Characterization of AFMP1: a novel target for serodiagnosis of aspergillosis

We cloned the AFMP1 gene, which encodes the first antigenic cell wall galac tomannoprotein in Aspergillus fumigatus. AFMP1 codes for a protein, Afmp1p, of 284 amino acid residues, with a few sequence features that are present in Mp1p, the antigenic cell wall mannoprotein in Penicillium marneffei that we described previously, as well as several other cell wall proteins of Sa ccharomyces cerevisiae and Candida albicans. It contains a serine-and threo nine-rich region for O glycosylation, a signal peptide, and a putative glyc osylphosphatidyl inositol attachment signal sequence. Specific anti-Afmp1p antibody was generated with recombinant Afmp1p protein purified from Escher ichia coli to allow further characterization of Afmp1p. Afmp1p has a high a ffinity for Galanthus nivalis agglutinin, a characteristic indicative of a mannoprotein. Furthermore, it was recognized by a rat monoclonal antibody a gainst the galactofuran side chain of galactomannan, indicating that it is a galactomannoprotein. Ultrastructural analysis by immunogold staining indi cated that Afmp1p is present in the cell walls of the hyphae and conidia of A. fumigatus. Finally, it was observed that patients with aspergilloma and invasive aspergillosis due to A. fumigatus develop a specific antibody res ponse against Afmp1p. This suggested that the recombinant protein and its a ntibody may be useful for serodiagnosis in patients with aspergilloma or in vasive aspergillosis, and the protein may represent a good cell surface tar get for host Immoral immunity.