Fig 1. L. infantum actively infects U937-derived macrophages.

A) U937-derived macrophages were infected with L. infantum promastigotes; after 6 h or 24 h cells were washed, stained with Hoechst dye and observed with a fluorescence microscope to monitor internalized parasites. Arrows indicate parasitized cells. B) Active infection was monitored by calculating infection index, considering at least 300 total macrophages per infection time (dotted line), and by a qPCR assay targeting kDNA of Leishmania (solid line). Both methods allowed to detect a significant increase in infection from 6 h to 24 h. The data are representative of three independent experiments. CTR, uninfected control. * p < 0.05.