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Biomedical subjects

H A Fields

Publications and source records attributed to H A Fields.

96 records · Page 6Linked to original sources
PubMed1977

Serodiagnosis of viral hepatitis A: detection of acute-phase immunoglobulin M anti-hepatitis A virus by radioimmunoassay.

A modified micro solid-phase radioimmunoassay (RIA) for antibody to hepatitis A virus (anti-HAV) was developed. This double antibody procedure was performed by coating the surface of a polyvinyl microtiter plate "well" with 200 microliter of a 1:1,000 dilution of a patient's test serum. Purified HAV and 125I-labeled immunoglobulin G (IgG) anti-HAV were then sequentially added to form an antibody sandwich. The specificity and sensitivity of the RIA procedure for anti-HAV were verified by examination of coded human and chimpanzee serum specimens. Radioimmunoassay of early-acute-phase serum specimens from human cases of hepatitis A revealed the presence of anti-HAV activity. Differential examination by RIA of IgG and IgM fractions of acute-phase sera from experimentally infected chimpanzees demonstrated that IgM contained the bulk of the anti-HAV activity. A modification of the RIA procedure for anti-HAV (RIA-IgM blocking), incorporating an incubation step with anti-IgM (Mu chain specific), was further shown to differentiate acute- from convalescent-phase hepatitis A sera. This adapted RIA-IgM blocking procedure required less than 1 microliter of a single acute-phase serum specimen for the diagnosis of viral hepatitis A.

Acute Disease↗
PubMed1977

Biochemical and biophysical properties of hepatitis B core particles derived from Dane particles and infected hepatocytes.

Hepatitis B core antigen (HBcAg) was purified from Dane particles and from infected hepatocytes. An identical isoelectric pH of 4.0 was determined for labeled preparations of both Dane-derived and liver-derived HBcAg. Unlabeled liver-derived HBcAg demonstrated a lower isoelectric pH of 3.7. Molecular weight determinations by Sepharose 4B column chromatogrpahy revealed that liver-derived HBcAg had a molecular weight of 8.5-9.0 X 10(6) daltons. The sedimentation coeficient of both Dane- and liver-derived HBcAg was found to be 124S. PAGE revealed that iodinated HBcAg derived from Dane particles was very similar in polypeptide structure to HBcAg derived from infected liver tissue. Twelve polypeptides were resolved from Dane core particles, and seven to nine were resolved from liver core particles. Several of the polypeptides in both preparations co-migrated with iodinated hepatitis B surface antigen (HBsAg). However, three polypeptides (mol. wt. 88,000, 79,000 and 59,000) were found in both Dane- and liver-derived HBcAg but not in HBsAg, which suggests that these polypeptides are HBcAg-specific. Endogenous DNA polymerase activity was observed in both Dane- and liver-derived core particles.

DNA-Directed DNA Polymerase↗
PubMedDate not supplied

Endogenous DNA polymerase-positive core particles from hepatitis-infected hepatocytes.

The purification is described of liver-derived hepatitis B core antigen (HBc Ag) from human hepatocytes demonstrating only intranuclear particles by electron microscopy. The purified preparation contained 5 x 10(11) particles per ml. The particles were mono-dispersed and relatively free of background material. DNA-dependent polymerase activity was present and had greater activity than an equal number of cores derived from Dane particles isolated from plasma. Specificity of the polymerase reaction was confirmed by precipitation of the activity with specific anti-HBc antiserum. A proportion of the liver-derived core particles was nonreactive for DNA polymerase activity. The polymerase-positive population of particles had a larger size than the polymerase-negative population of liver-derived cores as evidenced by gel filtration in Sepharose 4B.

DNA-Directed DNA Polymerase↗
PubMedDate not supplied

Comparative immunogenicity of plasma and recombinant hepatitis B virus vaccines in homosexual men.

A randomized, double-blind clinical trial of plasma-derived and DNA recombinant hepatitis B virus vaccines was conducted in 186 homosexual men. Nine months after the immunization series (three doses) began, the seroconversion rate in the plasma vaccine group was 88% (68/77); this was significantly higher than the 74% (60/81) response rate of the recombinant vaccine group. Men positive for antibody to the human immunodeficiency virus (HIV) had a considerably higher nonresponse rate to either vaccine than expected in non-HIV-infected homosexual men. The odds ratios of nonresponse to hepatitis B virus vaccine for HIV-seropositive vs HIV-seronegative subjects were 12.0 (95% confidence interval, 1.7 to 89.3) and 13.6 (95% confidence interval, 2.3 to 148.3) for the plasma and DNA recombinant vaccines, respectively.

Adult↗
PubMedDate not supplied

Viral hepatitis serological markers among pregnant women in Caracas, Venezuela: implication for perinatal transmission of hepatitis B and C.

Viral hepatitis serological markers were analyzed in two groups of pregnant women residing in Caracas from: 1) a maternity unit at the moment of delivery (106 sera, low income population), and 2) a private clinic during the third trimester of pregnancy (105 sera, medium-high economic class population). A higher percent positivity was observed in the maternity unit compared to the private clinic for hepatitis A virus (HAV) as measured by anti-HAV activity (96% vs 48%; p < 0.01%), for hepatitis B virus (HBV) as measured by anti-HBc activity (13% vs 2%; p < 0.01%), but not for HBV carriage, as measured by HBsAg (3.8% vs 0%; p = 0.06 %). These differences appear to correlate with the socio-economic level. All the HBsAg positive sera were HBeAg negative and negative for the presence of DNA by PCR, confirming the low rate of perinatal transmission observed in Venezuela. Two out of 106 sera (1.9%) were positive for HCV antibodies in the maternity unit and 0/105 in the private clinic, although these differences were non significant (N.S.). Two out of 106 sera (1.9%) were positive for HEV antibodies in the maternity unit and 1/80 (1.3%) in the private clinic (N.S.). The anti-HEV seropositivity probably reflects a past infection. The importance of testing these viral markers during pregnancy is discussed.

Female↗