Purification and characterization of staphylococcal pyrogenic exotoxin type B

Abstract

Staphylococcal pyrogenic exotoxin (PE) type B was purified and characterized biochemically and biologically. The exotoxin was purified from cell-free culture supernatant fluids by using differential precipitation with ethanol and resolubilization in pyrogen-free distilled water followed by preparative thin-layer isoelectric focusing. A final purification of 153-fold was achieved on the basis of the capacity of the exotoxin to produce fever. The toxin migrated as a homogeneous protein with a molecular weight of approximately 18 000 when tested with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Hyperimmune antisera raised against the purified exotoxin reacted with partially purified toxin in an immuno-diffusion assay to form a single precipitin line. The isoelectric point of the PE was estimated to be 8.5. Alanine was identified as the N-terminal amino acid. The exotoxin contained significant amounts of lysine but few aromatic amino acids. The PE was pyrogenic and enhanced host susceptibility to lethal shock and myocardial damage by endotoxin. In addition, the exotoxin was a potent nonspecific lymphocyte mitogen and suppressed immunoglobulin M synthesis against sheep erythrocytes.