Intradermal DNA Vaccination Enhanced by Low-Current Electroporation Improves Antigen Expression and Induces Robust Cellular and Humoral Immune Responses

Abstract

DNA represents an ideal vaccine platform for HIV and many infectious diseases because of its safety, stability, and ease of manufacture. However, the immunogenicity of DNA vaccines has traditionally been low compared with viral vectors, recombinant protein, and live attenuated vaccines. The immunogenicity of DNA vaccines has been significantly enhanced by delivery with in vivo electroporation. Further improvements now allow electroporation to be performed in the dermis, which could potentially improve patient tolerability and may further enhance immunogenicity. In this study we examined how the current of intradermal vaccination impacts antigen expression, inflammation, and the induction of both humoral and cellular immunity in guinea pigs and nonhuman primates. We observed that a lower (0.1 A) current reduced inflammation and improved antigen expression compared with a 0.2 A current. The improved antigen expression resulted in a trend toward higher cellular immune responses but no impact on HIV-and influenza-specific binding titers. This study highlights the need for optimization of electroporation conditions in vivo in order to balance enhanced plasmid transfection with a loss of expression due to tissue inflammation and necrosis. These results suggest that a lower, 0.1-A current may not only improve patient tolerability but also improve immunogenicity.

Comparison of intradermal and intramuscular delivery followed by in vivo electroporation of SIV Env DNA in macaques

“…Different EP delivery methods developed by Inovio have been reported which showed improved immunity including HIV/SIV DNAs in macaques using intradermal low-current EP, 51 or using intradermal/subcutaneous EP, 52 as well as devices that deliver DNA simultaneously to both skin and muscle of mice and guinea pigs 53 and intradermal route in mice. 54 Here, we directly compared the immune responses induced upon IM IM/EP immunized animals showed robust responses with a frequency of 0.1-0.6% of Env-specific IFN-γ + T cells (Fig.…”

“…shallow ID DNA delivery using a novel 4 × 4 minimally invasive needle array. 51,61 This ID device differs from other invasive EP devices in that the electrodes are minimally invasive (make contact with the skin surface but do not penetrate) and also operate at significantly lower voltages (15-25 V). The electrode configuration is designed to achieve threshold electric fields over a wider area at lower applied voltages.…”

An Enhanced Synthetic Multiclade DNA Prime Induces Improved Cross-Clade-Reactive Functional Antibodies when Combined with an Adjuvanted Protein Boost in Nonhuman Primates

“…Potentially, the inclusion of one of these plasmid adjuvants could help increase memory responses, leading to the maintenance of neutralizing antibodies. Additionally, novel delivery devices such as intradermal electroporation have shown promising preclinical results and the ability to induce improved humoral responses (22,26,61). Lastly, boosting with more than one dose of recombinant protein, protein from multiple clades, or recombinant epitope-scaffold proteins that focus the immune response on particular regions of the Env, as well as the use of alternative adjuvants, may further improve the breadth, magnitude, and maintenance of the HIV-specific response.…”

“…Intracellular staining of PBMCs was performed as previously described (26). Briefly, after isolation, PBMCs (1 to 2 ϫ 10 6 ) were stimulated with individual pools of either Gag, Pol, or Env A, B, C, or D for 6 h in a 96-well U-bottom plate.…”

“…Though DNA has previously been relegated to a priming role due to its inability to induce strong humoral responses, many advances in the field, including the use of DNA and RNA optimization strategies as well as the use of electroporation (EP), and better formulations have increased the effectiveness of this platform in stimulating primary immune responses (21)(22)(23)(24)(25)(26)(27). This once modest platform is now capable of inducing T-cell responses as good as or better than those induced by viral vectors (25).…”