Hepatitis B virus (HBV) mutations associated with resistance to lamivudine in patients coinfected with HBV and human immunodeficiency virus.
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Mutations associated with hepatitis B virus (HBV) resistance to lamivudine have not been extensively addressed in human immunodeficiency virus (HIV)-HBV coinfection. We have studied the HBV polymerase sequences from nine coinfected patients who experienced HBV recurrence while under lamivudine treatment. In seven of these nine patients, Met(550), belonging to the highly conserved YMDD motif, was mutated to Val and was associated with a substitution of Met for Leu(526) in each case. In the two remaining patients, we found a Met(550)-to-Ile change that was associated in only one case with a Leu(526)-to-Met mutation. No mutation was observed in three control patients not receiving lamivudine. This study demonstrates the emergence of particular genetic profiles in HBV-HIV-coinfected patients experiencing a loss of control of HBV infection despite high doses of lamivudine. (+info)
The X gene of hepatitis B virus shows a high level stimulation of the Rous sarcoma virus long terminal repeat in the methylotropic yeast, Pichia pastoris.
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In order to study the transactivational property of the X gene in the methylotropic yeast Pichia pastoris, a Rous sarcoma virus-chloramphenicol acetyltransferase (RSV-CAT) cassette was co-transformed and integrated into the host yeast strain as a reporter which showed an overwhelming CAT activity. Immunoprecipitation of the yeast cell extracts with an X-specific monoclonal antibody, however, showed a low level expression of the X gene. Therefore besides a trans-effect of the X protein, the enhanced reporter activity could be a manifestation of a cis-effect of the X gene sequences also. Therefore, unlike the transactivation studies with X gene in animal cells where limited functional activity is observed, P. pastoris appears to be an excellent system to study cis- and trans-aspects of gene regulation by the X gene. (+info)
Direct association and nuclear import of the hepatitis B virus X protein with the NF-kappaB inhibitor IkappaBalpha.
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The X protein of hepatitis B virus (HBV) is a transcriptional activator which is required for infection and may play an important role in HBV-associated hepatocarcinogenesis. It has been suggested that X acts as a nuclear coactivator or stimulates several signal transduction pathways by acting in the cytoplasm. One of these pathways leads to the nuclear translocation of NF-kappaB. A recent report indicates that X activates NF-kappaB by acting on two cytoplasmic inhibitors of this family of transcription factors: IkappaBalpha and the precursor/inhibitor p105. We demonstrate here that X directly interacts with IkappaBalpha, which is able to transport it to the nucleus by a piggyback mechanism. This transport requires a region of IkappaBalpha (the second ankyrin repeat) which has been demonstrated to be involved in its nuclear import following NF-kappaB activation. Using deletion mutants, we showed that amino acids 249 to 253 of IkappaBalpha (located in the C-terminal part of the sixth ankyrin repeat) play a critical role in the interaction with X. This small region overlaps one of the domains of IkappaBalpha mediating the interaction with the p50 and p65 subunits of NF-kappaB and is also close to the nuclear export sequence of IkappaBalpha, therefore providing a potential explanation for the nuclear accumulation of IkappaBalpha with X. This association can also be observed upon the induction of endogenous IkappaBalpha by tumor necrosis factor alpha (TNF-alpha) treatment of Chang cells expressing X. In accordance with this observation, band shift analysis indicates that X induces a sustained NF-kappaB activation following TNF-alpha treatment, probably by preventing the reassociation of newly synthesized nuclear IkappaBalpha with DNA-bound NF-kappaB complexes. (+info)
Localization of a unique hepatitis B virus epitope sheds new light on the structure of hepatitis B virus surface antigen.
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In a search for monoclonal antibodies (MAbs) that can bind hepatitis B virus surface antigen (HBsAg) with amino acid substitutions in the immune dominant 'a' region (escape mutants) we investigated the epitope recognition site of the human MAb 4-7B. Pepscan analysis and experiments with alanine substitution as well as substitutions known from nature pointed to residues 178-186 in the small S protein with the amino acid sequence PFVQWFVGL (key amino acids in bold) as the minimal epitope. Single amino acid substitutions at positions 122(R/K)(d/y), 134(Y/F), 145(G/R), 148(T/A) and 160(K/R)(w/r), representing 'a' region variants in recombinant HBsAg COS-I cells, did not influence binding of MAb 4-7B. Synthetic peptides (residues 175-189) including the 4-7B epitope sequence were able to evoke an anti-HBs response in rabbits. According to established polypeptide models, the 4-7B epitope region is located in the lipid layer of 20 nm HBsAg particles. The present results, however, suggest that residues 178-186 are exposed on the surface of the 20 nm particle. This may change our view of the structure of HBsAg. (+info)
Hepatitis B virus DNA in blood samples positive for antibodies to core antigen and negative for surface antigen.
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Anti-hepatitis B core antigen (HBcAg)-positive hepatitis B surface antigen (HBsAg)-negative plasma samples from blood donors were tested by nested PCR. DNA positivity was more significantly associated with high levels of anti-HBcAg than with low levels of anti-HBsAg antibodies. Analysis of a dilution of anti-HBcAg antibodies might result in a more rational exclusion of anti-HBcAg-positive HBsAg-negative samples, reducing the number of donations discarded and enabling more countries to incorporate anti-HBcAg testing. (+info)
Injections given in healthcare settings as a major source of acute hepatitis B in Moldova.
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BACKGROUND: Reported rates of acute hepatitis B are high in many former Soviet Union republics and modes of transmission are not well defined. METHODS: Two case-control studies were undertaken in Moldova to identify risk factors for acute hepatitis B in people aged 2-15 years (children) and > or =15 years (adults). Serologically confirmed acute hepatitis B cases occurring between 1 January 1994 and 30 August 30 1995, were matched on age, sex, and district of residence to three potential controls who were tested for hepatitis B markers to exclude the immune. Stratified odds ratios (SOR) were calculated using bivariate and multivariate methods. RESULTS: In multivariate analysis, compared with the 175 controls, the 70 adult cases (mean age 25 years, 66% male) were more likely to report receiving injections in the 6 months before illness during a dental visit (SOR = 21; 95% CI: 3.7-120), a hospital visit (SOR = 35; 95% CI: 7.2-170), or a visit to the polyclinic (SOR = 13; 95% CI: 2.4-74). Among children, receiving injections during a hospital visit (SOR = 5.2; 95% CI: 1.2-23) was the only exposure reported significantly more often by the 19 cases (mean age 8 years, 68% male) compared with the 81 controls. CONCLUSION: These results, along with reported unsafe injection practices in Moldova, suggest that injections are a major source of hepatitis B virus transmission and highlight the importance of proper infection-control procedures in preventing transmission of blood-borne infections. (+info)
Carboxypeptidase D is an avian hepatitis B virus receptor.
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The receptor molecules for human and animal hepatitis B viruses have not been defined. Previous studies have described a 170 to 180 kDa molecule (p170 or gp180) that binds in vitro to the pre-S domain of the large envelope protein of duck hepatitis B virus (DHBV); cDNA cloning revealed the binding protein to be duck carboxypeptidase D (DCPD). In the present study, the DCPD cDNA was transfected into several nonpermissive human-, monkey-, and avian species-derived cell lines. Cells transfected with a plasmid encoding the full-length DCPD protein bound DHBV particles, whereas cells expressing truncated versions of DCPD protein that fail to bind the pre-S protein did not. The DHBV binding to DCPD-reconstituted cells was blocked by a monoclonal antibody that neutralizes DHBV infection of primary duck hepatocytes (PDH) and also by a pre-S peptide previously shown to inhibit DHBV infection of PDH. In addition to promoting virus binding, DCPD expression was associated with internalization of viral particles. The entry process was prevented by incubation of reconstituted cells with DHBV at 4 degrees C and by the addition of energy-depleting agents known to block DHBV entry into PDH. These results demonstrated that DCPD is a DHBV receptor. However, the lack of complete viral replication in DCPD-reconstituted cells suggested that additional factors are required for postentry events in immortalized cell lines. (+info)
Analysis of the precore and core promoter DNA sequence in liver tissues from patients with hepatocellular carcinoma.
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To investigate the role of mutant hepatitis B virus (HBV) in the development of hepatocellular carcinoma (HCC), 20 patients with HCC were studied for precore and core promoter mutations in tumorous and nontumorous tissues. The precore and core promoter region was amplified and analyzed by direct sequencing. Among the 20 tumorous and nontumorous tissues, precore mutant HBV was found in 12 (60%) and 18 (90%), respectively. Of the 12 tumorous tissues with precore mutant, nine tissues had a single mutation (1896) and one tissue had another single mutation (1899). The remaining two tissues had a double mutation (1896 and 1899). A single mutation (1896) and a single mutation (1899) were found in 11 and two of the 18 nontumorous tissues with precore mutant, respectively. Among 20 tumorous and nontumorous tissues, HBV with a C to T mutation at nucleotide (nt) 1846 was detected in six and eight, respectively, and was associated with the virus carrying a mutation (1896 or 1899) except in two tumorous tissues. Mutations at nt 1762 and 1764 in core promoter were observed in 16 (80%) tumorous tissues and 18 (90%) nontumorous tissues. Mutations in the precore and core promoter region were found frequently in nontumorous tissue and in tumorous tissue (18/20 and 12/20 in precore region, 18/20 and 16/20 in core promoter respectively). The high prevalence of precore and core promoter mutations in liver tissue from patients with HCC suggests that these mutations may contribute to the development of HCC. (+info)