Plasmodium falciparum: Histidine-rich protein II is expressed during gametocyte development

Both early gametocytes (I-II) and asexual trophozoite stages of Plasmodium falciparum digest hemoglobin and detoxify haem by polymerizing it into para site pigment called hemozoin. The mechanism of polymerization is unclear bu t it has been proposed that histidine-rich protein II may facilitate transp ort of hemoglobin to the food vacuole and catalyze the polymerization in as exual stages. We describe the transcription of histidine-rich protein II in gametocytes by Northern blot analysis and the expression of the protein in these stages by immunoprecipitation and Western blotting. Localization of histidine-rich protein II within the gametocyte by immunofluorescence assay and immunoelectron microscopy clearly illustrated the presence of this mol ecule in the infected red cell cytosol in the early stages of gametocyte de velopment and internalization in the later gametocyte as it matures. There is a strong correlation between the stage-specific trafficking of histidine -rich protein II in gametocytes and the susceptibility of early but not lat e gametocytes to the antimalarial drug chloroquine. (C) 2000 Academic Press .