Purification of a mannan from Candida albicans which activates serum complement

Area of Science:

• Immunology
• Microbiology
• Biochemistry

Background:

• Candida species are known to activate the complement system via the alternative pathway.
• Epicutaneous application of Candida species can lead to neutrophil microabscesses in the epidermis.
• Complement activation by Candida albicans is associated with its cell wall components.

Purpose of the Study:

• To biochemically identify the specific component(s) of Candida albicans responsible for complement activation.
• To characterize the immunological and pathogenic properties of the identified C. albicans constituent.

Main Methods:

• Preparation of an ethyleneglycol extract from C. albicans blastospores.
• Acid hydrolysis and neutral sugar analysis to determine polysaccharide composition.
• Assays for complement activation (alternative pathway), neutrophil chemotaxis, Limulus lysate gelation, and immunodiffusion.

Main Results:

• The C. albicans extract was rich in mannose (82%), fucose (7%), and glucose (11%).
• The soluble, mannose-rich cell wall polysaccharide activated serum complement via the alternative pathway and induced neutrophil chemotaxis.
• The polysaccharide showed antigenicity against antisera for C. albicans and produced precipitin lines with sera from invasive candidiasis patients.

Conclusions:

• A mannose-rich polysaccharide (mannan) in the C. albicans cell wall is a key factor in activating the complement system.
• This mannan contributes to the pathogenic properties of C. albicans, including immune cell recruitment.
• The findings highlight mannan as a significant contributor to the host immune response during candidiasis.