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

This report describes the differences in isotype antibody reactivity against a crude Paracoccidioides brasiliensis antigenic preparation in the sub-acute (SAF) and chronic (CF) forms of paracoccidioidomycosis before treatment. IgG antibodies were detected in all patients, with a slightly but not significantly higher reactivity in the SAF. IgG1 antibodies were present, frequently 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 only a few CF patients. IgG4 was found mainly in SAF patients, whereas IgA was detected almost only in CF patients, probably due to a Th2 pattern of immune response in the more severe SAF, and the characteristic mucosal involvement of the CF, respectively. Immunoblot analysis showed that, in addition to the 43-kDa immunodominant fraction, other less well-characterised fractions were also recognised differentially by the isotypes and deserve further investigation.