ISOLATED APOLIPOPHORIN-III FROM GALLERIA-MELLONELLA STIMULATES THE IMMUNE-REACTIONS OF THIS INSECT

Apolipophorin III (apoLp-III) was isolated from the haemolymph of last instar larvae of Galleria mellonella. The ultraviolet (u.v.) spectrum and the N-terminal amino acid sequence reveal high similarities with the apoLp-III from Manduca sexta, The protein is heat-stable, The mole cular mass of apoLp-III was determined to be 18 077 Da using mass spec trometry, The heat treatment (90 degrees C, 30 min) resulted in a pI s hift from 6.6 for the non-heated to 6.1 for the heat-treated apoLp-III without change in the molecular mass, indicating that a conformationa l change might have been caused by the heat treatment, rather than cov alent alterations, Intrahaemocoelic injection of pure apoLp-III into l ast instar G. mellonella larvae is followed by a dose-dependent increa se of antibacterial activity in cell-free haemolymph of treated larvae 24 h after injection, Furthermore, pure apoLp-III enhances the phagoc ytic activity of isolated haemocytes in vitro, Tbe newly discovered ro le of apoLp-III in inducing immune-related functions in insects is dis cussed in regard to the known features.-of this molecule in lipid meta bolism, Arylphorin, another heat-stable protein in G. mellonella haemo lymph, was likewise isolated in this study, The protein was identified by N-terminal protein sequencing, the sequence obtained exactly match es the known sequence data for this protein. (C) 1997 Elsevier Science Ltd.