Transcriptomic Analysis of Vulvovaginal Candidiasis Identifies a Role for the NLRP3 Inflammasome

Abstract

Treatment of vulvovaginal candidiasis (VVC), caused most frequently by Candida albicans, represents a significant unmet clinical need. C. albicans, as both a commensal and a pathogenic organism, has a complex and poorly understood interaction with the vaginal environment. Understanding the complex nature of this relationship is necessary for the development of desperately needed therapies to treat symptomatic infection. Using transcriptome sequencing (RNA-seq), we characterized the early murine vaginal and fungal transcriptomes of the organism during VVC. Network analysis of host genes that were differentially expressed between infected and naive mice predicted the activation or repression of several signaling pathways that have not been previously associated with VVC, including NLRP3 inflammasome activation. Intravaginal challenge of Nlrp3−/− mice with C. albicans demonstrated severely reduced levels of polymorphonuclear leukocytes (PMNs), alarmins, and inflammatory cytokines, including interleukin-1β (IL-1β) (the hallmarks of VVC immunopathogenesis) in vaginal lavage fluid. Intravaginal administration of wild-type (WT) mice with glyburide, a potent inhibitor of the NLRP3 inflammasome, reduced PMN infiltration and IL-1β to levels comparable to those observed in Nlrp3−/− mice. Furthermore, RNA-seq analysis of C. albicans genes indicated robust expression of hypha-associated secreted aspartyl proteinases 4, 5, and 6 (SAP4–6), which are known inflammasome activators. Despite colonization similar to that of the WT strain, ΔSAP4–6 triple and ΔSAP5 single mutants induced significantly less PMN influx and IL-1β during intravaginal challenge. Our findings demonstrate a novel role for the inflammasome in the immunopathogenesis of VVC and implicate the hypha-associated SAPs as major C. albicans virulence determinants during vulvovaginal candidiasis.

The vaginal mycobiome: A contemporary perspective on fungi in women's health and diseases

“…The C. albicans extent of cell elongation 1 (ECE1) gene, which encodes the toxin they named Candidalysin, 86 is also among the most highly expressed genes during murine VVC. 87 Like many pathogenic bacteria, Candida species in general and C. albicans in particular, are efficient at biofilm formation within the human host.…”

Overexpression of Candida albicans Secreted Aspartyl Proteinase 2 or 5 Is Not Sufficient for Exacerbation of Immunopathology in a Murine Model of Vaginitis

“…2E). Rational selection of the TEF1 promoter to drive gene expression in vivo was based on our previously published data demonstrating high expression of this gene at the vaginal mucosa (6). Importantly, we also compared SAP expression levels in our hyphadefective strains to those in strain GP1 in vivo and determined that SAP2 and SAP5 were indeed overexpressed 8-fold and 3-fold, respectively, relative to those in the WT control (Fig.…”

“…Due to its previously identified consistently high expression in tissue culture and clinical vaginal samples and its role in mucosal pathogenesis, the secreted aspartyl proteinase Sap5 was further investigated for its role in VVC (7,8). Indeed, deletion of SAP5 alone (or deletion of a triad of hypha-associated SAP genes [SAP4, -5, and -6]) resulted in a modest but significant reduction in immunopathology in vivo, purportedly by reducing NLRP3 inflammasome activation (6).…”

“…In an effort to better understand host and fungal gene expression at the murine vaginal mucosa, we previously conducted an in vivo transcriptome sequencing (RNA-seq) study (6). Using analysis of the number of reads per kilobase per million (RPKM), approximately 50 of the most highly expressed fungal genes were elucidated.…”

Budding off: bringing functional genomics toCandida albicans

“…Here, gene transcription reflected the various chronological stages of attachment, hyphal production, cell invasion and tissue destruction [99]. A similarly ordered transcriptional profile was also identified using a murine model of vulvovaginal candidiasis [115,116]. More recently, RNA-Seq was used to evaluate both C. albicans and host transcriptomes during the interaction between fungal cells and human endothelial or oral epithelial cells [117].…”