Fig. 8.

palm^- parasites cannot finalize liver merozoite formation efficiently. A. Defect in liver-stage merozoite segregation in palm^- parasites. In vitro cultured P. berghei ANKA-GFP and palm^- ANKA-GFP liver stages, were fixed at various time points after sporozoite infection and visualized by immunofluorescence using monoclonal mouse anti-P. yoelii MSP1 and rabbit anti-P. berghei UIS4 antibodies. Nuclei were stained with the DNA-dye DRAQ5 (blue). palm^- ANKA-GFP parasites develop normally until late liver stages but rarely form merozoites. Shown are representative images of ANKA-GFP and palm^- ANKA-GFP at various time points. Bars, 10 µm. B. Quantification of productive liver merozoite formation. Liver stages from ANKA-GFP and palm^- ANKA-GFP parasites were scored at 48, 60 and 72 h after infection (ANKA-GFP n = 105, 94, 82; palm^-n = 99, 124, 107) according to the five categories indicated by the representative images in the inset. The categories are: no MSP1 (white), rim staining of MSP1 (light green), intracellular schizont staining of MSP1 (dark green), formation of MSP1-positive merozoites (yellow), and aberrant, external MSP1 staining (black). Note the high proportion of MSP1-positive schizonts in palm^- parasites, which correlates with a low production of MSP1-positive pathogenic merozoites.