INHIBITION OF THE ADHERENCE OF CHOLERA-TOXIN AND THE HEAT-LABILE ENTEROTOXIN OF ESCHERICHIA-COLI TO CELL-SURFACE GM1 BY OLIGOSACCHARIDE-DERIVATIZED DENDRIMERS

The adherence of either cholera toxin or the heat-labile enterotoxin o f Escherichia coli to monosialoganglioside gal(beta 1-3)galNAc(beta 1- 4)[sialic acid (alpha 2-3)]gal(beta 1-4)glc beta 1-ceramide (GM1) pres ent on the surface of epithelial cells lining the intestine is the fir st step of a series chat results in the induction of a watery diarrhea . While cholera is more severe, both can lead to death as a result of dehydration. To determine the potential of defined multivalent oligosa ccharides, synthesized by the covalent attachment of multiple phenylis othiocyanate (PITC) derivatives of gal(beta 1-3)galNAc(beta 1-4)[siali c acid(alpha 2-3)]gal(beta 1-4)glc (oligo-GM1) to the arms of a poly(p ropylene imine) dendrimer, as therapeutic agents for these diseases, t heir ability to inhibit adherence of the toxins to cell surface associ ated GM1 was determined. They not only inhibited choleragenoid (bindin g subunit of cholera toxin) binding to GM1-treated NCTC-2071 cells (ch emically transformed murine fibroblasts) at 5 degrees, but also inhibi ted adherence of the choleragenoid, cholera toxin, and heat-labile ent erotoxin of E. coli to GM1 treated NCTC-2071 cells at 37 degrees. Inhi bition was observed whether the toxin was preincubated with the oligo- GM1-PITC-derivatized dendrimer prior to addition to cells or given jus t after the addition of the derivatized dendrimer to cells. The deriva tized dendrimer had no effect on cell viability, as monitored by trypa n blue exclusion. Blue shifts in tryptophan fluorescence emission spec tra maxima induced by adherence of either choleragenoid, cholera holot oxin, or the heat-labile enterotoxin of E, coli to oligo-GM1-PITC-deri vatized dendrimers were similar to those induced by adherence to GM1 o r oligo GM1. Comparable shifts were not observed when the toxins were incubated with gangliosides that fail to function as receptors. (C) 19 98 Elsevier Science Inc.