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10 Plasmid Delivery Technologies Enhance Anti-HIV Immune Responses in Rhesus Macaques Given a DNA Prime-Protein Boost Vaccination Regimen
G. Otten*1, M. Schaefer1, B. Doe1, I. Srivastava1, J. Kazzaz1, Y. Lian1, H. Liu1, L. Leung1, M. Singh1, Y. Sun1, M. Ugozzoli1, J. zur Megede1, M. Lewis2, N. Miller3, G. Widera4, S. Barnett1, J. Donnelly1, D. O'Hagan1, J. Polo1, and J. Ulmer1
1Chiron Corp., Emeryville, CA, USA; 2Southern Res. Inst., Frederick, MD, USA; 3NIH, Bethesda, MD, USA; and 4Genetronics, San Diego, CA, USA
Background: Plasmid DNA has several features that make it attractive as a component of an HIV vaccine. However, clinical results suggest that the modest immunogenicity of plasmid DNA may limit its protective efficacy against HIV. In rhesus macaques, we have tested 3 distinct delivery technologies designed to overcome barriers that limit plasmid DNA immunogenicity.
Methods: The technologies consisted of intramuscular electroporation to increase DNA transfection efficiency in vivo, adsorption of plasmid DNA onto cationic poly(lactide-co-glycolide) (PLG) microparticles, and formulation of plasmid DNA with a cationic derivative of the adjuvant MF59. Using conventional CMV-promoter/enhancer-based plasmids and novel alphavirus-derived plasmids containing codon-modified HIV p55gag and gp140env sequences, these delivery technologies were compared with intramuscular injection of plasmid DNA in saline (naked DNA).
Results: The 3 technologies increased plasmid immunogenicity, with serum IgG ELISA titers and CD4 T-helper lymphoproliferative responses that appeared more quickly and reached higher levels than those obtained with naked DNA. Flow cytometric analysis of intracellular IFN-gamma TNF-alpha production demonstrated increased numbers of antigen-specific CD4 T cells in the peripheral blood of rhesus vaccinated by DNA/electroporation or with DNA/PLG. HIV-specific CTL activity was observed in rhesus vaccinated by DNA/electroporation, DNA/PLG, or naked DNA; however, CTL were almost undetectable after vaccination with DNA/MF59. The findings were corroborated by intracellular cytokine analysis of CD8 T cells. Immune responses were boosted further following the administration of a microparticle formulation of recombinant p55gag protein or recombinant oligomeric gp140env protein coadministered with the adjuvant MF59.
Conclusions: Our results suggest that these plasmid DNA delivery technologies may serve as important components of an effective DNA prime-protein boost vaccine.
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