A variant ECE1 allele contributes to reduced pathogenicity of Candida albicans during vulvovaginal candidiasis
Open Access
- 10 September 2021
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLoS Pathogens
- Vol. 17 (9), e1009884
- https://doi.org/10.1371/journal.ppat.1009884
Abstract
Vulvovaginal candidiasis (VVC), caused primarily by the human fungal pathogen Candida albicans, results in significant quality-of-life issues for women worldwide. Candidalysin, a toxin derived from a polypeptide (Ece1p) encoded by the ECE1 gene, plays a crucial role in driving immunopathology at the vaginal mucosa. This study aimed to determine if expression and/or processing of Ece1p differs across C. albicans isolates and whether this partly underlies differential pathogenicity observed clinically. Using a targeted sequencing approach, we determined that isolate 529L harbors a similarly expressed, yet distinct Ece1p isoform variant that encodes for a predicted functional candidalysin; this isoform was conserved amongst a collection of clinical isolates. Expression of the ECE1 open reading frame (ORF) from 529L in an SC5314-derived ece1Δ/Δ strain resulted in significantly reduced vaginopathogenicity as compared to an isogenic control expressing a wild-type (WT) ECE1 allele. However, in vitro challenge of vaginal epithelial cells with synthetic candidalysin demonstrated similar toxigenic activity amongst SC5314 and 529L isoforms. Creation of an isogenic panel of chimeric strains harboring swapped Ece1p peptides or HiBiT tags revealed reduced secretion with the ORF from 529L that was associated with reduced virulence. A genetic survey of 78 clinical isolates demonstrated a conserved pattern between Ece1p P2 and P3 sequences, suggesting that substrate specificity around Kex2p-mediated KR cleavage sites involved in protein processing may contribute to differential pathogenicity amongst clinical isolates. Therefore, we present a new mechanism for attenuation of C. albicans virulence at the ECE1 locus. Vulvovaginal candidiasis (VVC), caused primarily by the human fungal pathogen Candida albicans, results in significant quality-of-life issues for women worldwide. Candidalysin, a toxin derived from a polypeptide (Ece1p) encoded by the ECE1 gene, plays a crucial role in driving disease pathology. In this study, we aimed to determine if genetic variation of ECE1 existed across a collection of C. albicans clinical isolates. Using a targeted sequencing approach, we identified a conserved variant candidalysin isoform. We then constructed isogenic chimeric strains harboring swapped Ece1p peptides or HiBiT tags between representative isoforms and showed impaired secretion with the variant that was associated with reduced virulence in vitro and in vivo. We also elucidated a conserved pattern between key sequences near lysine-arginine cleavage sites involved in Ece1p polypeptide processing by the Kex2p enzyme that correlate with predicted and experimental candidalysin secretion. Therefore, we present a novel mechanism for attenuation of C. albicans virulence at the ECE1 locus that may partly underlie differential clinical outcomes and contribute to the balance between commensal and pathogen at the vaginal mucosa.Keywords
Funding Information
- National Institute of Allergy and Infectious Diseases (K22AI110541)
- National Institute of Allergy and Infectious Diseases (R21AI127942)
- National Institute of Allergy and Infectious Diseases (R21AI141829)
- National Institute of Allergy and Infectious Diseases (R01A134796)
- National Institute of General Medical Sciences (R01GM120642)
- National Institute of Dental and Craniofacial Research (R01DE022550)
- Wellcome Trust (214229_Z_18Z)
- UTHSC College of Pharmacy Center for Pediatric and Experimental Therapeutics
This publication has 51 references indexed in Scilit:
- A Recently Evolved Transcriptional Network Controls Biofilm Development in Candida albicansCell, 2012
- The Fungal Pathogen Candida albicans Autoinduces Hyphal Morphogenesis by Raising Extracellular pHmBio, 2011
- Candida Infections of the Genitourinary TractClinical Microbiology Reviews, 2010
- Processing of predicted substrates of fungal Kex2 proteinases from Candida albicans, C. glabrata, Saccharomyces cerevisiae and Pichia pastorisBMC Microbiology, 2008
- Murine model of concurrent oral and vaginal Candida albicans colonization to study epithelial host–pathogen interactionsMicrobes and Infection, 2007
- UCSF Chimera?A visualization system for exploratory research and analysisJournal of Computational Chemistry, 2004
- WebLogo: A Sequence Logo Generator: Figure 1Genome Research, 2004
- Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2−ΔΔCT MethodMethods, 2001
- CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choiceNucleic Acids Research, 1994
- Preparation of Yeast RNACurrent Protocols in Molecular Biology, 1993