Person having heterozygous sickle cell trait is protected from infection of-

Protection against plasmodium falciparum is obtained by Metabolically active intracellular parasites consume oxygen and decrease intracellular pH, both of which promote Hb sickling in AS red cells.These distoed and stiffened cells may be cleared more rapidly by phagocytes in spleen and liver helping to keep parasite load down Another effect of sickling is that it impairs the formation of membrane knobs containing a protein made by the parasite called PfEMP -1.Thesemembrane knobs are implicated in adhesion of infected red cells to endothelium which is believed to have an impoant pathogenic role in the most severe form of the disease cerebral malaria Ref: Robbins and Cotran Pathologic basis of disease.South Asia Edition -9;volume 1.page no. 635