Modulation of Zinc Homeostasis in Acanthamoeba castellanii as a Possible Antifungal Strategy against Cryptococcus gattii

Abstract

Cryptococcus gattii is a basidiomycetous yeast that can be found in the environment and is one of the agents of cryptococcosis, a life-threatening disease. During its life cycle, cryptococcal cells take hold inside environmental predators such as amoebae. Despite their evolutionary distance, macrophages and amoebae share conserved similar steps of phagocytosis and microbial killing. To evaluate whether amoebae also share other antifungal strategies developed by macrophages, we investigated nutritional immunity against cryptococcal cells. We focused on zinc homeostasis modulation in Acanthamoeba castellanii infected with C. gattii. The intracellular proliferation rate (IPR) in amoebae was determined using C. gattii R265 and mutants for the ZIP1 gene, which displays defects of growth in zinc-limiting conditions. We detected a reduced IPR in cells lacking the ZIP1 gene compared to wild-type strains, suggesting that amoebae produce a low zinc environment to engulfed cells. Furthermore, flow cytometry analysis employing the zinc probe Zinpyr-1 confirmed the reduced concentration of zinc in cryptococcal-infected amoebae. qRT-PCR analysis of zinc transporter-coding genes suggests that zinc export by members of the ZnT family would be involved in the reduced intracellular zinc concentration. These results indicate that amoebae may use nutritional immunity to reduce fungal cell proliferation by reducing zinc availability for the pathogen.

Genotypic and Phenotypic Diversity of Cryptococcus gattii VGII Clinical Isolates and Its Impact on Virulence

“…It is known that continued sub culturing affects phenotypic and genotypic characteristics of cryptococcal cells ( Cavalcante et al, 2007 ). However, the assessment of virulence profiles of the R265 strain by our group over the last decade did not revealed major differences ( Schneider et al, 2012 ; Godinho et al, 2014 ; Feder et al, 2015 ; Schneider Rde et al, 2015 ; Joffe et al, 2017 ; Ribeiro et al, 2017 ). In this way, the differences of virulence properties between CG strains and R265 could not be caused by sub culturing and should be considered due to inherent genotypic and phenotypic characteristics.…”

Two‐step method for isolating Cryptococcus species complex from environmental material using a new selective medium

“…Brazilian C. gattii VGII population was found with the highest diversity in the world, and the link between C. gattii VGII population in Brazil and other parts of the world indicates that Brazil is the origin of this subtype of C. gattii that spreads worldwide (Souto et al ., ). The survival of Cryptococcus cells within environmental amoebae had been demonstrated similar to the survival of Cryptococcus cells in macrophages, and some mechanisms, such as zinc homeostasis and polysaccharide accumulation, had been revealed related to the survival of intracellular Cryptococcus cells (Steenbergen et al ., ; Ribeiro et al ., ). It had also been shown that Cryptococcus could grow and reproduce on media with plant material or dead plant materials, which indicates that plants could be the ecological niche of this species (Springer et al ., ).…”

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

“…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. (187,188,189) One study identified Pseudomonas in Acanthamoeba isolates. (86) Another survey adopted a co-culture model between this FLA genus and methicillin-resistant Staphylococcus aureus, showing mutual effects on cell growth or differentiation.…”