Enzyme immunoassays for the detection of bacterial antigens utilizing biotin-labeled antibody and peroxidase biotin--avidin complex

Identification of schistosomal eggs. Description of an immunological spot assay for hatch fluid antigen

A number of parasitic worms produce large numbers of eggs which may be identified by microscopy in the excretions of the host. Alternative identification methods would be useful for epidemiological purposes and this paper describes a non-microscopical method for the demonstration of schistosomal eggs, which is based on the release of soluble material from eggs during hatching in water. Substances present in hatch fluid from Schistosoma mansoni eggs were adsorbed to nitrocellulose paper and then visualized as small stained spots using horseradish peroxidase (HRP)-labeled lectins or specific antibodies. In this way the number of living eggs present in the sample could be estimated. The method may be useful as a basis for the development of diagnostic assays.

Detection of respiratory syncytial virus in nasopharyngeal secretions by a biotin-avidin ELISA more sensitive than the fluorescent antibody technique

The presence of respiratory syncytial virus (RSV) was investigated by immunofluorescent antibody (IF) technique and by a biotin/avidin (BA) ELISA in 156 samples of nasopharyngeal secretions (NPS) obtained from infants and small children with acute respiratory disease. Of 70 RSV-IF-positive NPS, 68 were positive by BA-ELISA. Of 86 RSV-IF-negative NPS, eight were positive by BA-ELISA. BA-ELISA could detect 0.5-1.0 ng RSV-protein.

Oral administration of human serum immunoglobulin in immunodeficient patients with viral gastroenteritis. A pharmacokinetic and functional analysis

We examined the pharmacokinetics and immunological activity of human serum immunoglobulins (HSG) possessing anti-rota-virus activity which were orally administered to three children with primary immunodeficiency syndromes and prolonged gastrointestinal excretion of rotavirus. Detailed analysis of the excretion of immunoglobulins labeled with biotin or I125 revealed that approximately 50% of the recovered radioactivity was excreted in the stools over a 3-d period. Approximately half of the excreted radioactivity recovered in the stool was in a macromolecular form with immunological activity. The remainder of the recovered radioactivity was excreted in the urine as low molecular weight fragments or free iodide. In addition, immunological and chromatographic analyses revealed that the oral administration of HSG resulted in the generation of rotavirus-specific immune complexes in the gastrointestinal tract with a subsequent decrease in the presence of uncomplexed rotavirus antigen. These studies indicate that orally administered HSG can survive passage in the gastrointestinal tract in an immunologically active form, and that the oral administration of immunoglobulins with specific reactivities has potential for the prevention or treatment of gastrointestinal infections.

Comparative quantitation of abscisic acid in plant extracts by gas-liquid chromatography and an enzyme-linked immunosorbent assay using the avidin-biotin system

In this report we describe an enzyme-linked immunosorbent assay (ELISA) for the quantitation of abscisic acid (ABA) in plant extracts. A microtitration plate is coated with an ABA-protein complex. The ABA, standard or sample, is then added to each well with a limiting quantity of rabbit anti-ABA antibodies. During the following incubation period, antibodies bind either to free or to bound ABA on the plates. After washing, bound antibodies are indirectly labelled in two steps by the means of biotinylated goat antirabbit immunoglobulin-G antibodies which act as a link between rabbit anti-ABA antibodies and an avidin-alkaline phosphatase complex. The relative enzyme activity bound is measured spectrophotometrically. The detection limit of this method is 5 pg ABA and the measuring range extends to 10 ng. Gas-liquid-chromatography controls, with an electron capture detector, show a good correlation with ELISA results obtained using extracts of Lycopersicon esculentum, Nicotiana tabacum and Pseudotsuga menziesii samples purified by high-performance liquid chromatography. This provides a good argument for the accuracy of the immunoenzymatic method. The indirect labelling of antibodies, with the avidin-biotin amplifying system, should make this technique suitable for the quantitation of other plant growth substances against which specific antibodies are available.

Enzyme immunoassay inhibition assay for the detection of rat rotavirus-like agent in intestinal and fecal specimens obtained from diarrheic rats and humans

An enzyme immunoassay inhibition assay was developed to detect rat rotavirus-like agent (RVLA) or antigenically related viruses in intestinal washings and homogenates obtained from diarrheic rats and in fecal specimens obtained from diarrheic humans. In this assay, RVLA antigens in a test sample inhibited the binding of a biotin-labeled anti-rat RVLA antibody preparation to rat RVLA antigens bound to the solid phase. Intestinal washings and homogenates obtained 1 day after RVLA infection of suckling rats inhibited the binding of the biotin-labeled antibody to the solid-phase rat RVLA antigens by 76 to 100%. The inhibition was blocked by RVLA immune rat serum but not by nonimmune rat serum. Of 27 fecal specimens obtained from diarrheic humans, 6 produced disease characteristic of rat RVLA infection when inoculated into suckling rats. Four of these six specimens produced greater than 50% inhibition in the enzyme immunoassay. Fecal specimens obtained from diarrheic humans that were determined to be negative for RVLA produced an average inhibition of 9.2%. This enzyme immunoassay appears to be a useful diagnostic and research tool for the study of infections with at least one of the antigenically distinct rotaviruses.

Comparison of an avidin-biotin immunoassay with three commercially available immunofluorescence kits for typing of herpes simplex virus

An avidin-biotin complex system was compared with three commercially available immunofluorescence kits for serotyping herpes simplex virus isolates from clinical specimens. Sensitivity values showed that the Electro-Nucleonics and Immulok reagents were useful in detecting the presence of virus, whereas the predictive values showed that the Syva and Immulok reagents possessed adequate discrimination between the herpes simplex virus serotypes. The avidin-biotin complex system was equal or superior to the immunofluorescence reagents tested both in detecting herpes simplex virus antigens in cell culture and in serotyping herpes simplex virus isolates.

Rapid diagnosis of viral infections with fluorescent antisera

Viral immunofluorescence tests were performed with commercial antisera on 1046 specimens of respiratory, conjunctival corneal and dermal origin to compare the diagnostic effectiveness of direct examination by immunofluorescence with culture. The fluorescence assays were found to be highly sensitive for respiratory syncytial and measles virus in nasopharyngeal aspirates from children, but less satisfactory for other respiratory viruses. The test detected 38% of the adenovirus positives from conjunctival specimens and 67% of the combined herpes simplex virus positives from the latter 3 groups. Despite the reduced sensitivity of fluorescence for some viruses, a case is presented for more widespread use of fluorescence in routine microbiology laboratories because of its simplicity, speed and cost-effectiveness compared with culture which is labour-intensive and time consuming.

Detection of Norwalk virus antibodies and antigen with a biotin-avidin immunoassay

Biotin-avidin immunoassays (BAIs) were developed to detect Norwalk virus antigen and to measure Norwalk virus antibody. The BAI detected Norwalk virus infections by a fourfold titer rise in antibody in sera or by antigen in stool, with a sensitivity similar to or greater than that of the radioimmunoassay (RIA), and the BAI appeared to be more sensitive than the RIA for detecting antibody in single serum specimens. The BAI antigen test detected Norwalk antigen in all stools that were positive by the RIA, and in two stools negative by the RIA. Of 106 serum pairs tested by both the RIA and BAI, 94 demonstrated seroconversion, or lack of seroconversion, in both assays; 12 gave discordant results. Titers by the BAI generally exceeded those by the RIA by two- or fourfold. The BAI had advantages over the RIA in that it had added sensitivity in the detection of Norwalk antibody, was less time consuming, did not require frequent labeling of antibody, and did not have the problems associated with the use of isotopes.

Immunological relationships between Salmonella flagella and their potential application for salmonellae detection by immunoassay

Native flagella of ten Salmonella serotypes were shown to possess serotype-specific antigenic determinants as well as a multiple of common antigenic determinants, which varied in concentration. Each common antigenic determinant was shared by certain, but not all, serotypes. This has been demonstrated from agglutination and radioimmunometric assay (RIMA) results, using ten antisera raised in rabbits against purified polymeric flagellins from ten Salmonella serotypes as immunogens. The minimum detectable populations of salmonellae, as determined by RIMA varied considerably, due to variation in concentrations (and possibly types) of common antigenic determinants. However, the results demonstrated the feasibility of utilizing RIMA for the qualitative detection of salmonellae, using a mixture of only the ten antisera and 125I-labelled protein A as a general tracer. In this way, 77 different salmonellae were detected in less than 8 h after culturing in selective broth. The RIMA developed was specific for salmonellae and showed no cross-reactions with high populations of other members within the family Enterobacteriaceae.

Monoclonal antibodies to human immune interferon and their use in a sensitive solid-phase ELISA

Two stable hybridoma cell lines secreting specific antibodies against human gamma interferon (HuIFN-gamma) were established. Both monoclonal antibodies (designated as MD-1 and MD-2) belong to the IgG1/kappa subclass and neutralize the antiviral activity of natural and recombinant DNA derived HuIFN-gamma (nHuIFN-gamma and rHuIFN-gamma respectively), although MD-1 is far more effective than MD-2. MD-1 and MD-2 recognize different epitopes and do not compete with each other in binding to HuIFN-gamma as concluded from competition assays. In a 'Western' blot, both antibodies reacted with the 20 kDa and 25 kDa polypeptides present in nHuIFN-gamma preparations. A sandwich enzyme immunoassay using microtiter plates coated with unlabeled MD-2 was developed. Biotinylated MD-1 was used as the second antibody. Bound MD-1 was detected by an avidin/alkaline phosphatase enzyme reaction. This immunoassay is highly specific and as sensitive as a bioassay. A radioimmunoassay using MD-2 coated on polystyrene balls and 125I-labeled MD-1 as the second antibody showed a sensitivity comparable to that of the enzyme immunoassay.

A biotin-avidin enzyme immunoassay for the quantitation of serum ferritin

A biotin-avidin enzyme immunoassay (EIA) for measurement of ferritin in human serum is described. This procedure involves the use of specific antibody immobilized on beads, biotin-labeled specific antibody and enzyme-labeled avidin. Reproducible results were achieved within 2 h for ferritin in serum in the range of 5-500 ng/ml. Ferritin levels as low as 0.1 ng/ml can be measured. The biotin-avidin EIA, a radioimmunoassay kit, and an EIA kit were used to determine serum ferritin levels in healthy adults. Good agreement was found between the biotin-avidin EIA and the other methods.

Detection of circulating antigens in sera of rabbits infected with Toxoplasma gondii

Experiments were performed to investigate the usefulness of an enzyme-linked immunosorbent assay utilizing avidin-biotin interaction as a diagnostic tool for detection of Toxoplasma antigen in blood. The lower limit of sensitivity of the assay by this method was ca. 4 ng/ml, and standard assays provided a linear plot of antigen concentration over a range up to 250 ng/ml. In rabbits inoculated subcutaneously with trophozoites of the RH strain, Toxoplasma antigen became demonstrable in the circulation 3 days after injection, before emergence of antibody in serum and development of parasitemia. Analysis of the antigen in serum from infected rabbits by high-permeation liquid gel chromatography suggested the occurrence of antigens of four different molecular weights, greater than or equal to 400,000, 220,000, 130,000, and 45,000. Of these antigens, those of molecular weights 220,000 and 130,000 showed a conspicuous elevation with time after infection.

Antibody to human rotavirus in cow's milk

Rotavirus infection is an important cause of gastroenteritis in infants and young children. Since the virus replicates in the intestinal lumen, we investigated the presence and effectiveness of rotavirus antibody in three forms of milk: raw milk, pasteurized milk, and commercially available infant formulas. Both raw and pasteurized milk contained detectable levels of IgG1 antibody directed at rotavirus. On the other hand, little or no anti-rotavirus antibody was detected in commercially available infant formulas or other sterile milk preparations. The milk samples with rotavirus antibody were capable of inhibiting the replication of simian, bovine, and human rotaviruses in tissue culture. In addition, they were capable of protecting mice from infection and disease in a murine model of rotavirus infection. On the other hand, the formula preparations were incapable of modifying the in vitro replication of rotavirus strains in tissue culture and did not prevent symptomatic gastroenteritis in the mouse model. We conclude that the alteration of milk-processing procedures or the addition of effective antibodies to milk preparations commonly used in the nutrition of young children may alter the clinical course of rotavirus infection or decrease the transmission of rotavirus throughout susceptible populations.

Biotin-avidin amplified ELISA for quantitation of human IgA

A biotin-avidin amplified enzyme-linked immunosorbent assay (ELISA) for the measurement of human IgA in serum, colostrum, gastric juice, and supernatants of in vitro mitogen-stimulated human peripheral blood mononuclear cells is described. The ELISA reproducibly detects as little as one nanogram of IgA in a fifty microliter sample (20 ng/ml).

The use of beta-lactamase in enzyme immunoassays for detection of microbial antigens

The sensitivity and performance characteristics of enzyme immunoassays (EIA) depend to a great extent on the kinetics of the enzyme-substrate system used as indicator. We labeled a variety of polyclonal and monoclonal immunoglobulins with purified beta-lactamase and used them in sensitive EIA systems for the detection of a number of microbial antigens. Polyclonal antibodies to rotavirus, adenovirus, and Haemophilus influenzae type b polyribitol phosphate and monoclonal antibodies to dengue virus were labeled with beta-lactamase and used to provide sensitive direct EIA systems for the detection of the corresponding antigens. In addition, antibodies directed at animal immunoglobulins were labeled with beta-lactamase and used in indirect EIA for the detection of viral antigens with unlabeled anti-viral monoclonal and polyclonal antibodies. Similarly, avidin from Streptomyces was labeled with beta-lactamase and used to detect viral antigens tested for in an avidin-biotin format. Enzyme immunoassay systems with beta-lactamase-labeled antibodies were also used to detect rotaviral and adenoviral antigens in rectal swab specimens from children with acute gastroenteritis. The sensitivity of the beta-lactamase EIA compared favorably with that of analogous EIA systems using alkaline phosphatase or horseradish peroxidase. The results of a beta-lactamase EIA were easily determined by naked eye and a permanent record of the qualitative results obtained by the use of a standard office photocopier, obviating the need for an expensive colorimeter. Enzyme immunoassays using beta-lactamase have potential as practical assay systems for the detection of a wide range of microbial antigens using monoclonal and polyclonal antibodies.

Quantification of bands produced by isoelectric focusing using immunoperoxidase

An improved, rapid, and sensitive (to autoradiographic levels) method for the quantification of IgG bands from cerebrospinal fluid is presented. The principle of an internal standard is employed using the discrete bands of a paraprotein to correct for any run to run variability in the enzyme detection system which is linked to the immunoassay of immobilised antigen.

Enzyme immunoassay for detection of pneumococcal antigen in cerebrospinal fluid

A solid-phase immunoassay utilizing horse antiserum against the C polysaccharide of Streptococcus pneumoniae and biotinylated rabbit antibodies to type-specific pneumococcal polysaccharides was developed to detect pneumococcal antigens in human body fluids and in broth cultures. Pneumococcal antigen could be detected in broth cultures of serotypes of S. pneumoniae containing as little as 10(2) to 10(3) organisms per ml. The assay system detected pneumococcal antigen in all 25 cerebrospinal fluid specimens obtained from patients with documented pneumococcal meningitis. There were no positive reactions noted in specimens from patients infected with Neisseria meningitidis group A or from patients without evidence of bacterial infection. The solid-phase enzyme immunoassay utilizing these reagents is a sensitive and specific assay for the immunodetection of a wide range of pneumococcal antigens.

Biotin-labeled protein-A enzyme-linked immunosorbent assay for the detection of Japanese encephalitis antibody in sera from humans, swine and several animal species

Biotin-labeled protein-A was incorporated into enzyme-linked immunosorbent assay (ELISA) for seroepidemiological surveys of Japanese encephalitis (JE) virus infection in several vertebrates. The ELISA could detect the JE antibody in sera from man, rhesus monkey, swine, horse, dog, rabbit and mouse by the same reagent, but not in sera from cattle and pigeon. The titers of ELISA antibody were almost the same as those of 2-ME resistant HI antibody. Since non-specific reaction in ELISA was very low in the sera of swine and humans, the cut-off titer for the assay could be set at 1:5 for positive antibody.

Monoclonal antibodies reactive with all strains of Haemophilus ducreyi

We have isolated plasma cell hybridomas which secrete monoclonal antibodies directed against Haemophilus ducreyi. Two of these monoclonal antibodies recognize all strains of H. ducreyi tested to date and are capable of detecting the presence of H. ducreyi in skin lesions produced by this pathogen in experimental animals. These monoclonal antibodies which react with apparently all strains of H. ducreyi have the potential to be developed into a rapid immunodiagnostic test for chancroid.

Enzyme immunoassays in which biotinillated beta-lactamase is used for the detection of microbial antigens

The performance characteristics of enzyme immunoassays are determined to a great extent by the enzyme-substrate system utilized for the immunoassay. Beta-lactamases (penicillin amido-beta-lactamhydrolase EC 3.5.2.6) offer a number of advantages which might make them useful in immunoassay systems. We linked beta-lactamase from Bacillus cereus with biotin and used the biotinillated enzyme to devise immunoassay systems for the detection of a number of microbial antigens. An assay system in which antibodies to the polyribitol phosphate antigen of Haemophilus influenzae type b were used was capable of detecting between 0.4 and 1.6 ng of that antigen. Similarly, an assay in which antibodies to the common antigens of adenoviruses and biotin-linked beta-lactamase were used was capable of detecting between 1 and 10 50% tissue culture infective doses of a strain of enteric-type adenovirus. When applied to the detection of rotavirus, a similar system in which biotinillated beta-lactamase was used was capable of detecting small amounts of antigen in a standard rotavirus preparation. This assay could also detect virus in 36 of 37 stool specimens from children with rotavirus gastroenteritis. The positive specimens could easily be distinguished from negative ones by the naked eye, and a permanent record of the qualitative results could be obtained by the use of a standard office photocopying machine. Beta-lactamases have promise for use in practical enzyme immunoassay systems, especially in situations in which expensive colorimetric instrumentation is not available.

Biotin-avidin-amplified enzyme immunoassay for detection of herpes simplex virus antigen in clinical specimens

A biotin-avidin-amplified enzyme-linked immunosorbent assay (B-A ELISA) has been developed to detect herpes simplex virus type 1 (HSV-1) and HSV-2 antigens in clinical specimens. The test was designed as a solid-phase, double-antibody, sandwich assay in which plates were coated with a polyclonal rabbit immunoglobulin G anti-HSV reagent, and the sandwich antibody was a biotin-labeled mouse immunoglobulin M monoclonal antibody that reacts with a common antigen associated with HSV-1 and HSV-2. The test can be completed in 4 h if antibody-coated plates are available. The detection limit of the B-A ELISA, determined by titration of virus stocks, was found to be approximately 90 PFU or 6 X 10(3) physical particles of either HSV-1 or HSV-2 per 50 microliter of virus stock. The following results were obtained in a study in which swabs were taken from a variety of lesions and assayed for infectivity in tissue culture and by B-A ELISA. Of 421 suspected HSV lesions tested, 69 were positive by both tests and 159 were negative by both tests. A total of 122 were positive by B-A ELISA but negative for infectivity. Seventy-one were negative by B-A ELISA but contained infectious virus. The HSV specificity of the assay was substantiated by partial blocking of reactivity with rabbit immunoglobulin G anti-HSV and by the absence of reactivity with a nonspecific biotin-labeled mouse immunoglobulin M monoclonal antibody.