Protective effect of fungal extracellular vesicles against murine candidiasis

Abstract

Extracellular vesicles (EVs) are lipid bilayered compartments released by virtually all living cells, including fungi. Among the diverse molecules carried by fungal EVs, a number of immunogens, virulence factors and regulators have been characterised. Within EVs, these components could potentially impact disease outcomes by interacting with the host. From this perspective, we previously demonstrated that EVs from Candida albicans could be taken up by and activate macrophages and dendritic cells to produce cytokines and express costimulatory molecules. Moreover, pre‐treatment of Galleria mellonella larvae with fungal EVs protected the insects against a subsequent lethal infection with C. albicans yeasts. These data indicate that C. albicans EVs are multi‐antigenic compartments that activate the innate immune system and could be exploited as vaccine formulations. Here, we investigated whether immunisation with C. albicans EVs induces a protective effect against murine candidiasis in immunosuppressed mice. Total and fungal antigen‐specific serum IgG antibodies increased by 21 days after immunisation, confirming the efficacy of the protocol. Vaccination decreased fungal burden in the liver, spleen and kidney of mice challenged with C. albicans. Splenic levels of cytokines indicated a lower inflammatory response in mice immunised with EVs when compared with EVs + Freund's adjuvant (ADJ). Higher levels of IL‐12p70, TNFα and IFNγ were detected in mice vaccinated with EVs + ADJ, while IL‐12p70, TGFβ, IL‐4 and IL‐10 were increased when no adjuvants were added. Full protection of lethally challenged mice was observed when EVs were administered, regardless the presence of adjuvant. Physical properties of the EVs were also investigated and EVs produced by C. albicans were relatively stable after storage at 4, −20 or −80°C, keeping their ability to activate dendritic cells and to protect G. mellonella against a lethal candidiasis. Our data suggest that fungal EVs could be a safe source of antigens to be exploited in vaccine formulations.

RevisitingCryptococcusextracellular vesicles properties and their use as vaccine platforms

“…It was previously shown that the pre-treatment of Galleria mellonella larvae with fungal EVs stimulated a protective response against a lethal challenge with C. albicans or C. neoformans (Vargas et al 2015, Colombo et al 2019. More recently, it was also demonstrated that C. albicans EVs were also able to elicit a protective effect against murine candidiasis (Vargas et al 2020). Interestingly, C. neoformans EV have shown to be immune reactive with sera from patients with cryptococcosis, indicating that EVassociated proteins are produced during cryptococcal infection and that they might be used as vaccines (Rodrigues et al 2008).…”

“…Since many immunogenic proteins are often found to be associated with EVs, their vaccine potential has been explored mostly for bacterial and parasitic infections (Coakley et al 2017, Wang et al 2018, and more recently also for fungal infections (Colombo et al 2019, Vargas et al 2020. In the present study, we used the recently described protocol (Reis et al 2019), to obtain EV-enriched samples from Cryptococcus cells, together with cutting edge methodological approaches to revisit Cryptococcus EV structure, cargo, and biological functions.…”

Extracellular Vesicles Derived From Talaromyces marneffei Yeasts Mediate Inflammatory Response in Macrophage Cells by Bioactive Protein Components

“…The possible reason for this difference may be the different infection processes of TM and EVs in macrophages, and further research is needed. Acting as professional antigen-presenting cells, macrophage cells were also known to play an important role in the regulation of intercellular communication, in which co-stimulatory molecules were thought to have indispensable roles in inducing T-cell activation, antigen processing, and presentation ( Vargas et al, 2020 ). We have shown previously that macrophage cells stimulated with EVs could produce various inflammatory factors, which indicated that TM-related antigens on vesicles might be presented on the cell surface and regulate the immune cell activation.…”

Small molecule analysis of extracellular vesicles produced byCryptococcus gattii: identification of a tripeptide controlling cryptococcal infection in an invertebrate host model

“…The six peptides listed in Table 3 were also found in these extracts (data not shown). It has been recently reported that fungal EVs, including cryptococcal vesicles, protect mice and the invertebrate host Galleria mellonella against lethal challenges with pathogenic fungi (12,(21)(22)(23). The vesicular molecules responsible for the protection remained unknown.…”