Apolipophorin-III in Galleria mellonella potentiates hemolymph lytic activity

Heat-inactivated serum of non-immune Galleria mellonella larvae enhanced th e lyric activity of larval cell-free hemolymph against Micrococcus lysodeik ticus. The increase in bacterial lysis was due to a 17.2 kDa protein known previously to bind to bacterial lipopolysaccharides. The protein enhanced t he lytic activity of insect cell-free hemolymph and hen lysozyme in vitro a nd insect hemolymph in vivo. The hydrophobic protein, which adhered to M. l ysodeikticus. was identified by its amino acid sequence homology as apolipo phorin-III. The titer of apolipophorin-III in 200-250 mg last instar larvae was 8.7 mg/ml of hemolymph. Apolipophorin-III did not bind to lysozyme. A possible mode of action of apolipophorin-III with lysozyme in the insect is proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.