Recombinant human antibody single chain variable fragments reactive with Candida albicans surface antigens

A combinatorial phage display library expressing human immunoglobulin heavy and light chain variable regions was used to identify phage clones capable of binding to the surface of Candida albicans blastoconidia. Single chain antibody variable fragments (scFv) derived from three clones detected C. al bicans antigens by indirect immunofluorescence assay (IFA), enzyme-linked i mmunosorbent assay (ELISA), and Western blotting. The antigens detected wer e conserved among different strains of C. albicans and several other Candid a species. Two scFv clones detected antigens specifically expressed by C. a lbicans blastoconidia; the third detected antigens in both blastoconidia an d filamentous forms of C albicans. The antigens containing the epitopes rec ognized by all three scFv could be extracted from blastoconidia by dithioth reitol, suggesting attachment to the cell wall via sulfhydryl bonds. Epitop e detection by the scFv was sensitive to treatment of C. albicans blastocon idia with sodium periodate, but not proteinase K, indicating the cognate ep itopes were composed of carbohydrate. Antigenic determinants for each of th e three scFv were detected by immunohistochemical staining of skin sections from a model of cutaneous candidiasis, demonstrating expression in vivo. T hrough selection for the ability to bind intact organisms, the phage displa y system provides a means to rapidly identify monoclonal binding ligands to Candida surface antigens. Being entirely human, mature antibodies generate d from the scFv have potential utility in the treatment of candidiasis. (C) 2001 Elsevier Science B.V. All rights reserved.