Existence of novel β-1,2 linkage-containing side chain in the mannan of Candida lusitaniae, antigenically related to Candida albicans serotype A

Abstract

The antigenicity of Candida lusitaniae cells was found to be the same as that of Candida albicans serotype A cells, i.e. both cell wall mannans react with factors 1, 4, 5, and 6 sera of Candida Check. However, the structure of the mannan of C. lusitaniae was significantly different from that of C. albicans serotype A, and we found novel β-1,2 linkages among the side-chain oligosaccharides, Manβ1→2Manβ1→2Manα1→2Manα1→2Man (LM5), and Manβ1→2Manβ1→2Manβ1→2Manα 1→2Manα1→2Man (LM6). The assignment of these oligosaccharides suggests that the mannoheptaose containing three β-1,2 linkages obtained from the mannan of C. albicans in a preceding study consisted of isomers. The molar ratio of the side chains of C. lusitaniae mannan was determined from the complete assignment of its H-1 and H-2 signals and these signal dimensions. More than 80% of the oligomannosyl side chains contained β-1,2-linked mannose units; no α-1,3 linkages or α-1,6-linked branching points were found in the side chains. An enzyme-linked immunosorbent inhibition assay using oligosaccharides indicated that LM5 behaves as factor 6, which is the serotype A-specific epitope of C. albicans. Unexpectedly, however, LM6 did not act as factor 6.