Enhanced Immune Response Following DNA Immunization Through In Vivo Electroporation

DNA immunization offers the advantage of allowing for the initiation of animal immunogenicity studies while work to produce and purify the protein of interest is completed. In this study, we sought to evaluate in vivo electroporation (EP) as a means to enhance the antigen-specific immune response from DNA immunization. Mice were immunized thrice with DNA encoding the protein of interest through intramuscular (IM) or intradermal (ID) injections. Test animals were administered an electrical pulse into the muscle or dermis at the site of injection immediately following immunization. In addition, cardiotoxin was injected into the muscle of a subset of test animals 5 days before each DNA injection. Nine weeks following the final DNA immunization, mice were immunized with the encoded purified protein emulsified in Freund's adjuvant. Sera from EP mice taken 2 weeks following the final DNA immunization showed a significant enhancement in antibody response. Specifically, those mice treated with cardiotoxin, immunized IM and given EP showed a strong response, but this was only observed versus solid phase and not solution phase antigen, suggesting the resulting antibody was of low titer and affinity. Similar testing following the protein immunization revealed a significant improvement in relative affinity versus sera taken following DNA immunization. Our results suggest EP can enhance the immune response elicited by DNA immunization.