Characterization of humoral immunity after DNA injection.

Antibodies to the influenza virus nucleoprotein are produced after injection of a plasmid DNA expression vector containing the nucleoprotein gene. A single injection of 10 to 100 micrograms of DNA produces IgG antibodies which first appear four to six weeks post injection. Antibody titres peak at six to eight weeks and then remain stable in most animals for many months. The antibody response at early times is dose-dependent, with higher amounts of DNA producing a faster immune response as well as higher antibody titres. Titres observed many months after injection are less dependent on DNA dose.