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PubMed1983

Monoclonal antibodies to cholera toxin with special reference to cross-reactions with Escherichia coli heat-labile enterotoxin.

Seventy monoclonal antibodies to cholera toxin were prepared and characterized. All were of immunoglobulin G (IgG) isotypes (39 IgG1, 29 IgG2, and 2 IgG3). A total of 61 clones produced antibody directed against the B subunit, and 9 clones produced antibodies with specificity for the cholera toxin A subunit. Among both the anti-B and anti-A antibodies, there were representatives which showed full cross-reactivity with the heat-labile enterotoxin of Escherichia coli (14 clones), others which gave partial cross-reactions (12), and still others (44) which did not cross-react. Although 24 of 25 tested anti-B monoclonal antibodies could neutralize cholera toxin, none of the 9 anti-A clones had any detectable neutralizing ability. Among the anti-B antibodies, those which cross-reacted completely with E. coli heat-labile enterotoxin all had strong cholera toxin-neutralizing capacity, whereas those with lesser or no degree of cross-reactivity varied more in their neutralizing potency. The isolation of monoclonal antibodies that distinguish between enterotoxins of different bacterial origin suggests the possibility of developing immunodiagnostic methods allowing species-specific enterotoxin detection in stools of patients with diarrheal disease.

Antibodies, Monoclonal↗

PubMed1983

An outbreak of gastroenteritis due to a heat-labile enterotoxin-producing strain of Escherichia coli.

In April 1981, an outbreak of gastroenteritis, characterized by diarrhea and abdominal cramps, occurred in 282 of approximately 3,000 personnel at a large metropolitan hospital in San Antonio, Tex. There was a significant association between illness and eating at the hospital cafeteria (P = 0.0008), but no specific food could be incriminated. Stools or rectal swabs from 54 ill individuals produced almost pure cultures of Escherichia coli. Cultures from 51 of these subjects had identical antibiotic sensitivity patterns, and 38 had the same biotype. Isolates from 45 persons were tested for production of heat-stable and heat-labile enterotoxins, using the suckling mouse and Y-1 adrenal cell assays, respectively. Of 45 isolates, 41 produced heat-labile enterotoxins, while 0 of 45 produced heat-stabile enterotoxins. Two isolates were rough, and 34 of the remaining 43 were serotype O25:H-. Two strains were O25:H+. None of the 45 strains possessed hemagglutination patterns typical of colonization factor antigens I or II. Six of seven O25:H- heat-labile enterotoxin-positive strains selected at random were piliated as seen by electron microscopy but did not agglutinate with anti-colonization factor antigens I or II antisera.

Diarrhea↗

PubMed1983

Immunological relationships between cholera toxin and Escherichia coli heat-labile enterotoxin.

The antigenic relationships between heat-labile enterotoxin (LT) produced by a human strain of enterotoxigenic Escherichia coli (strain 286C2) and cholera toxin (CT) were examined by using antisera raised against LT and CT and specific antisera prepared against each subunit of both enterotoxins. Double immunodiffusion analysis revealed reactions of partial identity between the A subunits of LT and CT, as well as between the B subunits. Rabbit antisera raised against LT subunit A reacted with only subunit A, whereas rabbits immunized with LT subunit B produced antibodies which reacted with only subunit B. A high degree of CT neutralization was observed with antisera raised against LT. Data from neutralization assays with specific antisera to each enterotoxin showed that LT was more effectively neutralized by homologous anti-LT than CT (3.7-fold); however, anti-CT was only slightly more effective in neutralization of homologous CT compared with LT (1.9-fold). In contrast, antisera raised against the B subunit of CT (choleragenoid) exhibited significantly higher neutralization activity against CT than LT (5.8-fold); however, the amount of CT neutralized by anticholeragenoid was less (4.1-fold) than anti-CT. These results suggested that anti-CT serum contained neutralizing antibodies reactive with a shared determinant formed by interaction of the A and B subunits, whereas anti-LT and anti-choleragenoid sera did not. Sensitive solid-phase radioimmunoassays were developed to examine the affinity and degree of specificity involved in homologous and heterologous antigen-antibody interactions between LT, CT, their subunits, and specific antibodies. Only unlabeled LT competed with radiolabeled LT in polystyrene tubes coated with anti-LT, and only unlabeled CT competed with radiolabeled CT in tubes coated with anti-CT. However, when radiolabeled CT was incubated in tubes coated with anti-LT, competitive inhibition responses were observed with both unlabeled toxins. When radiolabeled LT was incubated with tubes coated with anti-CT, competitive inhibition responses were observed with both unlabeled toxins. Similar competitive inhibition responses were observed with the A subunits of LT and CT and with the B subunits using antisera specific for the subunits of each enterotoxin. Double immunodiffusion analysis and radioimmunoassay data supported the presence of unique and shared immunodeterminants in each subunit.

Antigen-Antibody Complex↗

PubMed1984

Identification, purification, and some physicochemical properties of staphylococcal enterotoxin C3.

A third staphylococcal enterotoxin C (C3) has been identified, purified, and characterized. Staphylococcal enterotoxin C3 was identified from a Staphylococcus aureus isolated received from England. The purified toxin was determined by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be a simple protein with a molecular weight of 26,900. The isoelectric point of the major band was determined by isoelectric focusing in polyacrylamide gels to be 8.15. The reaction of enterotoxin C3 with its specific antibody was not affected by tryptic digestion at pH 8.0 or peptic digestion at pH 4.5. The enterotoxin C3 consisted of 236 amino acid residues. Serine was shown to be the NH2-terminal amino acid residue by end group analysis. The protein was highly emetic in cynomolgus monkeys both per os and intravenously.

Amino Acids↗

PubMed1987

Fluid accumulation in infant mice caused by Vibrio hollisae and its extracellular enterotoxin.

Vibrio hollisae, a halophilic bacterium isolated from patients with diarrhea, was examined for virulence factor production. Intragastric administration of 2 X 10(7) CFU per mouse elicited fluid accumulation which peaked at ca. 6 h postchallenge in infant mice. An enterotoxin which elongated Chinese hamster ovary (CHO) cells was detected in extracts of infected-mouse intestines and in culture fluids from various growth media. The yield of the enterotoxin was maximal beginning at the onset of the stationary phase of growth in heart infusion broth supplemented with 0.5% NaCl. A concentrated preparation obtained by ammonium sulfate precipitation of culture supernatant fluids induced intestinal fluid accumulation which peaked at 2 h postchallenge in infant mice. The abilities of the enterotoxin preparation to elongate CHO cells and to elicit fluid accumulation in infant mice were inseparable by gel filtration, isoelectric focusing, and hydrophobic interaction chromatography. The enterotoxin has a molecular weight of ca. 33,000 by gel filtration and an isoelectric point of ca. 4 and is sensitive to heat.

Animals↗

PubMed1990

Enterotoxin and cytotoxin production by enteroinvasive Escherichia coli.

It has long been suspected that besides their ability to invade enterocytes, enteroinvasive Escherichia coli (EIEC) strains have the ability to elaborate an enterotoxin. We tested 35 EIEC strains for cytotoxins and 9 (1 per serogroup) for enterotoxins. All 35 strains exhibited low levels of Vero cell cytotoxins that are immunologically and genetically distinct from Shiga-like toxin I or II of enterohemorrhagic E. coli. Sterile supernatants and cell lysates of two EIEC strains were tested in rabbit ileal loops, and both stimulated moderate fluid accumulation (circa 0.5 ml/cm) without tissue damage; secretory activity was confirmed in Ussing chambers, where these two strains and the seven others tested significantly increased short circuit current without altering tissue conductance. Curing the 140-MDa invasiveness plasmid from an EIEC strain did not diminish enterotoxin production. Culture in minimal Fe2+ medium is necessary to detect expression of the enterotoxin which is circa 68 to 80 kDa in size and is distinct from the EIEC cytotoxin.

Animals↗

PubMed1995

Prevalence and association of the longus pilus structural gene (lngA) with colonization factor antigens, enterotoxin types, and serotypes of enterotoxigenic Escherichia coli.

Human enterotoxigenic Escherichia coli (ETEC) produces a plasmid-encoded type IV pilus termed longus (for long pilus). Regardless of the geographic origins of ETEC strains, the longus structural gene lngA was found to have the highest level of association with ETEC producing colonization factor antigen (CFA) CFA/II, followed by ETEC producing CFA/I and CFA/IV. ETEC bearing the less prevalent CFA/III and putative colonization factors and ETEC negative for CFA and putative colonization factor also contained lngA-related sequences. lngA was found in a considerable number of ETEC serotypes and was more often associated with ETEC producing heat-stable enterotoxins than with ETEC producing both heat-labile and heat-stable enterotoxins or heat-labile enterotoxin alone. lngA was found more often in strains isolated from children with diarrhea than in strains from healthy children, suggesting an association with intestinal disease. We conclude that longus is a widely distributed antigenic determinant in ETEC that is highly associated with known plasmid-encoded virulence factors, namely, CFAs and enterotoxins. A longus-specific probe may be a helpful epidemiological tool to assist in the identification of ETEC.

Bacterial Proteins↗

PubMed1996

Detection of the enteroaggregative Escherichia coli heat-stable enterotoxin 1 gene sequences in enterotoxigenic E. coli strains pathogenic for humans.

The sequence of the enteroaggregative Escherichia coli enterotoxin 1 ( EAST1) gene was present in most (or all) strains of human-colonizing enterotoxigenic E. coli (ETEC) with colonization factor antigen II (CFA/II) or CFA/IV (CS6). The EAST1 gene was also strongly associated with PCF09+ ETEC or CFA/I+ ETEC elaborating heat-liable enterotoxin (and heat-stable enterotoxin I). In contrast, CFA/I+ ETEC elaborating heat-stable enterotoxin I, CFA/III+ ETEC, or CS17+ ETEC exhibited very weak or no associated. E. coli from healthy volunteers had no EAST1 gene sequence. A CFA/I+ ETEC strain (H10407) possessed multiple copies of the EAST1 gene on the CFA/I-encoding plasmid and chromosome. In one CFA/II+ ETEC strain, the EAST1 gene was present on the CFA/II-encoding plasmid. The EAST1 gene sequences of the CFA/I+ and CFA/II+ ETEC strains were identical to each other and 99.1% homologous to the reported gene sequence of enteroaggregative E. coli. The data indicate that the EAST1 gene is distributed among ETEC strains with a case of the presence of multiple copies in a single cell and that this distribution is associated with the adherence factor type.

Amino Acid Sequence↗

PubMed1973

Factors affecting the regulation of staphylococcal enterotoxin B.

Several factors which regulate the synthesis of enterotoxin B were examined in Staphylococcus aureus S-6 and in its heme-requiring mutant S-6H2. The kinetics of enterotoxin B synthesis during anaerobic growth were identical to those observed under aerobic conditions; extracellular enterotoxin accumulated in the medium during the transition between exponential and stationary phase growth. Strain S-6H2 lacked a functional electron transport system unless the medium was supplemented with heme. In a casein hydrolysate medium, the presence or absence of a functional electron transport system had no effect upon the differential rate of toxin synthesis. The repression of toxin synthesis by glucose at either pH 6.0 or 7.7 or by pyruvate at pH 7.7 occurred in the absence of a functional electron transport system, but was enhanced significantly in its presence. Thus, a functional electron transport system appears to be involved in regulating the degree of glucose and pyruvate repression of enterotoxin B synthesis.

Anaerobiosis↗

PubMed1973

Differences in the response of rabbit small intestine to heat-labile and heat-stable enterotoxins of Escherichia coli.

The response of adult rabbit small intestine to the heat-stable (ST) and heat-labile (LT) enterotoxins of Escherichia coli has been investigated by employing the ligated loop technique. Fluid accumulation was determined in relation to enterotoxin dose and duration of gut exposure. The individual responses to ST and LT differed in a characteristic manner. Onset of net fluid accumulation in response to ST appeared to be immediate even at the lowest dose tested. Onset of net fluid accumulation in response to LT was rapid at high doses but delayed at low doses. Maximum volume per length ratios elicited by ST occurred between 4 and 6 h after injection of loops over the entire range of doses tested. However, maximum ratios elicited by LT occurred no less than 10 h after injection even at low doses. Fluid accumulation elicited by LT increased in duration with increasing dose; high doses of LT producing a response which was sustained for at least 18 h. The net effect of these differences in reaction characteristics is a sharp increase in the proportion of the cumulative net secretory response attributable to LT with time. Therefore, a 6-h assay time is appropriate for the titration of ST, whereas an 18-h assay is not. The 18-h assay was found more appropriate for toxin-antitoxin neutralization studies since only LT was neutralized by anti-enterotoxin serum. LT of E. coli (swine) strain P-263 and (human) strain 334 was neutralized by antibody stimulated by enterotoxin from E. coli (human) strain H-10407. LT was labile to mild acid conditions, whereas ST was not.

Animals↗

PubMed2005

Toll-like receptor 2 mediates cellular activation by the B subunits of type II heat-labile enterotoxins.

The type II heat-labile enterotoxins (LT-IIa and LT-IIb) of Escherichia coli have an AB5 subunit structure similar to that of cholera toxin (CT) and other type I enterotoxins, despite significant differences in the amino acid sequences of their B subunits and different ganglioside receptor specificities. LT-II holotoxins and their nontoxic B subunits display unique properties as immunological adjuvants distinct from those of CT and its B subunits. In contrast to type II holotoxins, the corresponding pentameric B subunits, LT-IIaB and LT-IIbB, stimulated cytokine release in both human and mouse cells dependent upon Toll-like receptor 2 (TLR2). Induction of interleukin-1beta (IL-1beta), IL-6, IL-8, or tumor necrosis factor alpha in human THP-1 cells by LT-IIaB or LT-IIbB was inhibited by anti-TLR2 but not by anti-TLR4 antibody. Furthermore, transient expression of TLR1 and TLR2 in human embryonic kidney 293 cells resulted in activation of a nuclear factor-kappaB-dependent luciferase gene in response to LT-IIaB or LT-IIbB. Moreover, peritoneal macrophages from TLR2-deficient mice failed to respond to LT-IIaB or LT-IIbB, in contrast to wild-type or TLR4-deficient cells. These results demonstrate that besides their established binding to gangliosides, the B subunits of type II enterotoxins also interact with TLR2. Although a ganglioside-nonbinding mutant (T34I) of LT-IIaB effectively induced cytokine release, a phenotypically similar point mutation (T13I) in LT-IIbB abrogated cytokine induction, suggesting a variable requirement for gangliosides as coreceptors in TLR2 agonist activity. TLR2-dependent activation of mononuclear cells by type II enterotoxin B subunits appears to be a novel mechanism whereby these molecules may exert their immunomodulatory and adjuvant activities.

Animals↗

PubMed1973

Time of enterotoxin formation and release during sporulation of Clostridium perfringens type A.

Clostridium perfringens enterotoxin was detected intracellularly about 3 hr after the inoculation of vegetative cells into sporulation medium. The subsequent increase in intracellular enterotoxin concentration roughly paralleled but followed by 2.5 to 5 hr the increase in number of heat-resistant spores. The increase in biologically active toxin coincided with the increase in enterotoxin antigen. Enterotoxin was released from the sporangium with its lysis, concomitantly with the mature spore release.

Animals↗

PubMed1981

Structure of a naturally occurring plasmid with genes for enterotoxin production and drug resistance.

A physical map of the 117-kilobase conjugative plasmid pCG86 was constructed using electron microscope heteroduplex analysis. This plasmid carries the genes elt, for heat-labile enterotoxin, and estA, for heat-stable enterotoxin, as well as the genes for resistance to tetracycline, streptomycin, sulfonamides, and mercury. These genes were mapped using deletions and Tn5 insertions as physical markers. Analysis of a heteroduplex between pCG86 and a previously described enterotoxin plasmid (EntP307) showed a 48-kilobase region of complete homology which included the genes elt and estA. An 8.8-kilobase BamHI fragment of EntP307 carrying elt, cloned by others, was also shown to be completely homologous with pCG86. The position of elt on the fragment was verified, and it was shown to carry estA as well. A 44-kilobase region of pCG86 showed partial homology with the region of EntP307 previously shown to contain conjugal transfer genes. The gene for tetracycline resistance is carried on a stem-loop structure with the dimensions of Tn10, and the genes for the other drug resistance markers are carried on a 14.6-kilobase segment that forms an insertion loop in heteroduplexes with EntP307. These studies suggest that pCG86 arose either by recombination between an enterotoxin plasmid of incompatibility group FI, like EntP307, and a multiple resistance factor of incompatibility group FII, or by transposition into EntP307 of two transposons.

Cloning, Molecular↗

PubMed1983

Thermoactivation of a periplasmic heat-stable enterotoxin of Escherichia coli.

Strains of Escherichia coli that host a plasmid that codes for the heat-stable (ST) enterotoxin showed 160 times more extracellular enterotoxin than intracellular activity. However, when washed bacteria were sonicated and incubated at between 50 and 85 degrees C, an activity similar to that of the ST enterotoxin was detected. No such effect was present in strains lacking the plasmid, in a plasmid ST- mutant, or in chromosomal mutants that lack a cyclic AMP-linked positive regulatory system which previously were shown to yield an ST- phenotype. The thermoactivation was inhibited by iodoacetamide and N-ethylmaleimide; chloramphenicol did not affect the phenomenon. The heat-activated ST-like enterotoxin was localized in the periplasmic space. The results are discussed in relation to the export of the toxin from the periplasm to the outside of the cell.

Chloramphenicol↗

PubMed1986

Characterization of a parasporal inclusion body from sporulating, enterotoxin-positive Clostridium perfringens type A.

Inclusion bodies (IB) synthesized during sporulation and enterotoxin formation by Clostridium perfringens NCTC 8239 and 8798 were isolated and characterized. IB were isolated by disruption of sporangia by sonication in the presence of tetrasodium EDTA and phenylmethylsulfonyl fluoride. Fractionation was carried out in a linear gradient of sodium bromide, sucrose, or diatrizoate sodium. Denaturing and reducing agents were necessary to solubilize the IB. An alkylating agent was required to prevent reaggregation of the subunits. Molecular weight, compositional, and serological analyses and peptide mapping revealed strong similarities between the IB subunits and the enterotoxin synthesized during sporulation by C. perfringens. IB appear to represent the structural component where overproduced enterotoxin accumulates intracellularly. Enterotoxin-like subunits in the IB appeared to be held together by noncovalent and disulfide bonds, which were generally resistant to the action of intracellular proteases of C. perfringens, trypsin, or trypsin plus bile salts.

Amino Acids↗

PubMed1986

Nucleotide sequence of the enterotoxin B gene from Staphylococcus aureus.

The complete nucleotide sequence of the enterotoxin B gene from Staphylococcus aureus, as well as the 5' and 3' flanking regions, was determined. Starting from an ATG initiator codon, an open reading frame encoded the enterotoxin B precursor that consisted of 266 amino acids (Mr, 31,400). The 5' terminal portion of the gene encodes a signal peptide 27 amino acids long. The deduced amino acid sequence matched, with a few exceptions, the published amino acid sequence of enterotoxin B. The structural gene was flanked on the 5' side by a promoter-like sequence and on the 3' side by a palindromic structure followed by a thymine-rich region that resembled a transcription termination signal. Downstream from the entB gene were two overlapping open reading frames corresponding to 134 and 185 amino acids in the opposite orientation. The signal sequence of the enterotoxin B precursor resembled that of other secreted proteins found in other bacteria.

Amino Acid Sequence↗

PubMed1963

PURIFICATION OF TYPE B STAPHYLOCOCCAL ENTEROTOXIN.

Frea, James I. (University of Wisconsin, Madison), Elizabeth McCoy, and F. M. Strong. Purification of type B staphylococcal enterotoxin. J. Bacteriol. 86:1308-1313. 1963.-A procedure for the production and isolation of type B staphylococcal enterotoxin in yields up to 4 mg per liter of toxic culture is presented. Staphylococcus aureus S6 was grown in shake flask cultures at 37 C for 24 hr in a medium consisting of 2% Hy-Case S.F., 0.3% yeast extract, calcium pantothenate, nicotinic acid, and thiamine. Cells were removed by centrifugation and the supernatant fluid was concentrated by dialysis against polyethylene glycol. Enterotoxin was isolated from the concentrate by ethanol precipitation, gel filtration on a G-100 Sephadex column, and Sephadex-column electrophoresis. The purified toxin was identical to type B reference enterotoxin on both disc electrophoresis and Ouchterlony gel diffusion. It contained no carbohydrates, lipids, or nucleic acids, gave positive tests for protein; and contained 11.6% N. The preparation showed no coagulase, alpha-hemolysin, or deoxyribonuclease activity. Emesis in monkeys resulted when the experimental toxin was injected at the rate of 0.26 mug of N per kg of body weight.

Animals↗

PubMed1966

Effect of sodium chloride and pH on enterotoxin B production.

Genigeorgis, Constantin (University of California, Davis), and Walter W. Sadler. Effect of sodium chloride and pH on enterotoxin B production. J. Bacteriol. 92:1383-1387. 1966.-The growth and production of enterotoxin B by Staphylococcus aureus strain S-6 in Brain Heart Infusion broth with 2 to 16% sodium chloride and an initial pH of 5.1 to 6.9 was studied during a 10-day incubation period at 37 C. Growth was good at pH 6.9 and with a 16% concentration of salt, but no cells survived after 10 days of incubation at pH 5.1 and with a 16% concentration of salt. With geldiffusion technique, enterotoxin B was detected in broth with pH 6.9 and up to 10% salt or pH 5.1 and up to 4% salt. Growth and enterotoxin production were better when pH was increased and salt concentration was decreased. The dependence of toxin production on the interaction of these two factors was demonstrated.

Enterotoxins↗