Coxiella burnetii fails to stimulate human neutrophil superoxide anion production

Abstract

This study investigated the release of superoxide anion (O2-) as an indicator of the oxidative metabolism of human neutrophils during the phagocytosis of Phase I Coxiella burnetti. Human neutrophils were incubated for 1 hr at 37 degrees C with opsonized or unopsonized viable Phase I Coxiella burnetii (MOI was 100 : 1) and superoxide anion formation was measured by the reduction of ferricytochrome C. The data revealed that during its phagocytosis by human neutrophils, C. burnetii (opsonized or unopsonized) fails to stimulate superoxide anion production. In contrast, the uptake of Staphylococcus aureus or zymosan was accompanied by the release of measurable O2-. This release of O2- was abrogated by the addition of 100 micrograms/ml of superoxide dismutase (SOD). These results suggest that the establishment of C. burnetii within neutrophils, as occurs during persistent infection, may be due to the failure to stimulate the metabolic burst during phagocytosis.