Humoral immune responses to mycetoma organisms: characterization of specific antibodies by the use of enzyme-linked immunosorbent assay and immunoblotting.

Levels of antibodies were determined by enzyme-linked immunosorbent assay (ELISA) in 13 patients with eumycetomas due to Madurella mycetomatis infections. Raised levels of specific IgM were observed in 12 patients, compared with normal human controls. By contrast, low levels of specific IgG were detected in some patients. Specific responses to separated protein antigens were investigated by immunoblotting. Of 10 patients' sera tested, IgM in 2 recognized up to 7 of the blotted antigens between 45 and 84 kDa. Gold-labelled protein A (which predominantly binds to IgG) indicated that sera from 2 patients reacted with at least 6 protein bands with relative molecular masses between 64 and 95. The demonstration of significant IgM levels by ELISA, but few antigenic bands in sera from the same patients by immunoblotting, may point to an antibody response against polysaccharide fungal antigens in mycetoma patients. The use of the ELISA to detect antibodies of different classes and the characterization of their antigenic specificities by immunoblotting may have both diagnostic and prognostic value.

Ultrastructural and immunogenic changes in the formation of mycetoma grains.

The differences in the fine structure and antigenic determinants of mycetoma fungi in the mycelial phase in vitro and in grains in vivo facilitate an interpretation of grain formation. Aggregates of hyphal elements with multiple and thickened walls was a feature of the fungi in vivo. Associated with hyphal wall material, numerous polysaccharide microfibrils were detected in grains of Madurella mycetomatis. These were not seen associated with hyphal elements in vitro and it is suggested that these structures may be concerned with the aggregation of fungal elements in the formation of grains. Antibodies directed against the fungi in vitro were shown, by indirect immunogold labelling, to bind at identical sites in fungal material grown in vitro as in mycetoma grains. However the grain matrix was not labelled, suggesting that part of the structure formed in vivo is composed of modified antigen or is host derived.