Antibodies against the major capsular
polysaccharide of Cryptococcus neoformans,
glucuronoxylomannan (GXM), and a minor secreted
polysaccharide,
galactoxylomannan (GalXM), were surveyed by indirect
enzyme immunoassay (EIA) in patients with
cryptococcosis, with other
mycoses, and in normal controls. Measurement of
IgG levels against GalXM revealed cross reactions in
candidiasis patients that were reduced by adsorption with Candida albicans cell walls. Measurement of
IgM levels were subject to fewer cross reactions. The combination of adsorption with C albicans cell walls and measurement of
IgM detected
antibodies in 12 of 55
cryptococcosis patients. An end point equal to or greater than a titer of 1/16 excluded reactions in normals and limited cross reactivity in
candidiasis patients to below 7%. This test has potential diagnostic significance in
cryptococcosis patients who show no evidence of cryptococcal
antigen circulating in the cerebrospinal fluid or serum. Reactions in this
IgM assay were not spuriously due to
rheumatoid factor. The major capsular GXM was much less serologically active and was subject to cross reactions with agents of bacterial
sepsis. The specificity of the GalXM is directed mainly by the
mannose and to a lesser extent by galactosyl residues.