Biochemical and biological properties of staphylococcal enterotoxin K

Staphylococcus aureus is an important human pathogen which is implicated in a wide variety of diseases. Major determinants of the virulence of this or ganism include extracellular virulence factors. Staphylococcal enterotoxins (SEs) are important causative agents in staphylococcal toxic shock syndrom e and food poisoning. Our study identified a novel enterotoxin, SEK, and ex amined its biochemical and biological properties. SEK had a molecular weigh t of 26,000 and an experimentally determined pi of between 7.0 and 7.5. SEK was secreted by clinical isolates of S. aureus. We demonstrated that SEK h ad many of the biological activities associated with the SEs, including sup erantigenicity, pyrogenicity, the ability to enhance the lethal effect of e ndotoxin, and lethality in a rabbit model when administered by subcutaneous miniosmotic pump. Recombinant SEK was shown to stimulate human CD4(+) and CD8(+) T cells in a V beta -specific manner; T-cells bearing V beta 5.1, 5. 2, and 6.7 were significantly stimulated to proliferate.