p52/p36-deficient parasites show a severe defect in LS development in vitro. P. yoelii wt LSs grow in HepG2-CD81 cells and complete development, but p52/p36-deficient LSs do not grow and do not persist in infected cells. (A) Forty-three hours p.i., wt LSs have developed to the late schizont stage. LSs are visualized by staining with anti-UIS4 Abs (red) and anti-Hsp70 Abs (green). Nuclei were visualized with DAPI (scale bar, 30 μm). (B) Higher magnification shows a late wt LS with multiple nuclei entirely surrounded by a PVM that is revealed by anti-UIS4 staining (scale bar, 5 μm). (C) p52/p36-deficient parasites do not grow in HepG2-CD81 cells. A small p52/p36-deficient growth-arrested LS is indicated by the white arrow (scale bar, 30 μm). (D) Higher magnification of a growth-arrested p52/p36-deficient parasite 43 h p.i. does not show a typical PVM using UIS4 staining. Some UIS4-positive vesicular structures are visible (scale bar, 5 μm).