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Biomedical subjects

R Y Dodd

Publications and source records attributed to R Y Dodd.

106 records · Page 6Linked to original sources
PubMedDate not supplied

The solid phase radioimmunoassay technique for hepatitis B (surface) antigen: effects of progressive modification.

Serum specimens submitted for confirmation of hepatitis B antigen (HBsAg) reactivity were tested by counterelectrophoresis (CEP) and by three modifications of the solid phase radioimmunoassay "sandwich" technique (SPRIA). In addition, the specificity of each reaction was determined for two of the SPRIA test methods. One hundred seventy-five of the 688 specimens were reactive by all techniques and a further 60 ere specifically reactive by two of modifications of SPRIA. An additional five specimens were positive by a third SPRIA modification. The primary SPRIA technique, using a homologous guinea pig antibody sandwich, detected 184 nonspecific reactive samples. With the same test done at 45C with a reduced incubation time, there were only 37 nonspecific reactive samples. None of the nonspecific samples was detected when the SPRIA technique used a heterologous guinea pig-human antibody sandwich. The results provide a basis for estimating the effectiveness of the SPRIA technique for HBsAg testing.

Animals↗
PubMedDate not supplied

Antibody to hepatitis B surface antigen: immunochemical purification from standard immune serum globulin.

Hepatitis B surface antigen (HBsAg) may be insolubilized onto a controlled pore glass (CPG) matrix by simple adsorption from acidified serum or plasma. The resultant complex has the properties of an HBsAg-specific immunoadsorbent. In this study, CPG-HBsAg complexes have been used to adsorb anti-HBs from standard immune serum globulin. Specific antibodies were eluted with acidic or chaotropic buffers. Recoveries ranging from 29 to 46 per cent, with purifications of approximately 1000-fold were obtained. Two procedures designed to inactivate hepatitis B virus had no effect upon the immunoadsorbent properties of the CPG-HBsAg complex. The possibility of using this simple method to prepare hepatitis B immune globulin is discussed.

Antibodies, Viral↗
PubMedDate not supplied

A simple technique for enhancing the sensitivity of a commercial solid-phase radioimmunoassay for hepatitis B surface antigen (HBsAg).

A simple procedural modification of a commercial solid-phase radioimmunoassay technique resulted in increased sensitivity for detecting HBsAg. The main feature of the modification consisted of agitation of the sample and solid-phase antibody during the first incubation. This was achieved by dispensing the bead and sample into a vial and rotating the vial gently during the incubation period. The modified technique resulted in the detection of HBsAg in the range of 1.0 to 1.2 ng/ml (ay subtype) and 0.16 to 0.38 ng/ml (ad subtype). Samples that were reactive by the rotation technique could be shown to be specific by using an immunological neutralization test. Plasma as well as serum could be tested by the rotation technique and gave comparable results when samples were incubated at 45 C or at room temperature. Three (1.3%) of 227 donor samples containing anti-HBc as the sole hepatitis B marker were specifically reactive for HBsAg by the modified procedure, although no sample was reactive by the standard technique.

Hepatitis B Surface Antigens↗
PubMedDate not supplied

Specificity of an assay for antibodies to hepatitis B surface antigen.

Eight percent of blood donors were found to have antibodies to hepatitis B surface antigen when tested by radioimmunoassay using commercial test kits. Four percent of positive reactions proved nonspecific when tested by the neutralization test using pooled surface antigen. The risks in relying solely on the reactivity in commercial-kit suggested that the specificity of the assay must be confirmed.

Antibodies, Viral↗
PubMedDate not supplied

Enzyme-linked immunoassay for hepatitis B surface antigen. An evaluation of commercial test kits.

A commercial, licensed test for hepatitis B surface antigen (HBsAg) based upon an enzyme-linked immunoassay principle was evaluated. The sensitivity, when tested under field conditions, was 0.65 and 0.9 ng/ml for ad and ay subtypes of HBsAg, respectively. Only 0.03 percent of 61,798 units of blood screened were reactive and specific for HBsAg while an additional 0.01% gave nonspecific (nonneutralizable) reactivity.

Blood Donors↗
PubMedDate not supplied

Relative specificity of enzyme-linked immunosorbent assays for antibodies to human T-cell lymphotrophic virus, type III, and their relationship to Western blotting.

A population of 73 donor samples was assembled on the basis of reactive results in routine screening with three different licensed human T-lymphotrophic virus type III (HTLV-III) antibody enzyme-linked immunosorbent assay (ELISA) procedures. The samples were retested by a number of licensed and developmental tests and by Western blot analysis. Our data indicate that nonspecific results are generated by ELISA tests and that many of these reactions appear to be directed against the cell substrate used to grow the virus. These findings suggest that combinations of currently licensed ELISA tests, based upon HTLV-III grown in H-9 cells, cannot be used to confirm the specificity of reactive samples.

Antibodies, Viral↗
PubMedDate not supplied

Use of a control serum containing a low level of HBsAg for monitoring proficiency in screening for HBsAg.

Aliquots of a serum preparation called "run control" containing low levels (1.4 ng/ml) of hepatitis B surface antigen (HBsAg) were tested by four American Red Cross Blood Services regions using a commercial test based on enzyme-linked immunosorbent assay (EIA). The run control was tested a total of 424 and 892 times by procedures A and C, respectively, as recommended by the manufacturer (Abbott Laboratories, North Chicago, IL) of the EIA test kit. Results of all the tests were analyzed and showed that the run control was stable and reliable under field conditions. Illustrative examples of different approaches for the use of the run control in monitoring quality control of HBsAg testing are discussed.

Blood Banks↗
PubMedDate not supplied

Stability of serum alanine aminotransferase activity.

In this study the authors examine the effects of common storage and handling procedures on serum alanine aminotransferase (ALT) levels. Clotted blood samples from 14 subjects were centrifuged at 280 X g for 10 minutes. Serum was tested immediately for baseline ALT levels and aliquots were stored at 22, 4, -20, and -80 degrees C. Additional serums were stored on the clot at 22 and 4 degrees C. ALT quantitation was performed at intervals of 3, 6, 9, and 24 hours and on Days 2, 4, 6, and 8. Unseparated tubes were sampled both proximal and distal to the red cells to determine ALT leakage from red cells lysis. For all storage conditions, gradual loss of activity occurred over time. Mean activity loss in separated serum at 2 days was 6 percent at 4 degrees C and 20 percent at 22 degrees C. Mean loss in unseparated serum was 3 percent at 4 degrees C and 12 percent at 22 degrees C. Marked ALT loss averaging 46 percent by day 6 occurred with storage at -20 degrees C, whereas storage at -80 degrees C resulted in an 8 percent decrease for the same period. For storage of up to 1 week, it is recommended that serum be separated early and retained at 4 degrees C. Frozen samples should be kept at -80 degrees C. Storage of separated or unseparated blood for up to 24 hours at 22 or 4 degrees C, as commonly found in blood centers, will marginally adversely affect the accuracy of ALT determination.

Alanine Transaminase↗
PubMedDate not supplied

American Red Cross experience with routine testing for hepatitis B core antibody.

The implementation of routine testing of blood donations for hepatitis B core antibody (anti-HBc) has allowed the characterization of the performance of the test in a large number of samples from apparently healthy individuals. This study reports the experience of the American Red Cross in testing 2.3 million donors for anti-HBc. The test protocol reproducibly identified a distinct population of donors. The anti-HBc-positive rate varied by region of the continental United States and by the time of year. In a case-control study, 85 percent of subsequent donations from anti-HBc-positive donors were anti-HBc positive. The predictions made in an earlier pilot study regarding the performance and impact of the test were borne out.

Blood Donors↗
PubMedDate not supplied

Inactivation of viruses in platelet suspensions that retain their in vitro characteristics: comparison of psoralen-ultraviolet A and merocyanine 540-visible light methods.

The ability of two fundamentally different photochemical procedures to inactivate model viruses in platelet suspensions was compared. Merocyanine 540 (MC 540) with visible light was used as an example of an oxygen-dependent chemical-directed at the viral membrane, and aminomethyl trimethyl psoralen (AMT) with ultraviolet A light (UVA) was used as an example of a nucleic acid-directed system. Antiviral conditions in petri dishes were identified and the effects of these procedures on platelet suspensions in plastic storage containers were studied. Concentrations of photochemicals in the 10 to 150 mumol range with 30 to 60 minutes of visible light (MC 540) or 1 to 2 minutes of UVA (AMT) readily inactivated 5 to 6 log10 of vesicular stomatitis virus (VSV) and other model viruses in platelet suspensions, provided the plasma concentration was reduced to about 15 percent by the use of a synthetic platelet storage medium. Extracellular pH, morphology scores, and aggregation response dropped markedly when platelets were treated with MC 540 and visible light. However, treatment with 136 mumol per L of AMT and 1 to 3 minutes of UVA could inactivate 5 log10 of VSV in platelet suspensions with retention of platelet characteristics for 4 days, particularly if oxygen levels were reduced during treatment. These studies demonstrate that AMT-UVA treatment meets the initial requirements for virus inactivation in platelet suspensions.

Blood Platelets↗
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Viral contamination of blood components and approaches for reduction of infectivity.

Currently, the United States blood supply offers a relatively low risk of viral infection. This is a result of careful selection of donors and extensive laboratory testing using sensitive procedures. Epidemiologic data show that there is some room for improvement in donor selection, but such improvements cannot be expected to entirely eliminate the collection of blood from infectious donors. Similarly, increased numbers of tests, along with improvements in the analytic sensitivity of these tests, may further reduce risk, but again, complete safety cannot be assured. Consequently, there is continuing interest in the development of safe and effective procedures for viral inactivation of single donor blood components. In order to establish appropriate expectations for such inactivation procedures, it is necessary to understand the titers and distributions of viral contaminants in blood components. Viruses may variously occur free in the plasma, as replicative forms in actively infected leukocytes, as integrated proviral DNA and perhaps, nonspecifically associated with cellular surfaces.

Blood↗
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Blood safety.

Since blood is a biologic product, it is unlikely that the risk for transfusion-transmitted infection will ever be reduced to zero. The approach to emerging infections associated with transfusion of blood and blood products includes assessing the transmissibility of the agent by this route; developing effective prevention strategies, including screening tests and donor deferral policies; improving viral and bacterial inactivation procedures; and surveillance for known, as well as emerging and poorly characterized, transfusion-transmitted agents. Vigilance is needed to help ensure proper balance between safety and the availability of blood. Finally, vigilance needs to extend to the developing world, where the basic elements to reduce transfusion-transmitted infections and systems of disease surveillance are often not available.

Biological Products↗
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The serology of hepatitis C virus in relation to post-transfusion hepatitis.

Natural history studies conducted over the past 15 years have shown that parenterally transmitted non-A non-B hepatitis infection frequently results in an indolent chronic disease with serious long-term consequences. The recent identification of nucleic acid sequences comprising the genome of hepatitis C virus (HCV) has allowed the development of a serological assay based upon recombinant viral proteins specifically associated with the major agent of non-A, non-B hepatitis infection. The HCV antibody assays have now been applied to sera from blood donors worldwide, as well as various population samples with increased hepatitis risk in the course of clinical trials conducted in both Europe and the United States. Data from these studies provide further encouragement that assays based on the hepatitis C virus recombinant proteins are highly specific for the major agent of non-A non-B hepatitis and will provide a firm basis for blood donor screening and future diagnostic tests.

Blood Transfusion↗
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A robotic system to prepare samples for HTLV-III testing.

A robotic handling system was adapted to perform the sampling and dilution steps needed in an assay to detect antibodies to the HTLV-III virus, the causative agent of AIDS. The system reduced the labor required to prepare the samples and provided standardization and accuracy in the preparation of the samples.

Antibodies, Viral↗