Halwani A E, Niven D F, Dunphy G B
Department of Natural Resource Sciences, McGill University, Macdonald Campus, 21 111 Lakeshore Road, Sainte-Anne-de-Bellevue, Quebec, H9X 3V9, Canada.
J Invertebr Pathol. 2000 Nov;76(4):233-41. doi: 10.1006/jipa.2000.4978.
We investigated the effects of lipoteichoic acids, surface components of Gram-positive bacteria, on the hemocytes and phenoloxidase activity in last instar Galleria mellonella larvae, as well as the binding of apolipophorin-III, an insect lipid-binding protein, to lipoteichoic acids. Binding of apolipophorin-III to lipoteichoic acid was studied using an assay based on 1,9-dimethylmethylene blue. Apolipophorin-III bound the lipoteichoic acids from Bacillus subtilis, Enterococcus hirae, and Streptococcus pyogenes and to intact cells of E. hirae. E. hirae lipoteichoic acid promoted the binding of apolipophorin-III to the cells of this species. All lipoteichoic acids tested caused a dose- and time-dependent drop in the total counts of hemocytes and, depending on the species of lipoteichoic acid, partial or complete depletion of plasmatocytes. Granulocyte counts were not affected. Apolipophorin-III prevented partially the loss of plasmatocytes due to B. subtilis lipoteichoic acid. All three lipoteichoic acids studied activated phenoloxidase in vitro; injections of B. subtilis lipoteichoic acid into the larvae elevated the phenoloxidase activity, whereas injections of E. hirae or S. pyogenes lipoteichoic acid, or apolipophorin-III alone, suppressed it. Apolipophorin-III decreased the activation of phenoloxidase by B. subtilis lipoteichoic acid.
