714. Attenuation of V- or C-Defective Measles Viruses: Infection Control by the Inflammatory and Interferon Responses of Rhesus Monkeys

Vaccine Delivery and Immune Responses for Infectious Diseases infects and multiplies its genome copy in most mammalian cells. Its replication is strictly in cytoplasm and independent of nuclear functions of host cells. Moreover, SeV does not have a DNA phase during its life cycle, so SeV-based vectors that express high-level of transgene do not need to be concerned about the transformation of cells by integration of vector materials into the host chromosomes. These properties of the vector enable us to propose the new concepts, CYTOPLASMIC VACCINATION with RNP-based treatment. We have already developed the Gag-expressing and fusion genedeleted SeV (SeV/∆F; non-transmissible type) vector for the AIDS vaccine. A trial of our DNA-prime/Gag-expressing SeV/∆F-boost vaccine in a macaque chronic AIDS model has shown its potential for efficiently inducing Gag-specific T cell responses, and further, in five of the eight vaccinees, successful containment of pathogenic simian immunodeficiency virus (SIVmac239) challenge. However, the administration of SeV/∆F vector was limited to single, because the immune response against viral vector was increased and believed to be ineffective for the boosting with repetitive administration. This time, we evaluated the ability of SeV/∆F-boost for the induction of CTL against AIDS when it was administered in the presence of anti-vector (SeV) antibody. After the first administration of Gagexpressing SeV/∆F vector, both anti-SeV (binding) antibodies and SeV-neutralizing antibodies were induced, their levels peaked in one month and maintained at relatively high levels more than several months. The second administration of Gag-expressing SeV/∆F was done in this condition, then, the efficient induction of Gag-specific CTL was observed. We found that SeV-neutralizing antibodies persisted for a relatively long time after the initial SeV vector administration. However, such SeV-neutralizing antibodies did not completely inhibit the induction of antigen-specicic CTL, suggesting the efficacy of multiple administrations of a SeV vector-based vaccine. In addition, this finding suggests that SeV vector-based vaccines would be capable of inducing antigen-specific CTL in individuals, who already have pre-existing neutralizing antibodies against SeV or related viruses such as human Parainfluenza viruses.

714. Attenuation of V- or C-Defective Measles Viruses: Infection Control by the Inflammatory and Interferon Responses of Rhesus Monkeys

Patricia Devaux,1 Gregory Hodge,2 Michael B. McChesney,2 Roberto Cattaneo.1 1 Molecular Medicine, Mayo Clinic, Rochester, MN; 2California National Primate Research Center, and Department of Pathology and Laboratory Medicine, University of California-Davis, Davis, CA.

Patients recruited in virus-based cancer clinical trials, and immunocompromised individuals in need of vaccination, would profit from viral strains with defined attenuation mechanisms. We generated measles virus (MV) strains defective for the expression of either the V protein, a modulator of the innate immune response, or the C protein, which has multiple functions. The virulence of these strains was compared with that of the parental wild type MV in a natural host, Macaca mulatta. Skin rash, viremia, and the strength of the innate and adaptive immune responses were characterized in groups of six animals. Replication of V- or C-protein defective viruses was short-lived and reached lower levels in peripheral blood mononuclear cells and lymphatic organs; none of the mutants reverted to wild type. Neutralizing antibody titers and MV-specific T-cell responses were equivalent in monkeys infected with any viral strain, documenting strong adaptive immune responses. In contrast, the inflammatory response was impaired selectively in monkeys infected with wild type MV, as revealed by inhibition of interleukin 6 and tumor necrosis factor-α transcription. The interferon response was also better controlled by the wild type than the defective viruses. Thus, both V and C proteins are required to control the inflammatory Molecular Therapy Volume 16, Supplement 1, May 2008 Copyright © The American Society of Gene Therapy

response and innate immunity. Viruses with defined attenuation mechanisms are promising candidates for specific oncolysis and vaccine applications.

715. A Phase I/II Clinical Trial of Threapeutic Vaccination with a DNA Plasmid Expressing the Hepatitis C Virus (HCV) Non-Streuctural 3/4A Complex Delivered by In Vivo Electroporation to Patients with Chronic HCV Infection

Matti Sallberg,1 Lars Frelin,1 Gustaf Ahlen,1 Iacob Mathiesen,2 Mike Fons,2 Rune Kjeken,2 Torunn Tjelle,2 Rolf Hultcrantz,3 Ola Weiland.4 1 Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden; 2 Inovio Inc, San Diego, CA; 3Medicine, Karolinska University Hospital, Stockholm, Sweden. We have developed a therapeutic vaccine for the treatment of chronic infections caused by the hepatitis C virus (HCV). Current therapies can effectively treat around 50% of patients but are expensive and have significant side effects. A large body of data suggests that clearance of HCV infections is associated with an activation of the host T cell responses. We have therefore developed a T cell vaccine based on a codon-optimized HCV non-structural (NS) 3/4A DNA gene delivered by in vivo electroporation (EP). DNA is poorly immunogenic in humans since the injected DNA stays outside the cell and becomes degraded. We have shown that in vivo EP acts as an adjuvant for the NS3/4A DNA by promoting plasmid uptake and expression. Importantly, recent data also shows that delivery of NS3/4A plasmid using in vivo EP improves the local inflammation and the infiltration of CD3+ cells. Extensive preclinical testing in transgenic mice and rabbits suggests that the vaccine regimen is highly immunogenic and safe. We have now started, to our knowledge, the worlds first clinical trial of a DNA vaccine delivered by in vivo EP for the treatment of chronic HCV infection. A total of 12 treatment naive patients with chronic HCV infection of genotype 1 and a low viral load will be enrolled. They are divided into four groups and the first three dose groups will receive four monthly vaccinations with plasmid at doses of 0,167 mg, 0,500 mg, or 1,500 mg, respectively. To date the three patients in the lowest dose group has started treatment and has received 1, 2, and 3 vaccinations respectively. No significant adverse events have been noted. All patients will be analyzed regarding safety parameters such as local tolerability and systemic effects, including liver function tests. In addition, all patients are analyzed for HCV NS3/4A-specific immune responses and the viral load in circulation. The clinical trial is currently ongoing and the design and most up to date data will be presented in detail.

716. Cellular and Humoral Immune Responses Correlate with Vaccine Protective Efficacy Against the 1918 (H1N1) Influenza Virus in Ferrets

Veronika van Messling,1 Darwyn Kobasa,4,5 Stephane Pillet,1 Michael Gray,2 Jason Gren,2 Shane Jones,2 Betty Luy,4 Tracy Taylor,4 Dominick Laddy,3 David Weiner,3 Heinz Feldmann,2,5 Gary P. Kobinger.2,5 1 INRS-Institut Armand-Frappier, University of Quebec, Laval, QC, Canada; 2Special Pathogens, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada; 3 Department of Pahology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA; 4Respiratory Viruses, National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, MB, Canada; 5Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, Canada. The influenza A viruses of the family orthomyxoviridae include a large number of known animals and human pathogens including avian influenza (H5N1) and 1918 pandemic (H1N1) viruses. Rising S267