Resumo

In recent decades there has been a significant increase in the incidence of fungal infections in the world. This increase is related to the high number of immunocompromised patients, as well as to medical advances that lead to situations of immunosuppression. In this context, members of the genus Trichosporon, including T. mucoides and T. asahii, are now considered important species causing disseminated infections in immunocompromised individuals. Despite this observation, the virulence attributes of these pathogens are still poorly understood. Several studies indicate that T. asahii produces glucuronoxilomannan (GXM), the main virulence factor of the encapsulated pathogen Cryptococcus neoformans. The production of this polysaccharide by T. mucoides, however, is controversial. In this study, we searched for GXM-like polysaccharides in three strains of T. mucoides (ATCC 204094, INCQS 40272, and DLC10). Through the use of protocols that were established for GXM extraction in other models, we detected GXM-like polysaccharides in the three strains by immunofluorescence with GXM-binding antibodies.The amount of GXM-like molecules produced by each strain was variable. Moreover, fungal cells of each isolate were differentially recognized by GXM-binding antibodies, suggesting structural differences. The effective diameter of these molecules in solution was measured by dynamic light scattering, which demonstrated distinct dimensions in polysaccharide fractions obtained from each strain. Analysis of the strain INCQS 40272 by flow cytometry revealed that only 28,8 % of the cells gave positive results for GXM. Based on this heterogeneity, we searched for GXM-containing colony forming units after cultivation of this strain in solid medium. Colonies that were positive or negative for GXM were selected for growth in fresh medium. Analysis of these clonal populations by flow cytometry revealed an expressive enrichment in cells staining positively or negatively for the presence of GXM in the new cultures. This observation may be translated into useful experimental models aiming at the elucidation of the functions of this polysaccharide in the pathogenesis of T. mucoides. In summary, our results indicate a great heterogeneity in the GXM-like molecules produced by T. mucoides, which may be determinant for the progress of the infections caused by this fungal pathogen.