Western immunoblot analysis of protein antigens of Penicillium marneffei.

Protein antigens of Penicillium marneffei prepared during the yeast and mould phases of in vitro growth were analyzed by gel electrophoresis and immunoblot assay. More than 20 yeast phase proteins were detected by Coomassie staining; among these, at least 10 reacted with IgG in the pooled sera of 28 AIDS patients with penicilliosis. Four immunogenic proteins of 200, 88, 54 and 50 kDa were produced in large quantity during the deceleration and early stationary phases of growth. When these proteins were reacted with individual sera derived from 33 AIDS patients with penicilliosis, reactivities to the 200, 88, 54 and 50 kDa protein were detected in 72.7, 93.9, 60.6 and 57.6%, respectively. The bands of 88, 54 and 50 kDa gave strong reactions with about a half of serum samples. In one serum derived from an AIDS patient, reactivities to the 54 and 50 kDa proteins could be strongly detected two months before the definite diagnosis by fungal culture. Protein components from the mould form were of lower yield and gave weaker signal in immunoblot analysis. These results indicate that at least two yeast-phase immunoreactive proteins (54 and 50 kDa) are relatively specific to the P. marneffei infection, thereby suggesting its potential for clinical application to the diagnosis of this emerging disease.