Galleria Mellonella as model host to study the virulance of Fusarium Musae strains obtained from plants and humans

Fusarium musae is a pathogenic species belonging to the Fusarium fujikuroi species complex. Described for the first time only in 2011, F. musae is the causative agent of the crown rot on banana, a devastating post-harvest disease, but it also causes keratitis and skin infections as well as systemic infections in immunocompromised patients in few cases. This makes it an ideal species for the comparative analysis of fungal virulence on plant and animal hosts. It’s not clear yet how humans acquire the infection, and the absence of experimentally verified proof of the transmission from one host to the other increases the need to build new models to better understand the interaction between the fungus and its hosts. With this work we aim at creating an in vivo model to further study the mechanisms involved in infection of Fusarium musae and to use it as a potential application towards screening system for therapy options. Given strong structural and functional similarities between insect immune system and innate immune response of mammals, insect species such as Galleria mellonella have been employed more and more to study microbe-host interactions. Likewise, in this work Galleria mellonella is used as a new alternative pathophysiological model to verify infection in a human proxy since it represents an ideal intermediate step between in vitro findings and in vivo studies in mice for the investigation of human pathogens. Here we work with 20 different F. musae strains collected worldwide from both infected patients and bananas. G. mellonella larvae (n=10/group) are injected with 10 µL of five different concentrations of spores (from 10² to 10⁶ spores/ml) in order to assess the level of susceptibility of this novel species and compare it with human pathogens already studied (such as Cryptococcus and Aspergillus spp). They are incubated at different temperatures: 37°C to mimic high body temperature of the host, 30°C that is more representative for skin and corneal infection and 24°C to observe if the temperature can affect fungal virulence. Survival and health score are measured daily for 7 days post infection and colony forming unit (CFU) counts of larval fungal load will be obtained at time of death. Also, the minimum concentration of spores needed to cause symptoms will be established. The project explores the possibility of considering G. mellonella as a successful in vivo model for investigation of the initial steps of Fusarium musae infection. In this first work we will observe that Fusarium musae is actually capable of infecting G. mellonella that in this way can be considered as a useful non-vertebrate infection model for studying infection mechanisms of F. musae on animal hosts. In addition the virulence of the different strains will be assessed. Our future work will focus on implementing our findings with the use of bioluminescence as additional readout of the investigation of the mechanisms of action of this pathogen in Galleria mellonella firstly but then also in mice. At the end we aim to use Galleria mellonella also as a potential application towards screening of therapeutic option since only few treatment options are currently available for Fusarium infections.