Skin targeted DNA vaccine delivery using electroporation in rabbits. I: efficacy

Genetic immunization through skin is highly desirable as skin has plenty of antigen presenting cells (APCs) and is easily accessible. The purpose of this study was to investigate the effects of electroporation pulse amplitude, pulse length and number of pulses on cutaneous plasmid DNA vaccine delivery and immune responses, following intradermal injection in vivo in rabbits. Expression of the delivered plasmid was studied using a reporter plasmid, coding for beta-galactosidase. The efficiency of DNA vaccine delivery was investigated using a DNA vaccine against Hepatitis B, coding for Hepatitis B surface antigen (HBsAg). Serum samples and peripheral blood mononuclear cells (PBMC) were analyzed for humoral and cellular immunity, respectively, following immunization. The expression of transgene in the skin was transient and reached its peak in 2 days post-delivery with 200 and 300 V pulses. The expression levels with 200 and 300 V pulses were 48- and 129-fold higher, respectively, compared with the passive on day 2. In situ histochemical staining of skin with X-gal demonstrated the localized expression of beta-galactosidase with electroporation pulses of 200 and 300 V. Electroporation mediated cutaneous DNA vaccine delivery significantly enhanced both humoral and cellular immune responses (p<0.05) to Hepatitis B compared to passive delivery. The present study demonstrates the enhanced DNA vaccine delivery to skin and immune responses by topical electroporation. Hence, electroporation mediated cutaneous DNA vaccine delivery could be developed as a potential alternative for DNA vaccine delivery.