Binding of the wheat germ lectin to Cryptococcus neoformans chitooligomers affects multiple mechanisms required for fungal pathogenesis

Abstract

The principal capsular component of Cryptococcus neoformans, glucuronoxylomannan (GXM), interacts with surface glycans, including chitin-like oligomers. Although the role of GXM in cryptococcal infection has been well explored, there is no information on how chitooligomers affect fungal pathogenesis. In this study, surface chitooligomers of C. neoformans were blocked through the use of the wheat germ lectin (WGA) and the effects on animal pathogenesis, interaction with host cells, fungal growth and capsule formation were analyzed. Treatment of C. neoformans cells with WGA followed by infection of mice delayed mortality relative to animals infected with untreated fungal cells. This observation was associated with reduced brain colonization by lectin-treated cryptococci. Blocking chitooligomers also rendered yeast cells less efficient in their ability to associate with phagocytes. WGA did not affect fungal viability, but inhibited GXM release to the extracellular space and capsule formation. In WGA-treated yeast cells, genes that are involved in capsule formation and GXM traffic had their transcription levels decreased in comparison with untreated cells. Our results suggest that cellular pathways required for capsule formation and pathogenic mechanisms are affected by blocking chitin-derived structures at the cell surface of C. neoformans. Targeting chitooligomers with specific ligands may reveal new therapeutic alternatives to control cryptococcosis.

The Unappreciated Intracellular Lifestyle of Blastomyces dermatitidis

“…Intracellular residence could enable B. dermatitidis to spread from the lungs to extra-pulmonary tissue. This “Trojan Horse” method of dissemination has been proposed for other intracellular fungi such as C. neoformans (41-45), where in a murine model of cerebral infection yeast have been detected in monocytes circulating in blood and in leptomeningeal capillaries of brain sections. New insight into how B. dermatitidis grows in host cells may likewise improve our understanding of how the fungus establishes itself in the lung and disseminates to visceral sites.…”

Modulation of Zinc Homeostasis in Acanthamoeba castellanii as a Possible Antifungal Strategy against Cryptococcus gattii

“…In order to evaluate possible molecules associated with the higher phagocytosis sensitivity of cell lacking the ZIP1 gene, we evaluated the distribution of chitin-like oligomers in the cryptococcal cells surface. These structures were show to be involved in the association of C. neoformans with murine phagocytes ( Fonseca et al, 2013 ). Confocal fluorescent microscopy analysis revealed no differences in the staining pattern of chitin-like oligomers in WT or Δ zip1 mutant strains ( Figure 1C ).…”

Cryptococcus neoformans: historical curiosity to modern pathogen

“…These include cell wall stains, e.g. Lucifer yellow (shown in Figure and Srikanta et al ., ), calcofluor white (Giles et al ., ) or eosin Y (Baker et al ., ); anti‐capsule antibodies (Belay et al ., ; Casadevall et al ., ; De Jesus et al ., ; Feldmesser et al ., ; Kozel and Follette, ; Moyrand et al ., ; Mukherjee et al ., ); and labelled lectins (Botts et al ., ; Fonseca et al ., ). Several proteins have also been epitope‐tagged or fused to fluorescent proteins for visualization.…”