Toll-deficient Flies Research Articles

Drosophila melanogaster as a model of systemic dermatophytosis.

Dermatophytosis is one of the most common fungal infections worldwide. The distribution of dermatophytes varies across continents, but the genera Trichophyton and Microsporum have emerged as the main isolated agents in humans and animals. To validate Drosophila melanogaster flies as a fast and feasible model to study dermatophytic infections. Wild-type (WT) and Toll-deficient D. melanogaster flies were infected by Trichophyton rubrum, T. mentagrophytes, Microsporum canis and Nannizzia gypsea by pricking with a needle previously dipped in inoculum concentrations ranging from 103 to 108 colony-forming units/mL. Establishment of infection was confirmed by survival curves, histopathological analysis and fungal burden. Thereafter, flies were treated with terbinafine, itraconazole and clioquinol. WT flies were predominantly resistant to the infection, whereas Toll-deficient flies succumbed to the four dermatophyte genera tested. The antifungal drugs protected flies from the infection, except for N. gypsea whose survival curves did not differ from the untreated group. This pilot study confirms that D. melanogaster is a suitable model to study the virulence and antifungal drug efficacy in dermatophyte species.

Drosophila melanogaster as a Rapid and Reliable In Vivo Infection Model to Study the Emerging Yeast Pathogen Candida auris.

While mammalian models remain the gold standard to study invasive mycoses, mini-host invertebrate models have provided complementary platforms for explorative investigations of fungal pathogenesis, host-pathogen interplay, and antifungal therapy. Specifically, our group has established Toll-deficient Drosophila melanogaster flies as a facile and cost-effective model organism to study candidiasis, and we have recently expanded these studies to the emerging and frequently multidrug-resistant yeast pathogen Candida auris. Our proof-of-concept data suggest that fruit flies could hold a great promise for large-scale applications in antifungal drug discovery and the screening of C. auris (mutant) libraries with disparate pathogenic capacity. This chapter discusses the advantages and limitations of D. melanogaster to study C. auris candidiasis and provides a step-by-step guide for establishing and troubleshooting C. auris infection and antifungal treatment of Toll-deficient flies along with essential downstream readouts.

Drosophila melanogaster as a model for the study of Malassezia pachydermatis infections

Malassezia pachydermatis is a yeast that is commonly found in the skin of most animals. Changes in the physical, chemical or immunological processes of the skin may render the host more susceptible to the yeast, which then may cause otitis, dermatitis or, less often, systemic infection. We tested the pathogenicity of M. pachydermatis in wild-type (WT) and Toll-deficient Drosophila melanogaster. Flies were inoculated in the thorax with a needle previously dipped in inoculum concentrations ranging from 103 and 107 yeast cells/mL. After infection, flies were housed at 29 °C and mortality was evaluated daily until day seven. WT flies were resistant to the infection, whereas Toll-deficient flies showed inoculum-dependent mortality rates. Fungal burden, assessed by histopathological analysis and by counting the number of colony-forming units of dead flies, corroborated the results. The D. melanogaster model is a promising minihost model for future large-scale studies of virulence mechanisms and antifungal drug activity in malasseziosis.

Drosophila melanogaster as a model to explore the effects of methicillin-resistant Staphylococcus aureus strain type on virulence and response to linezolid treatment

BackgroundUSA300 is a uniquely successful methicillin-resistant Staphylococcus aureus (MRSA) clone that has been associated with Panton-Valentine leukocidin (PVL) production and severe infections. However, conflicting experimental and epidemiological data exist regarding the virulence of USA300 relative to other MRSA clones. We aimed to address this issue using Drosophila melanogaster as a model host to study strain and PVL-dependent variations in virulence among MRSA clinical isolates. ResultsWe studied the relative virulence of 39 MRSA isolates: 17 (43%) were PFGE type USA300. Lethal MRSA infection was reproducibly induced both in wild-type (WT) and Toll-deficient D. melanogaster. USA300 strains had significantly lower lethality than non-USA300 strains in a WT background but not in Toll-deficient flies. PFGE type (USA300 versus non-USA300) and PVL status did not affect the response to treatment with linezolid. Virulence was similar in strains with high vancomycin MIC (≥2 μg/mL) versus those with vancomycin MIC<2 μg/mL. ConclusionsD. melanogaster is a potentially useful model host to study pathogenicity and response to antibiotic treatment in S. aureus. Our results imply that the attenuated virulence of PVL+/USA300 requires intact host innate immunity.

Toll-deficient Drosophila are resistant to infection by Pneumocystis spp.: additional evidence of specificity to mammalian hosts

Pneumocystis spp. are significant pathogens in a variety of mammals. We tried to establish a Drosophila model of pneumocystosis using either P. murina or P. carinii. Whereas the pathogens were competent in susceptible mice, no infection could be established even in corticosteroid-treated Toll-deficient flies. This further substantiates the tropism described for mammalian hosts.

Exploring the concordance ofAspergillus fumigatuspathogenicity in mice andToll-deficient flies

The pathogenicity of six mutants of Aspergillus fumigatus that had been previously characterized in mice was assessed in Toll-deficient Drosophila melanogaster flies. Four out of six mutants of A. fumigatus, which displayed attenuated virulence in mice due to defects in siderophore biosynthesis (DeltasidA, DeltasidD), PABA metabolism (H515), and starvation stress response (DeltacpcA), also had attenuated virulence in the fly model. In addition, similarly to previous findings in the mouse model, DeltasidG mutant that is defective in extracellular siderophore biosynthesis retained full virulence in Toll-deficient flies. Overall, our studies reveal a high level of concordance between fly and murine models of invasive aspergillosis.

Interstrain variability in the virulence ofAspergillus fumigatusandAspergillus terreusin aToll-deficientDrosophilafly model of invasive aspergillosis

Members of the genus Aspergillus are opportunistic fungal pathogens characterized by their genomic diversity. However, whether variations among Aspergillus strains and species at the genome level translate into significant differences in virulence is unclear. Therefore, we studied the interstrain and interspecies variations in virulence for a collection of Aspergillus fumigatus and Aspergillus terreus isolates using a previously described model of invasive aspergillosis in Toll-deficient fruit flies. We then looked for associations between survival in the fly model and strain relatedness as defined by repetitive-sequence polymerase chain reaction (rep-PCR). We observed no significant differences in the survival of flies infected with A. fumigatus vs. A. terreus or flies infected with colonizing vs. invasive isolates of either species. However, in both Aspergillus species we observed significant interstrain variability in fly survival (P<0.001 by the log-rank test). Using rep-PCR, we identified two dominant A. fumigatus clades that were associated with significantly different survival rates in Toll-deficient flies (P=0.007). We conclude that the fly model of invasive aspergillosis enables high-throughput screening of Aspergillus species for variations in virulence and may uncover distinct A. fumigatus clades that differ in their pathogenicity.

Interstrain variability in the virulence of Aspergillus fumigatus and Aspergillus terreus in a Toll-deficient Drosophila fly model of invasive aspergillosis

Members of the genus Aspergillus are opportunistic fungal pathogens characterized by their genomic diversity. However, whether variations among Aspergillus strains and species at the genome level translate into significant differences in virulence is unclear. Therefore, we studied the interstrain and interspecies variations in virulence for a collection of Aspergillus fumigatus and Aspergillus terreus isolates using a previously described model of invasive aspergillosis in Toll-deficient fruit flies. We then looked for associations between survival in the fly model and strain relatedness as defined by repetitive-sequence polymerase chain reaction (rep-PCR). We observed no significant differences in the survival of flies infected with A. fumigatus vs. A. terreus or flies infected with colonizing vs. invasive isolates of either species. However, in both Aspergillus species we observed significant interstrain variability in fly survival (P<0.001 by the log-rank test). Using rep-PCR, we identified two dominant A. fumigatus clades that were associated with significantly different survival rates in Toll-deficient flies (P=0.007). We conclude that the fly model of invasive aspergillosis enables high-throughput screening of Aspergillus species for variations in virulence and may uncover distinct A. fumigatus clades that differ in their pathogenicity.

Exploring the concordance of Aspergillus fumigatus pathogenicity in mice and Toll-deficient flies

Exploring the concordance of Aspergillus fumigatus pathogenicity in mice and Toll-deficient flies

Drosophila melanogaster as a model host to dissect the immunopathogenesis of zygomycosis

Zygomycosis is an emerging frequently fatal opportunistic mycosis whose immunopathogenesis is poorly understood. We developed a zygomycosis model by injecting Drosophila melanogaster flies with a standardized amount of fungal spores from clinical Zygomycetes isolates to study virulence and host defense mechanisms. We found that, as opposed to most other fungi, which are nonpathogenic in D. melanogaster (e.g., Aspergillus fumigatus), Zygomycetes rapidly infect and kill wild-type flies. Toll-deficient flies exhibited increased susceptibility to Zygomycetes, whereas constitutive overexpression of the antifungal peptide Drosomycin in transgenic flies partially restored resistance to zygomycosis. D. melanogaster Schneider 2 phagocytic cells displayed decreased phagocytosis and caused less hyphal damage to Zygomycetes compared with that to A. fumigatus. Furthermore, phagocytosis-defective eater mutant flies displayed increased susceptibility to Zygomycetes infection. Classic enhancers of Zygomycetes virulence in humans, such as corticosteroids, increased iron supply, and iron availability through treatment with deferoxamine dramatically increased Zygomycetes pathogenicity in our model. In contrast, iron starvation induced by treatment with the iron chelator deferasirox significantly protected flies infected with Zygomycetes. Whole-genome expression profiling in wild-type flies after infection with Zygomycetes vs. A. fumigatus identified genes selectively down-regulated by Zygomycetes, which act in pathogen recognition, immune defense, stress response, detoxification, steroid metabolism, or tissue repair or have unknown functions. Our results provide insights into the factors that mediate host-pathogen interactions in zygomycosis and establish D. melanogaster as a promising model to study this important mycosis.

Virulence Studies ofScedosporiumandFusariumSpecies inDrosophila melanogaster

We developed a model of infection, using 1 Fusarium species (F. moniliforme) and 2 Scedosporium species (S. apiospermum and S. prolificans), in wild-type and Toll-deficient Drosophila melanogaster flies by injecting them with a standardized conidia inoculum. Wild-type flies were resistant to infection with both S. apiospermum and S. prolificans but were susceptible to infection with F. moniliforme. When Toll-deficient flies were infected with any of the 3 pathogens, the result was acute infection and high mortality rates. Voriconazole mixed in fly food significantly protected flies infected with F. moniliforme or S. apiospermum but not those infected with S. prolificans.