Session 53Poster Presentations DNA Vaccines Session Day and Time: Thursday 1:30 - 3:30 pm Room: Hall D
449 Specific, Efficient, and Short-lived DNA Expression in Lymph Node Dendritic Cells Mediates DermaVir’s Immunotherapeutic Effects F Lori*1, J Trocio1, L Galluzzi1, P Markham2, C Fox3, J Lisziewicz1 1Res Inst for Genetic and Human Therapy, Washington, DC; 2Advanced BioSci Labs, Rockville, MD; and 3Univ of Arkansas, Little Rock
Background: Based on the postulate that HIV pathogenesis is largely mediated by viral expression in the lymphoid organs, a DNA-based topical vaccine (DermaVir) was designed to target Langerhans cells (LC) and ultimately be expressed by dendritic cells (DC) in the lymph nodes, thereby eliciting a T-cell mediated immune response capable of eliminating infected cells. DermaVir has been shown to induce cellular immune responses and to suppress SIVmac251 in chronically-infected macaques during treatment interruption. We wanted to explore whether the immunotherapeutic effects of DermaVir were mediated by its putative skin LC/lymph node DC transduction mechanism.
Methods: DermaVir was formulated with plasmid DNA encoding a reporter gene and mannosylated polyethylenimine (PEIm) in glucose solution. Mice (n = 16) and non-human primates (rhesus macaques, n=4) were used to assess the DermaVir mechanism of action, as well as DNA biodistribution and persistence (immunohistochemical staining, in situ hybridization, and PCR).
Results: We found that DermaVir is a mannosylated particle ca. 400 nm in size and neutral in charge, thereby suitable for LC transduction. After topical application, 9.4% transduction efficiency of LC in mice was achieved as compared to 0.8% with subcutaneous injection. Slight exfoliation of the skin improved the efficiency 2-3 fold. The transduced LC migrated to the draining lymph nodes and interdigitated as antigen expressing DC within 24 hrs after topical application. As little as 0.025 mg DNA resulted in ca. 1-4,000 and 20,000 DNA-expressing DC in mice and macaque lymph nodes, respectively. Transduced cells were not found in the blood or other highly vascularized organs. The half-life of DermaVir-derived DNA in the lymph node was less than 7 days.
Conclusions: The specificity and high efficiency of transduction of lymph node DC after topical DermaVir administration is conceivably responsible for the induction of naive T-cells and the potent viral suppression observed in non-human primates. The short half-life of the DNA enhances the safety profile and should allow for repeated administration of DermaVir.
