Patent ID: 7790696

Claim:
A method to generate an immune response to a target polypeptide in an animal, which method comprises administering to the animal a composition comprising liposomes suspended in an aqueous liquid and a polynucleotide comprising a promoter operatively linked to a nucleotide sequence encoding said target polypeptide, wherein the liposomes comprise a phosphatidylcholine (PC), a liposome-forming phosphatidyl ethanolamine (PE), and a cation selected from the group consisting of 1,2-dioleoyloxy-3-trimethyl ammonium propane (DOTAP) stearylamine and 3β[N-(N′N′-dimethylaminoethane)-carbamyl] cholesterol (DC-Chol); wherein said liposomes have diameters in the range 100 to 2,000 nm and comprise a lipid bilayer and an aqueous intravesicular space, wherein said polynucleotide is entrapped in the aqueous intravesicular space of said liposomes, wherein said lipid bilayer includes said cation in an amount such that the lipid bilayer has an overall cationic charge; whereby said polynucleotide is delivered to and is expressed in target cells whereby an immune response results; wherein said polynucleotide is administered in an amount sufficient to elicit said immune response.