Enhanced virulence of Histoplasma capsulatum through transfer and surface incorporation of glycans from Cryptococcus neoformans during co-infection

Abstract

Cryptococcus neoformans (Cn) and Histoplasma capsulatum (Hc) co-exist in the environment and occasionally co-infect individuals, which can lead to severe disease/lethal outcomes. We investigated specific interactions between Cn-Hc to determine the impact of synchronous infection in virulence and disease. Co-infected mice had significantly higher mortality than infection with either species or acapsular Cn-Hc. Coating of Hc with cryptococcal glycans (Cn-gly) resulted in higher pulmonary fungal burden in co-infected animals relative to control. Co-cultivation or addition of Cn-gly resulted in enhanced pellicle formation with a hybrid polysaccharide matrix with higher reactivity to GXM mAbs. Transfer and incorporation of Cn polysaccharide onto Hc surface was time and temperature dependent. Cn-gly transfer altered the zeta potential of Hc and was associated with increased resistance to phagocytosis and killing by macrophages. Mice infected with Hc and subsequently injected with purified Cn-gly died significantly more rapidly than Hc alone infected, establishing the precedent that virulence factors from one fungus can enhance the virulence of unrelated species. These findings suggest a new mechanism of microbial interaction involving the transfer of virulence traits that translates into enhanced lethality during mixed fungal infections and highlights the importance of studying heterogeneous microbial populations in the setting of infection.

Unravelling the interactions of the environmental hostAcanthamoeba castellaniiwith fungi through the recognition by mannose‐binding proteins

“…Ac biotinylated surface extract were also purified by affinity chromatography using a mannose‐coupled resin following manufacturer's instruction (Sigma‐Aldrich). For further characterization of binding to fungi, fluorescence microscopy and flow cytometry were used as described (Cordero et al, ; Guimaraes et al, ). Fungal cells were washed three times with PBS, and yeast surfaces were blocked with 2% BSA in PBS.…”

Host membrane glycosphingolipids and lipid microdomains facilitateHistoplasma capsulatuminternalisation by macrophages

“…In another set of experiments, oligo‐GM1 and GFP‐Hc were coincubated with Mφs for 1 hr. Association indexes were determined by flow cytometry as described above (Cordero et al, ). In addition, some systems where fungal cells were opsonised with anti‐HSP60 (13B7 or 7B6; Guimaraes, Frases, Gomez, Zancope‐Oliveira, & Nosanchuk, ) or M antigen‐specific mAbs (Guimaraes, Hamilton, de, Nosanchuk, & Zancope‐Oliveira, ) were also tested to evaluate whether opsonisation would impact infection.…”

Characterization of the antifungal functions of a WGA-Fc (IgG2a) fusion protein binding to cell wall chitin oligomers

“…Two strains of H. capsulatum , G184AR (ATCC 26027) and G217B (ATCC 26032; lacking α-1,3-glucan on the yeast cell surface), were grown in Ham’s F-12 medium supplemented with glucose (16 g/L), glutamic acid (1 g/L), HEPES (6 g/L) and cysteine (8.4 mg/mL) at 37 °C 25 . An encapsulated C. neoformans strain H99 (ATCC 208821) and an acapsular mutant cap59 (B-4131) were cultivated in a chemically defined minimum medium at 37 °C 63 . C. albicans (ATCC 90028) and Saccharomyces cerevisiae RSY225 were cultivated in Sabouraud at 37 °C.…”

“…Wells were washed 3 times with PBS, macrophages detached and phagocytosis was arrested by adding 4% paraformaldehyde. The phagocytosis rate was determined by flow cytometry, where the percentage of macrophages interacting with fungi (FL2+ ) was determined 15 , 16 , 63 . Experiments were performed three times.…”