REACTIVITY PATTERNS AND EPITOPE SPECIFICITIES OF ANTI-CRYPTOCOCCUS NEOFORMANS MONOCLONAL-ANTIBODIES BY ENZYME-LINKED-IMMUNOSORBENT-ASSAY AND DOT ENZYME ASSAY

Cryptococcus neoformans glucuronoxylomannans (GXM) are capsular polysa ccharides important for virulence in cryptococcosis. This study used d ot enzyme assays (DEA) and enzyme-linked immunosorbent assays (ELISA) to determine the reactivity patterns of 21 murine monoclonal antibodie s (MAbs) with structurally defined GXMs from five serotypes. The MAbs were categorized into eight groups on the basis of DEA and five groups on the basis of ELISA. MAbs 302, 339, and 439 were studied extensivel y for their binding to various native and chemically modified GXMs. Qu antitative variation in the inhibitory effects of GXMs on the binding of MAbs 302, 339, and 439 were observed by competitive ELISA. O-Deacet ylation of serotype A, B, and D GXM resulted in the complete loss of t heir inhibitory properties. Carboxyl group reduction of GXMs from sero types A and D resulted in a significant decrease of inhibitory activit y for MAb. Xylomannans and methyl glycosides exhibited no detectable i nhibitory activity on MAb binding to GXM. The results indicate (i) the existence of five to eight MAb-defined distinct epitopes in C. neofor mans GXM that can elicit antibody responses, (ii) MAb detection of ant igenic variation within GXMs assigned to a particular serotype, (iii) good correspondence between the patterns of MAb reactivities and polyc lonal rabbit factor sera, (iv) good agreement between MAb molecular st ructure and serotype reactivity, and (v) a dependence of the serotype reactivity profile for a given MAb on the technique used to measure bi nding.