Enhancement of hemolytic and cytotoxic activity of staphylococcal alpha-toxin in vitro by incubation with cultured fibroblasts. Brief communication.

Staphylococcal alpha-toxin (alpha-toxin) was incubated with 3T3 or SV40-virus transformed mouse 3T3 fibroblasts during 2 hrs at room temperature. This resulted in about a two-fold increase in the hemolytic activity of alpha-toxin toward rabbit RBC. The concentration of alpha-toxin causing 50% hemolysis of rabbit RBC was lowered from about 120 ng/ml to about 65 ng/ml. Release of 86Rb from labeled RBC and isolated rabbit vagus nerves also occured at lower concentrations of alpha-toxin after preincubation with fibroblasts. The enhancement of hemolytic activity of alpha-toxin was still exerted by cultured fibroblasts preheated to 56 degrees C, but fibroblasts exposed to 100 degrees C were ineffective. The hemolytic activity of alpha-toxin toward rabbit RBC was also slightly enhanced by leucine aminopeptidase (5--20 microgram/ml) and aminopeptidase M (30--300 IU/ml).