the virological and biochemical relapse after the emergence. Large-scale studies of each mutant type should be conducted in the future to confirm these findings.     

Factors associated with viral breakthrough in lamivudine monoprophylaxis of hepatitis B virus recurrence after liver transplantation

This study aimed to investigate the factors associated with viral breakthrough among liver transplant recipients who receive lamivudine monoprophylaxis. Consecutive patients receiving liver transplantation for HBV-related liver disease from June 1999 to October 2000 were studied. All patients received lamivudine 100 mg daily pre- and post-transplant. Serum samples were collected before lamivudine treatment, before liver transplantation, and then every 3-6 months after liver transplantation. Lamivudine-resistant mutations at the YMDD motif of HBV P gene were detected by direct sequencing and HBV DNA was quantified by real-time polymerase chain reaction (PCR). Ten patients, 7 males and 3 females, aged 50.5 +/- 7.9 years, were studied. Three patients had fulminant hepatitis and 7 patients had end-stage cirrhosis before liver transplantation. Lamivudine was started at 4.5 (range 0-40) weeks before liver transplantation. The median post-transplant follow-up was 16 (range 12-23) months. Four patients developed YMDD mutations 10.5 (0-16) months after transplantation with relapse of viraemia (median 1,294, range 51-3,135 MEq/ml). All patients who developed YMDD mutants had end-stage liver cirrhosis, and HBV DNA were detectable on the day of liver transplantation (median 0.62, range 0.086-1.63 MEq/ml). On the contrary, all 3 patients transplanted for fulminant hepatitis did not have YMDD mutation. Among the 3 end-stage cirrhotic patients who had negative HBV DNA before liver transplantation, none developed YMDD mutation. In conclusion, patients transplanted for fulminant hepatitis B and cirrhotic patients in whom HBV DNA could be rendered PCR negative before liver transplantation are unlikely to develop YMDD mutation on lamivudine monoprophylaxis.     

基因芯片检测拉米夫定治疗慢性乙型肝炎过程中HBV变异技术的建立和应用

目的建立乙型肝炎病毒变异基因诊断芯片对拉米夫定治疗慢性乙型肝炎过程中出现的肝炎病毒P基因区YMDD变异进行快速准确的检测诊断。方法设计特异性寡核苷酸探针阵列,特殊处理芯片载体。用点样法制备乙型肝炎病毒变异基因诊断芯片。在本院住院治疗患者中选择30例服用拉米夫定后,HBV DNA转阴(<500 copies/ml)168周后又反跳≥5 000 copies/ml的患者进行基因芯片杂交检测分析。同时用PCR直接测序法对上述30例患者血清标本进行双盲HBVDNA聚合酶活性区域测序对照。结果 30例服药后HBVDNA反跳患者中基因芯片测得HBV YMDD变异21例,其中YVDD变异11例。YIDD变异10例。HBVDNA PCR直接序列测定结果,有核苷酸A741变为G,使氨基酸由蛋氨酸552变为缬氨酸(氨基酸基序由YMDD变为YVDD)11例,并有6例核苷酸A669变为C,使氨基酸由亮氨酸528变为蛋氨酸。核苷酸G743变为T,使氨基酸由蛋氨酸552变为异亮氨酸(氨基酸基序由YMDD变为YIDD)10例。其中有3例伴有核苷酸T781变为C,使氨基酸由亮氨酸565变为脯氨酸。标本阳性变异序号与基因芯片检测结果完全一致。结论 乙型肝炎病毒变异基因诊断芯片可以同时检测YVDD,YIDD变异,同PCR直接测序法比较,准确率达100％,无假阳性。     

Emergence of YMDD motif mutants of hepatitis B virus during lamivudine treatment of immunocompetent type B hepatitis patients

Lamivudine is an effective antiviral agent for the treatment of chronic type B hepatitis. Recent studies have shown the appearance of lamivudine resistant viruses with mutations at the tyrosine-methionine-aspartate-aspartate (YMDD) motif of the viral polymerase in hepatitis B virus (HBV) infected patients who received orthotopic liver transplantation. In order to confirm the appearance of such mutant HBV in immunocompetent patients, the HBV sequences in and around the YMDD motif of HBV DNA polymerase were examined in the sera from 16 lamivudine treated and 10 untreated control patients. Approximately 200 bases including the YMDD motif of HBV DNA polymerase were amplified by polymerase chain reaction (PCR) and sequenced directly by an automated sequencer. Of the 16 patients receiving lamivudine, mutant viruses with mutations in the YMDD motif were found in 3 of 8 patients treated with lamivudine for 52 weeks. However, this mutation was not found in any of the 8 patients treated for 32 weeks or a shorter period. Mutant viruses appeared after 40 weeks of treatment and were undetectable within 12 weeks after the cessation of the treatment. Such mutant viruses were not detected in any of the 10 untreated patients. This study confirms the emergence of YMDD mutant viruses during long-term lamivudine treatment in immunocompetent type B hepatitis patients. The results from this study suggest the need for combination therapies to reduce the levels of such mutant viruses in some patients.     

乙型肝炎病毒耐拉米夫定多聚酶基因变异检测方法研究

目的 建立简便、准确、实用的检测乙型肝炎病毒耐拉米夫定多聚酶(P)基因变异的方法。方法 根据HBV基因序列，设计5只寡核苷酸引物，用巢式聚合酶链反应(nested PCR)分别扩增HBVP基因B区和C区片段，产物用NdeⅠ或NIa Ⅲ酶切，琼脂糖胶电泳，分析酶切产物长度多态性(RFLP)，建立检测P基因变异的方法。对30例长期服用拉米夫定的慢性乙型肝炎(慢乙肝)患者检测YMDD基序及526位点变异，16例未用拉米夫定的慢乙肝患者为对照。4份PCR产物作克隆测序以验证方法的准确、可靠。结果 所建的巢式PCR-RFLP方法操作简便、快速，从模板提取到酶切后电泳分析仅需11h；灵敏度高，可检测到10^3拷贝／ml的HBVDNA；结果准确，4份经酶切分别判断为野毒株或变异株的标本经测序证实。30例用拉米夫定的慢乙肝患者中，发现单纯YMDD变异8例(26．7％)，YMDD联合L526M变异3例(10．0％)，16例对照未检出上述位点的变异。结论 本方法简便、准确，适合较大样本检测。可用于临床筛检常见拉米夫定耐药性HBVP基因变异。     

Complete nucleotide sequences of hepatitis B virus genomes associated with epidemic fulminant hepatitis

Pre-core/core mutants are frequently observed in patients with fulminant hepatitis. To investigate the extent of molecular characteristics of hepatitis B virus (HBV) genomes implicated in the development of fulminant hepatitis, full-length HBV genomes were sequenced directly from sera of two patients with epidemic fatal fulminant hepatitis, after amplification by the polymerase chain reaction. These two genomes, of 3215 nucleotides, were 99.6% identical, indicating that a common source of HBV potentially caused fulminant hepatitis. Thirty unique nucleotide mutations were commonly found in the two entire HBV genomes. Three were located in the stem-loop structure, changing this element to a more stable structure. Twenty-five unique amino acid substitutions were found in each open reading frame, except for the X and pre-surface 2 genes. One was located in the pre-surface 1 gene; two were in the surface gene; three were in the pre-core gene, including codons 28 (tryptophan to stop codon) and 29 (glycine to aspartic acid); eight were in the core gene; and 11 were in the polymerase gene. The pre-core mutations at codons 28 and 29 were common to the two HBV strains reported previously in patients with epidemic fulminant hepatitis. Thus, HBV genomes associated with epidemic fatal fulminant hepatitis have numerous unique mutations, located mainly in the polymerase gene, as well as the pre-core/core gene, including mutations in the stem-loop structure of the pregenome encapsidation signal sequence. These mutations may be associated with the development of fulminant hepatitis. © 1996 Wiley-Liss, Inc.     

Monitoring the emergence of hepatitis B virus polymerase gene variants during lamivudine therapy using the LightCycler

Treatment of chronic hepatitis B virus (HBV) infection with lamivudine is associated with the appearance in the circulation of HBV variants with mutations in the YMDD (tyrosine, methionine, aspartate, aspartate) motif of the polymerase gene. Fluorometric real-time PCR with the LightCycler assay was used for the detection of resistant variants. Differences in the hybridization melting curve kinetics of probes bound to the sequences encoding the wild-type or the mutant YMDD motifs (YIDD or YVDD in which the methionine residue is altered to an isoleucine or a valine, respectively) distinguished the single-base changes responsible for the resistance phenotype. The LightCycler probe hybridization assay was applied to 40 serum specimens from 19 patients, and the results were correlated with the nucleotide sequences determined for the corresponding PCR products. All three variants could be identified in the specimens. PCR clones obtained from four patients early in the course and prior to lamivudine therapy were investigated for the appearance of YIDD and YVDD variants with the LightCycler assay. In one patient, a transient appearance of the YIDD variant was observed 6 weeks into therapy. Subsequently, after 11 months of lamivudine therapy, the YVDD variant emerged in that patient.     

Fatal liver failure with the emergence of hepatitis B surface antigen variants with multiple stop mutations after discontinuation of lamivudine therapy

Treatment of chronic hepatitis B virus (HBV) infection with lamivudine is effective and well-tolerated. However, discontinuation of the treatment is associated frequently with acute exacerbation of liver diseases. A patient suffering from acute liver failure after discontinuation of lamivudine treatment is described. The patient was treated with lamivudine for 4 months and ceased the treatment without consulting. After receiving lamivudine, the patient developed anti-HBs and became negative for hepatitis B surface antigens (HBsAg). However, HBV DNA reappeared to a level of 6.47 x 10(5) copies/ml. The patient died due to acute liver failure. Sequencing of HBV isolates revealed that mutations including G145R and stop codons occurred within the HBsAg coding region. In conclusion, HBV replication resumed after the uncontrolled cessation of lamivudine treatment in this patient and may have triggered the process leading to liver failure. Anti-HBs antibody appeared and may be the selective force for the emergence of HBV mutants.     

Characteristics of lamivudine-resistant hepatitis B virus (HBV) strains with and without breakthrough hepatitis in patients with chronic hepatitis B evaluated by serial HBV full-genome sequences

Lamivudine therapy often causes breakthrough of hepatitis B virus (HBV) DNA and breakthrough hepatitis. The aim of this study was to determine the viral factors that relate to HBV-DNA breakthrough with and without breakthrough hepatitis. Among 82 patients with chronic hepatitis B (CHB) who received lamivudine at a dose of 100 mg daily for more than 24 months, 23 patients had HBV-DNA breakthrough induced by a lamivudine-resistant mutant. Of these 23 patients, 16 had breakthrough hepatitis and 7 had only HBV-DNA breakthrough. Serial HBV-DNA full-genome sequences during therapy were examined in 10 (7 had breakthrough hepatitis and 3 did not) of these 23 patients by direct sequencing. Mutations in the S region were examined by cloning in representative patients. There were no significant differences in the baseline clinical backgrounds and virus marker between patients with and without breakthrough hepatitis. The HBV amino acid substitutions at breakthrough hepatitis were identical to those at HBV-DNA breakthrough. Cloning analysis revealed that monoclonal mutational strain appeared at breakthrough and no such mutations existed at baseline. Regarding HBV amino acid substitutions in the polymerase region, S region, X region, and precore-core region with breakthrough compared to baseline, there was no significant differences of the numbers of amino acid substitution between breakthrough hepatitis and non-breakthrough hepatitis. There were no common amino acid changes in patients with breakthrough hepatitis. Although monoclonal lamivudine-resistant strain emerged at HBV-DNA breakthrough in patients with CHB, there were no common amino acid changes, suggesting viral factor may have insignificant role in breakthrough hepatitis.     

Rapid detection of lamivudine-resistant hepatitis B virus polymerase gene variants

The amino acid substitution from methionine to valine or isoleucine at the YMDD (tyrosine, methionine, aspartate, aspartate) motif of the HBV polymerase gene is the main mutation responsible for resistance to lamivudine treatment. Detection of emerging HBV variants by direct sequencing of the HBV genome is excessively time-consuming for studying large numbers of clinical samples. The aim of the study was to analyse the emergence of lamivudine-resistant HBV genotypes by means of restriction fragment length polymorphism (RFLP) of the PCR product generated from a fragment of domain C of the polymerase gene, in clinical samples from patients receiving treatment. The results with this method were compared with those obtained with a direct sequencing technique. In total, 139 serum samples were studied from 37 patients with chronic hepatitis B, obtained at pre-treatment and at 9, 12, 18 and 24 months of treatment. Variants were detected by cleavage of the products of the three PCRs with the following enzymes: FokI (identifies the normal variant, YMDD, and the mutant variant YVDD), SspI (identifies the mutant variant, YIDD) and Alw44I (identifies the variant, YVDD). The digested fragments were separated by electrophoresis in 3% agarose gel. Of the 139 serum samples analysed, the wild-type YMDD sequence was detected in 106 (76%), the YVDD variant in 20 (15%) and the YIDD variant in 13 (9%) cases. The non-mutated variant, YMDD, was detected in all the pre-treatment samples. After 9 months of treatment the mutant variant was detected in four of 37 serum samples analysed (11%) (two YVDD and two YIDD). At 12 months, 12 of the 37 serum samples (32%) showed mutations in the YMDD sequence (seven YVDD and five YIDD). Among the 16 serum samples obtained at 18 months, nine had the YMDD variant (56%) (seven YVDD and two YIDD). At 24 months, variants in the YMDD sequence were detected in eight of the 12 patients treated (66%) (four YVDD and four YIDD). HBV genotypes were confirmed by direct sequencing, with consistent results. In 45% of cases, the emergence of HBV variants was not associated with ALT breakthrough. The PCR-RFLP assay used in this study, in perfect concordance with direct sequencing, is an accurate method for genotyping lamivudine-resistant HBV variants. Since it is a rapid low-cost technique, PCR- RFLP is suitable for large-scale screening of these polymorphisms in clinical samples.     

基因芯片检测拉米夫定治疗乙肝病毒感染耐药分析

目的 分析拉米夫定治疗乙肝病毒感染耐药性,旨在为指导慢性乙肝患者临床药物治疗提供新方法.方法 应用基因芯片检测255份51名拉米夫定抗乙肝病毒治疗自愿者不同阶段服药的临床标本及145份HBV DNA阴性血清耐药突变,并对突变进行分析.结果 经一年药物治疗10名患者产生耐药突变,耐药率19.6%（10/51）,产生突变阳性标本病毒载量＞105拷贝/ml.药物治疗后产生突变＞6个月.10例突变病毒株中,552密码子处突变9例,528密码子处突变3例,密码子555中未发现突变.5例血清存在混合感染,其中4例为野生型病毒与突变型的混合,野生型病毒所占比例皆在40%以下.1例血清出现在（4,4）位点的密码子ATT与（3,3）位点密码子TTG两种突变,两种突变类型病毒并行产生同步增长.（3,3）突变类型首次报道.结论 拉米夫定抗乙肝病毒治疗6个月以上易产生耐药,产生耐药病毒载量＞105拷贝/ml.主要发生在YMDD区,且存在两种突变类型病毒的混合感染,以上结果对慢性乙肝患者用药具有指导作用.