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.
Acknowledgements
This study was financially supported by the Thailand Research Fund (TRF) and the Ministry of Higher Education, Thailand. All work was performed and used the facilities in the Faculty of Medicine, Chiang Mai University. We thank Assoc. Prof. Dr Ariya Chindamporn (Chulalongkorn University, Thailand), Dr Joseph Wheat and Ann M LeMonte (MiraVista Diagnostics, Indiana, USA) for kindly provide the patient's sera of aspergillosis and histoplasmosis in this study.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
This paper was first published online on Early Online on 7 July 2010.