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Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A recombinant baculovirus was constructed containing a copy of the hepatitis B virus (HBV) genome which was inserted to produce an in-frame fusion of the precore (pre-C) coding region with the first 11 amino acids of the polyhedrin gene. The recombinant baculovirus expressed the 25K pre-C protein and two novel proteins, of approximately 93K and 72K. Both the 93K and 72K proteins are recognized by an anti-polymerase monoclonal antibody. Northern blot analysis of the mRNA produced during infection of Spodoptera frugiperda cells by the HBV recombinant baculovirus detected only one HBV mRNA species, suggesting that the three HBV-specific proteins expressed are translated from the same mRNA. No larger fusion proteins cross-reacting with either anti-core or polymerase antibodies were detected. These findings suggest that the two proteins encoded within the HBV polymerase gene are not produced via a core-polymerase fusion intermediate but by internal binding of ribosomes. These results are the first clear demonstration of efficient expression of two bona fide unprocessed polymerase proteins in a 1:1 ratio from an unspliced pre-C mRNA-like transcript. With the successful expression of the polymerase gene in insect cells it is now possible to produce large amounts of these proteins, allowing a more detailed structural and functional analysis of these proteins.
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PMID:Hepatitis B virus polymerase gene: expression of the long open reading frame using the baculovirus expression system. 160 71

A novel hepatitis B viral (HBV) protein of 35-40 kDa, characterized by antibodies and proposed as an X-C fusion protein, was previously described in core particles isolated from HBV-, WHV-, and GSHV-infected livers. The X and C genes are two adjacent genes in all mammalian hepadnaviruses but are not contiguous in WHV and GSHV. After examination of the X and preC/C junction sequences of 10 HBV, 4 WHV, and 1 GSHV, we found that the ORF of preC can be extended 7 more sense codons upstream so that X overlaps with the preC/C gene in all sequences. The number of overlapping base pairs (bp) is varied: 46 bp in HBV, 19 bp in WHV, and 10 bp in GSHV. In this region a conserved A-track was found to be followed by a pair of inverted repeats, suggesting that a ribosomal frameshift may occur for X-C fusion protein production. To assess this possibility, we have used an in vitro transcription and translation coupling system to identify X-C protein production. Two recombinant SP6 plasmids were used. One contained a full length of the X and preC/C gene of wild-type HBV-DNA and the other fused the X-preC/C gene by inserting a 10-bp HindIII linker at the junction of the X-preC/C region. No X-C fusion protein was detected from the wild-type plasmid. In contrast a large amount of X-C fusion protein was produced from the linker-inserted clone. It appears, therefore, that the X-C fusion protein is unlikely to be produced via the mechanism of ribosomal frameshifting.
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PMID:The hepatitis B virus X-C fusion protein is unlikely to be produced by the mechanism of ribosomal frameshifting. 221 9

We have examined the expression of duck hepatitis B virus (DHBV)-associated proteins in experimentally infected ducks by an immunoblot (Western) method. The DHBV-related core protein, C protein, was identified at the position of 35,000 Da (P35). Pre-S proteins were recognized as two major bands (P37 and P28), the former representing pre-S1 and the latter pre-S2 protein. Expression of the proteins was examined in the early phase of infection in ducklings sequentially sacrificed from 6 hr postinoculation to 10 days. C protein (P35) was detected as early as 24 hr postinoculation. This timing coincided with the exponential increase of RNA transcripts and double-stranded viral DNA. Pre-S1/S2 proteins were detected at 3 days postinoculation. The early appearance of C protein suggested that the proteins were utilized for nucleic acid packaging. On the other hand, the late appearance of pre-S1/S2 proteins suggested that they were utilized in the production of virions near the end of the replication cycle.
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PMID:Expression of pre-S1, pre-S2, and C proteins in duck hepatitis B virus infection. 318

We have previously cloned a mutant hepatitis B virus (HBV) genome which had one thymidine addition in the pre-C region resulting in a frameshift mutation in the pre-C region and fusion of the X and C genes. We constructed plasmids containing serially deleted and/or back-mutated (authentic) pre-C regions to study the effect of the frameshift mutation. COS cells transfected with plasmids containing the frameshifted pre-C region produced a 21K C protein (P21c) but not a 22K partially processed pre-C protein (P22). On the other hand, COS cells transfected with plasmids containing the back-mutated pre-C region produced P22. This result was also observed in HepG2-K8 cells producing the mutant HBV particles. Therefore, the pre-C region of HBV is likely to be non-essential for virus replication. COS cells transfected with the plasmid containing a fused X-C open reading frame (ORF) produced a 40K X-C fusion protein. This X-C fusion protein exerted transcriptional trans-activation. These results suggest that the mutant HBV has a C gene with a defective pre-C region and a fused X-C ORF, and hence cannot synthesize 16K HBeAg (P16e).
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PMID:Effect of frameshift mutation in the pre-C region of hepatitis B virus on the X and C genes. 815 6

Gene amplification may benefit from the construction of primers that augments the speed at which cloning and protein expression proceeds. Such primers include EcoRI or HindIII linkers as well as an in phase initiation or termination codon. PCR was carried out directly from viral particles of human hepatitis B virus (HBV) and woodchuck hepatitis virus (WHV) without DNA purification and from RNA extracted from WHV infected liver. Amplified products were directly cloned in the pKK223-3 expression vector under the control of the tac promoter. The characterization of the recombinant clones expressing the nucleocapsid protein (C protein) was done by direct incubation of the filter with 125I-labelled anti-HBc and confirmed by radioimmunoassay and Western-blot analysis. This procedure allows easy selection of recombinant clones expressing a given protein and could be applied to many other genes.
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PMID:Direct cloning and expression of PCR amplified DNA and RNA sequences: application to the hepadnaviruses nucleocapsid proteins. 851 45

One point mutation to make a stop codon in the precore (pre-C) region of the hepatitis B virus DNA in anti-HBe-positive patients has been reported recently. This mutation disturbs the formation of the pre-C protein that is processed to make HBeAg. The relationship between the point mutation and HBe antigen antibody status was investigated in B-viral liver diseases. The pre-C region was amplified by a polymerase chain reaction (PCR) method and the nucleotide sequences were determined by a direct sequencing method. In seven cases who were persistently HBeAg-positive, the wild type (no mutation in pre-C region) was detected in all. In 20 cases who were anti-HBeAg-positive at diagnosis, the mutant type (point mutation at nucleotide 1896 in pre-C region, which makes a stop codon) was detected in 16 cases and the wild type in two cases. In HBe seroconversion (SC) cases, the types of virus were investigated in serial blood samples. No mutant type was detected in initial sera during the HBeAg-positive period. In two 'natural' SC cases, the mutant type appeared before anti-HBe formation. However, in three anti-viral 'drug-induced' SC cases, the mutant type appeared after the formation of anti-HBe. In two 'reversed' seroconversion cases only the wild type was detected throughout the follow-up period. These data suggest that the appearance of a pre-C mutant may help to predict seroconversion from HBeAg to anti-HBe and may help distinguish 'natural' and 'drug-induced' seroconversion of HBeAg.
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PMID:Point mutation in precore region of hepatitis B virus: sequential changes from 'wild' to 'mutant'. 879 12

Acetylation phenotype was studied in 70 inpatients with acute viral hepatitis B. Of them, 51 had fast and 19 slow acetylation. Fast-type acetylation was associated with mild-severe form of hepatitis B, while slow-type acetylation--with recurrences and aggravations, severe form of hepatitis. The duration of HB antigenemia in the slow-type group was twice as long as in the fast-type group. Two patients, "slow acetylators", suffered from hepatitis B in the mild-severe form, later on chronic active hepatitis (CAH) developed. In "fast" acetylators the development of CAH was not observed. Thus, determination of phenotype by acetylation may be used for prognosis of acute viral hepatitis severity as well as for identification of high-risk groups and planning policy of follow-up.
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PMID:[The effect of the acetylation phenotype on the course severity and outcome of acute viral hepatitis B]. 904 69

Particulate hepatitis B core Ag (C protein) (HBcAg) and soluble hepatitis B precore Ag (E protein) (HBeAg) of the hepatitis B virus share >70% of their amino acid sequence and most T and B cell-defined epitopes. When injected at low doses into mice, HBcAg particles prime Th1 immunity while HBeAg protein primes Th2 immunity. HBcAg contains 5-20 ng RNA/microg protein while nucleotide binding to HBeAg is not detectable. Deletion of the C-terminal arginine-rich domain of HBcAg generates HBcAg-144 or HBcAg-149 particles (in which >98% of RNA binding is lost) that prime Th2-biased immunity. HBcAg particles, but not truncated HBcAg-144 or -149 particles stimulate IL-12 p70 release by dendritic cells and IFN-gamma release by nonimmune spleen cells. The injection of HBeAg protein or HBcAg-149 particles into mice primes Th1 immunity only when high doses of RNA (i.e., 20-100 microg/mouse) are codelivered with the Ag. Particle-incorporated RNA has thus a 1000-fold higher potency as a Th1-inducing adjuvant than free RNA mixed to a protein Ag. Disrupting the particulate structure of HBcAg releases RNA and abolishes its Th1 immunity inducing potency. Using DNA vaccines delivered intradermally with the gene gun, inoculation of 1 microg HBcAg-encoding pCI/C plasmid DNA primes Th1 immunity while inoculation of 1 microg HBeAg-encoding pCI/E plasmid DNA or HBcAg-149-encoding pCI/C-149 plasmid DNA primes Th2 immunity. Expression data show eukaryotic RNA associated with HBcAg, but not HBeAg, expressed by the DNA vaccine. Hence, codelivery of an efficient, intrinsic adjuvant (i.e., nanogram amounts of prokaryotic or eukaryotic RNA bound to arginine-rich sequences) by HBcAg nucleocapsids facilitates priming of anti-viral Th1 immunity.
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PMID:Priming Th1 immunity to viral core particles is facilitated by trace amounts of RNA bound to its arginine-rich domain. 1199 46

The hepatitis B virus (HBV) is an enveloped DNA virus with an icosahedral capsid replicating via reverse transcription. The crystal structure of the capsid is known. It has a diameter of 36 nm and is formed by one protein species (C protein). The viral envelope contains three different coterminal proteins (S, M, and L proteins) spanning the membrane several times. These proteins are not only released from infected cells as components of the viral envelope but in 10,000-fold excess as subviral lipoprotein particles with a diameter of 22 nm containing no capsid. Assembly of the capsid occurs in the cytosol and results in packaging of a 3.5 kb RNA molecule together with viral and cellular factors. This newly formed capsid cannot be enveloped. Rather, synthesis of the viral DNA genome in the lumen of the capsid by reverse transcription is required to induce a budding competent state. Envelopment then takes place at an intracellular membrane of the pre-Golgi compartment. The S and the L protein, but not the M protein, is required for this process. The L protein forms two different transmembrane topologies. The isoform exposing the N-terminal part at the cytosolic side of the membrane is essential for budding. In this domain, a 22 amino acid (aa) long linear stretch has been mapped genetically to play a vital role in the morphogenetic process. This domain probably mediates the contact to the capsid. A second matrix domain was mapped to the cytosolic loop of the S protein. A similar genetic approach identified two small areas on the capsid surface, which might interact with the envelope proteins during envelopment.
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PMID:Envelopment of the hepatitis B virus nucleocapsid. 1556 98

Cytoplasmic hepatitis B virus (HBV) capsids are not enveloped and secreted unless the packaged RNA pregenome is reverse transcribed. The expression of the capsid protein C, together with envelope proteins in the absence of pregenomic RNA, produced normal amounts of intracellular capsids, but the secretion of virion-like particles was greatly reduced. The I97L C protein mutant, allowing immature nucleocapsid envelopment in the background of an HBV genome, did not promote the envelopment of capsids lacking a pregenome, suggesting that this mutation is not sufficient to induce secretion competence independently of the pregenome.
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PMID:Hepatitis B virus particle formation in the absence of pregenomic RNA and reverse transcriptase. 1657 36


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