Evidence for different mannosylation processes involved in the association of beta-1,2-linked oligomannosidic epitopes in Candida albicans mannan and phospholipomannan.

A monoclonal antibody specific for beta-1,2-linked oligomannosides was used to study the association of these residues with Candida albicans mannan and phospholipomannan (PLM) in relation to growth conditions and in mannan mutant strains. Double immunofluorescence assays performed on cells grown under standard conditions indicated a highly heterogeneous cell surface expression of these epitopes in comparison with the homogeneous expression of alpha-linked oligomannosidic epitopes. Growth in the presence of tunicamycin, which inhibits mannan N-glycosylation, resulted in an absence of beta-1,2-oligomannosidic epitopes on the cell surface, although PLM synthesis still occurred as shown by autoradiography. Similarly, growth in acidic conditions, which inhibits the incorporation of beta-1,2-oligomannosides in mannan, resulted in an absence of beta-1,2-oligomannosidic epitopes at the cell surface, although they still associated with PLM as shown by Western blotting. Western blots of C. albicans mutant strains with reduced amounts or an absence of phosphorus and acid-labile beta-1,2-oligomannosides in their mannan confirmed that the association of beta-1,2-linked oligomannosides with mannan and with PLM involves different mannosylation processes.