Abstract
The cell walls of all medically important fungi contain a unique polyglucose compound, β(1–3) glucan. In the present study, murine monoclonal antibodies were produced against linear and β(1–6) branched β(1–3) glucans, and their specificities were characterized for reactivity to other β glucans, fungal cell wall fragments, and fungal cells. Their reactivity was also compared with that of rabbit polyclonal antibodies raised against the same immunogens. Two mouse monoclonal antibodies (AG and BG) recognized immunoreactive epitopes in β(1–3)(1–6) glucan by ELISA. In an inhibition assay of the anti-β(1–3)(1–6) activity of the monoclonals, the homologous antigen effectively inhibited the activity as expected, while β(1–3) also inhibited the assay but to a much lesser extent. No inhibition was obtained by β(1–3)(1–4) or β(1–6), while a cell wall extract of Candida albicans (PPM) effectively inhibited both monoclonals. Cell wall fragments of C. albicans (CaCW) and Cryptococcus neoformans (CnCW) inhibited the anti-β(1–3)(1–6) activity of AG, while BG was much less or not inhibited at all. Immunofluorescence confirmed the unique antibody specificity of AG by its recognition of a β(1–3)(1–6)-associated epitope on the cell surfaces of C. albicans,C. krusei, C. glabrata, and nonencapsulated C. neoformans. The epitope for the AG antibody is suggested to be present in the branching point of β(1–3)(1–6), or in the randomly coiled β(1–3) polyglucan due to the presence of branches. Thus, monoclonal antibodies to β(1–3)(1–6) glucans may have potential as tools in the laboratory diagnosis of invasive yeast infections.
