Highly specific and sensitive, immunoblot-detected 54 kDa antigen from Fonsecaea pedrosoi

Chromoblastomycosis (CBM) is a chronic subcutaneous mycosis caused by a group of different dematiaceous fungi, first described by Rudolph in 1914. In Brazil there is a clear predominance of Fonsecaea pedrosoi. Sixty sera samples obtained from patients with F. pedrosoi-caused CBM were analysed. Sera obtained from 36 sporothricosis (SPT) patients, 34 cutaneous leishmaniasis (CL) patients and from 48 blood donors (HBD) were used as control. F. pedrosoi metabolic antigen was obtained from F. pedrosoi sample no. 884 (Instituto de Medicina Tropical de São Paulo Collection). IE reaction disclosed an anodic migrating arch, which was eluted and used as antigen. Both metabolic and eluate F. pedrosoi antigens were submitted to SDS-PAGE and two fractions, weighing approximately 54 and 66 kDa were identified. The 66-kDa fraction reacted against 43 of 60 CBM (71.7%) sera samples and was recognized by 10 SPT and eight CL sera (15.3%). No reactivity was observed against HBD sera. The 54-kDa fraction reacted against 58 of 60 CBM sera (96.7% sensitivity) and was not recognized by HBD, SPT nor CL sera (100% specificity). Such high sensitivity and specificity levels suggest this antigenic fraction is immunodominant and might prove a useful tool for further studies on F. pedrosoi-caused CBM.