Using BLaER1 as model for L. major infection of human macrophages to
investigate the role of pyroptosis in parasite spreading
Abstract
Leishmania is the causative agent of the tropical neglected
disease leishmaniasis and infects macrophages as its definitive host
cell . In order to sustain and propagate infections,
Leishmania parasites have to complete cycles of exit and
re-infection. Yet, the mechanism driving the parasite spread to other
cells remains unclear. Recent studies reported pro-inflammatory
monocytes as replicative niche of L. major and showed prolonged
expression of IL-1β at the site of infection, indicating an activation
of the NLRP3 inflammasome and pointing towards pyroptosis as a possible
mechanism of parasite spread. To address the species-specific
inflammasome activation of human cells we characterized the BLaER1
macrophages as a model for L. major infection. We found that
Leishmania can infect, activate and develop in BLaER1 macrophages
similar as they can do in primary human macrophages. Harnessing the
possibilities of this infection model, we first showed that BLaER1
GSDMD-/- cells, which carry a deletion of the
pore-forming protein gasdermin D, are more resistant to pyroptotic cell
death and, concomitantly, display a strongly delayed release of
intracellular parasite. Using that knockout in a co-incubation assay in
comparison with wild type BLaER1 cells, we demonstrate that impairment
of the pyroptosis pathway leads to lower rates of parasite spread to new
host cells, thus, implicating pyroptotic cell death as a possible exit
mechanism of L. major in pro-inflammatory microenvironments.