Candida albicans serotypes have been reported to differ by their geographic distribution, their ability to infect immunocompetent or immunocompromised patients and by their resistance to antifungals such as 5-fluorocytosin. Nevertheless, C. albicans serotypes are sometimes difficult to identify since the expression of factor 6 is heterogeneous and dependent on growth conditions. This may explain the numerous reported discrepancies between serotyping methods. We have formerly evidenced in C. albicans strains and highly related species (C. stellatoidea, C. dubliniensis, C. tropicalis) a unique glycolipid, the phospholipomannan which was shown to be a mannosyl-inositolphosphophytoceramide. Its glycan part only contains • -1,2 Man linkages and is linked to the ceramide moiety through a new specific spacer including two phosphate groups. We further showed by western blotting that C. albicans serotypes A and B strains express phospholipomannans which differ in their relative molecular weight and their reactivity to the monoclonal antibody B6-1 (gift from JE. Cutler). In contrast to factor serum 6, these divergences appeared unaffected by growth conditions. In this study, we have analysed and compared by physico-chemical methods the molecular structure of PLMs from C. albicans serotypes A (strain VW32) and B (strain NIH B792) strains in order to explain theses divergences. Combination of CPG analysis of methanolysis products, mass spectrometry and NMR spectrometry showed that both phospholipomannans are highly heterogeneous in their composition and combine in their ceramide moiety a phytosphingosine C18 or C20 with a hydroxy fatty acid C25, C26 or mainly C24. The only difference observed in the lipidic moiety of phospholipomannans from both serotypes arises from the phytosphingosine C20/C18 ratio which is higher and always greater than 1 in phospholipomannan from serotype B whatever the growth temperature.
Full conference title:
The 15 th Congress of the International Society for Human and Animal Mycology
- ISHAM 15th (2003)