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Biomedical subjects

K F Bergmann

Publications and source records attributed to K F Bergmann.

16 recordsLinked to original sources
PubMed1992

Structural requirements for RNA editing in hepatitis delta virus: evidence for a uridine-to-cytidine editing mechanism.

Hepatitis delta virus (HDV) nucleotide 1012 is edited from uridine to cytidine in 10-40% of the RNA genomes during replication. This editing event is an important control point in the HDV life cycle because it results in both the packaging of viral RNA and the inhibition of HDV replication. We find that the editing event is highly specific for both the sequences neighboring nucleotide 1012 and the base-paired context of position 1012 within the unbranched rod structure of HDV RNA. Prior studies identified the base transition at nucleotide 1012 but were unable to distinguish between editing of the genomic versus the antigenomic strands [Luo, G. X., Chao, M., Hsieh, S. Y., Sureau, C., Nishikura, K. & Taylor, J. (1990) J. Virol. 64, 1021-1027]. In this study, comparisons of mutations that differentiate between base pairing in genomic and antigenomic RNAs indicate that the genomic strand of HDV is the actual editing substrate. We conclude that the virus uses a uridine to cytidine editing mechanism, which is provided by the host cell.

Animals↗
PubMed1992

Production of hepatitis B virus by stably transfected monocytic cell line U-937: a model for extrahepatic hepatitis B virus replication.

Human monocytic cell line U-937 was transfected with the hepatitis B virus (HBV) genome. Transfected cells releasing HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) into the culture supernatant were cloned and further characterized. The HBV genomes were present in these cells in both chromosomally integrated and episomal forms. Intracellular replicative intermediates of HBV DNA and HBV-specific RNA transcripts of 3.6 and 2.2 kb were also detected. Viral DNA was present in the culture supernatant in viral particles with the buoyant densities of mature HBV virions. Electron microscopy revealed the presence of 22-nm spherical HBsAg particles, and Western blot analysis detected pre-S1 and -S2 antigens in particles in the culture supernatant. HBV DNA in U-937 cells was found to be positively regulated by corticosteroids, interleukin-1 beta, and transforming growth factor-1 beta. The stably transfected cell clones can be used to study HBV replication and its regulation in cells of bone marrow origin and to investigate the influence of HBV on the function of cells of the immune system.

Blotting, Northern↗
PubMed1990

Riboprobe assay for HDV RNA: a sensitive method for the detection of the HDV genome in clinical serum samples.

We have used a new hybridization assay for the detection of the genome of hepatitis delta virus (HDV) in serum using a strand-specific RNA probe obtained by transcription of a recombinant riboprobe. This assay was tested on a panel of 30 sera from HBsAg carriers with hepatitis delta antigen (HDAg) in the liver. The riboprobe assay detected HDV RNA in the serum of 83% of the patients, while 63% were positive using the DNA hybridization assay. HDAg was detected in 73% of the same sera by immunoblotting. The riboprobe assay was also compared to other assays on serial samples from an experimentally infected chimpanzee. These results demonstrate that the Northern blot assay using the RNA probe is more sensitive than the homologous DNA probe for the detection of HDV in serum and is also more sensitive than the immunoblot assay for HDAg. The riboprobe assay is the most sensitive of currently available methods to measure HD viremia.

Adult↗
PubMed1989

Hepatitis delta antigen. Antigenic structure and humoral immune response.

Hepatitis delta virus (HDV) is a small RNA virus that is dependent on helper functions provided by hepatitis B virus. The hepatitis delta Ag (HDAg) is the only protein known to be made from the viral genome, from an ORF with a coding capacity of 214 amino acids. The immunogenic epitopes of HDAg and the immune response to it were mapped by the use of synthetic peptides, antipeptide antibodies, and human mAb. Antipeptide sera covering approximately 60% of the linear sequence reacted with liver-derived HDAg. Antisera from HDV-infected humans, chimpanzees, and woodchucks reacted with from 2 to 13 of 15 peptides. The epitopes of two human anti-HD mAb were mapped to overlapping but distinct epitopes in the region around residues 106-123. Sera from infected humans, chimpanzees, and woodchucks were also tested by competition with the mAb. Use of the peptides and antipeptide sera defined one region in the sequence (residues 52-93) which is immunodominant in the immune response to HDAg. Reactivity of both peptides and antipeptide antibodies was very broad, covering most or all of the linear sequence. Competition assays also provided information on conformational epitopes, as well as the sequential epitopes defined by direct assays. The peptides and antipeptide antibodies should be useful in new assay development, in dissecting the anti-HD response in terms of chronic vs self-limited infection, and in studying the role of anti-HD in infection and recovery.

Amino Acid Sequence↗
PubMed1988

Chronic hepatitis D virus (HDV) infection in hepatitis B virus carrier chimpanzees experimentally superinfected with HDV.

Chimpanzees that were chronic hepatitis B virus carriers and that were superinfected with hepatitis D virus (HDV) apparently developed acute, self-limited type D hepatitis. Reevaluation with a sensitive hybridization-based assay using RNA probes specific for the HDV genome, however, demonstrated that greater than 50% of these animals still had detectable signs of ongoing HDV replication an average of 2.4 y (range, 1-6.4 y) after inoculation. The only positive marker for the presence of HDV was serum HDV RNA; HDV antigen was undetectable in both serum and the liver by an immunoblot assay and immunofluorescence, respectively. Because the detected amount of viral genome was very low, the previous failure to identify the chronic HDV carrier state in the chimpanzee can be attributed to the lower sensitivity of previously described assays.

Animals↗
PubMed1987

A human monoclonal antibody that recognizes viral polypeptides and in vitro translation products of the genome of the hepatitis D virus.

Peripheral blood lymphocytes from a patient chronically infected with hepatitis D virus (HDV) were immortalized by Epstein-Barr virus transformation. Two stable monoclonal cell lines, derived from the same parent culture, were established and produced antibodies of the IgG isotype that were specific for the hepatitis delta antigen (HDAg). Both monoclonal antibodies (MAbs) recognized the major HDAg polypeptides of 24 kilodaltons and 27 kilodaltons that were previously detected by polyclonal antibodies to HDAg in both liver and serum from HDV-infected humans, chimpanzees, and woodchucks. This result indicates that the major polypeptides of HDAg share common epitopes. The MAbs also reacted with minor polypeptides of lower molecular weight, which were present in infected liver. In vitro translation products of HDV-specific RNA from infected liver were also detected by the MAbs; these polypeptides were 24 kilodaltons and 27 kilodaltons, respectively, and comigrated with liver- or serum-derived HDAg. In contrast, HDV RNA isolated from virions in serum was not translated into HDAg polypeptides in the in vitro system.

Animals↗