Biological activities of chemically modified endotoxins from Vibrio cholerae

Lipopolysaccharides from Vibrio cholerae, NIH 41, Ogawa 5321 and Inaba 66/64 were treated with succinic anhydride, phthalic anhydride and dinitrophenyl ethylene diamine, and the resultant derivatives, sodium succinyl lipopolysaccharide, sodium phthalyl lipopolysaccharide, and dinitrohpenyl lipopolysaccharide obtained respectively were investigated for various biological activities. The succinylation and phthalylation of lipopolysaccharide decreased the 3-hydroxy lauric acid, a major ester-linked fatty acid of these bacteria, and as a result of which these modified products exhibited lower toxic activities in chick embryos, mouse and in generalized local Shwartzmann reaction in rabbits than their parent lipopolysaccharides. The dinitrophenylation of lipopolysaccharide increased its toxicity in chick embryos and mice, but dinitrophenyl lipopolysaccharide was completely inactive in Shwartzmann reaction in rabbits. However, despite the loss of these biological activities, these modified derivatives of lipopolysaccharide retained and increased the activities in pyrogenecity and in various immunological properties.