Glycoconjugates and polysaccharides from the Scedosporium/Pseudallescheria boydii complex: structural characterisation, involvement in cell differentiation, cell recognition and virulence

Abstract

Peptidorhamnomannans (PRMs), rhamnomannans and α-glucans are especially relevant for the architecture of the Scedosporium/Pseudallescheria boydii cell wall, but many of them are immunologically active, with great potential as regulators of pathogenesis and the immune response of the host. In addition, some of them can be specifically recognised by antibodies from the sera of patients, suggesting that they could also be useful in diagnosis of fungal infections. Their primary structures have been determined, based on a combination of techniques including gas chromatography, electrospray ionization - mass spectrometry (ESI-MS), (1)H-COSY and TOCSY, (13)C and (1)H/(13)C NMR spectroscopy. Using monoclonal antibodies to PRM, we showed that it is involved in germination and viability of P. boydii conidia, in the phagocytosis of P. boydii conidia by macrophages and non-phagocytic cells and in the survival of mice with P. boydii infection. Also, components of the fungal cell wall, such as α-glucans, are involved. Rhamnomannans are immunostimulatory and participate in the recognition and uptake of fungal cells by the immune system. These glycosylated polymers, being present in the fungal cell wall, are mostly absent from mammalian cells, and are excellent targets for the design of new agents capable of inhibiting fungal growth and differentiation of pathogens.