Comparative studies on in vitro expression and in vivo immunogenicity of supercoiled and open circular forms of plasmid DNA vaccines.

Here we use tests for in vitro expression and in vivo immunogenicty to compare the biological activity of supercoiled and open circular forms of plasmid DNA vaccines. The different forms of vaccine DNA revealed no differences in the expression of mRNA or protein following DEAE-dextran-assisted transfection of cultured cells. In contrast, following intramuscular saline injections in mice, supercoiled DNA was three times more effective than open circular DNA at priming a MVA-boosted CD8 T cell response. Thus, under our experimental conditions, measurements for supercoiled vaccine DNA provided a more accurate assessment of the potential to prime a CD8 response than tests for expression in transiently transfected cells.