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Galleria mellonella as a model host to study Paracoccidioides lutzii and Histoplasma capsulatum
Luciana Thomaz1, Rocío García-Rodas, Allan J Guimarães
1Institute of Biomedical Science, Department of Microbiology, University of São Paulo, São Paulo, Brazil. lucithomaz@usp.br
Abstract:
Non-mammalian models have been used to investigate fungal virulence. In this work we have explored the use of Galleria mellonella as an infection model for the pathogenic dimorphic fungi Histoplasma capsulatum and Paracoccidioides lutzii. In mammalian models these fungi cause similar infections, and disease outcomes are influenced by the quantity of the infective inocula. We describe a similar aspect in a G. mellonella model and characterize the pathogenesis features in this system. Infection with P. lutzii or H. capsulatum, in all inoculum used, killed larvae at 25 and 37°C. However, there was a lack of correlation between the number of yeast cells used for infection and the time to larvae death, which may indicate that the fungi induce protective responses in a dynamic manner as the lowest concentrations of fungi induced the most rapid death. For both fungi, the degree of larvae melanization was directly proportional to the inocula size, and this effect was visibly more apparent at 37°C. Histological evaluation of the larvae showed a correlation between the inoculum and granuloma-like formation. Our results suggest that G. mellonella is a potentially useful model to study virulence of dimorphic fungi.
Insights
The greater wax moth (Galleria mellonella) effectively models infections by Histoplasma capsulatum and Paracoccidioides lutzii. This insect model reveals fungal virulence dynamics and host responses relevant to dimorphic fungi research.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Model Organisms
Background:
- Non-mammalian models are crucial for studying fungal virulence.
- Dimorphic fungi like Histoplasma capsulatum and Paracoccidioides lutzii cause significant infections.
- Mammalian models show disease outcomes influenced by inoculum size.
Purpose of the Study:
- To evaluate Galleria mellonella as an infection model for Histoplasma capsulatum and Paracoccidioides lutzii.
- To characterize pathogenesis features of these fungi in the G. mellonella model.
- To explore the relationship between inoculum size and host response.
Main Methods:
- Larval infection assays with H. capsulatum and P. lutzii at varying temperatures (25°C and 37°C).
- Assessment of larval survival, melanization, and histological changes.
- Correlation analysis between inoculum size and observed pathogenesis markers.
Main Results:
- Infection with either fungus killed G. mellonella larvae at both temperatures.
- Larval melanization was proportional to inoculum size, more pronounced at 37°C.
- Histological examination revealed granuloma-like structures correlating with inoculum size.
Conclusions:
- Galleria mellonella serves as a viable model for studying dimorphic fungal virulence.
- The model demonstrates inoculum-dependent host responses, including melanization and granuloma formation.
- This insect model offers insights into the pathogenesis of H. capsulatum and P. lutzii infections.
