Characterisation of the cellular and proteomic response of Galleria mellonella larvae to the development of invasive aspergillosis

Background: Galleria mellonella larvae were infected with conidia of Aspergillus fumigatus and the cellular and humoral immune responses of larvae to the pathogen were characterized as invasive aspergillosis developed. Results: At 2 h post-infection there was an increase in hemocyte density to 7.43 +/- 0.50 x 10(6)/ml from 0.98 +/- 0. 08 x 10(6)/ml at 0 h. Hemocytes from larvae immune primed for 6 h with heat killed A. fumigatus conidia displayed superior anti-fungal activity. Examination of the spread of the fungus by Cryo-imaging and fluorescent microscopy revealed dissemination of the fungus through the larvae by 6 h and the formation of distinct nodules in tissue. By 24 h a range of nodules were visible at the site of infection and at sites distant from that indicating invasion of tissue. Proteomic analysis of larvae infected with viable conidia for 6 h demonstrated an increase in the abundance of gustatory receptor candidate 25 (37 fold), gloverin-like protein (14 fold), cecropin-A (11 fold). At 24 h post-infection gustatory receptor candidate 25 (126 fold), moricin-like peptide D (33 fold) and muscle protein 20-like protein (12 fold) were increased in abundance. Proteins decreased in abundance included fibrohexamerin (13 fold) and dimeric dihydrodiol dehydrogenase (8 fold). Conclusion: The results presented here indicate that G. mellonella larvae may be a convenient model for studying the stages in the development of invasive aspergillosis and may offer an insight into this process in mammals.