Role of apolipophorin-III in the immediate antibacterial responses of Galleria mellonella larvae (Lepidoptera: Pyralidae) | Posted on:2001-09-30 | Degree:Ph.D | Type:Dissertation | University:McGill University (Canada) | Candidate:Halwani, Adla Edris | Full Text:PDF | GTID:1463390014954175 | Subject:Biology | Abstract/Summary: | | Apolipophorin-III is a hemolymph protein known for its role in lipid transport. Apolipophorin-III isolated from the hemolymph of last instar larvae of Galleria mellonella bound to the surface of the insect pathogenic Gram-negative bacterium Xenorhabdus nematophilus and to the lipid A moiety of its lipopolysaccharide. This binding reduced the toxicity of the lipopolysaccharide to hemocytes and decreased the inhibitory effect of the lipopolysaccharide on phenoloxidase. Apolipophorin-III also bound to the Gram-positive bacterium Micrococcus lysodeikticus; this enhanced the activity of hen egg lysozyme on the organism as well as the lytic activity of G. mellonella cell-free hemolymph.; The involvement of apolipophorin-III in the immune responses of G. mellonella larvae to lipoteichoic acids, surface components of Gram-positive bacteria, was examined. Lipoteichoic acids from Bacillus subtilis, Enterococcus hirae and Streptococcus pyogenes caused a dose- and time-dependent drop in the total counts of circulating hemocytes and a partial or complete depletion of plasmatocytes depending on the species of lipoteichoic acid. All lipoteichoic acids tested activated phenoloxidase in vitro; however, in vivo, only B. subtilis lipoteichoic acid elevated the phenoloxidase activity while the other two suppressed it. Binding of apolipophorin-III to lipoteichoic acids was demonstrated. Apolipophorin-III prevented the complete depletion of plasmatocytes and depressed the activation of phenoloxidase by lipoteichoic acid from B. subtilis. The concentration of apolipophorin-III in hemolymph two hours post injections of lipopolysaccharides or lipoteichoic acids into larvae of G. mellonella did not change with respect to control insects that received phosphate-buffered saline. The concentration of apolipophorin-III in hemolymph at the end of the feeding larval stage was 8--12 mg/mL of hemolymph. Apolipophorin-III was present in significant amounts in the prepupal, pupal and adult stages. The protein was detected immunologically in hemocyte lysates, plasma and fat body. Non-denaturing polyacrylamide gels and immunoblots of fresh hemolymph suggested that apolipophorin-III is associated with a 77 kDa protein. | Keywords/Search Tags: | Apolipophorin-iii, Hemolymph, Mellonella, Larvae, Protein, Lipoteichoic acids | | Related items |
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