Transport pathways of host-derived iron in schistosomes parasites

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This project will identify the diversity and biological roles of receptors for metabolic iron expressed on the body surface of the parasitic blood flukes (schistosomes) of humans. Schistosomes are a major health problem in many tropical countries and are responsible for significant human morbidity and lost productivity. Adult worms feed on human blood, from which derive amino acids for the production of many hundreds of eggs released per day into the human blood stream. The intense cellular response induced by parasite eggs trapped in body organs is the major cause of chronic human disease. We have discovered two intriguing phenomena of iron metabolism in schistosomes. Firstly, schistosomes have a greater reliance on iron than many other organisms, storing a surfeit in cells that produce the protein-rich egg shell. Secondly, a major transmembrane iron transporter of the parasites, thought to be involved in the uptake of iron, is found on the parasite external body surface and not in the parasite intestine. The extensive nutritional dependence of these worms on iron and the surface location of mediators of iron uptake raise the exciting possibility that we have uncovered a novel system that might be exploited for vaccine or drug-mediated control of these significant human parasites. If we can dissect the pathways schistosomes use to derive iron from their hosts, we may be able to generate vaccines to block this nutritional pathway, or use drugs to block embryogenesis. This project is a fact-finding mission that asks if the host-interactive tegument of these parasites is a major source of metabolic iron. Molecules we demonstrate to be present on the surface will be tested as vaccine candidates in mouse vaccine trials