Abstract: A therapeutic composition for inhibiting the function of a target polynucleotide sequence in a mammalian cell includes an agent that provides to a mammalian cell an at least partially double-stranded RNA molecule comprising a polynucleotide sequence of at least about 200 nucleotides in length, said polynucleotide sequence being substantially homologous to a target polynucleotide sequence. This RNA molecule desirably does not produce a functional protein. The agents useful in the composition can be RNA molecules made by enzymatic synthetic methods or chemical synthetic methods in vitro; or made in recombinant cultures of microorganisms and isolated therefrom, or alternatively, can be capable of generating the desired RNA molecule in vivo after delivery to the mammalian cell. In methods of treatment of prophylaxis of virus infections, other pathogenic infections or certain cancers.

Abstract: A soluble ionic complex is formed by an aqueous mixture of a benzylammonium group-containing surfactant and a polynucleic acid sequence. When the mixture forms a vesicular complex, the sequence is packaged therein. This composition is useful in pharmaceutical compositions and in methods of delivering the polynucleic acid sequence (which preferably encodes a protein or peptide) to a cell for expression. Such methods are useful in therapy, as vaccines and as gene therapy agents.