Provided herein is an adjuvant formulation comprising a monophosphoryl lipid A (MPLA)-containing liposome composition to saponin (e.g., QS-21), wherein the liposome composition comprises i) a lipid bilayer comprising phospholipids in which the hydrocarbon chains have a melting temperature in water of ≧23° C. and ii) cholesterol at a mole percent concentration of greater than about 50% (mol/mol), preferably about 55% to about 71% (mol/mol), or more preferably about 55% (mol/mol). The adjuvant formulation displays minimal toxicity of either lipid A or saponin.
