CELL SURFACE PROTEINS OF CRYPTOCOCCUS NEOFORMANS MEDIATE ADHERENCE AND INTERNALISATION INTO MAMMALIAN CELLS

Cryptococcus neoformans is an encapsulated fungal pathogen that caused severe disease primarily in immunocompromised patients. Adherence and internalization of microbial pathogens into host cells are often begin with engagement of microbes to the surface receptors of host. However, the mechanisms involved remain poorly understood. In this study, we investigated association of cell surface determinants of C. neoformans with mammalian cells. Our results showed that treatment with trypsin, but not paraformaldehyde or heat killing, has reduced host-cryptococci interaction, suggesting the involvement of cell surface proteins (CSPs) of C. neoformans in this interaction. We extended our investigations to determine roles of CSPs during cryptococci-host cells interaction by extracting and conjugating CSPs of C. neoformans to latex beads. Conjugation of CSPs with both encapsulated and acapsular C. neoformans increased the association of latex beads with mammalian alveolar epithelial cells, alveolar macrophages and monocyte-derived macrophages. Further examination on the actin organisation of the host cells implied the involvement of actin-dependent phagocytosis in the internalisation of C. neoformans in CSP-conjugated latex beads. We hypothesized that CSPs present on the cell wall of C. neoformans mediate the adherence and actin-dependent phagocytosis of cryptococci by mammalian cells. Our results warrant further studies on the exact role of CSPs in pathogenesis during cryptococcosis.