Galleria mellonella as a Model for Fungal Pathogenicity Testing
Insects are convenient models for assessing the virulence of microbial pathogens or for assessing the efficacy of antimicrobial drugs and give results comparable to those that can be obtained using mammals. Galleria mellonella larvae are easy to purchase
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Introduction The insect immune system shares a number of structural and functional similarities with the mammalian innate immune system and, as a consequence, insects may be used in place of mammals for screening microbial pathogens or for assessing the potency of antimicrobial drugs (1). Larvae of the greater wax moth Galleria mellonella are inexpensive to purchase, easy to inoculate, and can give results within 48 h. We have employed G. mellonella larvae to assess the virulence of yeast (2) and Aspergillus fumigatus (3), with strong correlations between the virulence in larvae and mice of Candida albicans (4) and Cryptococcus (5) demonstrated. The use of insects as a screening model is now well established for many pathogens
Alexandra C. Brand and Donna M. MacCallum (eds.), Host-Fungus Interactions: Methods and Protocols, Methods in Molecular Biology, vol. 845, DOI 10.1007/978-1-61779-539-8_33, © Springer Science+Business Media, LLC 2012
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(4–6), with Galleria and other insects, such as Drosophila and Manduca, often referred to as “mini-hosts” (7, 8). Changes in G. mellonella larva viability can be used to measure the relative virulence of microbial pathogens and/or mutants. Monitoring the insect immune response to microbial pathogens can also be useful as this gives an insight into the virulence of “weak” pathogens and provides information on how the mammalian innate immune system may respond. Measuring changes in the haemocyte density and the fungal load gives information on the cellular immune response to the pathogen and the proliferation of the pathogen in the host, respectively (9). In addition, it is also possible to monitor the expression of genes for selected antimicrobial peptides as a means of assessing the humoral immune response of larvae (10). Analysing changes in the proteome of infected larvae can also be very useful for monitoring alterations in expression of low molecular weight antimicrobial peptides. We have used this latter technique to demonstrate that larvae mount a “proportionate” immune response when inoculated with pathogen-derived material (11). Insects are also a useful in vivo screening system for assessing the potency of antimicrobial agents (12–15). In this application, larvae can be infected with the cells or conidia of a pathogen and then given a pre-determined dose of the antimicrobial agent. An alternative is possible where the larvae are given the agent in advance of the pathogen. It should be emphasised, however, that administration of an antimicrobial agent to larvae induces a protective immune response and that any protective effect could be due to the combined effect of the antimicrobial agent and the insect’s enhanced immune response (15). Controls to account for the increased immune response of the insect must be included in order to see the actual effect of the drug in vivo. The use of insects as in vivo models to assess fungal virulence has grown in popularity in recent years (1, 7, 8). Although there are many advantages to the use of insects
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