Identification of continuous B-cell epitopes on the protein moiety of the 58-kilodalton cell wall mannoprotein of Candida albicans belonging to a family of immunodominant fungal antigens

The 58-kiloDalton mannoprotein (mp58) on the surface of Candida albicans is highly immunogenic, is expressed by all C. albicans isolates tested, and e licits strong antibody responses during candidiasis, It belongs to a family of immunodominant fungal antigens with representatives also in different s pecies of Aspergillus. The amino acid sequence of the protein portion of mp 58 as deduced from the DNA sequence of its encoding gene (FBP1/PRA1) was us ed to synthesize a complete set of overlapping dodecapeptides (overlap, 7; offset, 5) covalently attached to the surface of derivatized polyethylene p ins. The pin-coupled peptides were used in a modified enzyme-linked immunos orbent assay (ELISA) to identify continuous epitopes recognized by a number of antiserum preparations containing anti-mp58 antibodies. This comprehens ive epitope-scanning study revealed the presence of multiple immunoreactive continuous B-cell epitopes within the protein sequence. Regions of increas ed reactivity included both the amino and carboxy termini of the mature pro tein (encompassing amino acid residues 16 to 50 and 286 to 299, respectivel y) and four internal regions spanning amino acids st positions 66 to 92, 12 1 to 142, 148 to 192, and 211 to 232, Further delineation of epitopic regio ns and identification of the boundaries of the antigenic sites was performe d upon ELISA testing with a second Pepset consisting of completely overlapp ing 8-mer peptides spanning these reactive regions in the protein moiety of mp58. The highly reactive epitopic region at the C terminus of the protein was further evaluated using both window net and replacement net analyses, A synthetic peptide corresponding to the last 10 amino acid residues at the C terminus of the protein was immunogenic when injected into mice after be ing coupled to a carrier protein, Moreover, antibodies in the resulting ser a specifically recognized the homologus mp58 in ELISAs and immunoblot assay s, Delineation of the antibody responses to mp58 could provide the basis fo r the development of novel immunity-based prophylactic, therapeutic, and di agnostic techniques for the management of candidiasis.