Effect of Escherichia coli alpha-hemolysin on human peripheral leukocyte viability in vitro

To gain further evidence that Escherichia coli alpha-hemolysin has a role in pathogenesis, its effect on human peripheral leukocyte viability was studied in vitro. Viability of leukocytes exposed to low doses of alpha-hemolysin decreased nearly 10-fold within 15 min of exposure. This response was dose and time dependent and was neutralized by antiserum, heat, proteases, and lipase. To gain further evidence that alpha-hemolysin was the molecule responsible for leukotoxicity, preparations of alpha-hemolysin were passed through a hydrophobic interaction chromatographic column. Alpha-hemolysin prepared in this way retained its leukotoxic activity. Both hemolytic and leukotoxic activities copurified at the same ratio and were inactivated to the same degree by heating at 56 degrees C. Lysis of leukocytes, if it occurs in vivo, would enhance the chances of survival for an invading hemolytic E. coli.