Enzyme-linked immunosorbent assay for detection of type A streptococcal exotoxin: kinetics and regulation during growth of Streptococcus pyogenes

Characterization of two novel pyrogenic toxin superantigens made by an acute rheumatic fever clone of Streptococcus pyogenes associated with multiple disease outbreaks

The pathogenesis of acute rheumatic fever (ARF) is poorly understood. We identified two contiguous bacteriophage genes, designated speL and speM, encoding novel inferred superantigens in the genome sequence of an ARF strain of serotype M18 group A streptococcus (GAS). speL and speM were located at the same genomic site in 33 serotype M18 isolates, and no nucleotide sequence diversity was observed in the 33 strains analyzed. Furthermore, the genes were absent in 13 non-M18 strains tested. These data indicate a recent acquisition event by a distinct clone of serotype M18 GAS. speL and speM were transcribed in vitro and upregulated in the exponential phase of growth. Purified SpeL and SpeM were pyrogenic and mitogenic for rabbit splenocytes and human peripheral blood mononuclear cells in picogram amounts. SpeL preferentially expanded human T cells expressing T-cell receptors Vbeta1, Vbeta5.1, and Vbeta23, and SpeM had specificity for Vbeta1 and Vbeta23 subsets, indicating that both proteins had superantigen activity. SpeL was lethal in two animal models of streptococcal toxic shock, and SpeM was lethal in one model. Serologic studies indicated that ARF patients were exposed to serotype M18 GAS, SpeL, and SpeM. The data demonstrate that SpeL and SpeM are pyrogenic toxin superantigens and suggest that they may participate in the host-pathogen interactions in some ARF patients.

Invasive and noninvasive group A streptococcal isolates with different speA alleles in The Netherlands: genetic relatedness and production of pyrogenic exotoxins A and B

Streptococcal pyrogenic exotoxin A (SPE-A) and SPE-B have been implicated in the pathogenesis of severe group A streptococcal (GAS) disease. We studied 31 invasive GAS strains including 18 isolates from patients with toxic shock syndrome and 22 noninvasive strains isolated in The Netherlands between 1994 and 1998. These strains were associated with the different allelic variants of the gene encoding SPE-A. We selected endemic strains with speA-positive M and T serotypes: speA2-associated M1T1 and M22-60T12 strains, speA3-associated M3T3 strains, and speA4-associated M6T6 strains. Since speA1-positive isolates were not frequently encountered, we included speA1 strains of different serotypes. The GAS strains were compared genotypically by pulsed-field gel electrophoresis and phenotypically by the in vitro production of SPE-A and SPE-B. All strains within one M and T type appeared to be of clonal origin. Most strains produced SPE-A and SPE-B, but only a minority of the speA4-positive isolates did so. Among our isolates, speA1- and speA3-positive strains produced significantly more SPE-A than speA2- and speA4-carrying strains, while SPE-B production was most pronounced among speA1- and speA2-containing strains. There was a marked degree of variability in the amounts of exotoxins produced in vitro by strains that shared the same genetic profile. We conclude that the differences in the in vitro production of SPE-A and SPE-B between our selected strains with identical M and T types were not related to either genetic heterogeneity or the clinical course of GAS disease in the patient from whom they were isolated.

Temporal production of streptococcal erythrogenic toxin B (streptococcal cysteine proteinase) in response to nutrient depletion

The effects of various growth conditions on the production of streptococcal erythrogenic toxin B (streptococcal pyrogenic exotoxin B [SPE B]) by Streptococcus pyogenes were analyzed. SPE B was detected in broth culture supernatant fluid only during the stationary phase of growth when glucose and other potential carbon sources were depleted from the medium. Additionally, SPE B production was inhibited when the concentration of glucose in the medium was maintained. These results suggest that SPE B is secreted under conditions of starvation and may be involved in nutrient acquisition.

Kinetics and regulation of erythrogenic toxins type A and C during growth of Streptococcus pyogenes

The production of erythrogenic toxins type A (ETA) and C (ETC) is described as a function of growth kinetics. Group A streptococcal strains C 203 S and NY 5 were cultivated in yeast-peptone extract, Todd-Hewitt medium and a synthetic medium. Two main growth phases occurred during growth: a first logarithmic phase and a second linear phase. These phases were separated by a short stationary interphase caused by limitation of the amino acids L-serine and L-leucine. Maximum production of ETC was observed during the logarithmic phase, it was correlated to a high level of viable cells. ETA was produced mainly during the short stationary interphase. The production of ETC is regulated by L-isoleucine. A stagnation or reduction of the concentration of viable cells was observed during the interphase. The phosphate limitation caused during streptococcal growth induced expression of the extracellular protein phosphatase and surprisingly, of a serine proteinase activity. The association between these results and the pathogenicity of streptococci is discussed.

Production and partial characterization of monoclonal antibodies against erythrogenic toxins type A and C from Streptococcus pyogenes

Hybridoma cell lines producing monoclonal antibodies against streptococcal erythrogenic toxins type A and C were established from fusions of immunized BALB/c mice splenocytes with P3X63-Ag8.653 myeloma cells. Six MAbs recognize ETA and 11 MAbs bind to ETC. Two MAbs (designated ETA-2 and ETC-10) were produced in ascitic fluid and further characterized. ETA-2 (IgG2a) binds to ETA with an affinity constant of 1.8 x 10(10) M-1 and ETC-10 (IgG1) binds to ETC with an affinity constant of 3.5 x 10(9) M-1. The specificities of the MAbs were evaluated by ELISA and immunoblotting. Both MAbs ETA-2 and ETC-10 are useful in developing specific double-sandwich ELISAs, in which the MAbs were used as solid-phase capture antibodies for the quantitative determinations of ETA and ETC.

Correlation of antibody titres induced by vaccination with protection in mouse typhoid

The ELISA method was used to titrate the humoral immune response in vaccinated mice. When mice were given two doses of a heat-killed salmonella vaccine 6 days apart, there was a steady but low-level increase of antibody synthesis. In contrast, if a booster vaccination was administered 21 days after the primary inoculation, the anamnestic response produced a significantly greater antibody titre, rapidly reaching its peak within 10 days. Such a heightened humoral response induced in the genetically susceptible C57BL/6J mice also coincided with effective protection against an otherwise lethal challenge with Salmonella typhimurium.

Comparative antibody response to Salmonella antigens in genetically resistant and susceptible mice

The ELISA was used to titrate the antibody response in mice inoculated with salmonella antigens. The genetically resistant A/J and susceptible C57BL/6J mice were either infected with the virulent or the avirulent Salmonella typhimurium. Alternatively, they were inoculated either once or twice with the heat-killed salmonella vaccine. No appreciable difference could be detected in the relative ability of these two strains of mice to produce antibodies against the lipopolysaccharide antigens of this pathogen under these four conditions.

Staphylococcal and streptococcal pyrogenic toxins involved in toxic shock syndrome and related illnesses

Toxic-shock syndrome (TSS) is an acute onset, multiorgan illness which resembles severe scarlet fever. The illness is caused by Staphylococcus aureus strains that express TSS toxin-1 (TSST-1), enterotoxin B, or enterotoxin C. TSST-1 is associated with menstrual TSS and approximately one-half of nonmenstrual cases; the other two toxins cause nonmenstrual cases, 47% and 3%, respectively. The three toxins are expressed in culture media under similar environmental conditions. These conditions may explain the association of certain tampons with menstrual TSS. Biochemically, the toxins are all relatively low molecular weight and fairly heat and protease stable. Enterotoxins B and C, share nearly 50% sequence homology with streptococcal scarlet fever toxin A; they share no homology with TSST-1 despite sharing numerous biological properties. Numerous animal models for development of TSS have suggested mechanisms of toxin action, though the exact molecular action is not known. The toxins are all potent pyrogens, induce T lymphocyte proliferation, requiring interleukin 1 release from macrophages, suppress immunoglobulin production, enhance endotoxin shock, and enhance hypersensitivity skin reactions. The genetic control of the toxins has been studied and suggests the exotoxins are variable traits. Some additional properties of TSS S. aureus which facilitate disease causation have been clarified.

Purification and characterization of streptococcal erythrogenic toxin type A produced by Streptococcus pyogenes strain NY-5 cultured in the synthetic medium NCTC-135. Comparison with the dialyzed medium (TP medium)-derived toxin

Streptococcal erythrogenic toxin type A (ET-A) was purified from culture filtrate of Streptococcus pyogenes strain NY-5 grown in a chemically defined synthetic medium NCTC-135. We succeeded in simplifying the purification procedure, and obtained a highly purified preparation of ET-A. The purification procedure was the combination of ultrafiltration with Amicon PM-10 and YM-10 membranes, chromatofocusing with PBE-94 exchanger (pH 4.0-6.0), and gel filtration through Sephacryl S-200. The purified toxin protein showed a single band with Mr 28,000 on SDS-PAGE and had pI 5.2 on agarose IEF. HPLC chromatography pattern of the toxin revealed one symmetric peak. The result of amino acid analysis of the toxin was in accordance with that of Gerlach et al and with Weeks and Ferretti who reported the nucleotide sequence of the spe A gene. Biological activities of the purified toxin were remarkably potent. The mitogenic activity for rabbit lymphocytes and one skin test dose in rabbit were found at the lower dose of 10 pg and 1 ng of the toxin, respectively.

Physiology of the potentiation of lethal endotoxin shock by streptococcal pyrogenic exotoxin in rabbits

Streptococcal pyrogenic exotoxin (SPE) dramatically potentiates the lethal shock induced by gram-negative bacterial endotoxin. To provide further understanding of the mechanism underlying the potentiating effect, the physiological basis for the toxic synergism of the two toxins was investigated. Pretreatment of rabbits with an intravenous (i.v.) dose (10 micrograms/kg of body weight) of SPE greatly enhanced the endotoxin lethality and reduced the 50% lethal dose to less than 5 micrograms of endotoxin per kg. The SPE pretreatment dose caused severe pathophysiological changes in combination with a small i.v. dose of endotoxin (1 microgram/kg). These changes included transient hyperglycemia followed by profound hypoglycemia, elevation of the blood lipoperoxide level, and an acute increase in plasma beta-glucuronidase activity. These changes were comparable with those in animals given a large i.v. dose of endotoxin (100 micrograms/kg) alone. An injection of SPE alone did not alter any of the parameters described above. These results suggest that SPE renders rabbits more sensitive to extensive pathophysiologic effects of endotoxin, and the potentiating effect on endotoxin lethality may thus involve a general potentiation of physiologic failures. The SPE pretreatment depressed the vascular clearance of a large dose of endotoxin (100 micrograms/kg) but failed to affect that of a small dose of endotoxin (1 microgram/kg). The data suggest that the potentiating effect is not readily explained solely on the basis of the decreased clearance of endotoxin.

Nucleotide sequence of the type A streptococcal exotoxin (erythrogenic toxin) gene from Streptococcus pyogenes bacteriophage T12

The gene specifying type A streptococcal exotoxin (speA), also known as erythrogenic toxin, was cloned from the Streptococcus pyogenes bacteriophage T12 genome and analyzed by nucleotide sequencing. The speA gene consists of 753 base pairs and codes for a 29,244-molecular-weight protein. The speA gene product contains a putative 30-amino acid signal peptide, resulting in a molecular weight of 25,787 for the secreted protein. A possible promoter and ribosome-binding site are present in the region upstream from the speA gene, and a transcriptional terminator is located 69 bases downstream from the translational termination codon. The amino acid sequence of the carboxy-terminal portion of the type A streptococcal exotoxin exhibits extensive homology with the carboxy terminus of Staphylococcus aureus enterotoxins B and C1.

The gene for type A streptococcal exotoxin (erythrogenic toxin) is located in bacteriophage T12

The infection of Streptococcus pyogenes T25(3) with the temperate bacteriophage T12 results in the conversion of the nontoxigenic strain to type A streptococcal exotoxin (erythrogenic toxin) production. Although previous research has established that integration of the bacteriophage genome into the host chromosome is not essential for exotoxin production, the location of the gene on the bacteriophage or bacterial chromosome had not been determined. In the present investigation, recombinant DNA techniques were used to determine whether the gene specifying type A streptococcal exotoxin (speA) production is located on the bacteriophage chromosome. Bacteriophage T12 was obtained from S. pyogenes T25(3)(T12) by induction with mitomycin C, and after isolation of bacteriophage DNA by phenol-chloroform extraction, the DNA was digested with restriction enzymes and ligated with Escherichia coli plasmid pHP34 or the Streptococcus-E. coli shuttle vector pSA3. Transformation of E. coli HB101 with the recombinant molecules allowed selection of E. coli clones containing bacteriophage T12 genes. Immunological assays with specific antibody revealed the presence of type A streptococcal exotoxin in sonicates of E. coli transformants. Subcloning experiments localized the speA gene to a 1.7-kilobase segment of the bacteriophage T12 genome flanked by SalI and HindIII sites. Introduction of the pSA3 vector containing the speA gene into Streptococcus sanguis (Challis) resulted in transformants that secreted the type A exotoxin. Immunological analysis showed that the type A streptococcal exotoxin produced by E. coli and S. sanguis transformants was identical to the type A exotoxin produced by S. pyogenes T25(3)(T12). Southern blot hybridizations with the cloned fragment confirmed its presence in the bacteriophage T12 genome and its absence in the T25(3) nonlysogen. Therefore, the gene for type A streptococcal exotoxin is located in the bacteriophage genome, and conversion of S. pyogenes T25(3) to toxigenicity occurs in a manner similar to the conversion of Corynebacterium diphtheriae to toxigenicity by bacteriophage beta.

Phage influence on the synthesis of extracellular toxins in group A streptococci

Phage conversion of group A streptococci to produce streptococcal exotoxins was shown to occur more widely than has been previously reported. Toxigenic conversion was found in 19 newly constructed lysogenic and pseudolysogenic strains resulting in synthesis of exotoxin types A and B. Conversion was accomplished by a positive conversion effector, which was a phage characteristic expressed by the prophage and vegetatively reproducing phage. Exotoxin production was determined by the rabbit skin test and by countercurrent immunoelectrophoresis with type-specific antisera. New lysogens and pseudolysogens were constructed with strains which failed to produce at least one exotoxin type. Phages were obtained from toxigenic strains isolated from cases of scarlet fever. Conversions were consistent and repeatable; loss of the recently introduced phage was accompanied by loss of the newly acquired toxin productivity. Conversion resulted in production of additional exotoxin type or types and never affected existing toxin synthesis. Converting phages were characterized by electron microscopy and negatively stained preparations and were all found to be of morphological class B1. All phage nucleic acid was double-stranded DNA. Though similar in structure, each converting phage had a different host range, and the nine new converting phages identified here did not react with antiserum prepared against the originally reported converting phage.

Phage-host interactions and the production of type A streptococcal exotoxin in group A streptococci

The infection of Streptococcus pyogenes nontoxigenic strain T 253 with bacteriophage T12 to form lysogen T 253 (T12) resulted in the production of type A streptococcal exotoxin (erythrogenic toxin or streptococcal pyrogenic exotoxin). Two lines of evidence indicated that lysogeny per se was not sufficient to promote toxigenic conversion of strain T 253. First, a virulent mutant of phage T12, unable to form stable lysogens, was able to affect type A exotoxin production by strain T 253. An unrelated virulent phage A25 did not affect type A exotoxin production after infection of strain T 253. Second, the temperate phage H4489A, which established stable lysogens with strain T 253 did not promote type A exotoxin production. These results suggest that there is a strain specificity to the phage-host interaction which affects type A exotoxin synthesis. Additional evidence is presented which indicates that type A streptococcal exotoxin was not a structural component of phage T12.