Inhibition of human polymorphonuclear leukocyte respiratory burst, bactericidal activity, and migration by pneumolysin

Abstract

The in vitro effects of pneumolysin, a sulfhydryl-activated toxin produced by Streptococcus pneumoniae, on various functions of human polymorphonuclear leukocytes (PMNLs) was investigated. Treatment of PMNLs with highly purified toxin significantly inhibited respiratory burst (in response to stimulation), ability to kill opsonized pneumococci, chemotaxis, and random migration. These inhibitions were observed at very low toxin doses (≤ 1 hemolytic unit (2 ng) per 106 PMNLs), which had no effect on PMNL viability. These results suggest that pneumolysin could function in pathogenicity by interfering with the ability of PMNLs to migrate toward and kill pneumococci.