Deciphering of Candida parapsilosis induced immune response in Drosophila melanogaster

Candida albicans infection model in Drosophila melanogaster suggests a strain-specific virulent factor boosting a stormy innate immune response

Intorduction

Pathogens drive the evolution of host defence strategies, with both innate and adaptive immune systems playing key roles. Priming enhances the innate immune system's readiness by functionally reprogramming immune cells after initial exposure to stimuli, like β-glucans. In this sense, Drosophila melanogaster is a valuable model to evaluate the role of innate immunity to control infections.

Objectives

In this study we aimed to set light on the immune priming effect of oral treatment with heat-killed M. manresensis and two different heat-killed C. albicans isolates upon systemic infection by C. albicans in the D. melanogaster model.

Methods

A clinical and a control ATCC 90028 Candida albicans strain were used. Flies were primed through oral administration of heat-killed C. albicans (hkCa), both clinical and control, and hk-Mycolicibacterium manresensis. After priming, flies were systemically infected with both C. albicans isolates. Host survival, pathogen load, and immune response in response to treatment and infection were evaluated.

Results

Both treatments showed a significant capacity to enhance the expression of antimicrobial peptides, in particular Diptericin, and Drosomycin in males. This response had a marked sexual dimorphism due to the difference in Upd3, Nox, and Duox expression. Surprisingly, even when priming was able to avoid the growth of both C. albicans strains, survival was not improved in the case of the clinical isolate, causing an unexpected mortality rate in hours, regardless of the host's sex. Gene expression analysis 24 hours post-infection showed an exacerbated increase in Diptericin, Drosomycin and Upd3 expression upon infection with the clinical strain.

Conclusion

Data herein suggests the presence of a strain-specific component in C. albicans as the booster of a "stormy" innate immune response, which must be further investigated, and position D. melanogaster as a useful model for evaluating virulent factors related to the modulation of the innate immunity.

The utility of Drosophila melanogaster as a fungal infection model

Invasive fungal diseases have profound effects upon human health and are on increase globally. The World Health Organization (WHO) in 2022 published the fungal priority list calling for improved public health interventions and advance research. Drosophila melanogaster presents an excellent model system to dissect host-pathogen interactions and has been proved valuable to study immunopathogenesis of fungal diseases. In this review we highlight the recent advances in fungal-Drosophila interplay with an emphasis on the recently published WHO's fungal priority list and we focus on available tools and technologies.

Bibliometric analysis and thematic review of Candida pathogenesis: Fundamental omics to applications as potential antifungal drugs and vaccines

Invasive candidiasis caused by the pathogenic Candida yeast species has resulted in elevating global mortality. The pathogenicity of Candida spp. is not only originated from its primary invasive yeast-to-hyphal transition; virulence factors (transcription factors, adhesins, invasins, and enzymes), biofilm, antifungal drug resistance, stress tolerance, and metabolic adaptation have also contributed to a greater clinical burden. However, the current research theme in fungal pathogenicity could hardly be delineated with the increasing research output. Therefore, our study analysed the research trends in Candida pathogenesis over the past 37 years via a bibliometric approach against the Scopus and Web of Science databases. Based on the 3993 unique documents retrieved, significant international collaborations among researchers were observed, especially between Germany (Bernhard Hube) and the UK (Julian Naglik), whose focuses are on Candida proteinases, adhesins, and candidalysin. The prominent researchers (Neils Gow, Alistair Brown, and Frank Odds) at the University of Exeter and the University of Aberdeen (second top performing affiliation) UK contribute significantly to the mechanisms of Candida adaptation, tolerance, and stress response. However, the science mapping of co-citation analysis performed herein could not identify a hub representative of subsequent work since the clusters were semi-redundant. The co-word analysis that was otherwise adopted, revealed three research clusters; the cluster-based thematic analyses indicated the severeness of Candida biofilm and antifungal resistance as well as the elevating trend on molecular mechanism elucidation for drug screening and repurposing. Importantly, the in vivo pathogen adaptation and interactions with hosts are crucial for potential vaccine development.