乙型肝炎病毒X基因准种特点的研究

以乙型肝炎病毒(HBV)X基因序列的异质性表现来探讨HBV准种在慢性感染者中的存在状态.以中国株HBV基因序列为依据,设计特异性多聚酶链反应引物,自9例慢性HBV感染患者血清中扩增HBV X基因,克隆入pGEM Teasv质粒,随机挑选克隆进行DNA测序以确定病毒的变异程度.37例测序结果提示来源于不同患者HBV X基因序列高度保守,但每个序列均不一致.X区除了存在广泛的碱基点替换突变外,序列的缺失突变占测序克隆总数的51.4%(19/37);氨基酸缺失及移框突变多发生于123位氨基酸残基之后,可导致X蛋白多种羧基端形式.结果提示HBV长期携带者体内有HBV准种共存,X区内存在热点缺失突变区,该区突变结果可能影响X蛋白反式激活功能.     

丙型肝炎病毒高变区基因变异特点初探

对两例ＨＣＶＲＮＡ持续阳性者分三个时间点随访五年,测定了ＨＣＶ的高变区基因序列,每个时间点平均测定２８个克隆,总共测定了１６８个克隆。研究发现ＨＣＶ高变区基因变异有五个明显特点：（１）变异程度大,高变区至少有８９％的核苷酸位点都可能发生变异;（２）变异形式多样,除常见的替代突变外,缺失突变（缺失１、２或３个核苷酸）的克隆数占总克隆数的２２．５％;（３）优势克隆明显,即有若干个克隆高变区的核苷酸和氨基酸序列相同;（４）类似株现象严重;（５）变异幅度大。该研究说明ＨＣＶ高变区基因变异具有高度复杂多样性。     

一例乙型肝炎患者体内不同HBV克隆的序列差异

采用ＰＣＲ扩增、噬菌体克隆和核苷酸序列分析的方法对一例乙型肝炎患者体内ＨＢＶ的ＨＢｓＡｇ编码区和部分前Ｓ２区进行序列分析。结果发现同一患者体内获得的不同ＨＢＶＤＮＡ克隆间存在个别碱基的差异,而这种差异并非方法学本身产生的。由此得出的结论是,这种碱基“突变”反映了乙型肝炎患者体内ＨＢＶ基因组实际存在的多态性。     

抗甜菜坏死黄脉病毒单链抗体表达载体的构建及其表达

用ＰＣＲ方法以分泌抗甜菜坏死黄脉病毒（ＢＮＹＶＶ）单克隆抗体的杂交瘤细胞的基因组为模板,扩增了编码ＢＮＹＶＶ单抗的重链可变区（ＶＨ）基因。测序表明,该ＶＨ序列属于小鼠ＩＩ（Ａ）亚类,全长为３６０ｂｐ,编码１２０个氨基酸。将其和先前克隆的轻链基因分别插入到一个含有连接ＶＨ和ＶＬ基因的连接序列的质粒之中,构建成单链抗体（ｓｃＦｖ）基因的表达载体ｐＴＣｓｃＦｖ。将质粒在大肠杆菌中表达,ＥＬＩＳＡ法检测出     

两例丙型肝炎病毒(HCV)和乙型肝炎病毒(HBV)重叠感染者的HCV核心区cDNA序列分析

从临床肝病患者中选择两例ＨＣＶ和ＨＢＶ重叠感染者ＨＳＱ和ＳＺＨ,他们血清中的生化指标丙氨酸转氨酶（ＡＬＴ）持续异常,肝活检病理示有严重的肝损伤。在ＡＬＴ异常期,血清学检测结果为ＨＢｓＡｇ、ＨＢｅＡｇ阳性,抗ＨＣＶＩｇＧ（包括Ｃ２２、Ｃ３３ｃ）阴性,但套式ＰＣＲ检测ＨＣＶＲＮＡ阳性,核心区ｃＤＮＡ序列分析发现该区有１个密码子（ＧＧＣｎｔ３８５—３８７）缺失,对应缺失的氨基酸是甘氨酸（ＧＬＹ）,从血清学检测和序列分析结果推测,在ＨＣＶ和ＨＢＶ重叠感染中,ＨＢＶ和ＨＣＶ均可处于持续复制状态,抗ＨＣＶＩｇＧ抗体阴性可能是ＨＣＶ的多蛋白前体翻译和病毒颗粒装配受到ＨＢＶ干扰的结果。     

乙型肝炎病毒X基因的分析与在大肠杆菌中的表达

以ＨＢＶ－ＮＣｌＤＮＡ为材料研究了其中的Ｘ基因,首先确定了此Ｘ基因的顺序,即用ＡＢＩ自动萤光测序议测序证明了此Ｘ基因的３８５位核苷酸后缺失１９个核苷酸,从而引起移码突变,使此Ｘ基因共有５１９个核苷酸,编码１７２个氨基酸,比另一种ａｄｒ型Ｘ蛋白多１８个氨基酸。在其第五位氨基酸上有一ＡＴＧ起始密码,也与另一Ｘ基因不同。经重组后获得在大肠杆菌中的热诱导表达,用Ｗｅｓｔｅｒｎｂｌｏｔ方法证明确为Ｘ蛋白,并有多态性。     

乙型肝炎病毒全基因序列的测定

测定７ 例慢性 Ｈ Ｂ Ｖ 携带者 Ｈ Ｂ Ｖ 基因组全序列,经同源性比较,确定基因型。２ 例基因型为 Ｂ 型,余均为 Ｃ 型;血清型ａｄｒ ４ 例,ａｄｗ ３ 例。各序列间 Ｘ 基因差异最大。未见 Ａ１８９６ 、 Ｔ１７６２ Ａ１７６４等重要位点的变异。结合已有的２ 株 Ｈ Ｂ Ｖ 中国流行株全基因序列,初步建立以中国流行株序列为基础的 Ｈ Ｂ Ｖ 标准序列,该标准序列与国外标准序列仅有２２ 个位点的差异     

黄瓜花叶病毒亚组Ⅰ和Ⅱ分离物外壳蛋白基因的序列分析与比较

对我国分离的经生物学和血清学鉴定为黄瓜花叶病毒（ＣＭＶ）亚组Ⅰ和Ⅱ的各一分离物（ＧＢ、ＸＢ）的外壳蛋白（ＣＰ）基因进行了序列分析和比较。以提纯病毒ＲＮＡ为模板,进行逆转录及ＰＣＲ扩增,并通过常规基因克隆方法得到插入ＣＰ基因片段的重组克隆。对插入ＧＢ和ＸＢ两个分离物ＣＰ基因片段的重组克隆进行全序列测定,结果表明重组克隆序列长分别为７７７ｂｐ和７９２ｂｐ,均只含一个开放读框（ＯＲＦ）,长度为６５７ｎｔ,可编码２１８个氨基酸;两个分离物的ＣＰ基因核苷酸序列同源率为７７５％,氨基酸序列同源率为８２６％。与我国已报道的７个ＣＭＶ分离物的ＣＰ基因序列比较,分离物ＧＢ的同源率为９１３％～９７３％,分离物ＸＢ的同源率为７６６％～７８４％。与国际上已报道部分ＣＭＶ株系的ＣＰ基因序列相比较,分离物ＧＢ与亚组Ⅰ株系有更密切的亲缘关系,而分离物ＸＢ则与亚组Ⅱ株系的亲缘关系更密切。     

人源抗肿瘤坏死因子—α噬菌体抗体的基因结构分析

从混合的噬菌体抗体库中筛选到了抗人ＴＮＦα的人源单克隆抗体,并对筛选到的抗体基因进行了序列测定和分析。结果表明,筛选到的４个特异性抗ＴＮＦα噬菌体抗体克隆的重链的重链基因序列相同,该重链基因长６８１ｂｐ,编码２２７个氨基酸残基,属于人免疫球蛋白第Ⅲ家族,其中１－１１９位氨基酸残基为重链可变区（ＶＨ）,１２０－２２７位为重链恒定区１（ＣＨ１）。４个噬菌体抗体克隆的轻链均缺失,因此实际上筛选到的是单重     

中国丙型肝炎患者中发现新的丙型肝炎病毒核苷酸序列

应用ＲＴ－ＰＣＲ和ＤＮＡ克隆重且技术从中国云南地区丙型肝炎患者血清中克隆到３个丙型肝炎病毒（ＨＶＣ）５?端非编码区（５’ＮＣＲ）核苷酸序列。这３个序列分别来自３个不同的再型肝炎患者。与国内外已发表的ＨＣＶ原型株同源序列比较研究发现,这３个ＨＣＶ５’ＮＣＲ序列中分别存在部分核苷酸序列的缺失或出现插入重复。在ＹＳ２２５－１ ５’ＮＣＲ序列－１５５￣－１７４位之间,有１８个核苷酸序列缺失;在ＹＳ２０３－     

乙型肝炎病毒逆转录酶区基因序列准种与变异特点

乙型肝炎病毒(Hepatitis B Virus,HBV)P基因编码产物从功能上分为末端蛋白(1～178aa)、间隔区(179～336aa)、逆转录酶区(337～682aa)和RNA酶H区(683～816aa),各区有相应的生物学功能;逆转录酶区包含S基因主蛋白编码区.近年来的研究提出HBV感染者体内存在有准种[1,2]的假说.我们以逆转录酶区序列为研究靶区域,应用聚合酶链反应(PCR)技术扩增慢性乙型肝炎患者血清中的靶基因序列,随机选择克隆测序,比较其结果,证明了HBV准种特点的存在,并发现多种基因突变形式.     

Hepatitis B Virus with X Gene Mutation Is Associated with the Majority of Serologically “Silent” Non-B,Non-C Chronic Hepatitis

Hepatitis B virus (HBV) with X gene mutations has been a putative pathogen of chronic hepatitis without serological markers of known hepatitis viruses. The aim of this study was to reconfirm whether the HBV with the X gene mutation is associated with these serologically “silent” non-B, non-C (NBNC) chronic hepatitis, alcoholic liver disease (ALD) and autoimmune hepatitis (AIH). HBV DNA was amplified from serum and sequenced in 30 patients with NBNC chronic hepatitis in comparison with 20 patients with ALD and 5 patients with AIH. HBV DNA was identified in 21 patients (70%) in NBNC chronic hepatitis by nested polymerase chain reaction while only one patient (5%) in ALD and none in AIH showed HBV DNA. Eighteen (85.7%) of the 21 identified HBV DNAs had an identical 8-nucleotide deletion mutation at the distal part of the X region. This mutation affected the core promoter and the enhancer II sequence of HBV DNA and created a translational stop codon which truncated the X protein by 20 amino acids from the C-terminal end. All the HBV DNAs had a precore mutation at the 83rd nucleotide resulting in disruption of HBe antigen synthesis. These results indicate that HBV mutants are closely associated with the majority of serologically “silent” NBNC chronic hepatitis cases and the population of such mutant HBV DNAs is not uniform.     

“Silent” Hepatitis B Virus Mutants Are Responsible for Non-A,Non-B,Non-C,Non-D,Non-E Hepatitis

Since the recent introduction of diagnostic kits for hepatitis C and E, some cases of nonA, non-B, non-C, non-D, non-E hepatitis (so-called hepatitis F) have been revealed. We attempted to demonstrate that so-called hepatitis F is caused by hepatitis B virus (HBV) variants. Polymerase chain reaction (PCR) was used to amplify serum HBV DNAs from 20 patients with acute hepatitis and 20 patients with chronic hepatitis who had been diagnosed as having so-called hepatitis F on the basis of conventional serological markers. The PCR technique successfully amplified HBV DNAs in 18 (90%) cases of acute hepatitis and 17 (85%) cases of chronic hepatitis. Sequencing of HBV DNAs of six patients (acute 3, chronic 3) revealed equally a T-to-C mutation of DR2 and an 8-nucleotide deletion of the 3′-terminus of the X gene coding region, giving rise to the generation of a C-terminally truncated X protein and probable damage to the enhancer II/core promoter elements. These mutations of the X gene coding region may lead to suppression of replication and expression of HBV DNAs. Thus virtually all cases of so-called hepatitis F appear to be caused by “silent” HBV mutants, at least in Japan.     

Polymorphism analyses of hepatitis B virus X gene in hepatocellular carcinoma patients from southern China

Chronic hepatitis B virus(HBV)infection is one of the major causes of hepatocellularcarcinoma(HCC),and the HBV X(HBx)gene plays a critical role in the molecular pathogenesis ofHBV-related HCC.We have investigated whether there are particular HBx gene mutations associated withHCC in patients from southern China.The HBx gene was examined in 51 paraffin-embedded tumor tissuesamples from patients with HCC and 25 serum samples from the HBV carrier by nested polymerase chainreaction(PCR),single-stranded conformational polymorphism and heteroduplex analysis.The HBx geneswith potentially important mutations from tumor tissue samples were cloned,sequenced and aligned withthe published HBx gene sequence.HBV genotypes in tumor tissue samples were analyzed by nested PCR.Analyses of HBx gene polymorphism showed that 31.3% of HBx gene fragments in tumor tissue sampleshad a special pattern.A common deletion at nt 382-400 of the HBx gene accompanied by 29 point mutationswas detected in four randomly selected tumor tissue samples with this pattern which caused a frame-shiftin the HBx open reading frame with a new stop codon at nt 1818,resulting in an HBx polypeptide chaintruncated at the C end in these cases.Among the four randomly selected samples,three were HBV genotypeB,and one was not detected by our present assay.In another tumor tissue sample,amplification of thefull-length HBx gene yielded a shorter fragment.Sequencing of this fragment revealed a 264 bp deletionbetween nt 1577 and 1840 of the HBV gene.These results suggest that HBx gene mutation occurs frequentlyin HCC samples,and the deletion at nt 382-400 of the HBx gene might play a role in carcinogenesis of HCCin southern China.     

HBV X 区基因部分序列的亚克隆与PCR 检测

目的：探讨HBVX区基因用于乙型病毒性肝炎早期诊断价值和意义。方法：设计特异性引物,将pBR322-HBV质粒X区部分序列PCR产物AT亚克隆至pBS—T载体,提取和纯化质粒DNA,再对HBVX区序列进行PCR扩增。结果：获得了预期希望的质粒。PCR的最佳退火温度为51℃,灵敏度达到101拷贝／2μl,线性范围101—1010拷贝／2μl。讨论：pBR322-HBV质粒中的靶基因成功地被亚克隆至pBS—T载体。pBR322-HBV中X区目的序列扩增产物为57bp,该小片段勿需纯化就可直接AT亚克隆至新载体,有利于后续的常规PCR检测和TaqMan MGB荧光定量PCR检测。     

Discovery of a Novel Mutation (X8Del) Resulting in an 8-bp Deletion in the Hepatitis B Virus X Gene Associated with Occult Infection in Korean Vaccinated Individuals

Universal infantile hepatitis B virus (HBV) vaccination may lead to an increase in vaccine escape variants, which may pose a threat to the long-term success of massive vaccination. To determine the prevalence of occult infections in Korean vaccinated individuals, 87 vaccinated subjects were screened for the presence of HBV DNA using both the nested PCR protocol and the VERSANT HBV DNA 3.0 assay. The mutation patterns of variants were analyzed in full-length HBV genome sequences. Their HBsAg secretion and replication capacities were investigated using both in vitro transient transfection and in vivo hydrodynamic injection. The presence of HBV DNA was confirmed in 6 subjects (6.9%). All six variants had a common mutation type (X8Del) composed of an 8-bp deletion in the C-terminal region of the HBV X gene (HBxAg). Our in vitro and in vivo analyses using the full-length HBV genome indicated that the X8Del HBxAg variant reduced the secretion of HBsAg and HBV virions compared to the wild type. In conclusion, our data suggest that a novel mutation (X8Del) may contribute to occult HBV infection in Korean vaccinated individuals via a reduced secretion of HBsAg and virions, possibly by compromising HBxAg’s transacting capacity.     

Complex Genotype Mixtures Analyzed by Deep Sequencing in Two Different Regions of Hepatitis B Virus

This study assesses the presence and outcome of genotype mixtures in the polymerase/surface and X/preCore regions of the HBV genome in patients with chronic hepatitis B virus (HBV) infection. Thirty samples from ten chronic hepatitis B patients were included. The polymerase/surface and X/preCore regions were analyzed by deep sequencing (UDPS) in the first available sample at diagnosis, a pre-treatment sample, and a sample while under treatment. HBV genotype was determined by phylogenesis. Quasispecies complexity was evaluated by mutation frequency and nucleotide diversity. The polymerase/surface and X/preCore regions were validated for genotyping from 113 GenBank reference sequences. UDPS yielded a median of 10,960 sequences per sample (IQR 16,645) in the polymerase/surface region and 11_,595 sequences per sample (IQR 14,682) in X/preCore. Genotype mixtures were more common in X/preCore (90%) than in polymerase/surface (30%) (p<0.001). On X/preCore genotyping, all samples were genotype A, whereas polymerase/surface yielded genotypes A (80%), D (16.7%), and F (3.3%) (p = 0.036). Genotype changes in polymerase/surface were observed in four patients during natural quasispecies dynamics and in two patients during treatment. There were no genotype changes in X/preCore. Quasispecies complexity was higher in X/preCore than in polymerase/surface (p = 0.004).The results provide evidence of genotype mixtures and differential genotype proportions in the polymerase/surface and X/preCore regions. The genotype dynamics in HBV infection and the different patterns of quasispecies complexity in the HBV genome suggest a new paradigm for HBV genotype classification.     

Virological Characteristics of Acute Hepatitis B in Eastern India: Critical Differences with Chronic Infection

Hepatitis B Virus (HBV) manifests high genetic variability and is classifiable into ten genotypes (A-J). HBV infection can lead to variable clinical outcomes, ranging from self-limiting acute hepatitis to active chronic hepatitis, cirrhosis and hepatocellular carcinoma. The present study characterizes HBV strains circulating among patients with acute (AHB) and chronic HBV infection (CHB). Among a total of 653 HBsAg positive cases, 40 manifested acute infection. After sequencing the surface(S), basal core promoter/pre-core(BCP/PC) and the X gene regions, phylogenetic tree was constructed using MEGA4 by neighbor-joining method. Statistical robustness was established with bootstrap analysis. Nucleotide diversity was determined by Shannon entropy per site using the Entropy program of the Los Alamos National Laboratories. Analyses of acute patients revealed that HBV/D2 is the major circulating sub-genotype and commonly associated with sexual promiscuity and the age group between15-30 years. Comparison of AHB and CHB patients revealed that HBeAg positivity, ALT levels and genotype D were significantly high in AHB, whereas CHB patients were predominantly male, had a high viral load, and were commonly associated with genotype C. The frequencies of mutations in the S, BCP/PC, and X gene were low in AHB as compared to CHB. Drug resistant mutations were not detectable in the polymerase gene of AHB. Average nucleotide diversity in AHB was considerably low as compared to CHB. Further, the highest average ΔH (average difference in entropy between chronic and acute infection) was observed in the BCP/PC region implying that this region was most vulnerable to mutations upon HBV persistence, especially in case of genotype C. Additionally, among all substitutions, the A1762T and G1764A BCP mutations were the strongest indicators of chronicity. In conclusion, the study exhibits a general portrait of HBV strains circulating among acute hepatitis B patients in Eastern India and their intricate differences with chronic patients which should be useful from the clinical point of view.