The induction of prolonged resistance against a lethal staphylococcic infection in mice with a single injection of an emulsified lipopolysaccharide

Abstract

The toxicity of a purified endotoxin, a lipopolysaccharide (LPS), for mice can be modified by administering it in a water-in-oil emulsion. Two to 4 times the LD 50 dose can be given safely in this manner, owing to the slow and prolonged release of the toxin from the emulsion. Administered in this manner, there is a profound and prolonged stimulation of the reticuloendothelial system as demonstrated by the increase in the weights of the liver and spleen. The toxicity of LPS is also reduced by the addition of FeCl 3. Mice treated with the emulsified LPS demonstrate marked and prolonged resistance against a lethal infection with a staphylococcus. A single injection of the emulsion induces variable degrees of heightened resistance for as long as 70 days. Evidence is also presented that, by emulsification of the LPS, the negative phase of reduced resistance to infection is shortened.