Free‐living amoebae (FLAs) are major reservoirs for a variety of bacteria, viruses, and fungi. The most studied mycophagic FLA,
Acanthamoeba castellanii (
Ac), is a potential environmental host for endemic fungal pathogens such as
Cryptococcus spp.,
Histoplasma capsulatum,
Blastomyces dermatitides, and
Sporothrix schenckii. However, the mechanisms involved in this interaction are poorly understood. The aim of this work was to characterize the molecular instances that enable
Ac to interact with and ingest fungal pathogens, a process that could lead to selection and maintenance of possible virulence factors. The interaction of
Ac with a variety of fungal pathogens was analysed in a multifactorial evaluation that included the role of multiplicity of infection over time. Fungal binding to
Ac surface by living image consisted of a quick process, and fungal initial extrusion (vomocytosis) was detected from 15 to 80 min depending on the organism. When these fungi were cocultured with the amoeba, only
Candida albicans and
Cryptococcus neoformans were able to grow, whereas
Paracoccidioides brasiliensis and
Sporothrix brasiliensis displayed unchanged viability. Yeasts of
H. capsulatum and
Saccharomyces cerevisiae were rapidly killed by
Ac; however, some cells remained viable after 48 hr. To evaluate changes in fungal virulence upon cocultivation with
Ac, recovered yeasts were used to infect
Galleria mellonella, and in all instances, they killed the larvae faster than control yeasts. Surface biotinylated extracts of
Ac exhibited intense fungal binding by FACS and fluorescence microscopy. Binding was also intense to mannose, and mass spectrometry identified
Ac proteins with affinity to fungal surfaces including two putative transmembrane mannose‐binding proteins (MBP, L8WXW7 and MBP1, Q6J288). Consistent with interactions with such mannose‐binding proteins,
Ac–fungi interactions were inhibited by mannose. These MBPs may be involved in fungal recognition by amoeba and promotes interactions that allow the emergence and maintenance of fungal virulence for animals.
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