Figure 4.

Secreted Sporozoite Factor(s) Contribute to Lysosome Redistribution during Invasion

(A) Hepa1-6 cells were infected with P. yoelii sporozoites or treated with sporozoite secretion-enriched supernatants at different sporozoite:hepatocyte (S:H) ratios. After 90 min, cells were processed using DAPI (blue) for DNA, phalloidin (white) for actin visualization, antibodies to LAMP1 (red) for LE/lysosomes, and CSP (green) for parasites and displayed as maximum intensity projections. Scale bar represents 5 μm. The isospots corresponding to lysosomes away from the nucleus and perinuclear lysosomes were depicted in cyan and magenta, respectively.

(B) Values represented in bar graphs correspond to percentage of perinuclear lysosomes identified in (A). Data represent the mean ± SD of at least 10 different microscopic fields per condition from three independent experiments.

(C) Hepa1-6 cells were infected with P. yoelii sporozoites or exposed to sporozoite secretion-enriched supernatants. Surface LAMP1 was analyzed by flow cytometry. Values represent the mean ± the SD of three independent experiments. *p < 0.001.

(D) Model of Plasmodium sporozoites promoting lysosome exocytosis. Sporozoites are depicted in yellow, hepatocytes in gray, lysosomes in red, and a Plasmodium-derived secreted factor in green.