Chloroquine resistance and the physiology of the malaria parasite s digestive vacuole

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Malaria is an infectious disease, caused by a single-celled parasite which invades the red blood cells of its human host. Each year, malaria causes the death of up to 3 million people, mostly children under the age of 5 The parasite has become resistant to most, if not all, of the antimalarial drugs presently available, and there is no vaccine. There is therefore an urgent need to develop new antimalarial drugs, and-or to devise strategies for overcoming the parasite s drug resistance mechanisms. Chloroquine was, for many years, the mainstay of antimalarial chemotherapy and was, in many senses, a 'wonder-drug' cheap, safe and effective. However the emergence and spread of parasites that are resistant to chloroquine has meant that the drug is now largely useless as an antimalarial. Chloroquine kills (sensitive) parasite through an effect on the parasite s digestive vacuole an internal acidic compartment in which the parasite breaks down protein taken up from its host red blood cell. This compartment plays a crucial role in the growth and proliferation of the parasite. Yet we understand very little about its basic physiology, and nor do we understand the mechanism by which chloroquine-resistant parasites are able to survive exposure to the drug. The aim of the work proposed here is to gain an increased understanding of some of the mechanisms underlying the physiology of the parasite s digestive vacuole, as well as some of the factors influencing the accumulation of chloroquine within this compartment. The former part of the work may well reveal new antimalarial drug targets. The latter part of the work will increase our understanding of the mechanism of chloroquine resistance, thereby laying the groundwork for strategies by which these mechanisms might be circumvented and chloroquine-related drugs thereby restored to the front-line of our ongoing and increasingly desperate fight against malaria.