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1.
Aims: This study was undertaken to determine the prevalence and characteristics of hepatitis B virus (HBV) genotypes, antigen subtypes, "a" determinant variants and pre-S gene mutations circulating on a large scale in Thailand. Methods: The sequences of the Pre-S1, Pre-S2 and S regions were determined in serum samples of 147 HBsAg and HBV DNA-positive subjects who had been enrolled from the nationwide seroepidemiological survey conducted on 6213 individuals in 2004. Results: The results showed that genotypes C, B and A accounted for 87.1%, 11.6% and 1.3%, respectively. The distribution of the HBV antigen subtypes was: adr (84.4%), adw (14.2%) and ayw (1.4%). Regarding the "a" determinant, 2/43 (4.65%) and 2/104 (1.92%) samples of vaccinated and non-vaccinated subjects, respectively, displayed mutations, all ofwhich were Thr126Asn. Sequencing analysis showed the pre-S mutations in 14 (9.5%) samples, with pre-S2 deletion as the most common mutant (4.1%) followed by pre-S2 start codon mutation (2.9%), both pre-S2 deletion and start codon mutation (2.0%), and pre-S1 deletion (0.7%). The pre-S mutations were associated with older age and higher mean serum HBsAg level. Conclusion: This study demonstrated that HBV genotype/subtype C/adr and B/adw were the predominant strains circulating in Thailand. The "a" determinant variants seemed to be uncommon, and might not be attributed to vaccine-induced mutation.  相似文献   

2.
目的研究慢性乙型肝炎患者HBV基因型和亚型流行情况。方法应用HBV基因型和亚型特异性引物PCR法对北京、长春、大连、西安、石家庄、郑州和合肥7个城市660份HBV DNA阳性慢性乙型肝炎患者血清进行基因型和亚型分析。结果在660份HBV DNA阳性血清中,B基因型、C基因型和B/C混合感染分别为16.67%(110/660)、74.54%(492/660)和8.79%(58/660);在C基因型中,C1亚型6例(1.22%)、C2亚型473例(96.14%)、C1/C2混合基因亚型13例(2.64%);B基因型均为Ba亚型,B基因型和C基因型混合感染者均为Ba与C2亚型混合感染,未发现其他基因型和基因亚型;不同基因型感染患者HBeAg阳性率差异无统计学意义(P=0.153);B基因型和C基因型患者之间血清HBV DNA水平差异无统计学意义(6.37±1.62lg copies/ml对6.29±1.76lg copies/ml),但均高于B和C基因型混合感染患者(5.25±1.65lg copies/ml)。结论这7个城市慢性乙型肝炎患者以B基因型和C基因型感染为主,有部分B/C基因型混合感染。HBV亚型以Ba和C2亚型占优势。  相似文献   

3.
目的研究乙型肝炎病毒(HBV)感染者中HBV基因分型及其临床分布情况。方法应用基因型和亚型特异性引物聚合酶链反应(PCR)法,对鲁西地区135例HBV感染者血清进行HBV基因型及亚型分型。结果未分型11例,已分型124例。其中C型111例(C2基因亚型87例、非C1/C2亚型24例);B型11例,其中Ba型8例、Bj型3例;B/C混合型2例均为BaC2亚型混和感染。在肝硬化和重度慢性乙型肝炎中C型所占比例较高,分别为100%、88%;无症状携带者中B型所占比例较高为8.51%;HBV基因型分型与性别无关。结论鲁西地区HBV感染者以C基因型为主,其中C2亚型占优势。  相似文献   

4.
The S gene encoding the major surface polypeptide of hepatitis B virus is preceded by the region pre-S(2) with a capacity to code for 55 amino acid residues. In the product of region pre-S(2), the sequence of 19 amino acid residues (amino acids 14-32 from the N terminus) representing an area of high local hydrophilicity is shared by viral strains of subtypes adr, ayw, and ayr; residue 22, phenylalanine, is replaced by leucine in a strain of the other subtype, adw. A synthetic peptide vaccine involving these 19 amino acid residues, when given to two chimpanzees, raised antibodies that bound to viral particles and protected the animals from challenge with 10(6) chimpanzee infectious doses of hepatitis B virus.  相似文献   

5.
苏南地区乙型肝炎病毒S基因序列的多态性研究   总被引:5,自引:0,他引:5  
目的:探讨乙型肝炎病毒(HBV)S基因序列的多态性,为研究HBV-S基因变异提供参照指导。方法:采用聚合酶链反应技术对81例乙型肝炎表面抗原阳性的HBV感染者的S基因进行扩增,再对扩增产物进行DNA测序,将结果与标准序列进行比较分析。结果:81价标本中,测得adr型38例,adw型43例,未发现有ayr及ayw型。38例adr型中氨基酸第121~125位点(AA121~125)、AA127~130、AA132、AA135~160高度保守,而AA126为异亮氨酸(Ile),也可为苏氨酸(Thr)或丝氨酸(Ser);AA131多为Thr,少数为天冬酰胺(Asn),1例为脯氨酸(Pro),AA133多为蛋氨酸,少数为Thr;AA134为苯丙氨酸,仅1例为精氨酸。43例adw型中,AA131均为Thr,而非Asn;AA126为Thr,也可为丙氨酸(Ala),少数为Ser;AA127多为Pro,少数为Thr;AA123为Thr,少数为Ala或Ile;AA141多为赖氨酸,少数为谷氨酸;AA133、AA140分别为Thr、Ile各1例。其他位点则高度保守。结论:HBV亚型分布具有地域性,苏南地区多以adw和adr型为主。HBV-S基因(“a”决定簇)序列存在多态性,其中adw亚型略为明显。  相似文献   

6.
7.
Viral hepatitis, type B, in experimental animals.   总被引:11,自引:0,他引:11  
Evidence of natural infection with hepatitis B virus (HBV) in chimpanzees was followed by demonstration that this species provides a highly sensitive animal model system for experimental type B hepatitis. With rare exceptions, inoculation of sero-negative chimps with materials containing infectious HBV produces serologic evidence of infection including appearance of circulating hepatitis B surface antigen (HBs Ag) and subsequently development of antibody to HBs Ag and hepatitis B core antigen. Serum enzyme elevations indicative of liver damage occurred in 31 of 46 aminals infected to date. The antigenic subtypes of HBV in the inocula breed true in the infected animals, and HBV titers of sera containing the adw and ayw subtypes have been established as 10(7.5) infectious units/ml. Rhesus monkeys also provide a valuable animal model for type B hepatitis, but they appear to be less sensitive than chimps, and they do not develop evidence of liver damage.  相似文献   

8.
There are eight genotypes and nine subtypes of HBV. Small differences in geographical origin are associated with sequence changes in the surface gene. Here, we compared core gene sequences from different genotypes and geographical regions. Specific combinations of 24 amino acid substitutions at nine residues allowed allocation of a sequence to a subtype. Six of these nine residues were located in different T cell epitopes depending on HBV geographical area and/or genotype. Thirty-seven nucleotide changes were associated uniquely with specific genotypes and subtypes. Unique amino acid and nucleotide variants were found in a majority of sequences from specific countries as well as within subtype ayw2 and adr. Specific nucleotide motifs were defined for Korean, Indian, Chinese, Italian and Pacific region isolates. Finally, we observed amino acid motifs that were common to either South-east Asian or Western populations, irrespective of subtype. We believe that HBV strains spread within constrained ethnic groups, result in selection pressures that define sequence variability within each subtype. It suggests that particular T cell epitopes are specific for geographical regions, and thus ethnic groups; this may affect the design of immunomodulatory therapies.  相似文献   

9.
Pre-S gene-encoded proteins of the hepatitis B virus (HBV) were studied in the liver by immunofluorescence and in serum by radioimmunoassay in 30 patients with chronic HBV infection. The results were compared with molecular hybridization analysis of HBV-DNA in liver and serum, with serum hepatitis B e antigen/antibody (HBeAg/anti-HBe) status and with underlying liver histology. Pre-S peptides were detected in the serum of 11 patients, 10 of whom were positive for serum HBV-DNA and/or liver hepatitis B core antigen. Only 4 of these patients were HBeAg positive. The prevalence of serum pre-S among HBV replicating carriers was 59% (10/17) compared to only 8% (1/13) among those with non-replicating virus (P less than 0.01). All patients with circulating pre-S peptides had active liver disease. Anti-pre-S was detected in the serum of only 4 patients, 3 with integrated HBV-DNA. In contrast to serum findings, pre-S peptides were detected in the liver of all patients with histochemically demonstrable hepatitis B surface antigen (HBsAg), regardless of HBV replicative status. HBsAg carriers with integrated HBV-DNA had abundant cytoplasmic pre-S1 and pre-S2 localized in numerous ground-glass hepatocytes. It is concluded that pre-S peptides are usually displayed in the liver simultaneously with histochemically detectable HBsAg; they are secreted in the serum in association with high HBV replication and release of HBV particles, but in the absence of episomal HBV replication, pre-S peptides seem to be largely retained within hepatocytic membranes.  相似文献   

10.
Stored sera from asymptomatic hepatitis B virus (HBV) carriers and hepatitis B virus surface antigen-positive hepatocellular carcinoma (HCC) patients were tested for HBV subtypes, such as subtype determinants d, y, w, r and also antigenic determinants isoleucine (i) and threonine (t) by direct S gene nucleotide sequencing. Significant changes in minor i and t determinants in hepatocellular carcinoma patients with adr hepatitis B carriers were seen. The adr subtype with t determinant was present in 14/25 (56%) of HCC patients compared with only two of 28 (7%) in asymptomatic hepatitis B carriers ( P < 0.001). However, the adr subtype with i determinant was present in nine of 25 (36%) of the HCC patients and also present in 24/28 (86%) of asymptomatic carriers ( P < 0.001). No significant changes were seen with the adw subtypes. These results show that i and t minor determinant changes are more common with adr subtypes associated with HCC than with the adw subtype. Whether these subtle changes are pathologically relevant or only a polymorphism of hepatitis B genotypes will depend on subsequent follow-up studies.  相似文献   

11.
AIMTo investigate the associations of different types of pre-S deletions with hepatitis B virus (HBV) genotypes.METHODSThe sequences of the pre-S region, basal core promoter (BCP) mutation, and precore (PC) mutation were examined through direct DNA sequencing or clonal analysis and sequencing in 273 HBV carriers, namely 55 asymptomatic carriers, 55 carriers with chronic hepatitis (CH), 55 with liver cirrhosis (LC), 53 with liver cirrhotic hepatocellular carcinoma (LC-HCC), and 55 with noncirrhotic HCC. A total of 126 HBV carriers (46.2%) harbored pre-S deletions. The DNA sequences of pre-S deletion mutants from 43 age-matched genotype B (HBV/B)-infected carriers and 43 age-matched genotype C (HBV/C)-infected carriers were further examined, aligned, and compared.RESULTSNo significant difference was observed in the mean age distribution (P = 0.464), male sex (P = 0.805), viral load (P = 0.635), or BCP mutation (P = 0.117) between the HBV/B and HBV/C groups. However, the rate of PC mutation was significantly higher in the HBV/B-infected carriers than in the HBV/C-infected carriers (P = 0.003). Both genotypes exhibited a high rate of deletion in the C-terminal half of the pre-S1 region and N-terminus of the pre-S2 region (86.0% and 79.1% in the HBV/B group; 69.8% and 72.1% in the HBV/C group, respectively). Epitope mapping showed that deletion in several epitope sites was frequent in both genotypes, particularly pS1-BT and pS2-B2. Conversely, the rate of pS2-B1 deletion was significantly higher in the HBV/B group (72.1% vs 37.2%, P = 0.002), and the rate of pS2-T deletion was significantly higher in the HBV/C group (48.8% vs 25.6%, P = 0.044). Functional mapping showed that the rate of deletion in three functional sites (the nucleocapsid binding site, start codon of M, and site for viral secretion) located in the N-terminus of the pre-S2 region was significantly higher in the HBV/B group (P < 0.05). One type of N-terminus pre-S1 deletion mutant with deletion of the start codon of the L protein was frequently observed in the HBV/C group (20.9% vs 9.3%, P = 0.228), particularly in the LC patients (42.9% vs 12.5%). Different patterns of pre-S deletions were also found between the HBV/B and HBV/C groups according to different clinical outcomes. In CH patients, deletion in the site for polymerized human serum albumin was more frequent in the HBV/B group (88.9% vs 36.4%, P = 0.028). In the LC-HCC patients, the rate of deletion in the pre-S2 region was significantly higher in the HBV/B group than in the HBV/C group (P < 0.05).CONCLUSIONHBV/B- and HBV/C-infected carriers exhibit different patterns of pre-S deletion, which may be associated with the progression of liver diseases.  相似文献   

12.
Two human monoclonal antibodies (mAbs) against hepatitis B surface antigen (HBsAg) generated in the Trimera mouse system are described. Both mAbs 17.1.41 and 19.79.5 are of the IgG1 isotype and have high affinity constants for HBsAg binding in the range of 10(-10) mol/L. Monoclonal antibody 17.1.41 recognizes a conformational epitope on the a determinant of HBsAg whereas mAb 19.79.5 recognizes a linear one. The 2 mAbs bind to a panel of hepatitis B virus (HBV) subtypes with distinct patterns. The neutralizing activity of these antibodies was tested in 2 different animal model systems. Administration of each mAb to HBV-Trimera mice, a system that provides a mouse model for human hepatitis B infection, reduced the viral load and the percentage of HBV-DNA-positive mice in a dose-dependent manner. These 2 mAbs were more effective than a polyclonal antibody preparation (Hepatect; Biotest Pharma, Dreieich, Germany) in both inhibition of HBV liver infection and reduction of viral load. A single administration of a mixture of these mAbs into HBV chronic carrier chimpanzees resulted in immediate reduction in HBsAg levels followed by recurrence to initial levels within few days. Thus, these mAbs may be potential candidates for preventive therapy or in combination with other antiviral agents against HBV. Further studies in humans are needed to assess these mAbs in various clinical indications.  相似文献   

13.
Although antibody to the hepatitis B surface antigen usually provides protection against hepatitis B virus (HBV) infection, recent reports indicate that this is not always the case. To study the possible role of immune responses to hepatitis B core antigen in immunity to HBV infection, chimpanzees were immunized with chimpanzee liver-derived or genetically cloned hepatitis B core antigen and later challenged with known infectious HBV. Two chimpanzees, which received liver-derived or cloned hepatitis B core antigen in Freund's adjuvant and developed hepatitis B core antibody and low-titer hepatitis B e antibody, were completely protected against HBV infection following challenge. In contrast, another chimpanzee, which received liver-derived hepatitis B core antigen without adjuvant, developed hepatitis B core antibody only in serum and had a subclinical HBV infection when challenged. These findings demonstrate that protection against HBV infection can be induced by immunization with hepatitis B core antigen in adjuvant and that protection, in this case, is not solely dependent on hepatitis B surface antibody. This fact has important implications in our understanding of the biology of HBV infection and in the design of future hepatitis B vaccines.  相似文献   

14.
AIMS: This study aims to examine the genomic variants of the 'a' epitope in chronic hepatitis B virus (HBV) carriers positive for both hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs). METHODS: Eighteen HBV carriers were studied. Hepatitis B virus (HBV) DNA was extracted and the 'a' epitope region was amplified and sequenced. RESULTS: Eighteen Chinese asymptomatic HBV carriers were studied. There were 13 patients who were positive for both HBsAg and anti-HBs. Of these, one patient had only wild-type HBV, three had a viral mixture, and five had only 'a' epitope variant HBV. Of the three patients with a viral mixture, all had variants in the less conserved region (123-137). Of the five patients with pure HBsAg mutants, three had variants in the less conserved region while two had variants in the highly conserved region. In this study with a limited number of patients, the serum alanine aminotransferase (ALT) levels were higher in patients with wild-type HBV, compared with those with either 'a' epitope variants or a viral mixture consisting of wild type and variants. CONCLUSION: Eight of the nine (89%) patients positive for both HBsAg and anti-HBs harbored an 'a' epitope variant. The lower ALT levels seen in patients who had either pure 'a' epitope variant or a mixture of wild type and mutants suggest that a closer monitoring of these 'a' epitope variants should be required, as patients carrying these infectious viral strains may remain asymptomatic.  相似文献   

15.
The presence of unique hepatitis B virus (HBV) variants has been investigated in two Chinese patients with chronic liver disease, whose sera were positive for HBV-DNA by dot blot hybridization or polymerase chain reaction (PCR) but hepatitis B surface antigen (HBsAg)-negative by conventional polyclonal antibody based immunoassays. PCR amplification of HBV-DNA followed by direct sequencing showed an insertion of six nucleotides, which introduced two additional amino acids between codons 122 and 123 in one patient (Isolate 1), whereas a nine nucleotide insertion in the other patient (Isolate 2) gave rise to three amino-acids between codons 123 and 124 immediately upstream from the ‘a’ determinant in the S gene. These insertions have not been described previously in any published sequences of the known subtypes and were absent from sequences of 30 HBsAg-positive Chinese patients from the same region. In the cases under study, the insertion is associated with four consecutive adenine molecules from nucleotides 516 to 519. It seems likely that this area is a hot spot for insertions in HBV. We found none of the previously described amino-acid deletions or substitutions in the pre-S1, pre-S2 and S genes, which are involved in unusual antigenic profiles. This finding suggests that genetic mutations in the S gene outside the ‘a’ determinant may be responsible for failure to detect HBsAg in some Chinese patients with chronic hepatitis caused by HBV infection.  相似文献   

16.
The emergence in vaccinated individuals of hepatitis B virus (HBV) mutants with amino acid substitutions within the a determinant of the surface protein has raised the possibility that such variants represent neutralization escape mutants. We previously demonstrated that one such mutant HBV, strain AS, with an arginine substituted for glycine at surface gene codon 145, was infectious and pathogenic in seronegative chimpanzees. In the present study, the protective efficacy of licensed hepatitis B vaccines was evaluated against challenge with this mutant virus. Four chimpanzees were immunized with 1 of 2 licensed recombinant hepatitis B vaccines. Shortly after the chimpanzees developed antibodies to hepatitis B surface antigen (anti-HBs), they were challenged intravenously with mutant HBV strain AS. Two unvaccinated chimpanzees served as positive controls. The 4 vaccinated chimpanzees did not develop evidence of HBV infection or hepatitis during 2 years following virus challenge. In contrast, the 2 unvaccinated chimpanzees developed HBV infection and hepatitis. Serum anti-HBs in the vaccinated chimpanzees reacted not only with wild-type surface antigen, but also with mutant surface antigen by competition enzyme-linked immunosorbent assay (ELISA). Thus, immunization of chimpanzees with licensed recombinant hepatitis B vaccines stimulates anti-HBs that is broadly reactive and affords protection against infection with a surface gene mutant of HBV, suggesting that properly immunized individuals are not at significant risk of infection with this prototype variant strain of HBV.  相似文献   

17.
In Thailand, chronic liver disease (CLD) as a consequence of infection with hepatitis B virus (HBV) constitutes a public-health burden. Control and treatment are complicated by the virus exhibiting an unusually high mutation rate, with some genotypes apparently causing more severe disease than others. Restriction-fragment-length-polymorphism (RFLP) analysis of the pre-S region of the viral genome, amplified by PCR, was used to determine which genotypes were most prevalent among Thai patients chronically infected with the virus. The patients were chronic HBV carriers (40) or cases of chronic hepatitis (34), cirrhosis (14) or hepatocellular carcinoma (30). As indicated by the results of earlier studies on CLD patients in South-east Asia, genotype C (68.6%) was clearly predominant. RFLP patterns permitted the C1 (12.7%), C7 (45.7%), C8 (10.2%) and B1 (29.7%) subtypes to be identified. Two samples that could not be typed by RFLP were analysed by direct sequencing, categorized as type C, and tentatively designated as subtype C9. As comparison of the present data with those previously obtained by direct sequencing of PCR products indicates that RFLP analysis is as specific and reliable as sequencing and less expensive and time-consuming, RFLP analysis may be particularly useful for epidemiological studies.  相似文献   

18.
We report the development of two models for synthetic hepatitis B vaccines. The models were based on the multiple antigen peptide (MAP) system and contained the relevant B- and T-cell epitopes without any macromolecular carrier. Two peptides, representing the a determinant of the S region (S protein) of hepatitis B surface antigen, a dominant serotype of hepatitis B virus infection found in humans, and residues 12-26 of the pre-S(2) region of the middle protein were incorporated as either monoepitope or diepitope MAP models. Immunizations of outbred rabbits with the monoepitope MAP that contains the pre-S(2) antigen resulted in high-titered antibody response to the middle protein, but the other monoepitope, containing only the a-determinant peptide antigen, resulted in poor immune responses to either the peptide antigens or to the S protein. The diepitope MAPs containing both the a and the pre-S(2) determinants produced high-titer antibodies reactive to the a-synthetic peptide and the S protein, as well as to the middle proteins. Thus, our results show that the diepitope MAP models eliminate the need for a protein carrier and that the pre-S(2) peptide determinant serves as a T-helper cell epitope that enhances the immune response of the S region and overcomes the poor immunogenicity encountered with a single epitope of the S region.  相似文献   

19.
Summary.  Hepatitis B virus (HBV) circulates in blood as closely related, but genetically diverse molecules called quasispecies. During replication, HBV production may approach 1011 molecules/day, although during peak activity this rate may increase 100–1000 times. Generally, DNA polymerases have excellent fidelity in reading DNA templates because they are associated with an exonuclease which removes incorrectly added nucleotides. However, the HBV-DNA polymerase lacks fidelity and proofreading function partly because exonuclease activity is either absent or deficient. Thus, the HBV genome and especially the envelope gene, is mutated with unusually high frequency. These mutations can affect more than one open reading frame because of overlapping genes. The S gene contains an exposed major hydrophilic region (residues 110–155), which encompasses the 'a' determinant that is important for inducing immunity. Nucleotide substitutions in this region are common and result in reduced binding or failure to detect hepatitis B surface antigen (HBsAg) in diagnostic assays. Adaptive immunity also depends on the recognition of HBsAg by specific antibody and variants pose a threat if they interfere with binding to antibody. Finally, genomic hypervariability allows HBV to escape selection pressures imposed by antiviral therapies, vaccines and the host immune system, and is responsible for creating genotypes, subgenotypes and subtypes.  相似文献   

20.
目的检测乙型肝炎病毒患者乙型肝炎病毒前-S1抗原(HBV pre-S1-Ag)、前-S2抗原(HBV pre-S2-Ag)、乙型肝炎病毒DNA(HBV DNA)和乙型肝炎病毒E抗原(HBeAg),探讨其相关性和临床应用价值。方法应用酶联免疫测定法(ELISA)分别检测HBV pre-S1-Ag、HBV pre-S2-Ag和乙型肝炎病毒标志物(HBV-M),荧光定量聚合酶链反应法(FQ-PCR)检测HBV DNA,并对检测结果进行统计学分析。结果 HBsAg阳性者中,pre-S1-Ag、pre-S2-Ag、HBV DNA阳性者分别为594例、541例、629例,其阳性率分别为66.29%、60.38%、70.20%。HBeAg阳性组pre-S1-Ag、pre-S2-Ag、HBV DNA的阳性率分别为90.21%、74.46%、93.32%,显著高于HBeAg阴性组的45.28%、48.01%、49.89%,差异有统计学意义(P〈0.01)。随着HBV DNA载量的增高,pre-S1-Ag、pre-S2-Ag、HBeAg阳性率随之增高。结论 pre-S1-Ag、pre-S2-Ag与HBV DNA和HBeAg阳性检出率具有显著相关性。联合检测pre-S1-Ag、pre-S2-Ag、HBV DNA及HBV-M,有助于HBV早期诊断、疗效观察和预后判断。  相似文献   

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