Virus-induced diabetes mellitus. X. Attachment of encephalomyocarditis virus and permissiveness of cultured pancreatic beta cells to infection.
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Biomedical subjects
R Chairez
Publications and source records attributed to R Chairez.
Immunological and biophysical properties of hepatitis B antigen labeled by the chloramine-T and by the lactoperoxidase methods.
Optimal conditions were sought for the radiolabeling of microgram quantities of hepatitis B surface antigen (HBs Ag) employing the chloramine-T or lactoperoxidase iodination procedures. Preparations of HBsAg labeled by these procedures are referred to as chloramine-T preparations and lactoperoxidase preparations, respectively. Labeled HBsAg having specific activities between 10-20 muCi/mug were found to display the greatest degree of sensitivity for unlabeled HBsAg and for anti-HBs using a double-antibody radioimmunoassay (RIA-DA). Increasing the specific activity above this level redulted in a decreased affinity of labeled 1251-HBs Ag for anti-HBs, indicating that soluble antigenic alterations had developed. At equivalent specific activities, chloramine-T preparations competed less effectively for unlabeled HBs Ag than lactoperoxidase preparations, and anti-HBs endpoint titers were slightly reduced, especially among preparations of high specific activity (greater than or equal to 65 muCi/mug). Chloramine-T preparations of HBs Ag (sp. act. 15--30 muCi/mug) showed essentially no antigenic deterioration over a 2-month period at minus 196 degrees C or minus 70 degrees C. Utilization of optimally labeled 1251-HBs Ag has increased the sensitivity of the RIA-DA for unlabeled HBs Ag 30-fold to a level below 1 ng/ml and enhanced antiamine-T method revealed that only the most acidic population was labeled (pH 3.75+/-0.5). In contrast, six antigenic components with distinct pI values ranging from 3.7 to 5.2 were detected by RIA-DA in both unlabeled HBs ag and in the chloramine-T preparation. This indicated that the chloramine-T method did not radically change the relative number or charge of each of the pI populations present in purified preparations of HBs Ag. Analysis of HBs Ag iodinated by the lactoperoxidase procedure revealed the presence of three of four populations of particles with pI values ranging from 3.9 to 4.5, suggesting that this procedure labels HBs Ag more uniformly.
Chloramines↗
Cell-mediated immunity in guinea pigs to subunits derived from hepatitis B surface antigen.
Guinea pigs immunized wit- hepatitis B surface antigen (HBSAg), types adw and ayw, and with two polypeptides (400,000 and 24,000 molecular weight) developed cell-mediated immunity (CMI), as determined by radioimmunoassay. Peritoneal exudate (PE) cells from guinea pigs immunized with the 40,000-molecular-weight polypeptide migrated poorly (30 to 88% inhibition) after challenge with the immunizing subunit or with purified HBSAg, type gdw or ayw. Response of the same PE cells to the 24,000-molecular-weight subunit was significantly reduced. Similar but less striking evidence for CMI was observed was PE cells derived from guinea pigs inoculated with purified type-specific HBSAg or with the 24,000-molecular-weight polypeptide. Humoral responses were predictable and showed a reasonable degree of correlation with the CMI response. PE cells from control animals inoculated with normal human serum or polyacrylamide gel were not inhibited after challenge with purified preparations of HBSAg or with the 400,000-molecular-weight polypeptide, but did show CMI with their respective immunogens. In addition, PE cells from guinea pigs inoculated with normal human serum were inhibited from migrating after challenge with the 24,000-molecular-weight subunit, suggesting that the latter may contain an antigenic determinant related to a human serum protein.
Animals↗
Comparative biophysical studies of hepatitis B antigen, subtypes adw and ayw.
Comparative biophysical and biochemical analyses were performed on purified preparations of hepatitis B antigen (HBs Ag) subtypes adw and ayw, including isoelectric pH evaluations, analysis of the different morphological forms, molecular weight determinations, and analysis of the polypeptides by polyacrylamide gel electrophoresis, Both HBs Ag-positive plasma and purified HBs Ag were analyzed by electrofocusing in a sucrose ampholyte gradient. Four distinct populations of HBs Ag with a pH range of 4.5 plus or minus 0.1 to 5.4 plus or minus 0.1 for unfractionated plasma samples and 3.9 plus or minus 0.05 to 4.9 plus or minus 0.05 for purified samples were detected in both adw and ayw preparations. Electron microscopic studies of each population of purified HBs Ag revealed 19- to 27-nm spheres in each fraction. Purified material labeled with 125I by the chloramine-T method behaved as one major population with an isoelectric pH value of 3.9 plus or minus 0.1. Purified adw preparations revealed a major population with a molecular weight of 3.7 times 10-6 and a second one of 4.6 times 10-6. Purified preparations of ayw contained one population with a molecular weight of 4.6 times 10-6. Polyacrylamide gel electrophoretic analysis of purified HBs Ag revealed nine polypeptides for ayw and seven for adw particles. These studies indicate that purified preparations of HBs Ag are heterogeneous and that distinct differences can be detected between the two subtypes.
Centrifugation, Density Gradient↗
Production of antibody to individual polypeptides derived from purified hepatitis B surface antigen.
Purified preparations of hepatitis B surface antigen (HBsAg) were solubilized with sodium dodecyl sulfate and urea under reducing conditions and subsequently fractionated by preparative sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis (PAGE). Pools of the individual fractions eluted from the preparative PAGE were concentrated and purified further by analytical PAGE. Five purified polypeptides were isolated from HBsAg, types adw and ayw, with molecular weights of 19,000, 24,000, 27,000, 35,000, and 40,000. Each preparations was emulsified in Freund complete adjuvant and injected into guinea pigs. Antibody to each HBsAg type was measured by radioimmunoassay. The 19,000 molecular weight polypeptide derived from ayw particles and the 27,000 molecular weight subunit obtained from both types failed to elicit an antibody response. The other three polypeptides derived from the ayw particles elicited group-specific antibody responses. Similar group-specific reactivities were observed in the testing of anti-adw 35,000 and anti-adw 40,000 molecular weight polypeptide sera. However, guinea pigs immunized with the 19,000 and the 24,000 molecular weight polypeptides of the adw type produced antibody that reacted preferentially with adw particles. This indicates that either these subunits carry predominately d determinants or that, because of the low levels of material used for inoculation, no immune response or an undetectable one was elicited to the a or w components.
Animals↗