Broad Antifungal Spectrum of the Pore-Forming Peptide C14R Against Cryptococcus and Candida Species from the WHO Fungal Priority Pathogens List

Abstract

The World Health Organization (WHO) prioritized 19 fungal species based on the significant impact of these pathogens on human health, including the emergence of antifungal resistance, which highlights the necessity of finding new antifungal therapies. Among these novel therapeutic approaches, the antimicrobial pore-forming peptide C14R has shown to be promising against Candida albicans and Candida auris. In this study, the antifungal in vitro efficacy of C14R was assessed against six additional species from the WHO priority list, Cryptococcus neoformans, Cryptococcus gattii, Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei, as well as against Candida dubliniensis. This study shows that C14R has good antifungal activity against several clinical isolates of the studied species, with MIC values between 0.8476 and 10.88 µg/mL. Most notably, some of the studied isolates are resistant to commonly used antifungal drugs but are susceptible to the peptide. C14R showed, moreover, its capacity to disrupt Cryptococcus capsules, beyond its already proven capacity to disrupt plasma membranes, and its antifungal activity was not affected depending on the serotype or species assessed. The inclusion of basidiomycete and ascomycete yeasts allowed us to display the broad-spectrum potential of C14R, highlighting it as a promising candidate as an antifungal agent.

Keywords: C14R; Candida; Cryptococcus; antifungal resistance; antimicrobial peptides; cryptococcosis; invasive candidiasis.

Figure 1

Chemical structure of the major polysaccharide glucuronoxylomannan (GXM) of the serotypes A (Cryptococcus neoformans) and C (Cryptococcus gattii) employed in this work. GlcAp: glucoronic acid, Xylp: xylose; Manp: mannose.; MC: α-D-Manp residues and SC: sidechain residues.

Figure 2

Interactions per residue of C14R with the polysaccharides of the capsules of the serotype A (Cryptococcus neoformans) and the serotype C (Cryptococcus gattii).

Figure 3

Cryptococcus neoformans membrane permeabilization ability of C14R. (A) Treatment with 25 µg/mL of C14R and staining of porous cells using rhodamine phalloidin (1250 Da), ATTO 488 alkyne (741 Da), propidium iodide (668 Da) or FITC (389 Da) as fluorescent dyes with untreated cells serving as negative controls and (B) using 0.4% Triton X-100 as positive control. The experiments were conducted in triplicate with error bars representing standard deviations. ns: not significant; ** statistically significant p-value < 0.01 and **** p-value < 0.0001.