Evaluation of Purine Salvage as a Chemotherapeutic Target in the Plasmodium yoelii Rodent Model; Annual rept. 1 Feb 2007-31 Jan 2008

摘要

Because resistance to current antimalarials is widespread new targets for malaria chemotherapy are needed to protect military personnel stationed in developing countries. Malaria parasites cannot make purines needed for RNA and DNA and must salvage purines from their host. We are investigating whether the malaria purine salvage pathway can be exploited to develop specific treatments for malaria that will be effective but not toxic. We perform our studies in Plasmodium yoelii a rodent malaria. We have genetically disrupted purine salvage enzyme purine nucleoside phosphorylase (PNP) and have shown that these P .yoelii parasites are attenuated and confer protective immunity to subsequent lethal challenge. We have also mapped residues in PNP responsible for the unique methylthiopurine activity. New protocols for transfection have been developed and we now have succeeded in attempts to disrupt adenosine deaminase (ADA). Both PNP and ADA deficient parasites are unable to form oocysts in the mosquito. We have developed GFP and GFP-luciferase reporter P. yoelii parasite lines that are able to complete the entire life cycle in mosquito and rodent hosts. The GFP-luciferase reporter parasites can be visualized in vivo by detection of bioluminescence both during intrahepatic and erythrocytic development. Initial studies suggest that we can use these parasites to test efficacy of drugs against exoerythrocytic malaria forms. We hope these experiments will lead to the development of new effective and nontoxic agents that can protect our military personnel from the lethal effects of malaria infection.