Optimization of skin electroporation in mice to increase tolerability of DNA vaccine delivery to patients.

Electroporation has, during the last years, proven to be a very successful delivery method for DNA vaccines and has now reached clinical evaluation. Although intramuscular electroporation is practical in animal models, intradermal electroporation might be more suitable for clinical administration. Skin is the most accessible organ of the body and has professional antigen-presenting cells in large amounts; thus, skin is an ideal target for DNA vaccine delivery. Moreover, intradermal electroporation has clear clinical benefits such as improved safety and tolerability. This article describes improvements for effective and tolerable DNA delivery to skin. The time of pulse delivery has been shortened by 90% and even pulse programs of 240-ms total duration generate robust immune responses. We show that a single vaccination using an optimized gene delivery generates (i) high and consistent protein expression in vivo, (ii) cytotoxic antigen-specific T cells expressing both IFNgamma and CD107a (lysosomal-associated membrane protein 1). Furthermore, application of a topical anesthetic cream prior to vaccination does not affect the number or function of the antigen-specific T cells induced. This suggests that local anesthesia can be used to further decrease the sensation of pulse delivery in patients.