Regulation of Canonical NF-κB Signaling in Macrophages by Cryptococcus neoformans Capsular Polysaccharide

Abstract

Cryptococcus neoformans (Cn) is a ubiquitous fungal pathogen that causes meningitis in immunocompromised individuals. The major virulence factor of Cn is a thick polysaccharide capsule composed of glucuronoxylomannan (GXM) and galactoxylomannan (GalXM). GXM has been implicated in altering NF-κB signaling in macrophages, which constitute one of the first defenses against Cn infection. Capsular polysaccharides were isolated from Serotype A Cn, wildtype strain H99S, GalXMnegative Uge1, and GXM-negative Cap59. RAW 264.7 NF-κB reporter cells with p65 expressed as a chimeric fusion protein with GFP (p65-EGFP) were treated with GXM and LPS or LPS alone and imaged via live single cell microscopy. GXM treatment was associated with profound suppression of p65 nuclear translocation. Coupled with studies involving whole Cn using this model of macrophage Cn infection, the results of this project will yield valuable insights into the mechanisms by which Cn subverts the host immune response.