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We are developing an automated system for the simultaneous, rapid detection of a group of select agents and toxins in the environment. To detect toxins, we modified and automated an antibody-based approach previously developed for manual medical diagnostics that uses fluorescent eTag reporter molecules and is suitable for highly multiplexed assays. Detection is based on two antibodies binding simultaneously to a single antigen, one of which is labeled with biotin while the other is conjugated to a fluorescent eTag through a cleavable linkage. Aqueous samples are incubated with the mixture of antibodies along with streptavidin-coated magnetic beads and a photoactive porphyrin complex. In the presence of antigen, a molecular complex is formed where the cleavable linkage is held in proximity to the photoactive group. Upon excitation at 680 nm, free radicals are generated, which diffuse and cleave the linkage, releasing the eTags. Released eTags are analyzed using capillary gel electrophoresis with laser-induced fluorescence detection. Limits of detection for ovalbumin and botulinum toxoid individually were 4 (or 80 pg) and 16 ng/mL (or 320 pg), respectively, using the manual assay. In addition, we demonstrated the use of pairs of antibodies from different sources in a single assay to decrease the rate of false positives. Automation of the assay was demonstrated in a flow-through format with higher LODs of 32 ng/mL (or 640 ng) each of a mixture of ovalbumin and botulinum toxoid. This versatile assay can be easily modified with the appropriate antibodies to detect a wide range of toxins and other proteins.

Internationally accepted designations of antigen content for toxoid vaccines are provided by the WHO in Lf (limes flocculationis) units, based on the formation of antigen-antibody complexes. The current assay method for Lf determination involves observation of the complexes by eye, making the development of a more objective system highly desirable. Here we report a novel detection system using a laser light-scattering platelet aggregometer. The system was highly reproducible and more objective than the current method. Only three sets of duplicate data were sufficient for statistically significant determination of toxoid Lf by parabolic regression.

Immunization of BALB/c mice by horse antiserum against diphtheria made it possible to obtain IgG1 monoclonal antibodies (MoAbs) 2B7E4 specific for light chains of horse immunoglobulin (Ig). Unlike commercial preparations of anti-horse immunoglobulin antibodies, which are specific for the whole Ig molecule or its Fc-fragment, the peroxidase (HRP) conjugate of the MoAb, 2B7E4-HRP did not interact with human, mouse, rabbit, and sheep Igs, or horse albumin. The conjugate obtained was used with MoAbs against bacterial toxins and commercial horse anatoxins, as a universal reagent in sandwich enzyme immunoassay (ELISA) for bacterial toxins and anatoxins. The detection sensitivity of diphtheria toxin/anatoxin equaled 0.0005 Lf/ml; tetanus toxin and anatoxin were detected with sensitivities of 20 LD50/ml and 0.005 UI/ml, respectively. A similar sandwich ELISA for botulinum anatoxins (group measurement) allowed types A, B, and E to be detected at 0.02, 0.002, and 0.001 UI/ml, respectively; selective measurement was only possible in the case of type E anatoxin (0.001 UI/ml).

Immunoassays were developed for the simultaneous detection of staphylococcal enterotoxin B and botulinum toxoid A in buffer, with limits of detection of 0.1 ng/ml and 20 ng/ml, respectively. The toxins were also spiked and measured in a variety of food samples, including canned tomatoes, sweet corn, green beans, mushrooms, and tuna.

Blue-green algae (cyanobacteria) in tablets and capsules, which are marketed as health food supplements, were investigated for the presence of neurotoxins related to anatoxin-a. These neurotoxins, which are nicotinic agonists, were investigated using isocratic micro-liquid chromatograph-tandem mass spectrometry (micro-LC-MS-MS). The investigated compounds were anatoxin-a and homoanatoxin-a, together with their degradation products, dihydroanatoxin-a, epoxyanatoxin-a, dihydrohomoanatoxin-a and epoxyhomoanatoxin-a which were synthesized from the parent toxins. The analytes were extracted with methanol followed by isocratic chromatography on a micro C18 reversed-phase column using acetonitrile-water, 50:50 (v/v), containing 20 mm acetic acid at 30 microl min(-1). The toxins were ionized in an ionspray (IS) interface operating in the positive ion mode, where the intact protonated molecules, [M + H]+, were generated at m/z 166, m/z 168, m/z 182, m/z 180, m/z 182 and m/z 196, for anatoxin-a, dihydroanatoxin-a, epoxyanatoxin-a, homoanatoxin-a, dihydrohomoanatoxin-a and epoxyhomoanatoxin-a, respectively. These served as precursor ions for collision-induced-dissociation (CID) and diagnostic product ions for these anatoxins were identified to carry out toxin confirmation by selected reaction monitoring (SRM) LC-MS-MS analysis. Dihydrohomoanatoxin-a and a novel isomer of epoxyanatoxin-a were identified in blue-green algae tablets. This finding suggests that a potential human health hazard could be associated with the consumption of these food supplements.

For routine immunogenicity testing of traditionally produced vaccines, animal tests are required by regulatory authorities, with potency estimated in International Units. A new concept focuses on assuring immunogenicity by monitoring batch-to-batch consistency in production. This concept is used for well-defined biologicals such as hormones. Through the use of immunochemical and bio- and physiochemical techniques the traditional products can be characterised as completely as possible. Developments in in vitro methodologies offer opportunities for immunogenicity testing in vitro. This study describes the possibilities for applying the consistency concept to the traditional products, tetanus and diphtheria toxoids. The sources of variation in these products were studied by flocculation time, SDS-PAGE, biosensor analysis, gel permeation chromatography and in vitro cytokine production studies. Batch-to-batch variation was shown using these in vitro techniques. Results indicate that it is possible to apply the consistency concept in the quality control of traditional vaccines like tetanus and diphtheria toxoids.

The development of acellular pertussis vaccines has raised a number of issues relevant to the control of these products. Of particular importance is the need for robust and accurate in vitro assays for the antigen content of the vaccines which might contain up to five different antigen components, each of which needs to be independently assayed. This paper describes a simple method for the quantification of three component antigens. Because relatively high doses of purified antigens are used in those preparations, the elimination of residual toxicity is a major concern. This is achieved by genetic modification of chemical treatment. The latter results in modification of the immunological reactivity of the antigens making direct assay by such methods as ELISA ineffective. A single radial diffusion technique using polyclonal antisera for the assay of pertussis toxoid (PTxd), chemically treated filamentous haemagglutinin (FHA) and pertactin (69 kDa) has been developed. The method uses low concentrations of antisera, allowing accurate and reproducible quantification of antigen content as low as 25 microg/ml of protein for pertussis toxoid and filamentous haemagglutinin and 5 microg/ml for pertactin. Since by the addition of detergent, diffusible subunits are produced irrespective of the original physical state of the antigens, the assay is suitable for assay of these antigens after detoxification/or stabilization by chemical treatment and is able to determine the differences between preparations which have the same protein concentration but different antigenic contents. This provides a means for assuring the consistency of the antigens after detoxification/or chemical stabilization which could be used as an in-process control method for acellular pertussis vaccines., (Copyright 1998 The International Association of Biological Standardization.)

The staphylococcal enterotoxins (SEs) are capable of causing both food poisoning and a toxic shock-like illness in man. In addition, SEs are known to act as superantigens, stimulating T-cells according to their T-cell receptor Vbeta type. Relatively little is known of their antigenic determinants and how these may relate to the structure and function of the toxins. As a step in the study of these relationships, the entire molecule of SEB was synthesized in duplicate as a series of octapeptides overlapping by seven residues. This series thus represented all the potential linear epitopes of eight residues or less. The reactivity of the octapeptide series with antisera raised to purified SEB and to formaldehyde-inactivated SEB has been used to locate several antigenic sites on native SEB and to identify antigenic differences in the toxoid. Three antigenic peptides identified from the antigenic profile were synthesized and characterized. These represented amino acids 21-32, 93-107 and 202-217 of SEB. None of these peptides affected SEB-induced T-cell proliferation. However, the occurrence or absence of cross-reactivity of these peptides with antibodies to native SEB corresponds to the degree of exposure and/or the rigidity of these regions within SEB.

In two double-blind, randomized, comparative studies involving a total of 218 children, an acellular pertussis (DTPa) vaccine containing diphtheria and tetanus toxoids and pertussis components filamentous haemagglutinin (FHA), pertussis toxoid (PT), and 69 kDa outer membrane protein (69 kDa OMP) was administered as a booster to 17-month-old and 5-year-old children with a history of routine whole-cell diphtheria-tetanus-pertussis (DTPw) vaccination. The control groups in these studies received DTPw vaccine. Among 17-month-old toddlers, significantly lower proportions of DTPa vaccine recipients had local pain (7.3%), redness (14.5%) and swelling (9.1%) than DTPw vaccine recipients (23.6%, 30.9% and 23.6%, respectively). A trend toward fewer local reactions was also seen in 5-year-old children vaccinated with DTPa in private practice and public clinics although differences were not statistically significant. Fever (rectal temperature > or = 38 degrees C) was reported more frequently for DTPw vaccine recipients in both age groups. While no differences existed between groups in terms of geometric mean antibody titres (GMTs) prior to booster vaccination, anti-PT antibody GMTs were higher among DTPa vaccine recipients than among DTPw vaccine recipients after booster vaccination. The difference was statistically significant in 5-year-old subjects. Furthermore, significantly higher anti-FHA and anti-69 kDa OMP GMTs were seen in DTPa vaccine recipients in both age groups. In pre-vaccination seropositive subjects and in pre-vaccination seronegative subjects the rate of immune response to pertussis antigens was higher for DTPa than for DTPw vaccine recipients with the exception of the rate of response induced to 69 kDa OMP in 5-year-old children.(ABSTRACT TRUNCATED AT 250 WORDS)

The usefulness of cytopathic indicators for the titration of Cl perfringens beta and epsilon toxins has been investigated. Neutralization experiments with monoclonal antibodies have shown that the entities responsible for the lethal and dermonecrotic effects of Cl perfringens beta toxin preparations are identical. However, the cytopathic effects of the same preparations are caused by other entities. Therefore, titrations based upon lethal and dermonecrotic indicators of beta toxin are equally valid but those based on cytopathic effects are not. Similar experiments with Cl perfringens epsilon preparations have shown that their lethal, dermonecrotic and cytopathic activities are all caused by the same entity. It follows that all three activities can be valid indicators for toxin neutralization tests. Cell culture titrations of Cl perfringens epsilon antitoxin performed on rabbit sera at the levels of test prescribed by the European Pharmacopoeia have produced consistent results which agree closely with the dermonecrotic test. This test has, in turn, been shown to reflect the results of the mouse lethal test accurately. Titrations of cattle and sheep sera at lower levels of test have also produced results in close agreement with the in vivo test. It is concluded that cell culture titration offers a valid in vitro alternative to the use of mouse lethal and guinea-pig dermonecrotic indicators for the titration of sera generated in the course of potency tests and field trials of Cl perfringens epsilon vaccines.

Potency of sixty antitoxic unit was reached after two immunizations in 2-week intervals of rabbits and horses with 10-25 mg Taiwan cobra (Naja naja atra) venom which was detoxified by 0.125% glutaraldehyde. Now this procedure has become a routine antivenine-producing method by which snake bivalent neurotropic antivenine is produced. The stability test showed that Taiwan cobra toxoid kept at 37 degrees C for 40 days, the antigenicity increased by 24% and toxicity decreased by 10% as compared to the toxoid maintained at 4 degrees C.

On the example of production of botulin toxoids of A, B and E types the authors demon strated the expediency of using the agar gel diffuse precipitation test for preliminary assessment of the toxoid activity, instead of a more expensive and complicated antitoxin-binding test.

Structural analysis of cholera toxin by sodium dodecylsulphate polyacrylamide electrophoresis demonstrated two types of non-covalentyly linked subunits, heavy (H) AND LIGHT (L), with respective molecular weights 28000 and 800 to 9000. The H:L protein ratio was I:2, indicating that the toxin of molecular weights of in ratio was I:2, indicating that the toxin of molecular weight 84000 consists of IH and 6 or 7 L subunits, linked into an aggregate with non-covalent bonds. Choleragenoid toxoid, a natural toxin derivative, contained only the L subunits of the toxin. Reduction and alkylation cleaved the H but not the L subunit. The specific clevage of the Hsubunit by reduction appeared to yield identical half-molecules; the smaller peptide seemed to originate from non-specific degradation. The H subunit also differed from L subunits by having a higher affinity for labelling with radioactive iodine and by precipitating below PH.3-5. In immunodiffusion studies the toxin possessed antigenic determinants shared with the toxoid as well as toxin-specific determinants. Comparative analyses with purified subunit preparations revealed that the toxoid-shared determinants reside in the L-type of subunit and the toxin-specific ones in the H subunit. By precipitation-in-gel, binding to ganglioside-coated tubes, and sodium dodecylsulphate polyacrylamide electrophoresis it was demonstrated that the ability of toxin to attach to the apparent receptor ganglioside, Gm1, is similar to that of choleragenoid toxoid, and is due to the Gm1-binding ability of the L subunits. The toxin Hsubunit did not react with the Gm1 ganglisoside. The results support our previous structural model for cholera toxin, and explain the antigenic and receptor-binding properties of the toxin in terms of component subunits.

The immunological effectiveness of two batches of adsorbed DPT vaccine, the batch with the normal content of antigens (control) and the batch with the content of diphtheria and tetanus toxoids reduced to 20 Lf/ml and 5 BU/ml respectively (test batch), has been studied under the conditions of controlled trial. As a result, the reduction of the antigenic content of adsorbed DPT vaccine has been found to exert no negative influence on the immunological effectiveness of the diphtheria, tetanus, and pertussis components of this preparation under the conditions of the new immunization schedule.

The authors discuss the results of studies on the choice of highly-reproducible and sufficiently informative methods of 9-antigen standardization in a new chemical vaccine against cholera (cholerogen-toxoid); materials were collected under conditions of controlled epidemilogical trial. Titration of O-antigen in industrial batches of the preparation with the aid of precipitation in gel against standard O-cholera serum could be used for its standardization. Quantitative limits of O-antigen responsible for the formation of vibration (antimicrobial) antibodies in the persons vaccinated were found by studying the immunogenicity and reactogenicity of a number of cholerogen-toxoid batches contrast by O-antigen content described by means of the precipitation test.

P. aeruginosa adsorbed toxoid has been obtained. The stabilization of exotoxins and the content of proteases, hemolysin, lecithinase in their structure have been found to enhance the immunogenic potency of preparations which protect test animals from death caused by the experimental injections of toxins, homologous and heterologous to bacterial strains of different O-serogroups, into these animals. Antibodies neutralizing the lethal action of P. aeruginosa exotoxin have been detected in the blood sera of immunized animals.

A toxoid of erythrogenic toxin type A (ET A) was prepared by formaldehyde treatment. Already 15 min after exposure to formaldehyde in isoelectric focusing the ET A band at pH 5.2 shifted to a band at pH 4.5. In Ouchterlony double diffusion test ET A and its toxoid were found to be identical, in fused rocket immuno-electrophoresis a reaction of partial identity was seen. Formaldehyde treatment of ET A resulted in an apparent increase of electrophoretic mobility. In contrast to ET A, its toxoid is non-mitogenic, non-pyrogenic and has lost its ability to induce delayed type hypersensitivity. Binding of ET A toxoid to human peripheral lymphocytes is of the same magnitude as binding of gold-labelled ET A.

The studies described in this work have indicated that cholera enterotoxin and its components (cholerogenoid and subunit B) can be detected in amounts of 0.25, 0.28 and 0.6 microgram of protein per 1 ml, respectively, by means of erythrocytes sensitized with gangliozide-containing complex. The conditions for erythrocyte sensitization have been established. The methods of cholerogen titration in the passive hemagglutination test by means of the erythrocytic gangliozide diagnostic reagent and in Craig's skin test have been shown to correlate. Similarly, the passive hemagglutination test is supposed to be suitable for detecting other bacterial toxins interacting with gangliozides.

Cholerogen-toxoid served as a complex vaccine preparation composed of the main pathogenicity factors of cholera vibrio--cholerogen (toxoid), endotoxin and a number of exoenzymes. The preparation contains 65 +/- 7.5% of protein, 12 +/- 1.2% of reducing sugars, 7 +/- 1.2% of lipids, and 2 +/- 0.3% of nucleic acids. Analytic disc-electrophoresis in polyacrylamide gel and immune disc-electrophoresis revealed at least seven individual proteins with the serological activity in the preparation. About 70% of these constituted toxoid proper; the content of O-antigen was 22%. In the cholerogen-toxoid there were revealed seven exoenzymes of cholera vibrio; proteinase, lecithinase, lipase, DNA-ase, RNA-ase, hyaluronidase, amylase. Antibodies against proteinase, lecithinase, amylase and RNA-ase of cholera vibrio were found in the serum of rabbits immunized with cholerogen-toxoid.

The neurotoxins (seven serotypes, Mr approximately 150,000) produced by Clostridium botulinum cause the neuroparalytic disease botulism. Prophylaxis, definitive diagnosis and the only effective therapy for botulism depend, at present, on chemically detoxified form(s) of the neurotoxins, i.e. toxoids (immunogens), and the antisera raised with the immunogens. And yet, the toxoids currently used for immunization of humans and animals and for raising antibody are very crude preparations (approximately 90% impure) of the neurotoxins. Hence, the highly heterogenous toxoids were not suitable for physicochemical studies. We have detoxified a pure (greater than 99%) neurotoxin (serotype A) with formaldehyde. The native neurotoxin is composed of two subunit chains (Mr 53,000 and 97,000). The physicochemical properties of the toxoid (immunogenic in rabbits) were analyzed. The chemical modification produced inter- and intrasubunit covalent links at multiple sites and thus extensive aggregation of the neurotoxin. The secondary structure parameters (alpha-helix, beta-sheet, beta-turn and random coil) of the native protein were not significantly altered. Tertiary structure, as measured by exposure of tyrosine residues and fluorescence quantum yield of tryptophan residues, was considerably altered. The data imply that conformational (topographical) antigenic determinants may not contribute significantly to the serological property of the neurotoxin.

Choleragenoid, a nontoxic aggregate of the B subunit of cholera toxin, has been purified from concentrated culture filtrates in a single step by ion-exchange chromatography on phosphocellulose or other cation-exchange resins. This procedure is far simpler than others currently used to isolate choleragenoid and yields a preparation essentially free from nucleic acid, lipopolysaccharide, toxin, and other proteins present in the crude culture filtrates. The purified choleragenoid retained the specific receptor-binding capacity of the toxin but exhibited no enterotoxic activity by either the ileal loop assay or the skin permeability assay. This purification methods may therefore be superior to others currently used for obtaining choleragenoid for immunization or other purposes.

There proved to be a serological similarity between the antigens of the human small intestine, the stomach and the liver, and the antigens of various cholera vibrio fractions. No antigenic similarity was revealed in examination of the heart and kidney. Heterogenous antigen was found not only in the somatic V. cholerae antigen, strain 569 (B), but also in the cholerogen-toxoid obtained from it. At present it is the most widespread prophylactic preparation.

Acrylamide gel electrophoresis demonstrated that the toxin of Vibrio cholerae is comprised of three polypeptide chains, alpha, beta, and gamma, of molecular weights 24,000, 9,700, and 9,700 daltons, respectively. Amino acid sequence analysis of intact toxin indicated a molecular composition of alpha gamma beta4. Acrylamide gel electrophoresis and sequence analysis confirmed that the natural toxoid (choleragenoid) is identical to the toxin beta-chain. The alpha- and gamma-chains of the toxin are disulfide-linked (fragment A) but are noncovalently bound to the beta-chains. About 50% of the primary structure of the N-terminal portion of the beta-chain has been identified and a small segment of the D-terminus has also been characterized. Twenty residues of the N-terminal portions of the alpha- and gamma-chains have been tentativly identified. The amino acid composition of the beta-chain was determined and compared to that of the natural toxoid.

Comparative experiments were conducted on rabbits and guinea pigs; a study was made of the immunological efficacy of the toxoids with a different content of the immunizing units (IU/ml). There was revealed a regular quantitative interrelationship between the content of the IU/ml in the toxoids, the level of the antitoxin formation and the extent of protection against the experimental gas gangrene in the immunized animals.

Approximately 85 samples of injectable biological products regulated by the Center for Drugs and Biologics of the United States Food and Drug Administration were surveyed for the presence of 11 elements, namely aluminum, arsenic, barium, cadmium, chromium, lead, mercury, selenium, thallium and zinc, by flame and flameless methods of atomic absorption spectrometry and flame emission spectrometry. The range of products tested included whole blood, red cells, plasma, normal serum albumin, antihemophilic factor, and other products derived from blood; allergenic extracts including honey bee venom and house dust allergenic extracts; vaccines such as measles virus vaccine and typhoid vaccine; and tetanus toxoid. The metal concentrations found in the majority of these products were low or undetectable. The metal levels varied from manufacturer to manufacturer, product and lot-to-lot of the same manufacturer's products. House dust allergenic extracts had the highest concentrations of arsenic (2.4 ppm), cadmium (0.28 ppm), chromium (0.6 ppm) and lead (1.5 ppm) found in the study. A high zinc concentration (24 ppm) in an immune serum globulin was attributed to the zinc-containing rubber stopper in contact with the product. A range of 0.36-3.30 ppm aluminum was found for seven 25% normal serum albumin samples from seven manufacturers. Values of 8.2, 17 and 18 ppm aluminum were found in one manufacturer's 25% normal serum albumin. These aluminum values appeared to be the result of an anomaly in this manufacturer's production that has not been repeated to date.

Pertussis toxin (PT) inhibited luminol-enhanced chemiluminescence induced in rabbit peritoneal neutrophils by N'-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) at doses as low as 0.8 ng.ml-1, even in the presence of a 10-fold higher concentration of filamentous haemagglutinin (FHA). A cell-free extract of Bordetella pertussis, containing predominantly PT and FHA, suppressed the neutrophil response to fMLP. After toxoiding with carbodiimide, the inhibitory activity of the extract was abolished and an enhancement of neutrophil chemiluminescence was observed due to FHA activity. Abrogation of the chemiluminescent response of neutrophils to fMLP is proposed as a sensitive, in vitro assay for pT, and may be useful for monitoring the residual toxin activity in pertussis toxoids and for determining the anti-toxic effects of anti-PT antibodies.