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Dendritic Cell-Mediated Genetic Immunization Induces Vigorous T-Helper and CTL Responses In Vitro and in Primates J. LISZIEWICZ*1, G. VARGA1, J. XU1, P. GREENBERG2, S. ARYA3, M. BOSCH2, and F. LORI1. 1Res. Inst. for Genetic and Human Therapy, Washington, DC, and Pavia, Italy; 2Univ. of Washington, Seattle; and 3NIH, Bethesda, MD HIV-specific T-helper and CTL responses decline with time in patients treated with HAART, even if they mount immune responses against new and recall antigens. To induce new HIV-specific immune responses, we used genetically modified dendritic cells (GM-DC) to provide efficient antigen presentation for naïve T-cells. GM-DC were generated from monocyte-derived DC transduced with a plasmid DNA encoding a replication and integration defective HIV vector using a novel non-viral gene delivery system (polyethylenimine-mannose). GM-DC elicited in vitro a potent activation of naïve CD4 and CD8 T-cells (up to 8% of CD3 gated cells expressed intracellular IFN-g) and generated vigorous CTL responses (27% of p55-specific lysis, E:T=100:1). Remarkably, these levels of HIV-specific immune responses were induced by a single stimulation of naïve cells. The in vitro observation was confirmed in vivo. Autologous GM-DC injection induced vigorous and long lasting CTL and T-helper responses against HIV in pigtailed macaques. 3 weeks after a single immunization, animals presented a vigorous effector CTL response (up to 50% of gag-specific lysis in the absence of in vitro antigenic restimulation, E:T=100:1). Interestingly, low levels of effector CTL were still found 7 months later (up to 12% of gag-specific lysis, E:T=100:1). At this time, a memory CTL response was also present (up to 40% of gag-specific lysis after antigenic stimulation, E:T=40:1). Interestingly, antibodies did not accompany these CTL responses, suggesting that GM-DC raised a pure Th1 type of immune response. No toxic side effect was documented. In conclusion, a novel genetic immunization approach, based on a non-viral transduction of an HIV vector into DC, induced unprecedented stimulation of naïve cells and CTL responses both in vitro and in vivo. Key Words: CTL, dendritic cells, HIV vector |
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© 7th
Conference on Retroviruses and Opportunistic Infections, |