Dose-dependent cellular and humoral responses in Galleria mellonella larvae following β-glucan inoculation

Abstract

Galleria mellonella larvae were inoculated with different doses of beta-glucan by injection into the haemocoel. Those larvae that had received high doses of beta-glucan (15, 30 or 60microg/larva) demonstrated increased survival following infection with the yeast Candida albicans. High concentrations of glucan induced an increase in haemocyte density and a reduction in yeast proliferation within the haemocoel. Proteomic analysis of glucan-treated larvae revealed increased expression of a variety of peptides some of which may possess antimicrobial properties. Analysis of expression profiles revealed that low doses of beta-glucan (3.75microg/larva) triggered the increased expression of certain peptides (e.g. hemolin) while high dose inoculation was required before the increased expression of others (e.g. archaemetzincin) was evident. These results indicate that low doses of beta-glucan induce a limited immune response while high doses induce an immune response that has the potential to curtail the threat within the haemocoel but also withstand a subsequent infection. Immune priming gives insects the ability to withstand a potentially lethal infection if exposed to a low level of the pathogen 24-48h previously. Immune priming has resource implications and this work indicates that a graded immune response is initiated depending upon the amount of the immune priming agent encountered.

Pre-exposure ofGalleria mellonellalarvae to different doses ofAspergillus fumigatusconidia causes differential activation of cellular and humoral immune responses

“…10,17 The results presented here indicate that exposure of G. mellonella larvae to low doses of A. fumigatus conidia (10 4 or 10 5 ) leads to an increase in the expression of a range of antimicrobial peptides and immune proteins which is indicative of an elevated immune response that could counteract a subsequent infection.…”

“…Prior exposure of larvae of Galleria mellonella to non-lethal doses of yeast cells provokes an immune response, which increases their resistance to a subsequent lethal inoculum. 9 Administration of microbial cell wall components 10 or stress (physical or thermal) 11,12 induce a similar protective response. The elevated immune response subsequent to the initial challenge is mediated by an increase in the hemocyte density and the elevated expression of antimicrobial peptides.…”

“…Previous work has demonstrated that the magnitude of the immune response is proportional to the size of the microbial challenge thus indicating that the insect immune response can distinguish between a low level, potentially non-lethal infection and one that threatens the survival of the individual. 10 Due to the strong structural and functional similarities between the insect immune response and the innate immune ©2 0 1 1 L a n d e s B i o s c i e n c e .…”

Assessment of in vivo antimicrobial activity of the carbene silver(I) acetate derivative SBC3 using Galleria mellonella larvae

“…Insects have the benefit of being inexpensive to purchase and house, and can give results in 24-48 h. Insect can also be used to evaluate the in vivo activity of antimicrobial drugs (Hamamoto et al 2004;) but caution must be exercised in their use as the introduction of foreign material into the insect haemoceol can provoke a non-specific immune response (Mowlds et al 2010;Kelly and Kavanagh 2011).…”

“…Previous work has demonstrated that introduction of selected agents (e.g. silver nitrate, caspofungin, b-glucan) into the haemocoel of G. mellonella larvae can prime the immune response and lead to an increase in the density of circulating haemocytes and in the expression of antimicrobial and immune related peptides (Rowan et al 2009;Kelly and Kavanagh 2011;Mowlds et al 2010). In order to exclude the possibility that the observed in vivo antimicrobial activity of SBC3 was due to the increased density of immune cells in the larvae, the density of circulating haemocytes in larvae was assessed.…”