Genetic immunization using liposome-incorporated DNA

Genetic immunization using naked plasmid DNA is based on DNA uptake by and expression in skeletal muscle cells which lack vital co-stimulatory molecules. Alternatively liposomes, which target antigen-presenting cells directly and protect DNA from nuclease attack, Perrie & Gregoriadis, (1997) may be preferable. We have recently shown, Gregoriadis et al(1997); Gregoriadis et al(1998) that Balb/c and outbred mice immunized by a variety of routes with the plasmid DNA pRc/CMV HBS (encoding the S region of HBsAg, subtype ayw) entrapped in cationic liposomes mounted much higher humoral (IgG and splenic IL-4) and cell mediated (splenic IFN-y) responses than when injected with naked DNA or DNA complexed to similar preformed liposomes. Here we report further studies on the effect of lipid composition of cationic liposomes entrapping the plasmid, on immune responses.