β-mannosyl linkages inhibit CAWS arteritis by negatively regulating dectin-2-dependent signaling in spleen and dendritic cells

Aims: CAWS, Candida albicans water-soluble fraction, is an extracellular mannoprotein produced by C. albicans NBRC1385. It is a ligand of dectin-2, the C-type lectin receptor for innate immunity, and has strong potency for induction of vasculitis in DBA/2 mice. The structure of this mannoprotein is known to be modulated by the culture conditions. To clarify the structure required for vasculitis, CAWSs were prepared in the two culture conditions with or without pH control, and biological properties were compared. Methods: CAWSs prepared by the standard protocol and pH controlled at 7.0 were designated as CAWS and CAWS727, respectively. The antigenicity was detected by the anti-Candida mannan IgG. These chemical structures were assessed by nuclear magnetic resonance analysis and the lectin array system. The in vitro activity of CAWSs was tested by tumor necrosis factor-alpha (TNF-alpha) induction using bone marrow-derived dendritic cells and spleen cell cultures. Results: The antigenicity of CAWS727 was similar to CAWS but the nuclear magnetic resonance analysis showed a higher ratio of beta-mannosyl linkages were detected in CAWS727. The lectin array showed relative affinities of CAWS727 to alpha-mannosyl specific lectins were weaker than those of CAWS. CAWS induced severe vasculitis in DBA/2 mice while CAWS727 did not. CAWS significantly induced TNF-alpha but CAWS727 did slightly. In addition, CAWS-induced TNF-alpha production was inhibited by mixing with CAWS727 in a concentration dependent manner. Conclusion: The alpha-mannosyl linkages of Candida mannan is a key molecule for the immunotoxicity. CAWS727, which conatins beta-mannosyl linkages, competitively bound to lectin receptors, and resulted in reductions in the inflammatory response.