A composition for the co-delivery to a cell of a nucleic acid and an
assistor protein, comprising vesicles, nucleic acid and protein, wherein
the nucleic acid operatively encodes an antigenic protein or portion
thereof which shares at least one epitope with the assistor protein, the
composition comprising said nucleic acid and said assistor protein
associated with the same vesicles as one another. A preferred embodiment
is a composition comprising liposomes formed from liposome forming
materials and, associated with the liposomes, nucleic acid operatively
encoding an antigenic protein and an assistor protein, wherein the
assistor protein shares at least one epitope with the antigenic protein.
The composition is for use as a vaccine and provides improved immune
response compared to non-vesicular compositions, or mixtures of liposomes
some of which are associated with nucleic acid and some of which are
associated with assistor protein.