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Biomedical subjects

W H Gerlich

Publications and source records attributed to W H Gerlich.

At least 55 records · Page 3Linked to original sources
PubMed1995

In vitro transformation by hepatitis B virus DNA.

There is strong epidemiological evidence that the hepatitis B virus (HBV) contributes to the development of hepatocellular carcinoma (HCC). In several immortalized cell lines, an in vitro transforming activity of HBV DNA and expression vectors for the viral protein X (HBx) has now been demonstrated. Furthermore, it appears as if still unknown parts of the HBV genome other than HBx contribute to the transforming activity of HBV DNA in vitro. Only one of several studies found that HBx-transgenic mouse lines develop HCC. A mouse line transgenic for the large surface protein of HBV develops HCC due to concomitant necroinflammatory infection. Growing evidence shows the importance of recombination of integrated viral DNA and cellular DNA for HCC development. A direct transforming potential of one of these viral integrates has been demonstrated. Chemical carcinogens are more effective in HBV-containing cell lines or transgenic mice.

Animals↗
PubMed1995

Immunological responsiveness of Pekin ducks to core antigen of duck hepatitis B virus.

Cellular immune responses to the HBc or HBe antigen of hepatitis B viruses contribute to the pathogenesis of hepatitis B and to the elimination of the virus. Insufficient cytotoxic immune reactions against the core antigen may be one major reason for viral persistence in the absence of severe clinical symptoms. We attempted to stop viral persistence in the animal model of congenitally infected ducks by injection of recombinant DHBc particles, together with the strong immunostimulator Freund's adjuvant. However, the duck HBc antigen (DHBcAg)-treated ducks did not develop detectable liver disease, nor was the virus persistence affected. The congenitally infected ducks did not contain antibodies against DHBcAg before injection despite continuous production of duck hepatitis B virus, and developed only a weak transient antibody response after injection of recombinant DHBcAg together with Freund's adjuvant. Noninfected ducks developed, in contrast, a strong antibody response to the injected DHBcAg. We conclude that congenitally infected ducks are immunotolerant to DHBcAg and cannot be cured by immunotherapy with exogenous recombinant DHBcAg.

Animals↗
PubMed1995

Age, sex and transaminase dependency of specific and nonspecific results from enzyme immunoassays for antibodies to hepatitis C virus and follow-up of blood donors.

BACKGROUND: Second-generation enzyme immunoassays (EIA-2) for antibodies to hepatitis C virus (anti-HCV) have an improved specificity and sensitivity compared to first-generation enzyme immunoassays (EIA-1). Therefore the question arises how many anti-HCV-positive blood donors were missed by the EIA-1, how many were false positive, how false-positive donors should be dealt with and how the results of the EIA-2 correlate with demographic data and surrogate testing for serum alanine aminotransferase (ALT). MATERIAL AND METHODS: A total of 208,544 individual North German blood donors not preselected for anti-HCV negativity were tested for anti-HCV with EIA-2 and, if repeatedly reactive (rr), with a licensed supplementary test (RIBA-2). RESULTS: Overall, 0.43% of the donors were EIA-2 rr, but only 0.12% of women and 0.09% of men were RIBA-2 positive. RIBA-2 positivity rates were very low in donors 18 to 27 years old (0.03% and 0.05%) and clearly rose with age in women but not in men. The rate of unspecifically positive EIA-2 results (entirely negative in RIBA-2) rose with age in both sexes and did not correlate with ALT. The ALT distribution was age dependent with a completely different pattern for men and women. Anti-HCV positivity was strongly correlated with ALT albeit on a very low level: more than 97% of donors with strongly elevated ALT were anti-HCV negative. Follow-up and comparison of EIA-1, EIA-2 and RIBA-2 results for the subsequent donations showed that only 8% of now RIBA-2-positive donors were not detected by EIA-1. Apparent seroconversions in EIA-2 are usually not specific: only one out of 66 apparent seroconversions could be confirmed by RIBA-2. 0.15% of the donor population showed an inconsistent EIA-2 pattern during follow-up. CONCLUSIONS: We therefore suggest that donors should not be excluded from further donations on the basis even of multiple EIA-1 positive results or on the basis of only one EIA-2-positive donation. The value of ALT screening for transfusion safety should be reconsidered.

Adolescent↗
PubMed1995

Recent studies on replication of hepatitis B virus.

Recent results are reviewed on the role of the HBx protein in virion production, the significance of phosphorylation in core protein for RNA encapsidation, intracellular transport of the HBV genome, the morphogenesis of virions, and the early stages of infection in cell cultures.

Biological Transport↗
PubMed1994

Post-translational alterations in transmembrane topology of the hepatitis B virus large envelope protein.

The preS domain at the N-terminus of the large envelope protein (LHBs) of the hepatitis B virus is involved in (i) envelopment of viral nucleocapsids and (ii) binding to the host cell. While the first function suggests a cytosolic location of the preS domain during virion assembly, the function as an attachment site requires its translocation across the lipid bilayer and final exposure on the virion surface. We compared the transmembrane topology of newly synthesized LHBs in the endoplasmic reticulum (ER) membrane with its topology in the envelope of secreted virions. Protease sensitivity and the absence of glycosylation suggest that the entire preS domain of newly synthesized LHBs remains at the cytosolic side of ER vesicles. However, virions secreted from transfected cell cultures or isolated from the blood of persistent virus carriers expose antibody binding sites and proteolytic cleavage sites of the preS domain at their surface in approximately half of the LHBs molecules. Thus, preS domains appear to be transported across the viral lipid barrier by a novel post-translational translocation mechanism to fulfil a dual function in virion assembly and attachment to the host cell.

Biological Transport↗
PubMed1994

Secretion of human hepatitis B virus is inhibited by the imino sugar N-butyldeoxynojirimycin.

The imino sugar N-butyldeoxynojirimycin (NBDNJ) is a potent inhibitor of the oligosaccharide-trimming enzyme alpha-glucosidase I. Hepatitis B virus (HBV) contains three surface proteins (HBs proteins) of different sizes that are singly or doubly N-glycosylated and are essential for the formation of infectious virus. Therefore, the replication and secretion of HBV in the human hepatoma cell line HepG2 were studied in the presence of NBDNJ. In the stably HBV-transfected HepG 2.2.15 cells and in HBV-infected HepG2 cells, NBDNJ suppressed secretion of HBV particles and caused intracellular retention of HBV DNA. The secretion of subviral particles was less affected. These data suggest that inhibitors of oligosaccharide trimming may be useful for antiviral therapy of hepatitis B and for the study of the intracellular transport of the viral glycoproteins.

1-Deoxynojirimycin↗
PubMed1994

Improved immunogenicity in mice of a mammalian cell-derived recombinant hepatitis B vaccine containing pre-S1 and pre-S2 antigens as compared with conventional yeast-derived vaccines.

The widely used hepatitis B virus (HBV) vaccines consist of the small hepatitis B surface (SHBs) protein produced in transfected yeast cells. The frequency of non-responders, especially among immunocompromised patients, has increased the demand for a more immunogenic vaccine. We evaluated the immunogenicity of recombinant HBs 20 nm particles secreted by transfected Chinese hamster ovary (CHO) cells, Bio-Hep-B (BioTechnology General Ltd, Israel), and compared it with yeast-derived vaccines. The CHO-derived vaccine contains the small hepatitis B surface antigen (SHBs protein) as the major component, as well as the middle HBs (MHBs, pre-S2) and the large HBs (LHBs, pre-S1) antigens. Nine groups of ten female Balb/c mice, 4-6 weeks old, were injected once intraperitoneally (i.p.) with 0.09, 0.27 or 0.81 micrograms of each of three vaccines: Bio-Hep-B or two conventional yeast-derived recombinant vaccines, Engerix-B (SmithKline Beecham, Belgium) and H-B-Vax II (Merck, Sharp & Dohme, USA) containing only non-glycosylated SHBs antigen. After 30 days, 40% of the mice injected with 0.09 microgram Bio-Hep-B had seroconverted, but none of the mice receiving the same dose of the other vaccines. The immunogenic dose in 50% of the mice at day 14 after injection was 0.13 microgram for Bio-Hep-B, but over 0.81 microgram for the other two vaccines. Mice of the strain B10/M (which are unresponsive to SHBs and MHBs antigens at the T-cell level) developed 100-fold higher anti-HBs titres after immunization with 1 microgram of Bio-Hep-B i.p., as compared with mice receiving the same amount of yeast-derived HBsAg vaccines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The value of quantitative measurement of HBeAg and HBsAg before interferon-alpha treatment of chronic hepatitis B in children.

Serum concentrations of HBsAg, HBeAg and hepatitis B virus DNA were measured quantitatively before interferon treatment in 23 children (17 boys, 6 girls) suffering from chronic hepatitis B, and correlated to the outcome of the treatment. Five children remained HBsAg- and HBeAg-positive throughout the treatment and 6 months after the end of the treatment (non-responders), 12 children eliminated HBeAg but not HBsAg (partial responders) and six eliminated HBeAg and HBsAg (complete responders). The five non-responders had significantly higher initial HBsAg and HBeAg concentrations and significantly lower alanine aminotransferase levels than the partial or complete responders. The six complete responders had significantly lower HBsAg concentrations than the partial or non-responders, and seemed to be younger. No significant difference in HBV DNA levels was found in the three response groups. These data suggest that quantitative assays of HBsAg and HBeAg are particularly useful in selecting patients with chronic hepatitis B for interferon therapy.

Adolescent↗
PubMed1994

Effect of core protein phosphorylation by protein kinase C on encapsidation of RNA within core particles of hepatitis B virus.

Phosphorylation of core particles derived either from hepatitis B viruses or from livers of hepatitis B-infected individuals has been long recognized, but the nature and function of the phosphorylating enzyme remained unknown. By immunoblotting with a monoclonal antibody, we have now detected protein kinase C within the liver-derived core particles. To study the significance of the encapsidated protein kinase C for the viral life cycle, we established an in vitro assembly system consisting of Escherichia coli-expressed core protein, protein kinase C, and in vitro-synthesized hepatitis B virus RNA. Phosphorylation of the core protein led to a reduced RNA encapsidation capacity of the core particles. Furthermore, RNA and protein kinase C competed for their target sequence, which is the carboxy-terminal arginine-rich domain of the core protein. This finding implies that phosphorylation of the nucleic acid binding site in the core protein occurs within the particles after encapsidation of protein kinase C, pregenomic RNA, and viral polymerase at a later step during viral genome maturation.

Antibodies, Monoclonal↗
PubMed1994

Safety and quality criteria for autologous blood donations. Committee for Virus Safety of the Society for Virology.

The authors discuss the quality control criteria for autologous blood donations. They recommend that all autologous donations be tested for serological markers of blood-transmissible diseases. Marker-positive donors should not donate autologous blood. If autologous donation seems indispensable, infectious donations should be clearly marked as infectious.

Blood Preservation↗
PubMed1994

[Comparison ov anti-HCV tests of the first and second generation and suggestions for a re-entry program].

After following up approximately 200,000 blood donors with 1st- and 2nd-generation anti-HCV tests the authors suggest: 1) to neglect earlier 1st-generation-positive anti-HCV results when the donor is negative in 2nd-generation ELISAs; 2) after a donation positive in a 2nd-generation test the following donation must not be used even if it is negative; a third, negative donation can be used; 3) a donor with two different donations positive in 2nd-generation ELISAs should be excluded from the donor pool.

Blood Donors↗
PubMed1993

Clinical and immunological aspects of hepatitis B virus infection in children receiving multidrug cancer chemotherapy.

For two reasons hepatitis B virus infection is an important problem in patients with cancer. First, multidrug cancer chemotherapy may reactivate or worsen a previously benign chronic HBV infection. Second, patients undergoing cancer chemotherapy are at an increased risk of acquiring and spreading HBV which may result in an endemic infection. HBV reactivation may precipitate into a severe acute disease including fulminant hepatitis. In contrast, the acquisition of HBV during cancer chemotherapy commonly takes a mild clinical course but frequently leads to persistently high viremia. This state of immunotolerance to viral antigens allows viral replication without any sign of liver cell destruction. Withdrawal of chemotherapy does not cause significant changes if infection occurred during cytotoxic chemotherapy. Infection with HBV during cancer chemotherapy, therefore, may be considered as a model of an induced antigen-specific immunotolerance. In agreement with this hypothesis, vaccination against HBV during cancer chemotherapy does not prevent spread of HBV in oncology wards as it does not produce significant anti-HBs titers. Furthermore, vaccination even suppresses the immune response to later booster doses after chemotherapy has been withdrawn.

Antineoplastic Agents↗
PubMed1993

Characterization of the endogenous protein kinase activity of the hepatitis B virus.

During the assembly of the nucleocapsid of the hepatitis B virus a protein kinase, probably of cellular origin, is encapsidated. This enzyme phosphorylates serine residue(s) localized within the lumen of the particle. By using purified, liver-derived core particles, we characterized the protein kinase activity in the presence of different ions and inhibitors. Controls were performed with cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) and recombinant core particles. We showed that the endogenous protein kinase of the core particles was not inhibited by H89, a specific inhibitor of PKA. Staurosporine, a selective inhibitor of PKC inhibited the endogenous kinase activity only within the first minutes of the reaction. In contrast, quercetine, a selective inhibitor of the protein kinase M (PKM) did not inhibit during the first minutes but inhibited efficiently during later phases of incubation. PKM represents an enzymatically active proteolytic fragment of PKC. These results suggest that PKC is encapsidated into human core particles and is converted to PKM during the in vitro reaction. This conclusion implies the association of a protease activity localized with the HBV nucleocapsid inside liver-derived core particles.

Cyclic AMP-Dependent Protein Kinases↗
PubMed1993

Studies on the attachment and penetration of hepatitis B virus.

There are two identified liver-specific attachment sites in the preS2 domain and one in the preS1 domain. Which mechanism leads to attachment in vivo is not known. The subsequent penetration seems to require proteolysis which does not occur spontaneously in HepG2 cells, but presumably in vivo. The role of the small HBs protein for attachment remains enigmatic so far, but it must have a function because an escape mutant exists against a monoclonal antibody which binds to an epitope of the small protein. The occurrence of this escape mutant in vaccinated persons proves that the standard hepatitis B vaccine does induce neutralizing antibodies, but it also suggests very strongly that the neutralizing preS epitopes be included in future hepatitis B vaccines.

Attachment Sites, Microbiological↗
PubMed1993

Identification of a new hepatitis B virus (HBV) genotype from Brazil that expresses HBV surface antigen subtype adw4.

The complete genome of a hepatitis B virus (HBV) from Brazil that expressed the subtype adw4 of HBV surface antigen (HBsAg) was cloned and sequenced. The genome, termed w4B, consists of 3215 bp. The overall genetic organization of typical hepadnaviruses with four open reading frames including the preC region was found to be conserved. When comparing the w4B sequence with 19 complete HBV genomes it was, however, found to be more divergent (15%) than any other HBV sequence thus far reported. Until now, no more than 11% divergence has been reported. Distinct from the five known HBV genotypes A to E, w4B made up a new, sixth genotype. The importance of the conserved third start codon in the HBV X gene became apparent in isolate w4B. By mutation, this ATG was out of frame, and by what appears to have been a linked mutation, a new start site two codons downstream was re-established. The significance of several other mutations is discussed.

Amino Acid Sequence↗