Liposomal adjuvant compositions

An essentially saponin-free liposome, wherein said saponin is absent or present at or below the limit of detection, comprising an external lipid bilayer membrane and an internal compartment, the external membrane comprising:

• a) a quaternary ammonium compound composed of four alkyl chains, two of which are C10-C20 alkyls and the remaining two are C1-C4 alkyls;
• b) a sterol selected from the group consisting of β-sitosterol, stigmasterol, ergosterol, ergocalciferol, and cholesterol;
• c) a phospholipid;
• and
• d) a glycolipid of formula I:
• wherein, R1 and R2 are independently hydrogen, or a saturated alkyl radical having up to 20 carbon atoms;
• X is —CH2—, —O— or —NH—;
• R2 is hydrogen, or a saturated alkyl radical having up to 20 carbon atoms;
• R3, R4, and R5 are independently hydrogen, —SO42−, —PO42−, —COC1-10 alkyl;
• R6 is L-alanyl, L-alpha-aminobutyl, L-arginyl, L-asparginyl, L-aspartyl, L-cysteinyl, L-glutamyl, L-glycyl, L-histidyl, L-hydroxyprolyl, L-isoleucyl, L-leucyl, L-lysyl, L-methionyl, L-ornithinyl, L-phenyalany, L-prolyl, L-seryl, L-threonyl, L-tyrosyl, L-tryptophanyl, and L-valyl or their D-isomers.