Determination of Antimicrobial Activity and Total Hemocyte Count in the Larval Hemolymph of Galleria mellonella (L.) (Lepidoptera: Pyralidae) Following Application with Fusarium proliferatum

Abstract

The impact of entomopathogenic viruses, bacteria, fungi and nematodes on the immune responses of insects has been extensively examined in model and medically important insects. However, the single time point selected in these studies presents a challenge in comprehensively understanding immune responses throughout infection in pest species. The objective of this study was to gain insight into the cellular and humoral immune responses of Galleria mellonella larvae, a model organism, to infection with the entomopathogenic fungus Fusarium proliferatum at two different time points (24h and 48h). In the antimicrobial activity tests conducted as part of the humoral immunity studies, hemolymph was induced by varying concentrations of conidial doses. After conidial dose applications, the largest zone diameters were observed against Klebsiella pneumonia, Saccharomyces cerevisiae, Salmonella typhimurium (15 mm/24h), Proteus vulgaris (16 mm/24h), and Escherichia coli (18 mm/48h). Topical application of fungal conidia to G. mellonella larvae in the later stages reduced the total hemocyte count in the larval hemolymph 24h and 48h after treatment. Our findings show that the immune system of G. mellonella responds differently to F. proliferatum depending on the infection timeline. Further studies on fungal regulation of the immune system could provide new pest control methods in agriculture.