Towards a humanized small animal model for in vivo analyses of sequestration of malaria infected red blood cells

The adherence of Plasmodium falciparum infected red blood cells (irbc) to capillary endothelium is believed to be responsible for a number of the severe pathologies associated with human malaria. This adherence is principally mediated by a family of P. falciparum proteins, Pfemp1, these proteins are transported and incorporated into the surface of the erythrocyte membrane by a complex parasite encoded transport machinery. Infected rbc of the rodent parasite, P. berghei, also sequester in certain organs of mice using the endothelial molecule, CD36, as a receptor. The P. berghei proteins involved in adherence and the genes encoding proteins the transport machinery are largely unknown. We have used proteomic and functional genomic approaches to identify P. berghei proteins exported to the host erythrocyte surface. The proteome analyses were performed on different red blood cell membrane fractions from non-sequestering and sequestering irbc. Parasite proteins identified from these analyses were investigated further to examine their role in irbc sequestration, by protein-tagging and gene-deletion experiments. Protein tagging experiments identified >10 proteins exported into the irbc, where two exported proteins distinctly localize on the surface of irbc membrane and gene deletion analysis revealed that one protein was involved in CD36-mediated sequestration. Identification of P. berghei proteins exported to the irbc surface offers possibilities to use these proteins as ‘vehicles’ to express P. falciparum derived molecules on rodent erythrocytes, thereby creating screening systems to test small molecules inhibitors that disrupt irbc adherence to endothelium in vivo.