HUMORAL AND CELLULAR-IMMUNITY TO AN ENCODED PROTEIN-INDUCED BY DIRECTDNA INJECTION

An immunization procedure with naked DNA that generates both humoral a nd cellular immune responses is described. A mammalian expression vect or encoding human factor IX as an example of immunogen was injected in to mice three times at 10-day intervals. Three of the 4 mice in which the DNA was injected intramuscularly and 5 of the 9 mice injected subc utaneously produced antibodies to human factor IX. Spleen cells from i noculated mice also showed significant cytotoxic T lymphocyte response to target cells expressing human factor IX. The titers of anti-single -stranded (ss)DNA antibodies were significantly higher in the subsets of genetically inoculated mice than in the control mice, but anti-doub le-stranded (ds)DNA antibodies were not detected in any serum samples. Thus, intramuscular and subcutaneous injection of plasmid DNA can ind uce immune responses against the encoded protein without an exposure t o virus particles, and this approach may serve as the basis for immuno therapy in the treatment of cancer and infectious diseases in humans.