Investigating the Motility of Plasmodium

Malaria is a life-threatening disease and the search for vaccine targets to the malaria parasite Plasmodium continues to be of utmost importance. Antibody mediated vaccines to the pre-erythrocytic stage of Plasmodium represent the best opportunity for vaccine development due to the potential to stop or decrease the number of sporozoites that reach the liver and trigger symptomatic disease. Plasmodium sporozoites are actively motile and this motility is critical to their infectivity. Inhibition of gliding has been used to assess whether particular surface proteins of the sporozoite good vaccine targets. We present a method that can be used to assess antibody mediated inhibition of gliding motility by quantifying the fluorescence intensity of the trails that sporozoites leave behind as they move. We demonstrate the functionality of the assay with the human malaria parasite Plasmodium falciparum and a known inhibitory monoclonal antibody 2A10. Our data suggests that the fluorescence intensity assay can be a useful in vitro method of assessing the efficacy of antigen based vaccines. Plasmodium surface proteins thrombospondin-related anonymous protein (TRAP) and circumsporozoite protein (CSP) play important roles in sporozoite motility. CSP is the basis of the RTS,S malaria vaccine but the relationship between TRAP and CSP has yet to be fully illuminated. We investigated the distribution of TRAP on the surface of wild type and Plasmodium berghei CSP repeat mutant sporozoites in gliding and non-gliding conditions. Our data suggests that there is a correlation between irregular gliding motility and decreased secretion of TRAP