IFAs using polyclonal mouse antisera directed against PfSUB1, PfabH and PfM16 were used to investigate the granular localization of these proteases in merozoite-containing mature schizonts (in green). The merozoites were visualized via immunolabelling with polyclonal rabbit antisera directed against PfMSP1 (in red). B) Immunolabeling of osmiophilic bodies using polyclonal rabbit antisera directed against Pfg377 (in red) was employed to demonstrate an accumulation of PfPM6, labeled with the respective mouse antisera (in green), in these organelles. Hoechst 33342 staining was used to highlight the parasite nuclei (in blue). Bar, 2 mm. Results are representative of two independent experiments. PfSUB3 was detected in granular-vesicular structures in the cytoplasm of schizonts and in the cytoplasm of gametocytes and macrogametes. PfabH accumulated in cytoplasmic granular structures in the asexual blood stages and gametocytes. Here, the granular localization was particularly prominent in mature schizonts, but did not coincide with the localization of the merozoites (A). PfM1-AP localized to a focused central granule in both the asexual and sexual blood stages. PfFLN was found in the cytoplasm of immature schizonts, while it concentrated in merozoites of mature schizonts. The protein also localized to the cytoplasm of gametocytes with high concentration in the gametocyte periphery as well as in the periphery of activated macrogametes. To gain more information on the localization of PfPM6 in female gametocytes, colocalization experiments were performed, using rabbit antibodies directed against the osmiophilic body protein. The double-labelling assays demonstrated that PfPM6 is present in these organelles.

Weißbach T, Golzmann A, Bennink S, Pradel G, Julius Ngwa C. Transcript and protein expression analysis of proteases in the blood stages of Plasmodium falciparum. Exp Parasitol. 2017 180:33-44.