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Published on: March 22, 2012
Characterization of AFMP1: a novel target for serodiagnosis of aspergillosis
1Department of Microbiology, The University of Hong Kong, Queen Mary Hospital, Hong Kong. microgen@hkucc.hku.hk
Abstract:
We cloned the AFMP1 gene, which encodes the first antigenic cell wall galactomannoprotein 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 Saccharomyces cerevisiae and Candida albicans. It contains a serine- and threonine-rich region for O glycosylation, a signal peptide, and a putative glycosylphosphatidyl inositol attachment signal sequence. Specific anti-Afmp1p antibody was generated with recombinant Afmp1p protein purified from Escherichia coli to allow further characterization of Afmp1p. Afmp1p has a high affinity for Galanthus nivalis agglutinin, a characteristic indicative of a mannoprotein. Furthermore, it was recognized by a rat monoclonal antibody against the galactofuran side chain of galactomannan, indicating that it is a galactomannoprotein. Ultrastructural analysis by immunogold staining indicated 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 response against Afmp1p. This suggested that the recombinant protein and its antibody may be useful for serodiagnosis in patients with aspergilloma or invasive aspergillosis, and the protein may represent a good cell surface target for host humoral immunity.
Insights
Researchers identified the AFMP1 gene, encoding a key Aspergillus fumigatus cell wall protein. This protein, Afmp1p, is a galactomannoprotein recognized by patient antibodies, suggesting its use in diagnosing aspergillosis.
Area of Science:
- Mycology
- Immunology
- Biochemistry
Background:
- Aspergillus fumigatus is an opportunistic fungal pathogen.
- Cell wall mannoproteins play roles in fungal structure and host interaction.
- Previous studies identified antigenic mannoproteins in related fungi.
Purpose of the Study:
- To clone and characterize the AFMP1 gene and its encoded protein, Afmp1p.
- To investigate the localization and immunological relevance of Afmp1p in Aspergillus fumigatus.
- To explore the potential of Afmp1p in the serodiagnosis of aspergillosis.
Main Methods:
- Gene cloning and protein expression in Escherichia coli.
- Biochemical characterization using lectin binding and antibody recognition.
- Immunogold electron microscopy for subcellular localization.
- Serological analysis of patient antibody responses.
Main Results:
- The AFMP1 gene was cloned, encoding Afmp1p, a 284-amino acid protein with O-glycosylation and GPI anchor signals.
- Afmp1p demonstrated characteristics of a mannoprotein and was recognized by an antibody against galactofuran.
- Afmp1p was localized to the cell walls of A. fumigatus hyphae and conidia.
- Patients with aspergilloma and invasive aspergillosis produced specific antibodies against Afmp1p.
Conclusions:
- Afmp1p is the first identified antigenic cell wall galactomannoprotein in Aspergillus fumigatus.
- Afmp1p is a potential target for host humoral immunity.
- Recombinant Afmp1p and its specific antibody may be valuable tools for the serodiagnosis of aspergillosis.
