Acanthamoeba castellanii as an alternative interaction model for the dermatophyte Trichophyton rubrum

Abstract

Summary Background Trichophyton rubrum (Tr) is the main aetiological agent of human dermatophytosis, being isolated from the environment and keratinised tissues. In the environment, Tr can interact with other organisms, such as free‐living amoebas (FLA), which can act as an alternative host system to study the interaction between microbes and phagocytic cells. Objectives To characterise the Acanthamoeba castellanii (ALX)‐Tr interaction. Methods Interaction was characterised in three conditions: trophozoites (PYG), late (PYG/NES) and early (NES) encystation stimulus, evaluating encystation kinetics, phagocytosis, exocytosis and fungicidal activity dynamics. Results Tr was able to induce ALX encystation and be internalised by ALX. The number of internalised conidia was high at 1 hour, and ALX presented fungicidal activity with increased intracellular ROS production and exocytosis. In PYG/NES, phagocytosis and ROS production were reduced, with decreased ALX’s fungicidal activity. However, in NES there was an increased fungal engulfment, and a reduced ROS production and higher fungal burden. Furthermore, exogenous mannose decreased phagocytosis of Tr conidia, and divalent cations induced ROS production and increased ALX’s fungicidal activity. Interestingly, phagocytosis was reduced in the presence of cytoskeleton inhibitor, but exocytosis was increased, suggesting that Tr conidia may have alternative pathways to escape ALX's cells. Conclusion A castellanii is a proper model for studying Tr‐FLA interaction, since ALX can engulf, produce ROS and kill Tr, and all these parameters are influenced by an encystation stimulus and divalent cations. Moreover, this interaction is likely to occur in the environment implicating in the adaptation to environmental stressful conditions in both organisms.

Drosophila melanogaster as a model of systemic dermatophytosis

“…Invertebrate models of infections have limitations—in the case of D. melanogaster , for example, the maximum temperature of 29°C used to incubated infected flies; the lack of precise pharmacokinetic/pharmacodynamic parameters; difficulties in parenteral drug administration; and lack of adaptive immunity 6,8 . Nonetheless, they are important to fulfil gaps left unanswered by the mammalian models, 19 which also have several constraints, such as the need to decrease immune functions to avoid spontaneous healing; difficulty to reproduce all types of dermatophyte presentations; ethical constraints; and risk of acquiring infection due to environmental contamination 17 . Here, we showed for the first time that Toll ‐deficient flies can be an appropriate model of systemic dermatophytosis, including virulence and drug efficacy studies.…”

State-of-the-Art Dermatophyte Infections: Epidemiology Aspects, Pathophysiology, and Resistance Mechanisms

“…Overall, in vitro investigations rely on substrates present in the host tissue, such as keratin, protein, and lipids, providing insights into dermatophyte metabolism and nutrient sensing during infection [ 36 , 37 , 38 ]. Moreover, in vitro interactions with cells, such as keratinocytes, macrophages, neutrophils, and Acanthamoeba , have also been used to understand fungal responses to host cells and immune defenses [ 39 , 40 , 41 ]. In vivo animal models include the use of guinea pigs, mice, and invertebrates (such as Galleria mellonella larvae), which have also been useful for evaluating the activity of antifungal drugs [ 38 , 42 , 43 , 44 ].…”

A history of over 40 years of potentially pathogenic free-living amoeba studies in Brazil - a systematic review

“…(184) Sixty-seven percent (39/58) of the auxiliary references describe investigations specific to ARMs. Fungi and FLA interactions addressed Trichophyton rubrum, (90) Fusarium, (85) Sporothrix, (185) Paracoccidioides spp., (186) and Cryptococcus species, (183,187,188) all associated with Acanthamoeba. Some of these reports highlight that fungi-FLA interactions in the environment mimic those found between fungi and host cells, possibly contributing to the development of virulence and immune escape strategies.…”

“…Some reports discuss interactions of FLAs with fungi and bacteria, addressing both endosymbionts and pathogens of concern in human health. (19,(85)(86)(87)(88)(89)(90) Another type of ARMs studied in Brazil comprises human adenovirus (91) and giant viruses such as the Tupanvirus, isolated from V. vermiformis and A. polyphaga mimivirus. (92,93) We discussed below other reports on giant virus classified in the auxiliary class.…”