Biomedical subjects

S P Halbert

Publications and source records attributed to S P Halbert.

At least 19 recordsLinked to original sources

PubMed1986

An enzyme immunoassay for immunoglobulin M antibodies to Toxoplasma gondii which is not affected by rheumatoid factor or immunoglobulin G antibodies.

An enzyme-linked immunosorbent assay (ELISA) for total antibodies to Toxoplasma gondii was modified to measure specific immunoglobulin M (IgM) antibodies. The assay requires three incubation periods totaling 2 h and enzyme-labeled-heavy-chain-specific antibodies to human IgM. The objective read-out in absorbance was normalized to percent of a standardized positive control for interpretations. No difference was observed between the assay results with or without previous absorption of the samples by Staphylococcus aureus protein A to remove most of the IgG antibodies. Addition of serum containing very high levels of IgG antibodies to another containing both IgG and IgM antibodies did not change the IgM assay values for the latter. None of the 22 sera containing high levels of IgM rheumatoid factor (RF) gave positive ELISA IgM results, even though 8 of them also had high levels of IgG toxoplasma antibodies. Mixtures of sera containing high concentrations of RF with sera having high levels of IgG toxoplasma antibodies also failed to show any false-positive reactions in the IgM toxoplasma assay. Thus, this ELISA for T. gondii IgM antibodies was not affected by IgG toxoplasma antibodies and RF.

Adult↗

PubMed1986

Quantitative estimation by a standardized enzyme-linked immunosorbent assay of human T-cell lymphotropic virus type I antibodies in adult T-cell leukemia and acquired immune deficiency syndrome.

Sera from patients with adult T-cell leukemia and asymptomatic carriers of human T-cell lymphotropic virus type I (HTLV-I) from widely separated areas of the world reacted strongly in a standardized quantitative enzyme-linked immunosorbent assay procedure with HTLV-I viral antigen prepared from a strain isolated in the United States. There was a sharp differentiation of the values seen in the patients as compared with a normal population. Of the 35 acquired immune deficiency syndrome patients with Kaposi's sarcoma, only 2 were positive for HTLV-I antibodies in this test, and the distribution of the negative assay values in the other acquired immune deficiency syndrome patient sera was similar to that seen in the normal sera. Sera which contained extremely high levels of antibodies to other unrelated viruses (rubella virus, cytomegalovirus, and herpes simplex virus) all showed negative anti-HTLV-I results, in a pattern similar to the normal sera. Sera from patients with several autoimmune disease (systemic lupus erythematosus, rheumatoid arthritis, thyroiditis) as well as those with infectious mononucleosis or myeloma all also showed the normal distribution of negative results, in spite of the presence of very high levels of the autoantibodies, etc., associated with their illnesses.

Acquired Immunodeficiency Syndrome↗

PubMed1986

Antibody levels for cytomegalovirus, herpes simplex virus, and rubella in patients with acquired immune deficiency syndrome.

Significantly higher proportions of patients with acquired immune deficiency syndrome (AIDS) or lymphadenopathy syndrome (LAS) were positive for antibodies to cytomegalovirus (CMV) and herpes simplex virus (HSV) compared with control groups of commercial blood donors. In contrast, no differences were found in the incidence of individuals positive for antibodies to rubella in these groups of subjects. Of those positive for antibodies to CMV and HSV in each group, the mean antibody levels were significantly higher in AIDS-LAS patients compared with the controls. The entire distribution of antibody concentrations to CMV and HSV in AIDS patients was shifted upward, so that significantly more patients showed high values and significantly fewer showed low values, indicating hyperactive humoral immune responses to these viruses. In sharp contrast, the AIDS patients with antibody levels for rubella showed the same distribution of antibody levels as did two groups of controls. No correlation was found between concentrations of CMV and HSV antibodies in individual AIDS-LAS patients.

Acquired Immunodeficiency Syndrome↗

PubMed1986

Treponemal antibody-absorbent enzyme immunoassay for syphilis.

An enzyme immunoassay for the diagnosis of syphilis (ELISA-SY) was developed with solid-phase extracts of Treponema pallidum, specimen diluent containing Reiter treponeme absorbent, and three 30-min incubations. The ELISA-SY results were determined in comparison with a standardized positive control and reported as a percentage of strong positive control. In tests with 1,005 serum samples from a venereal disease clinic and other sources, 98.2% agreement was found with fluorescent treponemal antibody-absorption (FTA-ABS) results, and 98.3% agreement was found with T. pallidum passive hemagglutination (PHA) findings. Only 1 of 29 sera originally considered to be biologically false-positive by ELISA-SY; the latter specimen was also positive by PHA and FTA-ABS tests performed in our laboratories. Serum samples from clinically diagnosed syphilitics (16 primary-stage isolates, 7 secondary-stage isolates, and 3-latent-stage isolates) were all positive by ELISA-SY, FTA-ABS, and PHA. Serum samples from 51 newborns suspected of having syphilis on the basis of positive cardiolipin flocculation tests showed 98% agreement of ELISA-SY results with FTA-ABS and PHA findings. Sera from all 61 patients with a variety of autoimmune and other diseases known to be associated with biologically false-positive reactions for syphilis were negative by this ELISA-SY. The specificity of the ELISA procedure for T. pallidum antibody was also confirmed immunologically by blocking experiments.

Antibodies↗

PubMed1986

Rapid dot enzyme immunoassay for the detection of antibodies to cytomegalovirus.

Cytomegalovirus (CMV) antigen was coated onto a white opaque plastic card as small dots inside circles marked in the microtiter plate well pattern. The card with antigen dots could be cut according to the number of test samples to be assayed. Small drops of undiluted serum samples, goat antibodies to human immunoglobulin G labeled with alkaline phosphatase, and finally substrate (5-bromo-4-chloro-3-indolyl phosphate) were sequentially added to the antigen spots and incubated in the open air at room temperature for 5 min each. The antigen dots showed blue color for sera with immunoglobulin G antibodies to cytomegalovirus but no color for those without. The developed antigen dots could be rinsed with water and kept as permanent records. For the assay of a large number of serum samples, a modified procedure with serum diluted 1:10 and longer first two incubations (20 min each) was found to be more comfortable to perform. The results of this assay for 123 undiluted and 256 diluted serum samples revealed very good correlations with those obtained by a commercially available test kit for immunoglobulin G antibodies to cytomegalovirus with 97 and 99% agreement, respectively. This dot test was very reproducible and required no instrumentation. The reagents, including coated antigen dots, are stable at room temperature for at least 2 months and are ready for use.

Adult↗

PubMed1984

The stability of prostatic acid phosphatase, as measured by a capture immunoenzyme assay.

A capture immunoenzyme assay (CIEA) for prostatic acid phosphatase (PAP) was developed and used to study the stability of this isoenzyme. Immunospecifically purified goat antibodies to PAP were covalently bound to special discs and used to capture the enzyme in serum samples in a weakly acidic medium during the first incubation (2 h) at 37 degrees C. The capture enzyme was then measured by its catalytic activity with p-nitrophenyl phosphate as substrate during the second incubation (1 h) at 37 degrees C. As much as 98% of the PAP in test specimens was captured and measured by this CIEA. The test results were expressed as enzymatic activity (U/l), extrapolated from a standard curve which was linear between 0.026 and 70 U/l. In test sera stored at 4 degrees C, the PAP was variably stable for 7 to 70 days, but the enzyme was quite stable in serum when stored at -20 degrees C for at least 156 days. At room temperature, when the sera were appropriately acidified, there was no loss of enzymatic activity for periods of 15 days, and in some cases, a large proportion of activity was still intact after 70 days. At 4 degrees C, as well as -20 degrees C, acidified serum and the partially purified PAP standard showed complete stability for at least 7 months. The CIEA reactivity of positive test specimens was inhibited by L(+)-tartaric acid, but not by cupric sulfate. The acid phosphatases of blood cell extracts were non-reactive in the CIEA procedure. The CIEA results of 224 serum samples from patients with and without prostate cancer correlated very well with those obtained by two direct enzymatic and two commercial RIA procedures, with correlation coefficients between 0.960 and 0.993, and diagnostic agreement between 86% and 100%.

Acid Phosphatase↗

PubMed1983

An enzyme-linked immunoassay for circulating immune complexes using solid phased goat Clq.

An ELISA procedure was developed for measuring circulating immune complexes (IC), using solid phased goat Clq. The use of purified Clq from this species significantly diminished the background uptake of the enzyme-labeled goat antibodies used in the assay, in comparison with Clq isolated from human, guinea pig or rabbit serum. The test specimen results are reported as micrograms equivalent (microgram eq)/ml of heat aggregated human immunoglobulin G (HAIgG), and are based on standard curves developed with this latter reagent for each assay. The 2 World Health Organization (WHO) reference preparations for immune complex determinations (HAIgG and a human tetanus antitoxin-toxoid immune complex) were assayed by this ELISA procedure, and the results obtained were in very good agreement with the WHO established values. All the reagents in the ELISA, including the lyophilized HAIgG standard and the solid phased Clq are stable for more than one year at 4 degrees C. The range of accurate quantitation in test serum is 2-500 micrograms/ml, when using a 1:100 specimen dilution. The total incubation is less than 2 h, with no preliminary preparation of test specimens. The average concentration of IC reactivity in 126 healthy adults was 6 micrograms eq/ml, and the normal upper limit was determined to be 12 micrograms eq/ml.

Adult↗

PubMed1983

A rapid standardized enzyme immunoassay for autoantibodies to thyroglobulin.

A rapid, specific, standardized, objective and sensitive quantitative enzyme immunoassay (ELISA) procedure has been developed for the detection of human autoantibodies to thyroglobulin. It involves three ten minute incubations, with the positive control serum adjusted to yield an absorbance of approximately 1.00. The results are reported as 'percentage of positive control' absorbance. The specificity of the reactions for thyroglobulin autoantibodies was supported by the good correlation found between the ELISA values obtained and the passive hemagglutination (PHA) titers of 348 sera from 333 patients suspected of having thyroid disturbances, as well as by antigen absorption experiments. Rheumatoid factor did not interfere with the assay. An appreciable proportion of passive hemagglutination-negative sera were confirmably positive for thyroglobulin autoantibodies by the ELISA method.

Autoantibodies↗

PubMed1983

Normalized enzyme-linked immunosorbent assay for determining immunoglobulin G antibodies to cytomegalovirus.

A normalized enzyme-linked immunosorbent assay for the determination of immunoglobulin G antibodies to cytomegalovirus is described. The rapid assay involves three 30-min incubations and permits the quantitation of antibody levels with a single-specimen dilution in conjunction with a reference antibody preparation. The results obtained with the normalized enzyme-linked immunosorbent assay correlated closely with the results of complement fixation titrations and another commercially available enzyme-linked immunosorbent assay. The specificity of the procedure was further demonstrated by viral absorption, using cytomegalovirus from two different sources and other viral antigen preparations, including rubella and influenza. The reproducibility of the normalized test results is good and allows for greater uniformity of reporting on a day-to-day basis, as well as between laboratories.

Antibodies, Viral↗

PubMed1983

Rubella antibodies detected by several commercial immunoassays in hemagglutination inhibition-negative sera.

Although a very good correlation was found between the level of rubella antibodies measured by a standard hemagglutination inhibition (HI) test and by an enzyme-linked immunosorbent assay (ELISA) procedure (Cordia R), an appreciable proportion (31%) of ELISA-positive specimens were encountered among HI-negative sera. The reverse was rarely seen. Many of the HI-negative, ELISA-positive sera were also found to be positive for rubella antibodies by one or more other assay methods, including an immunofluorescence assay (IFA) procedure (FIAX), passive hemagglutination (PHA) (Rubacell and PHAST), latex agglutination (Rubascan), and a second ELISA procedure (Rubelisa). The specificity of all of the ELISA-positive HI-negative specimens was substantiated by absorption experiments. In these tests, the ELISA reactivities were blocked by rubella antigens, but not by a variety of tissue culture control antigens or by influenza virus grown on the same cell line. The findings indicate that many of the newer methods available for rubella antibody detection are more sensitive than HI for detecting low levels of rubella antibodies. Until more clinical information is available concerning the protective nature of these low levels of antibody, caution should be exercised in assessing the significance of these results.

Antibodies, Viral↗

PubMed1982

Detection of infectious mononucleosis heterophil antibody by a rapid, standardized enzyme-linked immunosorbent assay procedure.

A rapid, specific, sensitive, standardized, a reproducible enzyme-linked immunosorbent assay (ELISA) procedure has been developed for detecting the heterophil antibody associated with infectious mononucleosis (IM). The IM heterophil antibody used for the solid phase was purified from bovine erythrocyte stroma. The test uses heavy-chain-specific anti-immunoglobulin M (IgM) labeled with alkaline phosphatase and three 10-min incubations. The quantitative results correlated well with horse erythrocyte agglutination titers. Absorption tests confirmed the specificity of the ELISA reactions for IM heterophil antibodies. Neither very high levels of IgM in myeloma sera nor high levels of rheumatoid factor caused false-positive reactions. A number of probable IM cases were encountered which positive by ELISA but negative by the horse erythrocyte slide agglutination test. Absorption studies indicated that these were true-positives for the IM heterophil antibody. The IM heterophil antibodies were confirmed to be predominantly of the IgM class, but moderate proportions of the IgM class were sometimes encountered.

Antibodies, Viral↗

PubMed1982

Anti-DNA, anti-deoxyribonucleoprotein and rheumatoid factor measured by ELISA in patients with systemic lupus erythematosus, Sjögren's syndrome and rheumatoid arthritis.

Serum concentrations of anti-DNA and anti-deoxyribonucleoprotein (NP) antibodies were measured in parallel by standardized ELISA methods with a polyvalent anti-immunoglobulin conjugate in patients with systemic lupus erythematosus (SLE), Sjögren's syndrome (SS) and rheumatoid arthritis (RA). High levels of these antibodies predominated in systemic lupus erythematosus. While an appreciable incidence of antibodies also occurred in SS and RA, they were mostly at lower levels. By using heavy chain-specific anti-immunoglobulin conjugates, IgG antibodies to both DNA and NP were found in SLE more frequently and at higher levels than were IgM antibodies. In contrast, IgM antibodies to DNA and NP predominated in SS and RA. The immunoglobulin class of the anti-DNA and anti-NP responses in a given SLE patient were not infrequently different. For example, a patient might show a very high IgG but low IgM anti-DNA value, with the reverse being true for anti-NP. IgG anti-DNA antibodies were significantly associated with depressions of C3. During changes in SLE serology, normalization of DNA binding by Farr radioimmunoassay and/or complement was most frequently associated with normalization of the IgG anti-DNA antibody concentrations. In patients simultaneously possessing elevated levels of anti-DNA, anti-NP and rheumatoid factor (RF), absorption with aggregated human IgG usually decreased only the RF activity. In some, however, such absorption decreased all three antibody values simultaneously. The latter findings support observations that some RF possess antinuclear properties.

Antibodies, Anti-Idiotypic↗

PubMed1982

Auto-antibodies in infectious mononucleosis, as determined by ELISA.

An increased incidence of abnormal values for anti-DNA, anti-deoxyribonucleoprotein (NP) and rheumatoid factor (RF) were found in heterophil antibody-positive infectious mononucleosis (IM). These positive auto-immune reactions were mostly at low levels. Those IM sera which revealed these auto-antibodies in the normal range showed mean values which were significantly higher than the mean values seen in normal sera. No correlation was found between the IM heterophil antibody levels and the concentrations of RF, anti-DNA or anti-NP. In the majority of cases, the anti-DNA and anti-NP responses in IM were predominantly of the IgM class.

Antibodies, Antinuclear↗

PubMed1981

Simple standardized enzyme-linked immunosorbent assay for human antibodies to Entamoeba histolytica.

A simple solid-phase enzyme-linked immunosorbent assay procedure for the detection of human antibodies to Entamoeba histolytica was developed which showed a high degree of correlation with the agar gel diffusion, counterelectrophoresis, and indirect hemagglutination methods, as well as with clinical data. The enzyme-linked immunosorbent assay is rapid (1 h 15 min, total incubation time), and the reported values are referenced to a positive control so that they correlate with levels of antibody sufficient to be detected by the gel diffusion methods. The enzyme-linked immunosorbent assay is highly reproducible, specific, and sensitive; it can be used qualitatively or quantitatively.

Animals↗

PubMed1981

Studies on autoantibodies to deoxyribonucleic acid and deoxyribonucleoprotein with enzyme-immunoassay (ELISA).

Simple, rapid, quantitative, and reproducible ELISA procedures were developed for the determination of antibodies to DNA and NP in human sera. The results are reported in International Units per milliliter, based on the WHO reference preparation of anti-nuclear factor serum. The results of both tests are significantly correlated with anti-dsDNA values obtained by an RIA (Farr technic) and by the Crithidia luciliae IF assay. The anti-DNA and anti-NP ELISA test results were more frequently positive in SLE sera than were screening tests for anti-dsDNA by the Crithidia procedure or anti-NP detection by a latex agglutination test. Parallel tests in 284 sera from patients for anti-DNA and anti-NP by ELISA showed a significant correlation between the two antibody values. However, 17% of the specimens were positive for antibodies to one antigen but not the other, whereas other specimens showed a strong predominance of one antibody over the other. Absorption studies confirmed the differing antibody specificities measured by the two assays. The ELISA anti-DNA results were inhibited by native DNA, NP, and denatured DNA in increasing order of efficiency. In contrast, the antibodies against NP were strongly inhibited by NP but only very slightly by dsDNA or denatured DNA. Other antigens, including histones, ribonucleic acid, extractable nuclear antigens, and aggregated human IgG, inhibited only slightly or not at all in either assay.

Antibodies, Antinuclear↗

PubMed1980

Quantitative determination of rheumatoid factor by an enzyme-labeled immunoassay.

The presence and quantity of rheumatoid factor (RF) in human serum were determined by an indirect enzyme-linked immunoabsorbent assay (ELISA). A human rheumatoid factor control serum, standardized against the WHO reference rheumatoid arthritis serum preparation, was used to derive a standard curve in each assay. The results of unknowns were estimated from the standard curve and reported in International Units (IU) per milliliter (ml). The ELISA assay was compared with the bentonite flocculation test. The overall coefficient of correlation between the two assays was 87%; it was 93.3% for patients with rheumatoid arthritis but only 67.5% for patients with undiagnosed conditions. The error of the ELISA assay (coefficient of variation) was generally less than 10% at both high and low concentrations of rheumatoid factor. The quantitative reproducible nature of the assay allows the detection of small variations of rheumatoid factor level and could be useful in the serial evaluation of patients.

Animals↗

PubMed1980

A quantitative enzyme immunoassay for IgM rheumatoid factor using human immunoglobulin G as substrate.

A quantitative "sandwich" enzyme-immunoassay for IgM rheumatoid factor (RF) using human immunoglobulin G as substrate covalently bound to small plastic discs is described. The findings indicate that it is a simple, sensitive, reproducible, and specific method for measuring RF activity. Test results are reported in IU/ml on the basis of the World Health Organization reference RF serum, permitting standardized reporting of this determination between laboratories using this method. Interassay and interlaboratory variability of results are less than 7%. The enzyme-linked immunosorbent assay (ELISA) results correlated well with those found by latex and bentonite flocculation titrations. A number of ELISA RF-positive specimens that were latex-negative and/or Waaler-Rose-negative were confirmed positive by inhibition of the assay with soluble aggregated human IgG, but not with nonaggregated human IgG. Comparison was made between ELISA RF results when using goat or human IgG as substrate. Human IgG was usually more reactive with RFs than was goat IgG.

Agglutination Tests↗

PubMed1980

Standardized quantitative enzyme-linked immunoassay for antibodies to Toxoplasma gondii.

A quantitative and standardized enzyme-linked immunosorbent assay is described which uses lyophilized antigen-coated disks for the detection of human antibodies to Toxoplasma gondii. It does not require serial dilution of the test specimen, and the objective absorbance readings are converted into international units per milliliter traceable to the World Health Organization's reference standard preparation of toxoplasma antibodies. It was shown to be highly specific, reproducible, and sensitive. The reagents were stable, without biohazard, and ready for use. Studies of various parameters in the assay indicated that the test conditions were relatively flexible. The enzyme-linked immunosorbent assay results correlated satisfactorily with the methylene blue dye test, the indirect immunofluorescence test, and the passive hemagglutination test.

Antibodies↗