DROSOPHILA ANTIBACTERIAL PROTEIN, CECROPIN-A, DIFFERENTIALLY AFFECTS NONBACTERIAL ORGANISMS SUCH AS LEISHMANIA IN A MANNER DIFFERENT FROM OTHER AMPHIPATHIC PEPTIDES

The effects of the antibacterial protein Drosophila cecropin A on deve lopmental forms of Leishmania were compared with the effect of Hyaloph ora cecropin A in vitro. Both cecropins had a potent lytic activity on the promastigotes at concentrations not far from those occurring in v ivo in the respective insect. Drosophila cecropin A had strong differe ntial effects on the two maturation forms of Leishmania aethiopica at high concentrations: inhibiting intracellular amastigotes and stimulat ing extracellular promastigotes to take up thymidine. Hyalophora cecro pin A also inhibited amastigotes by up to 50% at concentrations of gre ater than or equal to 0.250 mg/ml, and inhibited promastigotes at high concentrations but had no enhancing effects at any of the concentrati ons tested. In contrast to the results with Leishmania, Drosophila cec ropin A had no discernible effect on any developmental stage of P. fal ciparium and showed no lytic effects on haemocytes. The two enantiomer s of a synthetic amphipathic peptide, D- and L-KALA, were also tested. D- and L-KALA had some in vitro antimalarial effects at 0.025 and 0.0 5 mg/ml respectively but both forms were haemolytic at 0.1 mg/ml. Pote ntial uses of naturally occurring proteins and their derivatives in th e control of insect born infections and topical use of cecropins again st leishmaniasis are discussed.