Cytotoxic Molecules in Invertebrate Immunity

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Insects and other arthropods are vectors of numerous parasitic diseases of medical and veterinary importance, including malaria, trypanosomiasis (sleeping sickness, Chagas' disease) filariasis (eye worms, elephantiasis), and dog heartworm. Knowledge of the factors that regulate the infection process in the insect vector is essential for the development of counter strategies to protect humans and livestock from the adverse effects of insect-vectored parasites. Insects possess effective innate cellular and humoral immune mechanisms that exhibit striking parallels between the innate immune responses of mammals, suggesting a common ancestry for these critically important processes. With the exception of studies documenting and characterizing various immune effector responses for several insect species, little or nothing is known of the mechanisms underlying the initial non-self recognition response, or the identity and mode of action of killing molecules used by immune activated cells. The proposed research is designed to elucidate the nature of the cytotoxic components generated by insects that specifically target and destroy their internal parasites. The researchers plan to study the cellular defence responses made by the fruit fly Drosophila melanogaster against the metazoan parasite Leptopilina boulardi, and the cytotoxic responses of the reduviid bug Rhodnius prolixus against the protozoan parasite Trypanosoma. Using these two insect-parasite model systems, the production of various reactive oxygen intermediates (superoxide anion, hydrogen peroxide, and the hydroxyl radical) will be monitored, as will the production of reactive nitrogen intermediates (e.g., nitric oxide and peroxynitrite), and the activity levels of two important enzymes, NADPH oxidase and nitric oxide synthase. To investigate the changes in biochemistry and enzyme activity that occur during the immune responses elicited by Drosophila and Rhodnius against their respective metazoan and protozoan parasites, the investigators will employ high performance liquid chromatography with electrochemical detection, spectrophotometry, fluorometry and molecular techniques. This comprehensive approach for positively identifying specific cytotoxic molecules and the enzymatic mechanisms by which they are produced during insect immune responses will be extremely useful by providing important insights concerning cell-cell signaling and immune recognition in insects.