The epidermolytic toxin of Staphylococcus aureus: its failure to bind to cells and its detection in blister fluids of patients with bullous impetigo

ELISA estimation of the binding of epidermolytic toxin to neonatal mouse skin

A sandwich ELISA, with antisera from rat and rabbit, was used to determine epidermolytic toxin (ET) to a limit of about 0.01 ng at 0.1 ng/ml. The binding of ET to the epidermis of skin discs was measured in vitro. The ability of the assay to discriminate between the two forms of the toxin was used to demonstrate that there was a saturable component of toxin binding to the epidermis. The rate of uptake, the effect of the inhibitor EGTA and comparative experiments with the inactive nitrated toxin confirmed that the observed binding is associated with toxigenesis. From measurements at toxin concentrations from 0.25 microgram/ml to 100 micrograms/ml, it was calculated that the saturable binding component has a Kd of about 2 micrograms/ml (approximately 60 nM) and a capacity of 0.5 ng per skin disc (1 ng per cm2 of epidermis).

Immunofluorescence localization of the epidermolytic toxin target in mouse epidermal cells and tissue

An epidermolytic toxin target was observed in keratohyalin granules of sectioned epidermis by a 'direct' fluorescence procedure using FTC-toxin, but not by an 'indirect' procedure using sequential reaction with toxin, anti-toxin and FTC-secondary antibody. The investigation of the two procedures was extended to keratinocytes. A dispase digestion procedure yielded three fractions which corresponded to basal, spinous and granular cells according to biochemical and morphological criteria. It was shown that the 'direct' and 'indirect' procedures both detected the toxin target in the keratohyalin granules of granular cells, but that the 'indirect' procedure was very insensitive. In control experiments, the profilaggrin of keratohyalin granules was detected readily in cells by a 'direct' procedure using FTC-antiprofilaggrin but only weakly by an 'indirect' double antibody procedure. Insensitivity to 'indirect' procedures thus appears to be a particular property of the keratohyalin granule site. It was shown that the toxin target was readily accessible in permeable (trypsin-isolated) granular cells but inaccessible in impermeable (dispase-isolated) cells.

Action of staphylococcal exfoliative toxins on epidermal cell cultures and organotypic skin

In the staphylococcal scalded skin syndrome, spontaneous intraepithelial cleavages are due to the exfoliative toxins A or B (ETA or ETB). Until now, these toxins have been studied either on epidermis or on organotypic skin cultures. In the present study, we compare the effects of these toxins on human keratinocyte cell cultures to those on human and mouse organotypic skin cultures. With concentrations of ETA or ETB of 1 mg/ml for 3 hours, spontaneous intraepithelial cleavages were noted in both cell and organotypic cultures. Keratinocyte cell cultures were as sensitive as organotypic skin cultures to these toxins. Since keratohyaline granules may represent a possible binding site for ETA or ETB, we tried to correlate the expression of keratohyaline granules with the appearance of intraepithelial clefts due to the toxins. However, when cultured in liquid medium, epithelia were not differentiated enough to allow the detection of the binding site of ETA-ETB.

The binding of epidermolytic toxin from Staphylococcus aureus to mouse epidermal tissue

Fluorescein-labelled epidermolytic toxin (FTC-toxin) of Staphylococcus aureus and ferritin-toxin conjugate have been prepared and purified. FTC-toxin bound selectively to cryostat and resin-impregnated sections of neonatal mouse skin. Binding was localized at the keratohyalin granules and in the stratum corneum. In an epidermal cell (granular, spinous and basal) preparation, only keratohyalin granules of the granular cells bound FTC-toxin. Ferritin-toxin conjugate bound to skin sections at the same two sites as FTC-toxin and was competitive with the binding of free toxin. Keratohyalin granules in unstained sections had a novel 'patched' appearance under the electron microscope, and the ferritin-toxin conjugate bound preferentially to the electron-lucent areas. In the stratum corneum it was shown by quantitative estimation that the target density decreased as the surface of the tissue was approached.

Epidermolytic toxin from Staphylococcus aureus binds to filaggrins

The affinity of epidermolytic toxin from Staphylococcus aureus for proteins from the target tissue has been tested by a Western blotting procedure. Particular proteins in a 1 M phosphate extract of epidermis reacted on nitrocellulose blots with a probe prepared by the conjugation of toxin with peroxidase. Protein extracted into 50 mM Tris-HCl did not react. The probe detected profilaggrin, filaggrin and a smaller unidentified polypeptide. It is suggested that the interaction is relevant to the mode of action of the toxin.

Enzyme-linked immunosorbent assays for Staphylococcus aureus exfoliative toxins A and B and some applications

Two enzyme-linked immunosorbent assays were developed for detection of staphylococcal exfoliative toxins A and B (ETA and ETB) with a double-antibody sandwich protocol. Antibodies against both toxins were purified by affinity chromatography from sheep antisera raised against purified ETA and ETB. These affinity-purified antibodies were free of detectable amounts of antibodies to other staphylococcal antigens and neutralized the actions of ETA and ETB. Alkaline phosphatase was conjugated to these antibodies. The enzyme-linked immunosorbent assay, which could detect at least 3 ng of ETA and ETB per ml, was used to quantitate the toxins in the culture supernatant fluids of staphylococcal strains. Thus, the kinetics of ETA and ETB synthesis and of ETA and ETB release into the supernatant fluids were determined; other determinations included the roles of carbon dioxide concentration, pH, glucose concentration, temperature, and agitation on the production of ETA and ETB.

A circular-dichroism study of epidermolytic toxins A and B from Staphylococcus aureus

The far-u.v. circular-dichroism spectra of the two epidermolytic toxins was analysed into fractional contributions of 0.09 helix and 0.46 beta-sheet to each toxin structure. Trifluoroethanol perturbation caused an initial increase in dichroic absorption at 205 nm and then a change characterized as a beta-sheet-to-alpha-helix transition. The intense near-u.v. spectra suggested that the toxins have unusually rigid, though different, aromatic-side-chain arrangements.

A comparative study of two serotypes of epidermolytic toxin from Staphylococcus aureus

Two serotypes of epidermolytic toxin were purified from culture filtrates of different strains of Staphylococcus aureus. The amino acid composition of the proteins is similar, each containing no cystine and one methionine, but type ii contains no tryptophan, whereas type i has 1 mol/mol protein. The molecular weights of type i and type ii toxins were 30,000 and 29,500, respectively, as found by SDS-polyacryamide gel electrophoresis and confirmed by studies of CNBr fragments and tryptic peptides. Dansylation gave a single different N-terminal amino acid for each toxin; the C-terminus of each is lysine. Peptide mapping of tryptic digests showed that very few peptides are common to the two amino acid sequences.

The experimental production of high-level intraepidermal splits

The effects of trypsin at 37 degrees C and 4 degrees C on adhesion between keratinocytes in normal human epidermis were assessed by light and electron microscopy. The results provide evidence for the contribution of both extracellular and intracellular factors to keratinocyte adhesion and for changes in the nature of adhesion in the granular layer. Trypsinization at 4 degrees C produced a high-level intraepidermal split identical in location and intercellular route to that observed in the staphylococcal scalded skin syndrome.