Exploring the Galleria mellonella model to study antifungal photodynamic therapy
Lívia Mara Alves Figueiredo-Godoi1, Raquel Telles Menezes1, Jéssica Shiotani Carvalho1
1Department of Biosciences and Oral Diagnosis, São Paulo State University (Unesp), Institute of Science and Technology (ICT), São José dos Campos Campus, São Paulo, Brazil.
Background:
Antimicrobial photodynamic therapy (aPDT) shows antimicrobial activity on yeast of the genus Candida. In aPDT, the depth at which the light penetrates the tissue is extremely important for the elaboration of the treatment. The aim of this study was to evaluate the action of aPDT on experimental candidiasis and the laser impact in the tissue using Galleria mellonella as the infection model.
Methods:
G. mellonella larvae were infected with different Candida albicans strains. After 30 min, they were treated with methylene blue-mediated aPDT and a low intensity laser (660 nm). The larvae were incubated at 37 °C for seven days and monitored daily to determine the survival curve, using the Log-rank test (Mantel Cox). To evaluate the distribution of the laser as well as its depth of action in the larva body, the Interactive 3D surface PLOT of Image J was used. The effects of aPDT on the immune system were also evaluated by the quantification of hemocytes in the hemolymph of G. mellonella after 6 h of Candida infection (ANOVA and Tukey's test).
Results:
In both the ATCC 18,804 strain and the C. albicans clinical strain 17, aPDT prolonged the survival of the infected G. mellonella larvae by a lethal fungal dose. There was a statistically significant difference between the aPDT and the control groups in the ATCC strain (P = 0.0056). The depth of laser action in the insect body without the photosensitizer was 2.5 mm and 2.4 mm from the cuticle of the larva with the photosensitizer. In the larvae, a uniform distribution of light occurred along 32% of the body length for the group without the photosensitizer and in 39.5% for the group with the photosensitizer. In the immunological analysis, the infection by C. albicans ATCC 18,804 in G. mellonella led to a reduction in the number of hemocytes in the hemolymph. The aPDT and laser treatment induced a slight increase in the number of hemocytes.
Conclusion:
Both aPDT and laser treatment positively influenced the treatment of experimental candidiasis. G. mellonella larvae were a useful model for the study of light tissue penetration in antimicrobial photodynamic therapy.
Insights
Antimicrobial photodynamic therapy (aPDT) effectively treated experimental candidiasis in wax moth larvae. This study highlights aPDT
Area of Science:
- Microbiology
- Biomedical Engineering
- Photomedicine
Background:
- Antimicrobial photodynamic therapy (aPDT) demonstrates efficacy against Candida yeast.
- Light penetration depth is critical for aPDT treatment success.
- Galleria mellonella serves as a model for studying candidiasis and laser-tissue interactions.
Purpose of the Study:
- To evaluate the effectiveness of aPDT against experimental candidiasis.
- To assess laser light distribution and penetration depth in the Galleria mellonella model.
- To investigate the impact of aPDT on the host immune response.
Main Methods:
- Infection of G. mellonella larvae with Candida albicans strains.
- Treatment with methylene blue-mediated aPDT and low-intensity laser (660 nm).
- Monitoring of larval survival, laser penetration depth, light distribution, and hemocyte counts.
Main Results:
- aPDT significantly prolonged survival in larvae infected with C. albicans.
- Laser penetration depth was approximately 2.4-2.5 mm with and without photosensitizer.
- aPDT and laser treatment led to a slight increase in hemocyte counts following Candida infection.
Conclusions:
- Both aPDT and laser treatment positively impacted experimental candidiasis.
- Galleria mellonella is a suitable model for studying light penetration in aPDT.
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