Antibody isotypes to a Paracoccidioides brasiliensis somatic antigen in sub-acute and chronic form paracoccidioidomycosis

This report describes the differences in isotype antibody reactivity agains t a crude Paracoccidioides brasiliensis antigenic preparation in the sub-ac ute (SAF) and chronic (CF) forms of paracoccidioidomycosis before treatment . IgG antibodies were detected in all patients, with a slightly but not sig nificantly higher reactivity in the SAF. IgG1 antibodies were present, freq uently at high levels, in both forms, whereas IgG3 was always low or absent . IgG2 antibodies were detectable in most patients, but at high levels in o nly a few CF patients. IgG4 was found mainly in SAF patients, whereas IgA w as detected almost only in CF patients, probably due to a Th2 pattern of im mune response in the more severe SAF, and the characteristic mucosal involv ement of the CF, respectively. Immunoblot analysis showed that, in addition to the 43-kDa immunodominant fraction, other less well-characterised fract ions were also recognised differentially by the isotypes and deserve furthe r investigation.