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Biomedical subjects

C R Howard

Publications and source records attributed to C R Howard.

At least 91 records · Page 5Linked to original sources
PubMed1984

Hepatitis B surface antigen containing immune complexes occur in seronegative hepatocellular carcinoma patients.

IgG, IgM and hepatitis B surface antigen (HBsAg) containing immune complexes (IC) were detected by the Clq and conglutinin solid phase assays in both HBsAg+ and HBsAg- groups of patients with primary hepatocellular carcinoma (HCC). No differences were observed between the two patient groups either in the levels of antigen non-specific and HBsAg specific complexes or in the immunoglobulin isotype in the complexes. The results show that HBsAg can occur in an IC form in the sera of patients classified as HBsAg- by sensitive commercial assays and provides evidence of a further association of hepatitis B virus (HBV) and HCC in antigen negative patients. Furthermore, the HBsAg IC in HCC patients differ from those in other HBV infected subjects in that they are preferentially detected by the Clq assay.

Antigen-Antibody Complex↗
PubMed1983

Hepatitis B virus infection in two Gambian villages.

The prevalence of hepatitis B virus infection was markedly different in two neighbouring Gambian villages. 62% of children in Manduar aged 2-4 years were infected whereas in Keneba, the other village, only 27% of this age-group were infected. However, in both villages few infants were infected--none under 6 months of age and only 2 of 58 between the ages of 6 and 12 months. Carriage of hepatitis B surface antigen (HBsAg) was high, reaching a peak of 36% in the 5-9 age-group in Manduar and 17.6% in the 2-4 age-group in Keneba. 86% of all the children under the age of five who were HBsAg-positive also carried hepatitis B e antigen (HBeAg). This proportion fell to 17.6% for children aged 10-14 years and to 12.9% for mothers. Infection clustered in families, transmission from sib to sib being of major importance. The chances of a child being an HBsAg carrier were approximately 42% if an elder sib carried the antigen, 27% if either mother or father was a carrier, and 15% if neither mother or father was a carrier. There were 4 HBeAg-positive mothers who were highly infectious, since 10 of 11 of their children became HBsAg carriers. Carriage of surface antigen lasted many years; 63% of those carrying the antigen in 1972 were still positive in late 1980. 4 cases of primary hepatocellular carcinoma out of 672 adults have been diagnosed in the past five years. All 4 were in HBsAg carriers.

Age Factors↗
PubMed1983

A protein kinase activity in lymphocytic choriomeningitis virus and identification of the phosphorylated product using monoclonal antibody.

A cyclic AMP-independent protein kinase activity was found in purified preparations of the Armstrong CA 1371 strain of lymphocytic choriomeningitis virus (LCMV). Using the exquisite sensitivity of monoclonal antibodies to LCMV polypeptides, the internal nucleocapsid N protein was identified as the major virus-specific phosphorylated product of the endogenous protein kinase activity. This was accompanied by an increase in the electrophoretic mobility of N protein as detected by SDS-PAGE. After solubilization of the virus with 1% Nonidet P40 approximately 81% of the endogenous protein kinase activity remained associated with LCMV nucleocapsids recovered by equilibrium centrifugation at a density of 1.25 g/cm-3 in a linear renograffin gradient. Specific phosphorylation of N protein was reconfirmed in the purified nucleocapsid fraction and both phosphoserine and phosphothreonine found to be the phosphorylated products of the kinase reaction. Although the significance of this enzyme remains unclear, the presence of a protein kinase within LCMV may allow the regulation of LCMV replication and maturation by phosphorylation of virus-specific polypeptides. These events may in turn play a key role in determining the nature and outcome of LCMV infection.

Amino Acids↗
PubMed1983

Chemical inactivation of hepatitis B virus: the effect of disinfectants on virus-associated DNA polymerase activity, morphology and infectivity.

The inactivation of hepatitis B virus (HBV) using two commercially available disinfectants was analysed. Indirect evidence of virus inactivation was obtained by examining the decrease in HBV-associated DNA polymerase and HBcAg activities after treatment with increasing concentrations of disinfectant. Inactivation was accompanied by the irreversible loss of all morphological forms typically found in hepatitis B-positive sera and in particular 42-nm HBV particles were absent. Physiochemical analysis confirmed that the exposure of HBV to either product resulted in the degradation of virus particle structure. Direct evidence of HBV inactivation was obtained by treatment of virus pellets prior to inoculation into susceptible chimpanzees. No evidence of hepatitis B was found in animals receiving treated HBV thereby confirming the suitability of certain disinfectants for the inactivation of potentially infectious material.

1-Propanol↗
PubMed1983

Fine structure analysis of Pichinde virus nucleocapsids.

The structure and organization of the ribonucleoprotein (RNP) complex of an arenavirus, Pichinde virus, was investigated. The basic configuration of the RNP was found to be a linear array of globular subunits or nucleosomes, 4 to 5 nm in diameter, that represent individual molecules of the major N polypeptide. This filament appears to fold progressively through a number of intermediate helical structures, 12 to 15 nm in diameter, that reveal an increasing number of nucleosomes associated with each turn of the helix. They range from a fragile configuration of two or three nucleosomes per turn to a more stable fibre in which the nucleosomes cannot be resolved. The strands were shown to form closed circles and it appeared that the twisting of these circular forms resulted in the formation of 20 nm-thick fibres which were seen in isolated viral core structures. The association of these RNP structures with other viral components is discussed.

Arenaviridae↗
PubMed1983

Chronic liver disease: the detection and characterization of circulating immune complexes.

Circulating immune complexes containing IgG, IgM and hepatitis B surface antigen (HBsAg) in sera from groups of patients with various liver diseases were detected by both the C1q and conglutinin solid phase assays. Elevated levels of antigen non-specific immune complexes were observed in sera from all groups and complexes containing IgG were present to a greater extent than were IgM-containing complexes. Higher levels of complexes were generally obtained using the conglutinin assay than the C1q assay and the two assays were shown to preferentially bind complexes of different size ranges and antigen-antibody ratios. Only sera from HBsAg-positive patients had complexes containing HBsAg, and although serum HBsAg titres and levels of HBsAg-containing complexes were correlated, the correlation coefficient was low. The mean levels of immune complexes and the frequency of positive sera varied between different disease categories, but there was little correlation between levels of the three types of complexes detected by the two tests. Assay of immune complexes in sequential serum samples from an individual patient revealed considerable variation in the levels of the three complex types, demonstrating that the measurement of complexes in single serum samples is of limited value in assessing the potential significance of circulating immune complexes in hepatitis B.

Antigen-Antibody Complex↗
PubMed1983

Circulating immune complexes in hepatitis B: levels, immunoglobulin class of antibody and the presence of hepatitis B surface antigen.

Circulating immune complexes containing IgG, IgM and HBsAg in sera from groups of patients with various liver diseases were detected by the Clq and conglutinin solid phase assays. Elevated levels of antigen-non-specific complexes were observed in sera from all groups and complexes containing IgG were present to a greater extent than were IgM-containing complexes. However, only sera from HBsAg-positive patients had significant levels of complexes containing HBsAg.

Antigen-Antibody Complex↗
PubMed1982

Immunogenicity in chimpanzees of experimental hepatitis B vaccines prepared from intact hepatitis B virus, purified polypeptides, or polypeptide micelles.

The immunogenicity of three experimental hepatitis B vaccines was evaluated in chimpanzees. Although no antibody to hepatitis B surface antigen (anti-HBs) was detected in two chimpanzees that received an aqueous polypeptide vaccine subcutaneously, a strong anti-HBs response was observed two and ten weeks, respectively, following challenge with hepatitis B virus. Inoculation of two additional chimpanzees with a micellar preparation of these polypeptides by the intravenous route resulted in anti-HBs production in one of the chimpanzees. Two chimpanzees inoculated subcutaneously with an aqueous vaccine of formalin-inactivated intact hepatitis B virus developed anti-HBs in low titers, but the development of antibody to the hepatitis B core antigen following challenge inoculations suggested that subclinical HBV infections may have occurred despite prior vaccination.

Animals↗
PubMed1981

Hepatitis B polypeptide vaccine preparation in micelle form.

The immunoprophylaxis of hepatitis B is hampered by the lack of a technique for growing hepatitis B virus (HBV) in tissue culture. Plasma from persistently infected individuals, one source of viral antigen, contains characteristic 22-nm spherical particles which share a common antigen (the hepatitis B surface antigen or HBsAg) with the outer envelope of the 42-nm double-shelled DNA virus. Highly purified inactivated 22-nm particles have been shown to be safe and to confer protective immunity against HBV in a recent large-scale clinical trial. We have already described the extraction from the particles of a complex of two proteins which are antigenic determinants of HBV--the polypeptide with molecular weight (MW) between 22,000 and 24,000 (called p23) and the glycosylated polypeptide (called gp28) with MW in the range 26,000--29,000 which is thought to be the glycosylated form of p23. We now report the preparation from this complex of water-soluble protein micelles which may be a suitable basis for a second-generation hepatitis B vaccine.

Animals↗
PubMed1981

Detection of HBsAg in a clone derived from the PLC/PRF/5 human hepatoma cell line.

A total of 28 clones were established from the PLC/PRF/5 hepatoma cell line by a plating procedure. All clones were found to secrete HBsAg into the supernatant culture fluids. Of these, one clone (No. 23) free of detectable mycoplasma contamination and showing smooth epithelial morphology was selected for further study. Maximum accumulation of HBsAg occurred 9 days after sub-culture and intracellular antigen was detected by indirect immunofluorescence both in the cytoplasm and at the plasma membrane. Granules and perinuclear staining reactions were also observed in clone 23 cells and these findings are compared to the previously published properties of the parental PLC/PRF/5 cell line.

Carcinoma, Hepatocellular↗
PubMed1981

The use of markers in immune electron microscopy.

Immune electron microscopy (IEM) cannot be used successfully for structures that do not have recognisable morphology. However, at least some of these structures or components are related antigenically to recognisable antigens or viruses. We have therefore mixed unknown antigens with known markers and looked for the presence of mixed aggregates. The present study examined a low molecular weight subunit of rotavirus and a micellar form of hepatitis B surface antigen. In both cases mixed immune aggregates were found showing that the unknown components had antigens in common with the established virus or antigen.

Antigen-Antibody Complex↗
PubMed1981

Effects of amphotericin B on hepatitis B virus.

We investigated the effects of amphotericin B (AmB) on the ultrastructure and biochemistry of hepatitis B virus (HBV) and hepatitis B surface antigen (HBsAg) particles. These effects were compared with those reported for AmB and other polyene antibiotics on other lipid-enveloped viruses and artificial membranes. Treatment of HBV particles with concentrations of AmB ranging from 5 to 250 microgram/ml resulted in (i) an increase in HBV deoxyribonucleic acid polymerase activity as the concentration of Amb increased; (ii) changes in the electron microscopic appearance of HBV ranging from increased penetration of negative stain into the lipid envelope to disruption of the virus; and (iii) an increase in density form 1.165 to 1.225 g/ml. In addition, AmB treatment of HBsAg particles resulted in disruption into a nonparticulate HBsAg-reactive fraction and an HBsAg-AmB complex fraction with no HBsAg immunoreactivity.

Amphotericin B↗
PubMed1981

Nondetection of infectious hepatitis B virus in a human hepatoma cell line producing hepatitis B surface antigen.

The PLC/PRF/5 human hepatoma cell line producing hepatitis B surface antigen (HBsAg) was studied to determine whether infectious hepatitis B virus (HBV) was also being produced. 2 chimpanzees with no previous exposure to HBV and no serologic markers of past or active HBV infection were inoculated intravenously with 50 ml of either tissue culture supernatant fluid (357 ng/ml HBsAg) or a suspension of cells disrupted by repeated freeze-thaw cycles (57 ng/ml HBsAg). No evidence of HBV infection was detected in either chimpanzee during 6 months of evaluation. This study suggests that the expression of a portion of the HBV genome, when a portion or all of that genome has been incorporated into a host cell, can result in the production of HBsAg without infectious HBV. If it becomes possible to produce a similar expression of this portion of the genome by itself in nonmalignant cells, HBsAg without HBV may be produced in vitro for use in hepatitis B vaccines.

Animals↗