9504796 Nappi The overall objective of the proposed project is to gain a better understanding of the insect immune system by studying the cytotoxic responses made by the fruit fly Drosophila melanogaster against the parasitoid Leptopilina boulardi. When infected, immune reactive insects typically form darkly colored, melanotic capsules around the foreign objects, but virtually nothing is known of the cytotoxic molecules that specifically target and destroy encapsulated parasites. The Drosophila Leptopilina model provides an excellent genetic system for the systematic analysis of the cellular and biochemical processes involved in insect immunity. Using genetically well-defined strains of D. melanogaster, Dr. Nappi will monitor the parasite-induced generation of such potentially cytotoxic substances as melanin precursors (e.g., quinones, semiquinones), and reactive oxygen species (e.g., superoxide anion, hydroxyl radical and hydrogen peroxide). The identification of cytotoxic molecules and knowledge of the mechanisms by which they are produced will be extremely useful in answering some of the fundamental questions concerning immune recognition in insects. Parasite-induced changes in melanin precursors and antioxidant enzymes will be monitored in known resistant and susceptible host strains, and in antioxidant deficient strains, by using high pressure liquid chromatography with electrochemical detection, UV/vis spectroscopy, and fluorometric detection. Such a comprehensive approach for investigation the formation of cytotoxic molecules promises to provide interesting insights into the importance of certain free radicals and reactive precursors of melanin in insect immunity. ***
