Comparative evaluation of the commercial Sevatest ELISA immunoenzyme set and other serological tests for detecting Toxoplasma gondii antibodies

This work analyzes the results of 4 serologic tests used for the diagnosis of toxoplasmosis: the complement fixation (CFT), indirect immunofluorescence (IIF), passive hemagglutination (PHAT) tests, and the enzyme-linked immunosorbent assay (ELISA). The last-mentioned one was made with the use of the commercial kits Sevatest ELISA IgG/Toxo Micro I. The results of ELISA were in good correlation with those yielded by the traditional tests: 70% coincidence with CFT, 80% with IIF, 84% with PHAT; besides, ELISA has shown a higher sensitivity in the screening of sera.     

Use of solid-phase immunoenzyme analysis for the serodiagnosis of pseudotuberculosis

The diagnostic test system based on the solid-phase enzyme immunoassay (EIA) for the detection of antibodies to Yersinia pseudotuberculosis in the sera of patients with the use of Soviet-made preparations and reagents has been developed. The test has been performed in microchambers for immunological reactions, thus making it possible to decrease the consumption of reagents 10-20 times in comparison with the traditional technique with the use of plates. The results of the titration of 42 sera in EIA and in the passive hemagglutination test (PHAT) are indicative of the presence of positive correlation (r = 0.78; p less than 0.05) between antibody titers in EIA and PHAT. A fourfold or greater increase in antibody titers has been determined by means of EIA in 80% of cases and with the use of PHAT in 55% of cases. The minimum diagnostic titer yielded by EIA has been determined: 1:256.     

Use of the indirect hemagglutination reaction in studying ornithosis infection. III. The diagnostic value of the IHR with an ornithosis erythocytic diagnosticum]

In both experimental and clinical conditions the passive hemagglutination test (PHAT with the use of an ornithosis erythrocytic diagnostic preparation was found to be sufficiently sensitive and specific as compared with the complement fixation test (CFT), a routine testing method. The study of the dynamics of immune response in infected animals and ornithosis patients allowed to regard the PHAT as a comparatively early method of serological analysis. Hemagglutinins were also found to circulate in the patients' blood sera only for a short time (on the average for 1 1/2--2 months). The CFT and the PHAT with erythrocytic diagnostic preparation, used in combination, will make it possible not only to diagnose ornithosis in patient more effectively, but also to differentiate between the cases of infection and anamnestic reaction.20     

Use of the immunofluorescence reaction for evaluating the immunological transformation in those inoculated with a chemical typhus vaccine

The results of the serological examination of persons immunized with chemical typhus vaccine (CTV) are presented. The examination was carried out by means of the complement fixation test (CFT), the passive hemagglutination test (PHAT), the toxin neutralization test (TNT) and the immunofluorescence test (IFT). The acetone-fixed live culture of Rickettsia prowazekii, strain Breinl, served as antigen in IFT. If persons immunized with CTV showed positive titers in CFT, TNT and PHAT, the results of IFT were highly correlated with the CFT titers. In 6-12 months after immunization with CTV the titers of CFT, TNT and PHAT became negative, while the IFT titers remained positive for several subsequent years.     

A trial application of the latex test for evaluation of antibody level in rabbit immune sera]

A latex test was elaborated which served for evaluation of quality of rabbit immune sera for antigen 0 of selected Gram-negative bacteria. Sensitivity and specificity of this test in comparison with passive hemagglutination and immunoenzymatic DOT-ELISA reactions was evaluated. These studies were performed on immune sera for antigen O of Salmonella groups B, C1, C2, D and E, Yersinia pseudotuberculosis and in antigen preparations for above listed microorganisms both in homologous and heterologous systems. It was found that sensitivity of the latex test is 9 to 160 times lower than that of passive hemagglutination and 7 to 307 lower than for DOT-ELISA. Sensitivity of the latex test and passive hemagglutination reaction was evaluated on the basis of results of cross reaction between studied antigens and unabsorbed rabbit sera, establishing so called sensitivity indexes, which were informing how many times heterologous titer is lower than homologous titer. So evaluated sensitivity of the latex test was close to sensitivity of the passive hemagglutination reaction. It was found that slide latex test is characterized by satisfactory sensitivity and good sensitiveness and may be used for evaluation of antibody level 0 antigens of Salmonella and Yersinia. The value of this test is characterized by high repeatability of results, as well as low work and time-consuming.     

Specificity and Sensitivity of the Streptozyme Test for the Detection of Streptococcal Antibodies

A comparison between the results of the streptozyme hemagglutination test and serological titers for anti-streptolysin O (ASO), anti-hyaluronidase (AH), anti-deoxyribonuclease B (ADN-B), and anti-nicotinamide adenine dinucleotidase (ANAD) was made in two groups of human sera. In one group, serological titers for all the four antibodies were lower than the threshold of sensitization reported by the producing firm. In the second group, the titer of at least one of the four antibodies was equal to or higher than the threshold. False-positive and false-negative reactions occur with those sera when one or more antibody titer is at or near the threshold of the test as described by the manufacturer. The test was positive for all sera where either the ASO was greater than 166 or the ANAD was greater than 270, and for 98% of the sera with ADN-B greater than 360. It is, therefore, concluded that the streptozyme test can be used as an adjunct to the clinical diagnosis of streptococcal infections and their nonsuppurative sequelae. It is less useful to assess the levels of antibodies in sera from general population surveys. For such sera, the relative specificity and sensitivity of the test might yield misleading results. Until more experience is gained with the test, caution should be used in its application to infant and older adult age groups, where significant streptococcal antibody titers are frequently near the threshold of the test.     

Comparative evaluation of antibody positive titer by ELISA and IFA in Theileria annulata vaccinated cattle in Iran

An enzyme linked immunosorbent assay (ELISA) was used to evaluate antibody positive titer in vaccinated and non-vaccinated cattle using schizont infected myeloid cells as an antigen. The result was compared with indirect fluorescent antibody level in the same animals. For this study 116 milking cows, 95 vaccinated and 21 non-vaccinated, were bleeded in order to prepare sera. They were tested with both ELISA and IFA tests. 94 sera had positive antibody titer and 22 sera were negative through ELISA test but, with IFA test, only 89 sera showed positive antibody titer and 27 were negative. Thereby, it was concluded that the sensitivity and specificity of ELISA test in comparison with IFA test was 95.5% and 66.6% respectively. This study generally indicated that ELISA could be an effective test for sero-epidemiological investigations of bovine tropical theileriosis, and it is considered to be valid as an additional test to distinguish the vaccinated from the non vaccinated cattle in order to schedule vaccination programs.     

A new capture test using conjugated peptides for the detection of HIV antibodies.

A new capture test utilizing conjugated peptides has been developed for the detection of antibodies elicited against HIV-1. Human sera diluted 1:1000 were incubated in ELISA plates precoated with protein G. The captured IgG were allowed to react with three synthetic peptides corresponding to the gp41 sequence (591-611) YLKDQQLLGIWGCSGKLICTT, the gp120 sequence (314-329) IRIQRGPGRAFVTIGK and the p27 sequence (182-198) EWRFDSRLAFHHVAREL. The peptides were used in the form of N-hydroxysuccinimido-biotin ovalbumin conjugates. Peroxidase-labelled streptavidin was used to detect antigen-antibody complexes. The sensitivity and specificity of detection of antibodies were analyzed with 40 HIV positive sera, 10 seroconverting sera and 21 normal human sera (NHS). The results were compared with a commercial indirect ELISA in which a single conjugated gp41 peptide was used as antigenic probe. This indirect ELISA recognized 100% of the HIV positive and the seroconverting sera. The new capture test using the gp41 conjugated peptide also recognized 100% of the HIV positive sera but was more specific since it gave no false positive results whereas the indirect test did. The gp120 and p27 conjugated peptides detected 35/40 (87.5%) and 31/40 (77.5%) of HIV positive sera respectively and also detected 9/10 (90%) and 10/10 (100%) of the seroconverting sera respectively, without any false positive results (0/21). The proposed new capture test is a very sensitive and specific assay for detecting HIV antibodies.     

A new capture test using conjugated peptides for the detection of HIV antibodies

Abstract A new capture test utilizing conjugated peptides has been developed for the detection of antibodies elicited against HIV-1. Human sera diluted 1:1000 were incubated in ELISA plates precoated with protein G. The captured IgG were allowed to react with three synthetic peptides corresponding to the gp41 sequence (591–611) YLKDQQLLGIWGCSGKLICTT, the gp120 sequence (314–329) IRIQRGPGRAFVTIGK and the p27 sequence (182–198) EWRFDSRLAFHHVAREL. The peptides were used in the form of N -hydroxysuccinimido-biotin ovalbumin conjugates. Peroxidase-labelled streptavidin was used to detect antigen-antibody complexes. The sensitivity and specificity of detection of antibodies were analyzed with 40 HIV positive sera, 10 seroconverting sera and 21 normal human sera (NHS). The results were compared with a commercial indirect ELISA in which a single conjugated gp41 peptide was used as antigenic probe. This indirect ELISA recognized 100% of the HIV positive and the seroconverting sera. The new capture test using the gp41 conjugated peptide also recognized 100% of the HIV positive sera but was more specific since it gave no false positive results whereas the indirect test did. The gp120 and p27 conjugated peptides detected 35/40 (87.5%) and 31/40 (77.5%) of HIV positive sera respectively and also detected 9/10 (90%) and 10/10 (100%) of the seroconverting sera respectively, without any false positive results (0/21). The proposed new capture test is a very sensitive and specific assay for detecting HIV antibodies.     

Reiter protein complement fixation test; a preliminary comparison of the TPI test with the complement fixation test employing a soluble protein antigen derived from the Reiter strain

A comparative study of the specificity of the Reiter protein complement fixation (RPCF) test and the Treponema pallidum immobilization (TPI) test on 180 sera showed that the results in 178 instances or 98.9 per cent were in agreement. The sensitivity of the RPCF test, when compared to the TPI test, on 189 sera from patients known to have syphilis was in agreement in 182 or 96.3 per cent, assuming a correlation exists between positive TPI and both the "reactive" or "weakly reactive" RPCF test results. As to reproducibility of results, the RPCF test results agreed in 84 of the 87 sera tested (95.4 per cent). The sera were tested at least three times on different days. Anticomplementary reactions were observed in three of 91 normal sera.     

Comparative evaluation of methods for detecting HBsAg in sera

The results of the analysis of 1209 serum samples, made with a view to detecting those containing HBsAg, are presented. This analysis was made by the radioimmunoassay (RIA) on a polyethylene film, by the standard RIA technique with the use of a diagnostic kit obtained from Abbott Laboratories (USA) and by the passive hemagglutination (PHA) test. The RIA film technique was found to have the sensitivity of about 2 ng/ml HBsAg, which is similar to the sensitivity of the kit from Abbott Laboratories and exceeds the sensitivity of the PHA test approximately 50-fold. The percentage of detected HBsAg-positive sera, yielded by analysis with the use of the RIA film technique and the standard RIA technique, is the same. The RIA technique make it possible to detect more positive sera than the PHA test by about 2.5%.     

A comparison of neutralization tests for the detection of antibodies to Herpesvirus simiae (monkey B virus)

Neutralization tests used in one laboratory in the USA and one laboratory in England to detect antibodies to Herpesvirus simiae have been compared. Complete concordance in results was obtained with 53 (90%) of 59 monkey sera. The remaining six sera all had titers no greater than 1:3. Four were positive only in the American test, and two were positive only in the British test. The importance of using complement if maximum sensitivity is to be achieved in detecting antibodies to this virus has been confirmed.     

The development of an enzyme-linked immunosorbent assay for Trypanosoma vivax and its use in a seroepidemiological survey of the Eastern Caribbean Basin

An enzyme-linked immunosorbent assay (ELISA) for IgG antibodies against a South American (New World) strain of Trypanosoma vivax was developed and used for mass screening of cattle from 20 islands in the Eastern Caribbean Basin. The sensitivity and specificity of antigens prepared from a bovine-derived field strain and a murine-adapted laboratory strain of T. vivax, both of New World origin, were compared using an indirect fluorescent antibody (IFA) test, and an antigen prepared from the murine-adapted strain was subsequently used to develop an ELISA test. The results of the ELISA test were then compared with the results of a concurrently run IFA test. There was no cross-reactivity with either test using serum from a Trypanosoma theileri-infected cow. Both tests were weakly cross-reactive with sera from a T. brucei-infected steer, and the IFA test was moderately cross-reactive with several serum samples from a T. evansi-infected steer. For bovine sera collected from herds on islands in the Eastern Caribbean region, only five of 640 tested positive with the ELISA test. Thirty five of 653 sera tested were positive by IFA although the fluorescence elicited was weak as compared to that elicited by sera from known infected animals. Sera collected from 27 cattle in a region known to be free of T. vivax (OH, U.S.A) were negative with the ELISA test, whereas seven of 30 sera from a herd in French Guiana known to be infected with T. vivax were positive.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development and evaluation of Leishmania infantum rK26 ELISA for serodiagnosis of visceral leishmaniasis in Iran

The purpose of this study was to prepare recombinant K26 antigen from Leishmania infantum and evaluate its performance by enzyme-linked immunosorbent assay (ELISA) test for serodiagnosis of visceral leishmaniasis (VL) in endemic regions of Iran. The results were compared with those obtained by direct agglutination test (DAT) and whole cell ELISA using crude parasite antigen. Of 93 sera from patients with confirmed VL, 90 sera were positive with rK26 ELISA (sensitivity=96.8%), whereas 85 sera were positive with DAT (sensitivity=91.4%) and 89 sera were positive with whole cell ELISA (sensitivity=95.7%). Of 130 subjects who either had other infectious diseases (n=30) or were healthy (n=100), rK26 ELISA were negative in all cases (specificity=100%), whereas DAT were negative in 116 cases (specificity=89.2%) and whole cell ELISA was negative in 114 cases (specificity=87.7%). The results of this study indicate that the rK26 ELISA is more sensitive and specific than conventional methods and could be used for reliable diagnosis of VL caused by Leishmania infantum.     

Non-symmetric score matrices and the detection of homologous transmembrane proteins

Given a transmembrane protein, we wish to find related ones by a database search. Due to the strongly hydrophobic amino acid composition of transmembrane domains, suboptimal results are obtained when general-purpose scoring matrices such as BLOSUM are used. Recently, a transmembrane-specific score matrix called PHAT was shown to perform much better than BLOSUM. In this article, we derive a transmembrane score matrix family, called SLIM, which has several distinguishing features. In contrast to currently used matrices, SLIM is non-symmetric. The asymmetry arises because different background compositions are assumed for the transmembrane query and the unknown database sequences. We describe the mathematical model behind SLIM in detail and show that SLIM outperforms PHAT both on simulated data and in a realistic setting. Since non-symmetric score matrices are a new concept in database search methods, we discuss some important theoretical and practical issues.     

Evaluation of the Qualitative and Automated Quantitative Microhemagglutination Assay for Antibodies to Treponema pallidum

Qualitative and quantitative microhemagglutination assays for antibodies to Treponema pallidum (MHA-TP) were performed on 314 syphilitic and 597 presumably nonsyphilitic sera, and the results were compared with those of the fluorescent treponemal antibody-absorbed (FTA-ABS), the Treponema pallidum immobilization (TPI), and the Veneral Disease Research Laboratory (VDRL) tests. MHA-TP sensitivity was similar to that of the other tests in all stages of syphilis except primary syphilis, in which MHA-TP reactivity was only 64% compared with 82% in the FTA-ABS test, 73% in the VDRL test, and 67% in the TPI test. MHA-TP specificity was satisfactory and comparable to that of the other treponemal tests. Quantitation of the MHA-TP test was automated by use of Autotiter II equipment. Titers tended to become elevated later in the course of syphilis and to remain elevated longer than did VDRL titers. Reproducibility of the quantitative MHA-TP test was satisfactory, with duplicate tests agreeing within one doubling dilution on 97.5% of 351 reactive sera. Poor reproducibility was obtained with sera giving minimal reactions in the qualitative test, and such sera should be routinely retested. The MHA-TP is less time-consuming and costly than the FTA-ABS test and could be used in conjunction with the VDRL or another reagin test for syphilis to eliminate a large number of the FTA-ABS tests now required.     

Serodiagnosis of extrapulmonary tuberculosis by enzyme-linked immunosorbent assay (ELISA)

Antibodies against Mycobacterium tuberculosis antigenic glycolipids were determined by enzyme-linked immunosorbent assay (ELISA). The 720 sera were collected from adult patients under investigation, suspected with extrapulmonary tuberculosis. The test performance was estimated according to definitive diagnosis in terms of specificity, sensitivity, positive predictive value and negative predictive value. These parameters calculated on 142 sera from patients with extrapulmonary tuberculosis and on 578 sera from patients with different nontuberculosis diseases were 92%, 81.6%, 70.9% and 95.1%, respectively. The specificity decreased to 85% when tuberculosis was associated with cancer or hepatic cirrhosis. In reactivated tuberculosis the sensitivity and the positive predictive value were 86.9% and 83.3%, respectively. Our results showed that ELISA was conclusive for patients with active tuberculosis, before the initiation of the treatment. The sensitivity decreased to 30% in inactive forms. It was demonstrated that ELISA was positive in cases with negative microscopy genitourinary tuberculosis. ELISA could be used as a supporting test in the laboratory diagnosis of active extrapulmonary tuberculosis in adults, disregarding the site involved.     

Carbon immunoassay--a simple and rapid serodiagnostic test for feline toxoplasmosis

A serodiagnostic test, simpler and more rapid to perform than traditional methods, was sought to identify Toxoplasma gondii antibody in research cats. The reliability and sensitivity of the direct and indirect carbon immunoassay (CIA) tests were compared to each other and to the indirect immunofluorescent antibody (IFA) test. The three tests were used to detect the presence or absence of T. gondii antibody in the sera of 94 cats. The results of this study show that the CIA tests correlate with one another and the IFA test nearly 99%, indicating they are highly reliable. Comparison of titers of the positive sera indicate a high degree of sensitivity as well.     

Report of a new radioimmunologic technic for the assay of HBs antigen

We tested a new radiometric assay (Hépatube Wellcome) using a complete automatic device, in hepatitis B surface antigen detection with I 125 marked antibody. The additional advantage of this reagent is its very long life-span (twelve weeks after the date of manufacture). The hepatube system is fully automatic, micro processor-controlled and designed to complete all washing and tracer addition steps in the hepatube test sequence after addition of the patient's sample. The results were compared in the same protocol with those obtained by the method currently used in our group (Ausria II 125). This study has been carried out on 7.589 sera or plasma samples; blood donors 5.352; medical and chirurgical patients 1.292; sera panel 87; repeated tests 367; positives and negatives control sera 421; assays ran the first day 70 The 153 positive results (2.3%) were confirmed by another assay before neutralisation. The sensitivity of both techniques was compared using a reference panel containing samples showing varying degrees of positivity, and representative of both main subtypes. We repeated the assay on this panel 2 months after issue of materials and again 3 months later. This new system is more sensitive than Ausria II 125. Of 6 644 patients the false positive was found in 1,1% of the cases, this was superior to the results found with Ausria II 125 but there is no false negative with this new method. There was no difference when serum or plasma was used.     

A comparison of enzyme-linked immunosorbent assay (ELISA) with the toxin neutralization test in mice as a method for the estimation of tetanus antitoxin in human sera

An enzyme-linked immunosorbent assay (ELISA) has been developed for the measurement of tetanus antitoxin in human sera as an alternative to the toxin neutralization test in mice, the currently accepted method of assay. The ELISA was found to be simple and quick to perform and required only small amounts of materials. In addition, the assay was found to give reproducible estimates of antitoxin levels and to measure antitoxin at levels as low as 0.01 IU per ml, a sensitivity similar to that of the neutralization test. Furthermore, a comparison of the results of the ELISA and the neutralization test involving 80 human sera, including sera with both high and low antitoxin levels, showed close agreement in antitoxin levels obtained by the two methods. It was concluded that ELISA was an acceptable alternative to the toxin neutralization test in mice for the measurement of tetanus antitoxin levels in human sera.