Defective in Lipophosphoglycan Biosynthesis Interferes With Activation of Human Neutrophils.

Visceral leishmaniasis (VL) is often associated with hematologic manifestations that may interfere with neutrophil response. Lipophosphoglycan (LPG) is a major molecule on the surface of promastigotes, which has been associated with several aspects of the parasite-vector-host interplay. Here, we investigated how LPG from (.) , the principal etiological agent of VL in the New World, influences the initial establishment of infection during interaction with human neutrophils in an experimental setting . Human neutrophils obtained from peripheral blood samples were infected with either the wild-type (WT) strain or LPG-deficient mutant (). In this setting, parasites displayed reduced viability compared to WT ; such finding was reverted in the complemented + parasites at 3- and 6-h post-infection. Confocal microscopy experiments indicated that this decreased survival was related to enhanced lysosomal fusion. In fact, LPG-deficient parasites more frequently died inside neutrophil acidic compartments, a phenomenon that was reverted when host cells were treated with Wortmannin. We also observed an increase in the secretion of the neutrophil collagenase matrix metalloproteinase-8 (MMP-8) by cells infected with compared to those that were infected with WT parasites. Furthermore, collagen I matrix degradation was found to be significantly increased in parasite-infected cells but not in WT-infected controls. Flow cytometry analysis revealed a substantial boost in production of reactive oxygen species (ROS) during infection with either WT or . In addition, killing of parasites was shown to be more dependent on the ROS production than that of WT . Notably, inhibition of the oxidative stress with Apocynin potentially fueled fitness as it increased the intracellular parasite viability. Thus, our observations demonstrate that LPG may be a critical molecule fostering parasite survival in human neutrophils through a mechanism that involves cellular activation and generation of free radicals.