Adjuvant activity of Klebsiella O3 lipopolysaccharide: comparative study using defined uniform salt forms

Previously we showed that Klebsiella O3 lipopolysaccharide (KO3 LPS) is much more potent than other kinds of LPS including Escherichia coli O127 LPS (EO127 LPS) in adjuvant activity in augmenting antibody response and delayed-type hypersensitivity to protein antigens and in the ability to enlarge the regional lymph node. Various defined uniform salt forms, the triethylamine, sodium, potassium, ammonium, tris(hydroxymethyl)aminomethane, and calcium salt forms, of KO3 LPS and EO127 LPS were prepared by removing basic materials present in LPS preparations by electrodialysis and neutralizing the electrodialyzed LPS preparations with various kinds of alkali. The triethylamine salt form showed the best solubility and consisted of the smallest granules and, on the other hand, the calcium salt form showed the lowest solubility, compared with the natural form and the other uniform salt forms. Even if the natural forms of KO3 LPS and EO127 LPS were converted to the defined uniform salt forms, adjuvanticity of KO3 LPS and EO127 LPS in augmenting delayed-type hypersensitivity to ovalbumin and the ability to enlarge the regional lymph node did not significantly differ from those of the respective natural forms. From these results it is concluded that the difference in strength of the adjuvanticity between KO3 LPS and EO127 LPS is not due to the difference in their salt forms, solubility or physical state. Moreover, there were no significant differences in lethal toxicity for mice by the intraperitoneal route among the natural form and all the uniform salt forms of KO3 LPS tested.