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Characterization of an MPLP6, a gene coding for a yeast phase specific, antigenic mannoprotein in Penicillium
Monsicha Pongpom1, Nongnuch Vanittanakom
1Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand. patthamapp@yahoo.com
Abstract:
A gene encoding an antigenic mannoprotein of Penicillium marneffei, MPLP6, was isolated by an antibody screening approach and characterized. The polypeptide chain containing deduced 220 amino acids has a predicted molecular mass of 24 kDa. It has high similarity to Mp1p, the first mannoprotein antigen isolated from P. marneffei. The polypeptide sequence presents the property of cell wall mannoproteins by containing a putative N-terminal signal peptide and potential O-linked glycosylation sites. However, absence of a GPI-anchored signal sequence suggested that this protein is secreted. The MPLP6 transcript was present specifically in the pathogenic yeast form. The transcript was completely absent in the mold phase and conidia. The fusion protein produced in E. coli was Western immunoblotted with P. marneffei-infected human sera and 95% of the patients' sera were positive in the assay. None of the sera obtained from patients with aspergillosis, tuberculosis, histoplasmosis or cryptococcosis tested positive. These results suggest that Mplp6 can be used as a marker in a serodiagnostic assay.
Insights
Researchers identified a new Penicillium marneffei antigen, MPLP6, found only in the yeast form. This mannoprotein shows promise as a specific diagnostic marker for Penicilliosis marneffei infections.
Area of Science:
- Mycology
- Immunology
- Molecular Biology
Background:
- Penicillium marneffei causes disseminated infections, particularly in immunocompromised individuals.
- Mannoproteins are key components of fungal cell walls and can act as antigens.
- Previous identification of Mp1p highlighted the potential of mannoprotein antigens in P. marneffei diagnostics.
Purpose of the Study:
- To isolate and characterize a novel antigenic mannoprotein from P. marneffei.
- To investigate the expression pattern of the identified gene (MPLP6).
- To evaluate the diagnostic potential of the MPLP6 protein in serological assays.
Main Methods:
- Antibody screening was used to isolate the MPLP6 gene.
- Bioinformatic analysis predicted polypeptide chain characteristics, including signal peptides.
- Gene expression was analyzed by examining transcript presence in different fungal forms (yeast, mold, conidia).
- Western immunoblotting was performed using fusion protein and patient sera.
Main Results:
- The MPLP6 gene encodes a 24 kDa mannoprotein with high similarity to Mp1p.
- MPLP6 possesses characteristics of secreted cell wall mannoproteins, lacking a GPI-anchored signal sequence.
- MPLP6 transcripts were exclusively detected in the pathogenic yeast form of P. marneffei.
- A high percentage (95%) of sera from P. marneffei-infected patients were positive, while sera from other fungal infections were negative.
Conclusions:
- MPLP6 is a secreted mannoprotein antigen specific to the yeast phase of P. marneffei.
- The high specificity and sensitivity observed suggest MPLP6 is a valuable candidate for serodiagnostic applications.
- MPLP6 can serve as a reliable biomarker for diagnosing Penicilliosis marneffei.
