EVIDENCE FOR THE PRESENCE OF COLLAGENOUS DOMAINS IN CANDIDA-ALBICANS CELL-SURFACE PROTEINS

Rabbit polyclonal antibodies (PAbs) directed towards the amino-termina l cysteine-rich 7S domain (PAb anti-7S), the major internal collagenou s domain (PAb anti-type IV), and the C-terminal noncollagenous region (PAb anti-NC1) of the type IV collagen molecule were probed by indirec t immunofluorescence against Candida albicans blastoconidia and germin ated blastoconidia. Most nongerminating cells and mother blastoconidia from which germ tubes originated showed strong fluorescence when PAb anti-7S was used, whereas with PAb anti-type IV, fluorescence was foun d almost exclusively on the surface of filamentous forms. A patched fl uorescent pattern rather than a homogenous confluent fluorescence was observed in ail cases. No fluorescent cells were observed with PAb ant i-NC1. By Western immunoblotting, PAb anti-type IV cross-reacted prima rily with a polypeptide of 37 kDa present in wall extracts obtained fr om intact cells of both growth forms by treatment with beta-mercaptoet hanol, whereas PAb anti-7S recognized a major 58-kDa antigen also pres ent in both extracts, along with some other high-molecular-mass (>106- kDa) polydisperse species present only in the material released from b lastoconidia with beta-mercaptoethanol. No reactive bands were observe d when PAb anti-NC1 was used as a probe in Western immunoblotting expe riments. The sensitivities or resistances to collagenase digestion of the different polypeptides that cross-reacted with PAbs anti-type IV a nd anti-7S suggest the existence of cell wall components in C. albican s that contain epitopes that mimic the collagenous domains of the type IV collagen molecule.