Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ELISA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed1988

Enzyme linked (ELISA) immunoabsorbent assay for the detection of hidden 19S IgM rheumatoid factors in juvenile rheumatoid arthritis.

Determination of hidden IgM rheumatoid factors (RF) in juvenile rheumatoid arthritis (JRA) offers advantages for diagnosis and in following disease activity. Sera from 30 patients with JRA were assayed for RF by latex fixation test (LFT), sensitized sheep cell agglutination test (SCAT), nephelometry, and by ELISA. IgM containing fractions were prepared by chromatography and assayed for hidden RF by the hemolytic method and ELISA. Ten patients were seropositive by LFT. All of them gave positive tests on the serum for RF with the SCAT, nephelometry, and ELISA, and on the IgM containing fractions by the hemolytic assay and ELISA. Seventeen patients seronegative by LFT were positive for hidden RF by the hemolytic test and ELISA on the IgM containing fraction. When unfractionated serum was used, 15 were positive by ELISA. Three patients were seronegative and also negative for hidden RF by the hemolytic assay and ELISA. Thus, only 2 of 30 patients had discordant results between the hemolytic assay on the IgM containing fraction and the ELISA on the serum. Our results indicate the ELISA on the serum in conjunction with the LFT offers a simple, rapid, alternative test for hidden 19S IgM RF in JRA patients.

Agglutination Tests↗
PubMed1983

[Enzyme-linked immunosorbent assay (ELISA) for IgG- and IgM antibodies in chlamydial infections of humans].

The development and evaluation of an indirect ELISA for IgG and IgM antibodies in human sera against the genus-specific chlamydial antigen is described. Application of commercial anti-immunoglobulins for production of conjugates usually resulted in direct conjugate/antigen reactions. Therefore, all immunoreagents had to be prepared by the authors. Using anti-immunoglobulins purified by affinity chromatography for the production of anti-human IgG(H + L)-peroxidase conjugates, these conjugates showed high specific activity and could be diluted 1/10,000 for the test, whereby direct reactions with antigens were negligible (12 +/- 12 ELISA units). Results with the mu-chain-specific IgM ELISA could be verified additionally by rheumatoid factor analysis and gel-chromatographic investigations. Reactions with sodium deoxycholate extracted antigen from cells not infected with chlamydiae ("negative antigen") were observed with sera from persons working with cell cultures. In comparison with microimmunofluorescence (MIF) test and radioimmunoassay (RIA), the ELISA was the most sensitive method. However, for differentiation of urogenital infections associated with chlamydiae, the type-specific MIF test was superior to the genus-specific ELISA. In comparison to persons with chlamydia-associated prostatitis, the high percentage of IgM-positive reactions in patients with nongonococcal urethritis (10% and 56%, respectively) pointed to a predominant participation of genus-specific IgM antibodies in recent infections. As compared to ELISA values of patients with infections of the urogenital tract (up to 875 ELISA units), in some apparently healthy blood donors significantly higher ELISA values (up to 1400 ELISA units) were recorded. Such reactions may be attributed to systemic infections, e.g. chlamydial pneumonias. The importance to differentiate between IgG and IgM antibodies in such infections is discussed.

Antibodies, Bacterial↗
PubMed1994

Detection of insulin antibodies by radioassay and ELISA: interrelation and correlation with metabolic control in type I diabetes.

1. The literature suggests that the radioassay (RA) and ELISA detect different types of insulin antibodies (IA) (Wilkin et al., 1989. Diabetes, 38: 172-181). 2. In the present study we evaluated the relationship between these two antibodies and their involvement in the metabolic control of Type I diabetic (DMI) patients. 3. IA were measured by RA and ELISA in sera obtained from 34 patients (age: 9-16 years, median = 12.5 years; clinical duration of DMI: 0.1-11.0 years, median = 1.7 years) treated with different types of insulin [purified (bovine + porcine) N = 18, and monocomponent (porcine or human) N = 16] and submitted to various degrees of metabolic control as assessed by glycosylated serum protein (GSP) levels: range, 3.4-13.5%; median = 8.7%; normal value, 0.8-2.4%. 4. Insulin antibody levels measured by RA were: 3264 +/- 300 nU/ml (mean +/- SEM, normal value < 60 nU/ml) and by ELISA: 0.74 +/- 0.11 ELISA index (EI) (normal value, < 0.53). No correlation was found between IA levels measured by RA and ELISA, or between duration of the disease or insulin daily necessity and IA by either method. GSP was positively correlated with IA determined by ELISA (rS = 0.43, P < 0.01) but not with IA determined by RA. 5. The patients on purified bovine + porcine insulin had higher titers of IA by ELISA, compared to those of patients on monocomponent (0.96 +/- 0.15 vs 0.50 +/- 0.13 EI, P < 0.03, while IA levels measured by RA did not differ between groups. 6. These data show that RA or ELISA assays provide different serum titers of IA in insulin-treated diabetics and data obtained with ELISA correlated best with the metabolic control of Type I diabetic patients.

Adolescent↗
PubMed1994

Diagnosis of Babesia caballi infections in horses by enzyme-linked immunosorbent assay (ELISA) and western blot.

From Babesia caballi in vitro cultures a preparation of 100% infected erythrocytes was obtained. From this, B. caballi antigens were extracted with the detergent 3-[(3-Cholamidopropyl)-dimethylammonio]-1-propane-sulfonate (CHAPS) and used as ELISA antigens. A control antigen of normal erythrocytes from the same donor horse was prepared in an identical manner. The ELISA and Western blot were validated by testing of sera from horses experimentally infected with B. caballi or B. equi or not infected with Babesia spp. ELISA and Western blot results were compared with those obtained by the immunofluorescence antibody test (IFAT) and complement fixation test (CFT). The sensitivity of the ELISA of 98.3% obtained for sera from day 14 after infection was superior to the Western blot (94.9%), the IFAT (96.6%) and the CFT (28.8%). No positive results were obtained in the ELISA and Western blot with 106 sera from horses not infected with Babesia spp. resulting in a calculated specificity of 100% for both tests. Cross reactions of B. equi-positive sera did occur to a larger extent in the ELISA (20%) than in the IFAT (4%). No cross reactions were observed with the Western blot and the CFT. The higher sensitivity of the ELISA was also demonstrated by testing of 132 field sera: more positive results were obtained by ELISA (112) as compared to IFAT (92) or CFT (41). The validity of these results was confirmed by testing of sera by Western blot. The ELISA as the most sensitive test provides the best method for the identification of carrier horses to prevent the introduction into non-endemic areas (export testing).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Monoclonal antibody-based dot-blot ELISA for the detection of Salmonella in foods.

Monoclonal antibody (MAb) produced to polysaccharides in the LPS molecule of salmonellae was used in a dot-blot ELISA for detecting Salmonella in 873 food samples, ie 100 fresh chicken, 261 frozen chicken, 78 pork, 84 beef, 100 hen eggs, 100 duck eggs, 50 sea-mussels, 50 shrimps and 50 squids in comparison with the conventional culture method. Salmonella culture from foods involved the following steps: pre-enrichment, enrichment in selective medium, isolation on selective and indicator media, followed by biochemical and serological identification of appropriate colonies, respectively. The whole culture procedure took 5 days. Food samples from the selective enrichment medium were also subjected to the MAb-based dot-blot ELISA. The whole procedure of dot-blot ELISA took less than 2 hours. Among 873 food samples, salmonellae could be recovered from 7.4% of the samples by the bacterial isolation method (16% of fresh chicken, 8.8% of frozen chicken, 24.4% of pork, 3.6% of beef and 2% each of hen eggs and duck eggs, respectively). Salmonella derby were predominant among pork samples while S.paratyphi B biovar java predominated in chicken. The MAb-based dot-blot ELISA were positive in 19.5% of the food samples, i.e. 30% of fresh chicken, 27.6% of frozen chicken, 34.6% of pork, 21.4% of beef, 20% of shrimp, 16% of sea-mussels, 2% of hen eggs and 4% of duck eggs. The sensitivity and specificity of the MAb-based dot-blot ELISA compared to the bacterial culture method were 81.5% and 85%, respectively. The discrepancy of the data between the culture method and the dot-blot ELISA might be due to the fact that the culture method could detect only living cells at numbers that gave at least one isolated colony on the selective/differential plate while the dot-blot ELISA detects any form of Salmonella antigen. The monoclonal antibody-based dot-blot ELISA offers several advantages over the conventional bacterial culture method when it is used for screening of Salmonella contamination in foods, especially export foods. These include rapidity, cost-effectiveness and simplicity (the dot-blot ELISA does not need highly trained personnel or equipment, in contrast to the culture method). The test can be performed in field conditions and the result can be read visually. It also offers multisample analysis at one time which renders more samples of food for screening possible, thus false negative results are fewer which, in turn, assures the quality of the export food in a cost-saving, short time frame.

Antibodies, Monoclonal↗
PubMed1998

Evaluation of an expanded two-ELISA approach for confirmation of reactive serum samples in an HIV-screening programme for pregnant women.

Serum specimens were collected from 31,232 pregnant women in Amsterdam between 1988 and 1995 in a screening programme for human deficiency virus (HIV) infection. The sera of 56 (0.179%) women tested were confirmed as positive for HIV. A total of 67 sera reacted positive or borderline by the screening enzyme-linked immunosorbent assay (ELISA) and indeterminate or negative by HIV-1 Western blot; 42 of these specimens were available for evaluation of the strategy for diagnosis of HIV infection. A two-ELISA approach with the second ELISA based on a principle different from that of the screening ELISA, expanded with the use of a membrane immunoassay based on two synthetic peptides specific for HIV-1 gp41 and HIV-2 gp36 envelope proteins, was compared with the Western blot analysis. Indeterminate results were resolved with a nucleic acid sequence-based amplification assay (NASBA) for HIV-1 RNA and a strip immunoassay (SIA) for the simultaneous detection of antibodies to HIV-1 or HIV-2 and HIV-1 p24 antigen. Eleven samples were weakly or borderline positive by the screening test and gave indeterminate results by Western blot. The expanded two-ELISA approach designated these sera as HIV-negative, and confirmed negative by NASBA and the SIA. Twenty-one samples showed borderline or positive results on the screening test and negative results by Western blot. Again, these sera were characterised as HIV-negative by the expanded two-ELISA procedure, and this characterisation was confirmed by both NASBA and the SIA. Five HIV-2-positive serum samples were recognised by the expanded two-ELISA approach and the SIA; these sera were negative by NASBA. Finally, another five serum samples were weakly or borderline positive by both ELISAs and positive by the membrane immunoassay; of these five, two sera generated positive patterns and the other three indeterminate patterns on Western blots, and four were positive by the NASBA assay. Follow-up serum specimens from these five women were negative and the reactivity of the initial specimens was thus likely to have been the result of cross-contamination. Our results demonstrate the effectiveness of a simple confirmation approach of two HIV ELISAs expanded with a membrane spot assay to discriminate between infection with HIV-1 or HIV-2. The data also indicate the importance of retesting individuals with indeterminate or positive confirmational results to exclude the possibility of contamination as the cause of reactivity of the original specimen.

Enzyme-Linked Immunosorbent Assay↗
PubMed1984

An enzyme-linked immunosorbent assay (ELISA) for IgG and IgA antibodies to respiratory syncytial virus in low dilutions of secretions of human serum and secretions.

An enzyme-linked immunosorbent assay (ELISA) has been developed for titration of IgG and IgA antibodies to respiratory syncytial (RS) virus in low dilutions of human serum, colostrum, and nasopharyngeal secretions. Previously the sensitivity of RS virus ELISA on such specimens has been limited by nonspecific absorption of antibody, particularly IgA, to crude antigen preparations. For IgG antibody estimation in infant sera, this unwanted binding was reduced to workable levels by increasing the serum, salt, and detergent concentration of the diluent. Residual nonspecific binding of IgA in colostra appeared mainly due to antigen lipids or to lipoproteins. This was markedly reduced by partitioning Triton X-100-treated infected cell lysate antigens in Arklone. Using the modified ELISA technique for anti-RS virus IgA, good correlations were found with unfixed cell membrane immunofluorescence (MIF) for colostra (r = 0.81, P less than 0.001) and nasal secretions from adult volunteers. In several samples nonspecific absorption of antibody precluded MIF assay, but did not affect the ELISA. Although there was an overall correlation between ELISA for anti-RS IgG antibody in sera, the complement fixation test (r = 0.75, P less than 0.001), and MIF test (r = 0.82, P less than 0.001), the sensitivity of ELISA for antibody responses in convalescent sera of infants from 3 months to 2 years was poor. Conversely, the sensitivity of ELISA for antibody in the sera of older children and for transplacentally acquired antibody in very young infants was higher than that for the other two tests. ELISA was thus less reliable than either CF or MIF for detecting antibody rises in paired infant sera, particularly where maternally acquired antibody remained in the acute serum. The reasons for this apparent disparity are discussed.

Adult↗
PubMed1987

Detection of serum antibody responses to RIT 4237 rotavirus vaccine by ELISA and neutralization assays.

Immunoglobulin class-specific determination by ELISA and a virus neutralization test (NT) were compared for the detection of the serum antibody responses after vaccination of infants with the RIT 4237 rotavirus vaccine (of bovine origin). A capture method was applied for specific IgM determination by ELISA because of its greater sensitivity and reproducibility over the conventional ELISA-IgM test. NT was improved through the use of an enzyme-labelled antibody for the detection of non-neutralized virus. In 6-12-month-old children, the most sensitive single test to detect an antibody response was the ELISA-IgM capture method, but the combination of ELISA-IgM and IgG tests or ELISA-IgM and NT detected the highest seroconversion rate of 79%. In newborn infants high levels of maternal antibody made the ELISA-IgG test unsuitable. ELISA-IgM gave a response rate of 31%, but NT with homologous virus was the most sensitive indicator of a serological response to the vaccine in this age group, yielding a 45% response rate.

Antibodies, Viral↗
PubMedDate not supplied

[Detection of dsDNA antibodies in diagnosis of systemic lupus erythematosus--comparative studies of diagnostic effectiveness of 3 ELISA methods with different antigens and a Crithidia luciliae immunofluorescence test].

Antibodies to double-stranded DNA (anti-dsDNA, dsDNA-Ab) are frequently found in systemic lupus erythematosus (SLE), especially during active disease and differ with respect to immunoglobulin class and avidity. The detection of anti-dsDNA is one of the diagnostic criteria for SLE according to the American College of Rheumatology (ACR). Most of the commercial ELISA test systems have great advantages in routine laboratory testing but often detect dsDNA-Ab which are not specific for SLE and therefore give false positive results for non-SLE patients. The newly developed ELISA presented here, using human recombinant dsDNA (h-Rek) is compared to two commercial ELISA tests with genomic dsDNA from salmon testes (L-dsDNA) or plasmid dsDNA (P-dsDNA) and to the Chrithidia luciliae immunofluorescence test (CLIF) as well. In this study 143 sera were tested, 48 derived from patients with SLE, 40 from rheumatoid arthritis patients, 26 from non-rheumatoid patients whose sera were ANA-negative but L-dsDNA-Ab-positive and 30 from healthy volunteers. All patients were followed and clinically defined by the rheumatology outpatient clinic of our hospital. The prevalence for SLE of all sera was 32%. The sensitivity was 0.73 (h-Rek), 0.83 (L-dsDNA), 0.81 (P-dsDNA) and 0.57 (CLIF); specificity was determined 0.84 (h-Rek), 0.62 (L-dsDNA), 0.63 (P-dsDNA) and 0.98 (CLIF). The diagnostic efficiency of the L-dsDNA- and P-dsDNA-assay was identical, 0.69, and amounted to 0.81 for the h-Rek and 0.84 for the CLIF. Comparing all the ELISA tests and CLIF, the human recombinant dsDNA ELISA is much more sensitive than the CLIF, but considerably more specific than the ELISA assays using genomic or plasmid DNA, whereas the diagnostic efficiency is very close to that of the CLIF. This new generation of anti-dsDNA ELISA using human recombinant dsDNA seems to be a much better diagnostic tool for the detection of highly specific anti-dsDNA antibodies in the diagnosis of SLE than other commercial ELISAs. These results can only be explained by the use of a human recombinant antigen instead of undefined genomic or recombinant plasmid DNA for immobilization.

Animals↗
PubMed1978

Amplification of the enzyme-linked immunosorbent assay (ELISA) in the detection of class-specific antibodies.

A modification of the standard enzyme-linked immunosorbent assay (ELISA) is described which circumvents the requirement for specifically purified antibodies from which antibody-enzyme complexes are made. The assay utilizes the principle of a soluble anti-alkaline phosphatase immune complex (AP-A-AP) and has been called the amplified ELISA. Methods for preparing and evidence for the specificity of rabbit anti-rat gamma-FC, IgM (mu) and IgA (alpha) are presented. These reagents are used to measure anti-DNP antibodies belonging to classes IgG, IgM and IgA in rat serum. Using antiglobulin and anti-enzyme reagents prepared in guinea pigs, anti-ovalbumin antibodies are measured in rabbit serum. Titration curves are similar when the amplified ELISA is compared to the standard ELISA. A change in slope suggesting an effect of saturation of antigen sites, occurs at the same input antibody concentration for both assays. Determination of the anti-DNP concentration of unknown sera by extrapopulation from titration graphs of a known serum suggests that the value is overestimated, i.e., amplified when the amplified ELISA is used. In addition, the amplified ELISA has an improved ability to detect low levels of antibody. Evidence is presented which illustrates how the use of optimally conjugated DNP-proteins, age of conjugates, and optimal dilutions of secondary antiglobulins and the AP-A-AP reduce non-specific binding in the amplified ELISA. The amplified ELISA is capable of detecting 2.4 ng of antibody to ovalbumin in a one: one million dilution of rabbit serum with high reproducibility and low background.

Animals↗
PubMed1990

An ELISA employing a Haemophilus influenzae type b oligosaccharide-human serum albumin conjugate correlates with the radioantigen binding assay.

An ELISA measuring total Ig antibodies to the capsular polysaccharide of Haemophilus influenzae type b (HbPs) in human sera using an antigen composed of Haemophilus b oligosaccharides conjugated to human serum albumin (HbO-HA) was shown to have an excellent correlation to the radioantigen binding assay (RABA). When 214 sera with different anti-HbPs levels were assayed for total Ig by HbO-HA ELISA and by RABA the correlation coefficient was 0.917 and the paired t test p value was 0.575. Use of competitive ELISA employing soluble HbPs, HbO-HA and human albumin as competitors, showed that the HbO-HA ELISA was specific for antibodies to HbPs. The HbO-HA ELISA yielded reproducible results both within and between laboratories. The HbO-HA ELISA can also be used to determine the isotype of anti-HbPs antibodies by using isotype specific enzyme conjugates. The sum of the IgG, IgA and IgM HbO-HA ELISA results had excellent correlation to the RABA results (correlation coefficient = 0.976). Thus, the HbO-HA ELISA can be substituted for the classical RABA and also be utilized for quantitating the isotype of the anti-HbPs antibodies.

Adult↗
PubMed1991

An isotype-specific spot-ELISA for the enumeration of antibody-secreting hybridomas and the determination of isotype switch variants.

A solid-phase spot enzyme-linked immunosorbent assay (spot-ELISA) using rat monoclonal antibodies (MAbs) and an image-processing system is described. This isotype-specific spot-ELISA permits the enumeration of antibody-secreting cells irrespective of the specificity of the secreted antibodies. When used in combination with an ELISA, the antibody production per cell can also be evaluated. In addition, isotype switch variants, which arise spontaneously in antibody-producing cell lines, can be determined. This study compared four assays: three antigen-specific spot-ELISAs, using enzyme-conjugated polyclonal antibodies as well as rat MAbs; and an isotype-specific spot-ELISA using rat MAbs. There were no significant differences between these four spot-ELISA systems. For one tested cell line (alpha huIgA1/gamma 1), the number of antibody-secreting cells fluctuated between 60% and 95% during several passages. For the other tested cell line (alpha huIgA1/gamma 2b), the number of antibody-secreting cells decreased from 90% to 70% after several passages. The results of the spot-ELISA were in agreement with flow cytometric (FC) analysis of cytoplasmic IgG. This indicates that for these two cell lines, the synthesized IgG was also secreted into the culture fluid. Using the isotype-specific spot-ELISA, the switch frequency of five murine hybridomas (alpha huIgA1/gamma 1, alpha huIgA1/gamma 2b, alpha HRP, RIV6, MN12) was determined. The switch frequencies varied from 1/82,000 for the alpha HRP cell line to 1/660,000 for the alpha huIgA1/gamma 2b cell line.

Animals↗
PubMed1996

Quantitation of the density of cell surface carbohydrate antigens on cancer cells with a sensitive cell-suspension ELISA.

The density of carbohydrate epitopes on the surface of tumor cells is a governing factor for immune recognition and antibody-mediated targeting of tumor-associated carbohydrate antigens in cancer immunotherapy. A sensitive cell-suspension ELISA (cs-ELISA) is developed for quantitation of the functionally exposed carbohydrate epitopes on the cell surface. The factors affecting the measurement of tumor-cell surface glycoconjugates are evaluated using three human melanoma cell lines before and after exposure to various cell preservation treatments. The results of cs-ELISA are compared with the quantitative profile obtained by biochemical and flow cytometry assays. Cs-ELISA measures the density of the functionally exposed specific sugar epitopes on the surface of tumor cells, even in the presence of other similar carbohydrate antigens, provided that the monoclonal antibodies to carbohydrate epitopes are monospecific and sensitive, and that the cells are viable and present in optimal density. Of the three melanoma cell lines, M10-v and M101 expressed disialolactosyl residues of GD3 at concentrations of 5-6 pmol/10(6) cells and 2-3 pmol/10(6) cells, respectively. In both cell lines, the cell-surface GD2 was less than 1.0 pmol/10(6) cells. M24 melanoma cells expressed trace quantities (< 0.1 pmol/10(6) cells) of GD3 and GD2. Trypsinization of M10-v and M101 cells significantly reduced the cell-surface expression of GD3, suggesting GD3 loss, but increased the expression of GD2, suggesting crypticity of membrane-bound GD2. Cs-ELISA results showed that cryopreservation with 10% DMSO and irradiation at 15 krad decreased melanoma cell viability and ganglioside expression for M10-v but not M101 and M24. Formalinization did not affect cs-ELISA measurement of cell-surface carbohydrates. Cs-ELISA was used to monitor the quantity of incorporation of exogenous GD3 onto the surface of GD3-deficient M24 cells. Cs-ELISA for assessment of density of cell surface carbohydrate epitopes may be useful to characterize different types of tumors, to develop carbohydrate-based whole cell vaccines from tumor biopsies, to monitor the effects of cell preservation treatments commonly used in a whole cell vaccine preparation, and to evaluate the incorporation of a particular glycolipid (antigen or adjuvant) into glycolipid-deficient cells that are useful for carbohydrate-based active specific immunotherapy.

Antibodies, Monoclonal↗
PubMed1987

Evaluation of ELISA for the diagnosis of paragonimiasis westermani.

Possible applicability of an enzyme-linked immunosorbent assay (ELISA) for the diagnosis of paragonimiasis westermani was examined using crude extract of adult Paragonimus westermani (Pw) as the test antigen. The mean ELISA values of the sera from Pw egg-positive cases and from clinically suspected cases were more than 22 times higher than that of the healthy control. No, or only marginal, cross-reactivity was observed against Pw antigen using sera from patients with various parasitic diseases other than paragonimiasis, except that from schistosomiasis and clonorchiasis cases. When serum samples from the endemic area were tested by ELISA and double diffusion (DD), sera from skin test (ST)-positive and DD-positive cases were all positive with ELISA, whereas approximately 19% of ST-positive but DD-negative cases were positive for ELISA. Diagnosis by ELISA values correlated well with, and seemed to be more sensitive than, that by DD test. In some definite paragonimiasis cases, the ELISA value was markedly reduced after drug-treatment with bithionol. These results suggest that ELISA is useful not only in mass screening but also in the evaluation of the efficacy of drug treatment in paragonimiasis.

Animals↗
PubMedDate not supplied

Field evaluation of the use of an ELISA to detect chloroquine and its metabolites in blood, urine and breast-milk.

The evaluation of an enzyme-linked immunosorbent assay (ELISA) for chloroquine and its metabolites in blood, urine and breast-milk is reported. ELISA blood levels, following standard treatment with chloroquine of pregnant and non-pregnant women, showed mean values comparable to other analytical methods. Blood chloroquine concentrations were estimated at day 0, 350-400 ng/ml; day 2, 1000-1500 ng/ml; day 14, 350-400 ng/ml; day 28, 180-350 ng/ml. In a separate sample a significant association was observed between history of chloroquine use in the previous 2 weeks and blood ELISA values (P less than 0.01). Mean ELISA values in breast-milk were higher than in corresponding whole blood samples. High concentrations of chloroquine in urine were observed. There was a weak association of the ELISA of urine and blood samples collected at the same time (P = 0.076). This study confirms the low sensitivity (less than 55%) of the Dill-Glazko test in urine, which is 100-1000 times less sensitive than the ELISA; the latter can detect 10-20 ng chloroquine per ml. A cut-off value for blood positivity 2 weeks following therapeutic drug ingestion was determined (40% ELISA inhibition), which can be used to make decisions about subject selection in drug sensitivity tests or population surveys. There are several advantages with the ELISA under field conditions. These include direct measurement of whole blood concentration; avoidance of problems of urine collection; suitability of finger-prick samples, especially with young children; application to population surveys to monitor drug use; and selection of subjects for drug sensitivity tests and monitoring of blood levels during in vivo tests.

Chloroquine↗
PubMed1988

Measurement of IgG blocking antibody in human serum: comparison of ELISA with monoclonal antibody and fluorogenic substrate and Staphylococcus protein A solid-phase RIA.

We compared ELISA with mouse monoclonal antihuman gamma-chain antibody and a fluorogenic substrate with the Staphylococcus protein A solid-phase radioimmunoassay (SPRIA) in the measurement of specific IgG antibody to short ragweed pollen. Sera from 51 ragweed-allergic patients undergoing allergen immunotherapy were evaluated for ragweed-specific IgG antibodies with the same ragweed extract in the two assay systems. With optimal conditions, the ELISA and SPRIA displayed comparable positive thresholds (approximately 1 ng/ml of ragweed-specific IgG). Both assays also demonstrated consistently parallel dilution curves with 51 sera (mean interdilutional coefficient of variation [CV] less than 8.8% for ELISA and less than 8.6% for SPRIA). Reproducibility was determined by constructing precision profiles for intra- and interassay variations over the working ranges of each assay (ELISA, 0.8 to 100 ng/ml; SPRIA, 1 to 250 ng/ml). ELISA intra-assay CVs ranged from 13% near threshold to less than 5% at higher antibody concentrations; SPRIA intra-assay CVs ranged from 4.3% to 2.8%. Interassay reproducibility was somewhat better for SPRIA (4.6% to 9.6%) than for ELISA (10% to 18%). In direct comparison, 41 (80%) of the 51 sera were concordant in the two assays (r = 0.91; p less than 0.001). Although each assay result was reproducible, 10 (20%) of the sera elicited consistently discrepant results in the two assays. In eight of the 10 discordant sera, the SPRIA results were higher than ELISA, suggesting the possibility that some ragweed allergen may be better represented on the short ragweed-pollen extract agarose than on ELISA plate wells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies↗
PubMed1984

Nitrocellulose-enzyme-linked immunosorbent assay (NC-ELISA) - a sensitive technique for the rapid visual detection of both viral antigens and antibodies.

A modification of the enzyme-linked immunosorbent assay (ELISA) is described for sensitive and rapid direct visual detection of antigens of four adenoviruses (Ad) and anti-Ad antibodies using nitrocellulose (NC) membrane discs as high-capacity solid phase. The NC-ELISA was performed in microtitre plates containing NC-discs. Small amounts of crude supernatants from Ad-infected cells as antigen were bound to the discs. Additional binding capacity was blocked with an excess of bovine serum albumin. The subsequent reaction of virus antigen with specific rabbit antibody was visualized using alkaline phosphatase-conjugated anti-rabbit IgG and histochemical substrates. The sensitivity of the NC-ELISA for the detection of Ad-antigens was found to be 8-10-fold higher than a conventional ELISA using polystyrene solid phase supports. The sensitivity levels were estimated to be similar comparing NC-ELISA and tissue culture assay results. The quantitative determination of anti-Ad antibodies by NC-ELISA showed 8-fold higher sensitivity compared to microneutralization test. The NC-ELISA could detect purified immunoglobulin at a level of 1 ng using a direct test procedure and 10 ng using the indirect method. The detection limits are good compared to other highly sensitive assays. The use of crude antigen combined with high sensitivity and easy technical performance makes the NC-ELISA useful as a tool for rapid viral diagnosis.

Adenoviridae Infections↗
PubMed1986

Improved ELISA for the detection of adenovirus antigen in faeces extracts by the biotin/streptavidin interaction.

Two enzyme-linked immunosorbent assays for detection of adenovirus antigen in faecal extracts have been established. A conjugate of rabbit anti-(human) adenovirus immunoglobulin and horseradish peroxidase (HRP) prepared by means of a hetero-bifunctional reagent, N-succinimidyl-3-(2-pyridyldithio) propionate (SPDP), was used in the conventional ELISA, and a biotin-labelled antibody in combination with a streptavidin/peroxidase complex in the other (BS-ELISA). A collection of 60 faecal extracts, in which adenovirus had been demonstrated by immunosorbent electron microscopy (ISEM) in 29 samples, was selected and examined by ELISA and BS-ELISA. The presence of adenovirus was demonstrated in 38 (63%) of the samples by BS-ELISA compared to 34 (58%) by ELISA, showing the advantage of the biotin/streptavidin system for setting up ELISA assays. Comparison of the three different techniques showed that the biotin/streptavidin (BS-ELISA) is the most sensitive assay for detection of adenovirus antigen in faecal samples.

Adenoviruses, Human↗