Background This study tested a low-volume (20–30 μl/20–30 μg DNA) jet injection method for intradermal delivery of a DNA vaccine. Jet injection offers the advantages of a needle-less system, low-cost, rapid preparation of the injected DNA solution, and a simple delivery system. More than one construct can be injected simultaneously and the method may be combined with adjuvants.

      Results
      Low-volume jet injection targeted delivery of a DNA solution exclusively to the dermis and epidermis of rabbits. A three injection series of plasmid DNA, encoding the Hepatitis B Surface Antigen stimulated a humoral immune response in 2/5 rabbits. One rabbit developed a significant rise in antibody titer after 1 injection and one following 2 injections. There were no significant differences between jet injection and particle bombardment in the maximal antibody titers or number of injections before response. A three injection series of the same plasmid DNA by particle bombardment elicited a significant rise in antibody titer in 3/5 rabbits. One rabbit developed antibody after 1 injection and two after 3 injections. In contrast, 0/5 rabbits receiving DNA by needle and syringe injection responded. In the jet injection and particle bombardment groups, gene expression levels in the skin did not predict response. While immune responses were similar, luciferase gene expression levels in the skin following particle bombardment were 10–100 times higher than jet injection.


      Conclusion
      Low-volume jet injection is a simple, effective methodology for intradermal DNA immunization.