Leishmania amazonensis fails to induce the release of reactive oxygen intermediates by CBA macrophages

CBA mouse macrophages effectively control Leishmania major infection, yet are permissive to Leishmania amazonensis. It has been established that some Leishmania species are destroyed by reactive oxygen species (ROS). However, other species of Leishmania exhibit resistance to ROS or even down-modulate ROS production. We hypothesized that L. amazonensisinfected macrophages reduce ROS production soon after parasitecell interaction. Employing a highly sensitive analysis technique based on chemiluminescence, the production of superoxide (O-2(center dot-)) and hydrogen peroxide (H2O2) by L. major- or L. amazonensis-infected CBA macrophages were measured. L. major induces macrophages to release levels of 3.5 times higher than in uninfected cells. This production is partially dependent on NADPH oxidase (NOX) type 2. The level of accumulated H2O2 is 20 times higher in L. major-than in L. amazonensis-infected cells. Furthermore, macrophages stimulated with L. amazonensis release amounts of ROS similar to uninfected cells. These findings support previous studies showing that CBA macrophages are effective in controlling L. major infection by a mechanism dependent on both production and H2O2 generation. Furthermore, these data reinforce the notion that L. amazonensis survive inside CBA macrophages by reducing ROS production during the phagocytic process.