Immunological protection of rabbits infected with Staphylococcus aureus isolates from patients with toxic shock syndrome

Characterization and biological properties of a new staphylococcal exotoxin

Staphylococcus aureus strain D4508 is a toxic shock syndrome toxin 1-negative clinical isolate from a nonmenstrual case of toxic shock syndrome (TSS). In the present study, we have purified and characterized a new exotoxin from the extracellular products of this strain. This toxin was found to have a molecular mass of 25.14 kD by mass spectrometry and an isoelectric point of 5.65 by isoelectric focusing. We have also cloned and sequenced its corresponding genomic determinant. The DNA sequence encoding the mature protein was found to be 654 base pairs and is predicted to encode a polypeptide of 218 amino acids. The deduced protein contains an NH2-terminal sequence identical to that of the native protein. The calculated molecular weight (25.21 kD) of the recombinant mature protein is also consistent with that of the native molecules. When injected intravenously into rabbits, both the native and recombinant toxins induce an acute TSS-like illness characterized by high fever, hypotension, diarrhea, shock, and in some cases death, with classical histological findings of TSS. Furthermore, the activity of the toxin is specifically enhanced by low quantities of endotoxins. The toxicity can be blocked by rabbit immunoglobulin G antibody specific for the toxin. Western blotting and DNA sequencing data confirm that the protein is a unique staphylococcal exotoxin, yet shares significant sequence homology with known staphylococcal enterotoxins, especially the SEA, SED, and SEE toxins. We conclude therefore that this 25-kD protein belongs to the staphylococcal enterotoxin gene family that is capable of inducing a TSS-like illness in rabbits.

Production of toxic shock syndrome-like illness in rabbits by Staphylococcus aureus D4508: association with enterotoxin A

Staphylococcus aureus D4508, obtained from a patient with nonmenstrual toxic shock syndrome (TSS), produced enterotoxin A while not making other known enterotoxins or TSS toxin 1. Concentrated culture fluids of the organism, administered subcutaneously in miniosmotic pumps, induced TSS-like symptoms (four of six animals succumbed). Identical culture fluids pretreated with anti-enterotoxin A serum failed to induce symptoms except for fever (none of six animals succumbed). Purified staphylococcal enterotoxin A also had the ability to induce TSS-like symptoms. These data suggest that enterotoxin A is the major TSS-associated toxin made by strain D4508.

Mitogenic properties of two distinct forms of toxic shock syndrome toxin-1 separated on hydroxyapatite by high-performance liquid chromatography

The homogeneity of a purified staphylococcal toxic shock syndrome toxin-1 (TSST-1) was tested by high-performance methods. This preparation was homogenous in ion-exchange chromatography and isoelectric focusing (pI = 7.4), but was resolved into two distinct peaks by high-performance hydroxyapatite chromatography. Both components, TSST-1hA and TSST-1hB had similar molecular weights (22 kD) and amino acid compositions. TSST-1 did not dimerize or polymerize upon heating at 60 degrees C for 30 min or in solutions with pH varying from 4.0 to 8.5. TSST-1hA and TSST-1hB showed similar immunological reactivity to native TSST-1 goat polyclonal antibodies. TSST-1hA and TSST-1hB as well as staphylococcal enterotoxin A and staphylococcal exfoliative toxin were potent mitogens in lymphocyte proliferation assays. The lymphocyte proliferative response to 10 pg of TSST-1hB was comparable to a response elicited by 10 ng of TSST-1hA, suggesting that the former component is a more potent mitogen. Rabbit or goat polyclonal antibodies to native TSST-1 efficiently neutralized both TSST-1 components. Heat treatment at 80 degrees C for 15 min had minimal or no effect on the mitogenic properties of TSST-1hA and TSST-1hB.

Ovine-associated Staphylococcus aureus protein with immunochemical similarity to toxic shock syndrome toxin 1

A toxic shock syndrome toxin 1 (TSST-1) antibody-binding protein produced by an ovine-associated strain of Staphylococcus aureus was examined. The protein showed total identity to TSST-1 by immunodiffusion analysis. Western blots (immunoblots) of proteins separated by isoelectric focusing revealed that the TSST-1 antibody-binding protein had a pI of 8.6 rather than 7.0, the pI of standard TSST-1.

Determination by western blot (immunoblot) of seroconversions to toxic shock syndrome (TSS) toxin 1 and enterotoxin A, B, or C during infection with TSS- and non-TSS-associated Staphylococcus aureus

Serum antibody responses to toxic shock syndrome (TSS) toxin 1 (TSST-1) and staphylococcal enterotoxins A, B, and C were determined by western blot (immunoblot) analysis of acute- and convalescent-phase paired sera from 18 TSS- and 31 non-TSS-associated Staphylococcus aureus infections. Compared with non-TSS cases, seroconversion to TSST-1 was significantly more frequent among both menstrual (5 of 8 versus 1 of 31; P less than 0.001) and nonmenstrual (3 of 10; P less than 0.05) patients. Seroconversion to staphylococcal enterotoxin A was also more frequent among both menstrual (2 of 8 versus 0 of 31; P less than 0.05) and nonmenstrual (2 of 9; P less than 0.05) TSS patients. In general, patients with TSS associated with TSST-1-positive S. aureus were more likely to seroconvert exclusively to TSST-1 (4 of 12 versus 0 of 6; P = 0.16), whereas those associated with TSST-1-negative S. aureus were more likely to seroconvert exclusively to enterotoxins (3 of 6 versus 0 of 11; P less than 0.05). Concurrent seroconversions to multiple exoproteins were more frequent among both menstrual (3 of 8; P less than 0.05) and nonmenstrual (2 of 9; P less than 0.05) TSS patients compared with persons without TSS (0 of 31). These data suggest but do not prove that enterotoxins (especially staphylococcal enterotoxin A) in addition to TSST-1 may be involved in both menstrual and nonmenstrual TSS. Furthermore, since exposure to multiple exoproteins is more likely to occur during TSS-associated than non-TSS-associated S. aureus infections, the possibility of additive or synergistic effects of these putative toxins in the pathogenesis of TSS should be further explored.

Tissue cages for study of experimental streptococcal infection in rabbits. III. Influence of immunization with erythrogenic toxin type A (ET A) and its toxoid on subsequent infection with an ET A producing strain

Purified erythrogenic toxin type A (ET A) and the corresponding toxoid, prepared by formalin treatment, were used for the immunization of rabbits (200 micrograms per rabbit). The impact of anti-erythrogenic toxin and toxoid immunity was investigated under the conditions of experimental infection with the ET A-producing Streptococcus pyogenes strain SF 130 (type 1). Whereas non of the immunized rabbits (n = 14) died after infection, 40% of nonimmunized animals did not survive (Table 1). The increase of the spleen weight after infection was significantly smaller in the immunized groups (Table 2). The immunized rabbits responded after infection with a significantly lower increase of fever which did not exceed 0.8 degree C (2 degrees C in infected non-immunized animals). Humoral antibodies to ET A were detected after immunization by means of ELISA. The challenge infection acted as a booster leading to a further increase of antibodies. The antibodies were found to be neutralizing the nonspecific mitogenicity of ET A in vitro in relation to the antibody titer. Cell-mediated immunity was tested in the lymphocyte transformation reaction with peripheral lymphocytes. The nonspecific mitogenicity of ET A, ET B, ET C and Con A was pronounced after immunization, whereas the nonimmunized rabbits responded to these antigens to a lower degree. The toxoid was found to be nonmitogenic. The altogether higher lymphocyte stimulation was also observed using spleen lymphocytes of immunized animals after infection.

Toxic shock syndrome

In the past 10 years, we have learned much about TSS and S. aureus and its toxins. A number of important biologic principles have been reemphasized in this first decade of TSS research: S. aureus is a very complex organism, one not likely to yield quick answers; in vitro observations must always be confirmed in the patient; animal models may not always be reliable replicates of human disease; and epidemiologic associations cannot be equated with causation. Toxic shock is an intricate phenomenon with many interesting scientific facets. Unraveling its mysteries will undoubtedly teach us more about the complex interaction of patients and microorganisms.

Protection of rabbits in an infection model of toxic shock syndrome (TSS) by a TSS toxin-1-specific monoclonal antibody

An anti-TSST-1-specific monoclonal antibody (MAb 8-5-7) was tested for its protective capacity in a rabbit infection model to toxic shock syndrome (TSS). The challenge strain of Staphylococcus aureus (RN4710), which contained a plasmid encoding TSS toxin-1, was introduced into previously implanted chambers. Purified monoclonal antibody (1.25 mg of immunoglobulin G) administered parenterally 1 day before and 1 day after initiation of infection provided complete protection against the TSS-like syndrome and the mortality which occurred in unprotected rabbits.

Synergistic induction of interleukin-1 by endotoxin and toxic shock syndrome toxin-1 using rat macrophages

We studied interleukin-1 (IL-1) secretion by rat peritoneal exudate macrophages stimulated with purified toxic shock syndrome toxin-1 (TSST-1). TSST-1 was observed to be a more potent inducer of IL-1 than was endotoxin. The induction of IL-1 secretion by TSST-1 was not blocked by polymyxin B but could be blocked by monoclonal antibodies directed against TSST-1. Synergistic induction of IL-1 was observed when the cells were stimulated with TSST-1 and endotoxin. The sequence of addition was found to be important for the synergistic response. Enhanced IL-1 production was observed only when macrophages were exposed to endotoxin before or simultaneously with TSST-1. Prior exposure of macrophages to TSST-1 had no enhancing effect on endotoxin-induced IL-1 secretion. We conclude that stimulation of the macrophage by endotoxin enhances the responsiveness of the cells to TSST-1 and may thereby play a role in the pathogenesis of toxic shock syndrome.