Resumo

The fungal pathogens Cryptococcus neoformans and C. gattii form the C. neoformans complex. The main virulence factor used by these species to cause to damage host cells is a polysaccharide capsule mostly composed of glucuronoxylomannan (GXM). Our group previously described that β-1,4-N-acetylglucosamine oligomers (chito-oligomers) are distributed throughout the capsule and are involved with surface architecture in the C. neoformans pathogenic complex. In this work we aimed to establish connections between capsule architecture, chito-oligomer distribution and interaction with phagocytes in pathogenic Cryptococcus species. Blocking of chito-oligomers using the wheat germ lectin (WGA) revealed that these structures are important for the association of most isolates of C. neoformans and C. gattii with macrophages. Interestingly, an opposite profile was observed with a serotype C C. gattii isolate (strain WM779). This observation led us to evaluate capsular architecture in this strain through fluorescence and scanning electron microscopy (SEM) techniques. The WM779 strain showed low reactivity with anti-GXM monoclonal antibodies although SEM analysis revealed a normal capsular morphology. We extended this analysis to other serotype C isolates of C. gattii by performing similar assays with three other strains belonging to the same serotype. Two of them were regularly recognized by anti-GXM antibodies. Blocking of chito-oligomers in these two inhibited phagocytosis, as observed for most strains analyzed in this study. One of the isolates, however, manifested capsular serological properties and profiles of interaction with macrophages that were similar to those observed for strain WM779. Our results revealed an important diversity among the surface components in the C. neoformans complex, suggesting functional variation of and revealing the need for a detailed exploration of the relationship between structure and pathogenic potential of surface glycans in the Cryptococcus genus.