Effects of beauverolide L and cyclosporin A on humoral and cellular immuneresponse of the greater wax moth, Galleria mellonella

The effects of beauverolide L and cyclosporin A, cyclic peptidic metabolite s, produced by several genera of entomopathogenic fungi on immune responses of last instar larvae of the greater wax moth Galleria mellonella have bee n examined. Intrahemocoelic injection of either metabolite-coated silica pa rticles or dissolved metabolites in a concentrations ranging between 10 and 30 mu g per larva caused no mortality but activated humoral responses in G . mellonella larvae. The challenge induced a significant release of lysozym e and cecropin-like activity into the hemolymph, suggesting stimulatory act ivity on humoral immune responses. Injected metabolite-coated particles wer e rapidly surrounded by hemocytes which subsequently accomplished formation of melanized nodules, which increased in size and number compared with con trols. In vitro assays with dissolved metabolites indicated no adverse effe cts of beauverolide L or cyclosporin A on attachment or spreading of isolat ed plasmatocytes but dose-dependent inhibition of their phagocytic activity . Isolated plasmatocytes incubated with cyclosporin A or beauverolide L exh ibited cytoskeleton alterations that differed from those observed in plasma tocytes from infected G. mellonella larvae or reported from other fungal se condary metabolites. The experiments provided further data to elucidate the role of fungal secondary metabolites in development of mycoses in insects. (C) 1999 Elsevier Science Inc. All rights reserved.