New trends in the use of Al(OH)3-conjugated endotoxins and their subunits from the S- and R-forms of Shigella dysenteriae serovar 1 for model vaccination purposes.

The lipopolysaccharides, lipopolysaccharide-protein complexes and their lipids A, isolated from Shigella dysenteriae 1, exhibited lethal toxicity (LD50 300-400 micrograms per mouse), pyrogenicity (0.01-1.0 microgram), activity in the Limulus test (10(-3)-10(-12) mg ml-1) and produced a positive local Shwartzman reaction. It was found that these substances bound to Al(OH)3 were capable of successfully protecting mice from challenge with both homologous and heterologous infections (up to 90% of mice survived a challenge with LD100), whereas immunization with substances with no biological carrier exhibited very low or zero protective effects. Furthermore, the positive cross-reactivity of lipids A in the agar immunodiffusion test confirms the wide applicability for vaccination purposes.