Effect of pre-incubation temperature on susceptibility of Galleria mellonella larvae to infection by Candida albicans

Abstract

The use of insects for evaluating the virulence of microbial pathogens and for determining the efficacy of antimicrobial drugs is increasing. When larvae of the greater wax moth Galleria mellonella were incubated at 4 or 37°C for 24 h. prior to infection, they manifested increased resistance to infection by the yeast Candida albicans compared to larvae that had been pre-incubated for 24 h at 30°C. Incubation at 4 or 37°C led to an increase in haemocyte density and the expression of genes coding for gallerimycin, transferrin, an inducible metalloproteinase inhibitor (IMPI) and galiomicin. Peak expression of these genes was recorded at approximately 24 h after the commencement of the 4 or 37°C incubation. These results indicate that exposure of larvae to mild thermal shock conditions induces a protective cellular and humoral immune response mediated by increased numbers of haemocytes and elevated expression of antimicrobial peptides.

Drosophila and Galleria insect model hosts

“…47 Therefore, because flies are infected and maintained at 29°C, certain aspects of fungal virulence in mammals may not be accurately modeled in this organism; Galleria, which can be maintained at 37°C, the mammalian physiologic temperature, may be used instead, taking into account however that increasing the temperature of Galleria to 37°C itself alters cellular and humoral immune responses. 48,49 Second, the alb1-deficient Aspergillus fumigatus mutant, which is hypovirulent in mice and flies, 11,50 was hypervirulent in Galleria, in which it appears to trigger dysregulated immunopathology. 51 Thus, the absence of virulence of a fungal strain in one host does not preclude its pathogenicity in another pathosystem.…”

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

“…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.…”

Galleria mellonella experimental model for bat fungal pathogen Pseudogymnoascus destructans and human fungal pathogen Pseudogymnoascus pannorum

“…The present study provided proof that the G. mellonella experimental system is amenable to an extended temperature range from 5°C to 37°C. It is well-known that temperature affects G. mellonella immune response to pathogens; however, the relevant previous studies focused on the effects of pre-incubation periods as they related to the immune responses [28,29]. Importantly, the current study differs from earlier publication in that the larvae were maintained at room temperature until infection and were not placed at 5°C and 15°C until after infection.…”

“…It is likely that in this case, the lower temperature was conducive both for the growth of the fungal pathogens and G. mellonella . The fact that robust immune response is invoked in G. mellonella kept at 4°C might have contributed to the lack of P. destructans - and P. pannorum -induced mortality in this study [27,29]…”