The skin is an attractive tissue for vaccination in a clinical setting due to the accessibility of the target, the ease of monitoring and most importantly the immune competent nature of the dermal tissue. While skin electroporation offers an exciting and novel future methodology for the delivery of DNA vaccines in the clinic, little is known about the actual mechanism of the approach and the elucidation of the resulting immune responses. To further understand the mechanism of this platform, the expression kinetics and localization of a reporter plasmid delivered via a surface dermal electroporation (SEP) device as well as the effect that this treatment would have on the resident immune cells in that tissue was investigated. Initially a time course (day 0 to day 21) of enhanced gene delivery with electroporation (EP) was performed to observe the localization of green fluorescent protein (GFP) expression and the kinetics of its appearance as well as clearance. Using gross imaging, GFP expression was not detected on the surface of the skin until 8 h post treatment. However, histological analysis by fluorescent microscopy revealed GFP positive cells as early as 1 h after plasmid delivery and electroporation. Peak GFP expression was observed at 24 h and the expression was maintained in skin for up to seven days. Using an antibody specific for a keratinocyte cell surface marker, reporter gene positive keratinocytes in the epidermis were identified. H&E staining of treated skin sections demonstrated an influx of monocytes and granulocytes at the EP site starting at 4 h and persisting up to day 14 post treatment. Immunological staining revealed a significant migration of lymphocytic cells to the EP site, congregating around cells expressing the delivered antigen. In conclusion, this study provides insights into the expression kinetics following EP enhanced DNA delivery targeting the dermal space. These findings may have implications in the future to design efficient DNA vaccination strategies for the clinic.
Andre, S.; Seed, B.; Eberle, J.; Schraut, W.; Bultmann, A.; Haas, J. Increased immune response elicited by DNA vaccination with a synthetic gp120 sequence with optimized codon usage. J. Virol. 1998, 72, 1497–1503.
Martinon, F.; Kaldma, K.; Sikut, R.; Culina, S.; Romain, G.; Tuomela, M.; Adojaan, M.; Mannik, A.; Toots, U.; Kivisild, T.; et al. Persistent immune responses induced by a human immunodeficiency virus DNA vaccine delivered in association with electroporation in the skin of nonhuman primates. Hum. Gene Ther. 2009, 20, 1291–1307, doi:10.1089/hum.2009.044.
Widera, G.; Austin, M.; Rabussay, D.; Goldbeck, C.; Barnett, S.W.; Chen, M.; Leung, L.; Otten, G.R.; Thudium, K.; Selby, M.J.; et al. Increased DNA vaccine delivery and immunogenicity by electroporation in vivo. J. Immunol. 2000, 164, 4635–4640.
Kopycinski, J.; Cheeseman, H.; Ashraf, A.; Gill, D.; Hayes, P.; Hannaman, D.; Gilmour, J.; Cox, J.H.; Vasan, S. A DNA-based candidate hiv vaccine delivered via in vivo electroporation induces CD4 responses toward the α4β7-binding V2 loop of HIV gp120 in healthy volunteers. Clin. Vaccine Immunol. 2012, 19, 1557–1559, doi:10.1128/CVI.00327-12.
Diaz, C.M.; Chiappori, A.; Aurisicchio, L.; Bagchi, A.; Clark, J.; Dubey, S.; Fridman, A.; Fabregas, J.C.; Marshall, J.; Scarselli, E.; et al. Phase 1 studies of the safety and immunogenicity of electroporated HER2/CEA DNA vaccine followed by adenoviral boost immunization in patients with solid tumors. J. Transl. Med. 2013, 11, e62, doi:10.1186/1479-5876-11-62.
Vasan, S.; Hurley, A.; Schlesinger, S.J.; Hannaman, D.; Gardiner, D.F.; Dugin, D.P.; Boente-Carrera, M.; Vittorino, R.; Caskey, M.; Andersen, J.; et al. In vivo electroporation enhances the immunogenicity of an HIV-1 DNA vaccine candidate in healthy volunteers. PLoS One 2011, 6, e19252, doi:10.1371/journal.pone.0019252.
Zhang, L.; Li, L.; Hoffmann, G.A.; Hoffman, R.M. Depth-targeted efficient gene delivery and expression in the skin by pulsed electric fields: An approach to gene therapy of skin aging and other diseases. Biochem. Biophys. Res. Commun. 1996, 220, 633–636, doi:10.1006/bbrc.1996.0455.
Heller, R.; Cruz, Y.; Heller, L.C.; Gilbert, R.A.; Jaroszeski, M.J. Electrically mediated delivery of plasmid DNA to the skin, using a multielectrode array. Hum. Gene Ther. 2010, 21, 357–362, doi:10.1089/hum.2009.065.
Zhang, L.; Nolan, E.; Kreitschitz, S.; Rabussay, D.P. Enhanced delivery of naked DNA to the skin by non-invasive in vivo electroporation. Biochim. Biophys. Acta 2002, 1572, 1–9, doi:10.1016/S0304-4165(02)00270-2.
Broderick, K.E.; Kardos, T.; McCoy, J.R.; Fons, M.P.; Kemmerrer, S.; Sardesai, N.Y. Piezoelectric permeabilization of mammalian dermal tissue for in vivo DNA delivery leads to enhanced protein expression and increased immunogenicity. Hum. Vaccin. 2011, 7, 22–28, doi:10.4161/hv.7.0.14559.
Connolly, R.J.; Rey, J.I.; Lambert, V.M.; Wegerif, G.; Jaroszeski, M.J.; Ugen, K.E. Enhancement of antigen specific humoral immune responses after delivery of a DNA plasmid based vaccine through a contact-independent helium plasma. Vaccine 2011, 29, 6781–6784, doi:10.1016/j.vaccine.2010.12.054.
Roos, A.K.; Moreno, S.; Leder, C.; Pavlenko, M.; King, A.; Pisa, P. Enhancement of cellular immune response to a prostate cancer DNA vaccine by intradermal electroporation. Mol. Ther. 2006, 13, 320–327, doi:10.1016/j.ymthe.2005.08.005.
Gronevik, E.; von Steyern, F.V.; Kalhovde, J.M.; Tjelle, T.E.; Mathiesen, I. Gene expression and immune response kinetics using electroporation-mediated DNA delivery to muscle. J. Gene Med. 2005, 7, 218–227.