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Biomedical subjects

C R Howard

Publications and source records attributed to C R Howard.

At least 109 records · Page 6Linked to original sources
PubMed1981

Induction of cell-mediated immunity to HBsAg polypeptides.

Adult male guinea pigs were immunized with hepatitis B virus polypeptides prepared by Triton X-100 solubilization of purified 22-nm hepatitis B surface antigen (HBsAg) particles. A virus-specific subunit containing both the 28,000 molecular weight glycoprotein and the 23,000 molecular weight protein stimulated both cell-mediated and humoral immunity. A whole-blood-cell transformation assay additionally showed that the 64,000 molecular weight component of HBsAg, previously shown to contain host-specific antigens, also stimulated a cellular response to purified intact HBsAg particles, suggesting the additional presence of virus-specific material in this fraction. Immunization of animals with the 28,000--23,000 molecular weight polypeptides subsequently prepared in micelle form enhanced the demonstration of a cell-mediated reaction after only a single dose of immunogen. The results provide further evidence as to the suitability of HBsAg polypeptides prepared by Triton X-100 solubilization for hepatitis B prophylaxis.

Animals↗
PubMed1980

Hepatitis B surface antigen production as a growth cycle-related terminal event in PLC/PRF/5 hepatoma cells.

The dynamics of hepatitis B surface antigen production of PLC/PRF/5 hepatoma cells were studied using a quantitative radioimmunoassay method. Maximum rates of antigen production were found in nutrient-depleted, non-dividing cultures and were temporally related to cytological changes preceding cell death. These results indicate that antigen production may be cell-cycle related and represent a terminal event.

Carcinoma, Hepatocellular↗
PubMed1980

Evaluation of plaque size reduction as a method for the detection of Pichinde virus antibody.

The reaction between Pichinde virus and homologous antisera has been studied using a plaque size reduction method. The incorporation of antiserum in the overlay of infected Vero cell monolayers revealed a pattern of virus-cell interactions which were manifested by both a significant reduction in the diameter of virus plaques, and regeneration of cells in the centre of each. Electron microscopy demonstrated that antibody molecules were bound to virus particles budding from the surface of infected cells resulting in the formation of extracellular virus-antibody complexes. These aggregates were subsequently detected in vacuoles of freshly-infected cells. In the absence of virus neutralization, reaction of Pichinde virus with homologous antiserum leads to the formation of infectious aggregates which due to their larger size restrict the rate of plaque development.

Animals↗
PubMed1980

The polypeptides of infectious bronchitis virus (IBV-41 strain).

The Massachusetts strain of avian infectious bronchitis virus was purified from embryonated hens' eggs. Four major species of apparent mol. wt. 90 000, 52 000, 29 000 and 26 000 were resolved by SDS-polyacrylamide gel electrophoresis. Omission of reducing agent failed to resolve the 29 000 mol. wt. component. Labelling of acrylamide gels with 125I-concanavalin A indicated that polypeptides of mol. wt. 90 000, 29 000 and 26 000 were glycosylated and, in the absence of reducing agent, that the 29 000 species migrated as a dimer in the 5000 mol. wt. region. Purified IBV radio-iodinated with Bolton and Hunter reagent, which banded as a single peak of radioactivity in Metrizamide gradients, was found to contain bands of radioactivity when analysed by SDS-PAGE, corresponding to the polypeptides of mol. wt. 90 000, 52 000 and 29 000 resolved in stained gels. Disruption of IBV particles in Triton X-100 released two subviral particles, a 16 nm spike which comprised polypeptides of 90 000, 52 000 and 29 000 mol. wt. and another denser spherical particle of 25 to 45 nm which contained RNA and the 52 000 and 26 000 polypeptides.

Bromelains↗
PubMed1979

The separation and analysis of hepatitis B e antigen.

A solid-phase radioimmunoassay has been used successfully for detecting hepatitis B e antigen in fractionated hepatitis B virus-containing serum. Ammonium sulphate precipitation followed by gel filtration through a column of Sepharose CL-6B resulted in two fractions of antigen-containing material with molecular weights of 220,000 and 130,000. The smaller of these two fractions was found to possess an average isoelectric point of 4.9 and consisted of two major polypeptide species with estimated molecular weights of 66,000 and 17,000 respectively. Affinity chromatography on Blue Sepharose showed that e antigen was not retained under conditions which bound serum albumin. These results are discussed in relation to the immunopathogenesis of hepatitis B.

Carrier State↗
PubMed1979

Analysis of hepatitis B surface antigen components solubilized with Triton X-100.

Three glycoproteins of intact hepatitis B surface antigen (HBsAg) with mol. wt. of 32 000, 30 000 and 28 000 respectively were identified by reaction with 125I-concanavalin A (Con A) after separation by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The antigen was effectively disrupted with Triton X-100 to produce a structure with a sedimentation coefficient of 3.9S. Affinity chromatography of disrupted HBsAg using concanavalin A-Sepharose 4B (Con A-Sepharose) resulted in two fractions. The first contained material which did not bind to the lectin and consisted of a single polypeptide of mol. wt. 64 000. Further studies revealed this component to be serologically identical to serum albumin and to lack any affinity for antibody to HBsAg. A comparison of the tryptic peptide map of this polypeptide with that of purified serum albumin demonstrated identical amino-acid sequences. The second fraction contained material which bound to Con A and contained two polypeptides with mol. wt. of 28000 and 23000 respectively. HBsAg reactivity was associated with this fraction. This procedure allows the prepartion of HBsAg sub-units in milligram quantities for further immunological studies.

Animals↗
PubMed1979

Effects of human leucocyte interferon on hepatitis B virus replication and immune responses in patients with chronic hepatitis B infection.

Eight patients with chronic hepatitis B infection (seven with chronic active hepatitis and one with chronic persistent hepatitis) were treated with daily intramuscular injections of human leucocyte interferon for periods of 5 to 8 weeks and in one case for 5 months. In one patient there was a marked fall in virus-associated DNA polymerase activity and in the number of DNA containing viral particles during each of two courses of interferon. Hepatitis Be antigen (HBeAg) also disappeared, the aspartate transaminase levels fell and liver histology improved. In the four other patients with detectable DNA polymerase activity there was an early fall but this was transient and in one of these patients there was a continuing rise in activity despite treatment. One other patient became HBeAg negative but hepatitis B surface antigen (HBsAg) titres were mostly unaffected by treatment. A marked decrease in T-lymphocyte mediated cytotoxicity towards HBsAg coated target cells was demonstrated and raises the possibility that an immunosuppressant action of interferon may offsets its direct anti-viral action but may also account for the improvement in liver function which occurred in some patients.

Adult↗
PubMed1978

Hepatitis B outbreak among chimpanzees at the London Zoo.

Persistent carriage of hepatitis B virus in extremely high titre was identified in 5 out of 9 chimpanzees kept at the London Zoo. Antibody to this virus was present in the other 4 chimpanzees. Serological survey of the other primates in the Regent's Park collection did not reveal the presence of the surface antigen in 2 gorillas, 11 orang-utans, and 2 gibbons, although surface antibody was present in the serum of 1 gorilla and 2 orang-utans. 3 of the carrier chimpanzees were born at the Zoo and were the offspring of either a carrier mother or a carrier father, and perinatal transmission may have occurred. A strict safety code of practice was introduced and hepatitis B immunoglobulin was given at intervals to designated staff members. Sero-conversion did not occur in any of the 38 staff members under surveillance for more than 2 years. Treatment of the carrier state in the chimpanzees was attempted with human leucocyte interferon, with and without ribavirin ('Virazole'), and with adenine arabinoside, but the effects were mostly temporary.

Animals↗
PubMed1978

Effect of ethanol during hepatitis B virus infection in chimpanzees.

To determine whether the use of ethyl alcohol (ethanol, C2H5OH) may increase the liver damage caused by hepatitis B virus infection, ethanol was infused into four chimpanzees on one or two occasions during the course of natural or experimentally induced hepatitis B virus infections. A fifth chimpanzee, without active hepatitis B virus infection, served as a control. Moderate elevations of serum aspartate or alanine aminotransferases occurred in four of the five chimpanzees, including the control chimpanzee, in direct association with ethanol infusion; pre-existing enzyme elevations persisted in a fifth chimpanzee. No alteration occurred in the titers of hepatitis B surface antigen or of antibody to hepatitis B core antigen in three of the four infected chimpanzees. There was no significant alteration in the course of hepatitis B virus infection by ethanol infusion in these chimpanzees.

Acute Disease↗
PubMed1978

The labelling of galactose residues in hepatitis B surface antigen glycoprotein.

The 20 to 25 nm particles of hepatitis B surface antigen were purified from the serum of a carrier chimpanzee. Five major polypeptide species were revealed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Treatment of the particles with neuraminidase (EC 3.2.1.18) and galactose oxidase (EC 1.1.3.9) followed by reduction with tritiated sodium borohydride labelled galactose residues in a single glycoprotein with an apparent mol. wt. of 28 000. The glycoprotein was not labelled when neuraminidase treatment was omitted, indicating that the galactose residues are in subterminal positions in the oligosaccharide chains. There was no significant incorporation of radiolabel into lipid. The serological activity of the antigen, as measured by a competitive double-antibody radioimmunoprecipitation assay, was not altered by the labelling procedure nor by exposure to neuraminidase alone.

Animals↗
PubMed1978

Viral antigens and antibodies in hepatitis B infection.

Hepatitis B virus antigens and antibodies were detected in the sera of acute and persistently infected patients. Evidence of active virus replication was confined to immediately before or during the initial detection of hepatitis B surface antigen during acute hepatitis B. Hepatitis B core antibody appeared during the period of antigenaemia and preceded recovery. Hepatitis B e antigen was dound in a proportion of sera which contained significant levels of virus particles. In contrast, all sera containing hepatitis B virus particles from persistently infected patients treated by maintenance haemodialysis also contained the e antigen. Among a group of 50 persistent carriers of hepatitis B virus, significant levels of virus production occurred in the presence of antibody to e antigen. In addition, evidence of exposure to hepatitis B virus was found among 3% of blood donors in whose sera the surface antigen was not detected by radioimmunoassay. The significance of these findings is discussed in relation to the aetiology of hepatitis type B.

Antibodies, Viral↗
PubMed1977

Core antigen and circulating anti-core antibody in hepatitis B infection.

Core antigen was obtained from the sera of persistent chronic carriers of hepatitis B virus by centrifugation and treatment with Nonidet P40 and 2-mercaptoethanol. The separated core antigen was radiolabelled and identified as a nucleoprotein structure of buoyant density 1.36 g/cm3 and possessing an isoelectric point of 4.4. This material was employed in a radioimmunoassay procedure of high sensitivity for the detection of core antibody. In a series of sera from patients with acute type B hepatitis, core antibody was demonstrated 2 to 3 weeks after the onset of jaundice during the period of surface antigenaemia. The presence of core antibody may therefore provide an accurate serological marker for the detection of active or recent virus replication in future epidemiological studies of hepatitis B infection.

Animals↗