All Accessible Epitopes in the Salmonella Lipopolysaccharide Core Are Associated with Branch Residues

Antisera generated against each of the nine known chemotypes of Salmonella lipopolysaccharide (LPS) core were characterized in order to delineate cross-reactive epitopes and define the bases for their accessibility. Strongly cross-reactive epitopes were associated with three chemotypes: Ra and Rb(4), which recognized α-GlcNAc-1→2-α-Glc, and Rd(1), which recognized l-α-d-heptose-1→7-l-α-d-heptose. Both these disaccharides and the more weakly cross-reactive α-Gal-1→6-α-Glc terminal in Rb(3) LPS represent branch points along the core oligosaccharide. Therefore, branch points in endotoxin core oligosaccharides may generally be cross-reactive.