The quantitative analysis of lipopolysaccharide antigen in the blood serum of patients with salmonellosis by using complement-bound liposome lysis]

Titration of group B Salmonella O-antigen in the blood sera of patients and donors was carried out by means of the complement-dependent lysis of liposomes sensitized with S. typhimurium LPS. Good correlation (r = 0.95) of the levels of S. typhimurium somatic O-antigen in the patients' sera determined by liposomal immunoassay and aggregate hemagglutination test was established. The concentration of the antigens in the tested samples was within 0.5-50 micrograms/ml. Statistical analysis of the results obtained by liposomal immunoassay techniques demonstrated differences in the distribution functions for the blood sera of patients with different diseases and of donors.     

HBs antigenemia in glomerulonephritis in children

Altogether 194 glomerulonephritis patients were examined by three methods: countercurrent immunoelectrophoresis, passive hemagglutination test, and enzyme immunoassay. Use of the most sensitive method, viz. enzyme immunoassay, has yielded the highest HBsAg detection rate: 29.1% in acute glomerulonephritis and 21.4% in chronic glomerulonephritis. This method may be recommended for the examination of glomerulonephritis patients whose sera contain HBsAg in low titers.     

Cross reactions between Staphylococcus aureus and Neisseria meningitidis

The results of the study of rabbit antisera to meningococci A, B, C in the double diffusion in gel, passive hemagglutination test and enzyme immunoassay with antigenic preparations isolated from S. aureus strains are indicative of the presence of common antigenic determinants of protein and polysaccharide nature in S. aureus and N. meningitidis.     

Effect of levamisole immunocorrective therapy on the dynamics of infectious O-antigenemia and the clinical manifestations in dysentery patients

The immunocorrecting agent levamisole decreases the duration of infectious O-antigenemia, determined in the O-aggregate hemagglutination test and in the enzyme immunoassay, essentially accelerates the progress of convalescence and considerably decreases the possibility of the prolonged relapsing course of the disease in comparison with common methods of treatment.     

The possibility of using equine serum albumin in place of bovine serum albumin and ovalbumin in radioimmunological and immunoenzyme analyses and in virological practice

Horse serum albumin has been shown to meet the requirements to protein preparations for microanalysis and thus to be suitable for use in kits of reagents for the radioimmunological determination of insulin and myoglobin, for the determination of tick-borne encephalitis virus antigen by the method of the enzyme immunoassay and for the stabilization of proteins in the hemagglutination test and the hemagglutination inhibition test.     

Erroneous information in the epidemiological surveillance of hepatitis B

False positive results obtained in the determination of the immune markers of hepatitis A by the methods of the passive reverse hemagglutination test and the enzyme immunoassay distort the course of the registration of the epidemic process and deteriorate the quality of the antiepidemic measures ensured to the population. The necessity of the standardization of available test systems is postulated.     

The immune status of children in foci of measles infection studied by an immunoenzyme method

Children immunized with live measles vaccine in the foci of measles infection varying in intensity (1-9 cases per focus) have been subjected by two methods: the hemagglutination inhibition (HAI) test and the enzyme immunoassay (EIA). As shown in this study, in most cases (98% of all blood serum samples) the correlation between the results of the HAI test and EIA is not high (r = 0.5), which is linked with the detection of a wider spectrum of antibodies in EIA. The percentage of seronegative children detected by these two methods was practically the same (4.05 and 4.4, respectively). The analysis of the results obtained in this study indicates that EIA is a more informative and sensitive method, which confirms the effectiveness of its use for the determination of the level of collective immunity.     

Comparison of the diagnostic value of methods for determining antibodies against the Salmonella group-B O-antigen

The analysis of serum samples from 124 patients with the bacteriologically confirmed diagnosis of group B salmonellosis has revealed that the specific neutralization variant of the enzyme immunoassay (EIA) makes it possible to detect IgA, IgG and IgM more effectively than the indirect EIA variant and the passive hemagglutination test.     

Enzyme immunoassay of serum testosterone.

An enzyme immunoassay of serum testosterone using the testosterone-glucoamylase complex is described. Testosterone was estimated by the enzyme immunoassay after extraction with hexan: ether (4:1) for serum from men and additional thin layer chromatographic step for serum from women. The within and between assay errors, measured as the coefficient of variation were 11.1 percent (n=8) and 12.0 percent (n=12). The sensitivity of this assay was 0.25 ng. The mean testosterone concentration (+/- SD) in 19 normal men and 4 normal cycling women were 5.3 +/- 1.8 and 0.52 +/- 0.12 ng/ml, respectively. The level of testosterone found by the present assay compared favorably with those obtained by other methods.     

Immunoenzyme method in the diagnosis of human brucellosis

The optimum conditions for the determination of specific antibodies in the sera of brucellosis patients by means of enzyme immunoassay (EIA) have been selected. The comparative study of the specificity and sensitivity of EIA and other serological tests has demonstrated that EIA has high diagnostic effectiveness in the diagnosis of acute and chronic brucellosis. The presence of direct correlation between the results of EIA and Coombs' test is observed, which is indicative of the capacity of EIA for detecting both complete and incomplete specific antibodies. It should be pointed out that in all cases the titer of specific antibodies in EIA has been found to be 5-16 times higher than in Coombs' test, the passive hemagglutination test, and agglutination test.     

Field trial of an immunoenzyme method using beta-lactamase as the monoclonal antibody marker for the capsular antigen of the plague microbe

Beta-lactamase (penicillinase) has been used as a marker of monoclonal antibodies in the enzyme immunoassay made with a view to the detection of Y. pestis capsular antigen and antibodies to it. The trial of the enzyme immunoassay with the use of the beta-lactamase conjugate in laboratories and under field conditions has revealed the advantage of this assay over hemagglutination tests commonly used for this purpose.     

Immunoenzyme analysis in a system of serologic evaluation of louse-borne typhus vaccines

The blood sera of persons immunized with different typhus vaccines have been studied in the complement fixation test, the indirect hemagglutination test and the enzyme immunoassay. The data thus obtained indicate that the enzyme immunoassay is highly sensitive and can be universally used for the determination of antibodies to Rickettsia prowazekii after primary and booster immunization with different typhus vaccines. This method detects specific antibodies both at an early period and, which is of particular importance, at a remote period after immunization (3 years later) when complement-binding and hemagglutinating antibodies are absent. This is seemingly indicative of the two-phase character of postvaccinal immunity induced by live typhus vaccine.     

Pili (fimbriae) of the causative agents of plague and pseudotuberculosis: their detection in the hemagglutination reaction, the passive hemagglutination reaction and in an immunoenzyme analysis system

Newly developed serological methods for the detection of pili in the passive hemagglutination (PHA) test with the use of immunoglobulin erythrocytic diagnosticum and in the enzyme immunoassay (EIA) with the use of specific immunoglobulins labeled with horse radish peroxidase have been found to exceed the method of detecting pili, based on the determination of their hemagglutinating activity, in sensitivity and specificity. Besides, the PHA test and EIA have proved to be capable of detecting low molecular fragments of pili, obtained by sonication and having lost their hemagglutinating activity.     

Basal level of prostaglandin D2 in rat brain by a solid-phase enzyme immunoassay

A solid-phase enzyme immunoassay for prostaglandin D2 (PGD2) was developed in which PGD2 was labeled with horseradish peroxidase. After competitive binding to the immobilized antibody between enzyme-labeled and free PGD2, the activity of the enzyme bound to the antibody was assayed fluorometrically using 3-(p-hydroxyphenyl)-propionic acid and hydrogen peroxide as substrates. The procedure allowed determinations of 3-100 pg for PGD2. The IC50 value for PGD2 in the solid-phase enzyme immunoassay was about 25 pg and the sensitivity was improved about 10 times compared to those in radioimmunoassay and in solution-phase enzyme immunoassay. The solid-phase enzyme immunoassay was applied to the measurement of PGD2 content in rat brain and thereby an octadecylsilyl silica cartridge and a reversed-phase HPLC were sequentially used for sample preparations. Heads were immediately frozen in liquid nitrogen after decapitation to avoid a postmortem formation of PGD2. PGD2 contents measured by solid-phase enzyme immunoassay correlated well with the values obtained by radioimmunoassay (r = 0.966) after raising its contents by intravenous administration of PGD2. The in vivo level of PGD2 in rat brain was extremely low but determined to be 0.11 +/- 0.03 ng/g tissue (mean +/- S.E.M.) with this enzyme immunoassay. The result was equal to the value extrapolated to zero time from the postmortem change.     

An enzyme immunoassay for secretin

A sensitive and specific enzyme immunoassay for secretin was developed with the use of enzyme-labeled antigens. Synthetic porcine secretin and its carboxy-terminal fragments (residues 11-27 and 18-27) were conjugated with beta-D-galactosidase for use in the immunoassay, and the assay method with the latter fragment (residues 18-27) linked to beta-D-galactosidase was found to be the most sensitive. The minimum amount of secretin detectable by this method was 1-2.5 pg/assay. Serum levels of secretin after intravenous injection of the peptide in rats were determined by both the enzyme immunoassay and a commercial radioimmunoassay kit. The correlation coefficient between the levels measured by the two methods was 0.984. The enzyme immunoassay could detect immunoreactive secretin levels in normal human sera, giving a value of 16.9 +/- 2.2 pg/ml (mean +/- SE of six human subjects).     

Use of monoclonal antibodies for the production of a plague antibody erythrocyte diagnostic agent

Monoclonal antibodies to Yersinia pestis capsular antigen were fixed onto the surface of formulated sheep red blood cells. The preparation thus obtained was compared with commercial antibody erythrocyte diagnosticum in the passive hemagglutination test aimed at the search for the capsular antigen in the suspensions of Yersinia pestis museum cultures and in the antigen neutralization test aimed at the search for antibodies in the sera of wild and laboratory animals having had plague. Monoclonal erythrocyte diagnosticum proved to be suitable for the detection of both the capsular antigen and antibodies. The comparison of the results of the passive hemagglutination test and the enzyme immunoassay demonstrated the presence of very close relationship between them.     

Purification of an enzyme aggregate containing 3',5'-cyclic-nucleotide phosphodiesterase and nucleotidase

Several steps of purification (octyl-Sepharose chromatography, Blue Sepharose 6B chromatography and sucrose density gradient centrifugation) led to a highly purified aggregate of the enzymes, 3',5'-cyclic-nucleotide phosphodiesterase (PDE) and nucleotidase. The purified enzyme aggregate showed an S value of 7.3 (SE +/- 0.3, n = 10). Further analysis by SDS-polyacrylamide gel electrophoresis (PAGE) revealed two proteins near 67 and 60 kDa. Dissociation of the 7.3 S enzyme aggregate showed a 3.6 S PDE form and a nucleotidase form at 4.2 S. Additionally, higher S value forms of the nucleotidase up to 17 S have been observed. Apparently, they had formed by self-association. SDS-PAGE of the 17 S nucleotidase form showed only one band at 67 kDa. This was taken as evidence for the homogeneity of the 17 S nucleotidase form and the self-association of the nucleotidase after dissociation from the 7.3 S enzyme aggregate. Furthermore, from this it could be concluded that the 67 kDa protein of the 7.3 S enzyme aggregate should be identified with the nucleotidase, and thus the 60 kDa band represents the PDE.     

Use of commercial highly sensitive tests for detecting HbsAg in healthy persons]

The study has revealed the possibility of the contamination of serum with HBsAg under laboratory conditions during its treatment and preparation for analysis, which may be the cause of false positive results of HBsAg detection by the enzyme immunoassay (EIA). Excluding the factors of contamination, the authors demonstrate the efficacy of commercial systems, such as the passive hemagglutination test system "Gorky" and the EIA systems "Gorky" and "DIAplus", for the detection of HBsAg in the blood of donors in Moscow and Tashkent.     

Recording and interpretation of the results obtained by using the ELISA Sevatest commercial immunoenzyme kit for detecting Toxoplasma gondii antibodies

The results of the repeated tests of 295 serum samples from patients, previously examined by means of enzyme immunoassay screening and traditional serological tests (complement fixation, indirect immunofluorescence, and indirect hemagglutination) and 115 serum samples from healthy donors, studied by enzyme immunoassay techniques with the use of the commercial kits Sevatest ELISA, have been analyzed. The methodological approach permitting the determination of the final titer of the serum under study, taken in a dilution of 1:800, by its optical density has been used. The mean geometric titer for the control group of donors, determined in the enzyme immunoassay, has been 1:800. This fact suggests that titers exceeding 1:1,600 should be considered diagnostically significant.     

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.