Dynamic imaging reveals surface exposure of virulent Leishmania amastigotes during pyroptosis of infected macrophages
Résumé
Leishmania spp are obligate intracellular parasites that infect phagocytes, notably macrophages. No information is available on how Leishmania parasites respond to pyroptosis of their host cell, known to limit microbial infection. Here, we analyzed the pyroptotic process and the fate of intracellular amastigotes at the single cell level using high-content, real-time imaging. Bone marrow-derived macrophages were infected with virulent L. amazonensis amastigotes and sequentially treated with lipopolysaccharide and adenosine triphosphate for pyroptosis induction. Real-time monitoring identified distinct pyroptotic phases, including rapid decay of the parasitophorous vacuole (PV), progressive cell death, and translocation of the luminal PV membrane to the cell surface in 40% of macrophages, resulting in the extracellular exposure of amastigotes that remained anchored to PV membranes. Electron microscopy analyses revealed an exclusive polarized orientation of parasites, with the anterior pole exposed toward the extracellular milieu, and the parasite posterior pole attached to the PV membrane. Exposed parasites retain their full infectivity towards naïve macrophages suggesting that host cell pyroptosis may contribute to parasite dissemination.
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