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RECOMBINANT VARICELLA-ZOSTER VIRUS AS A REPLICATING VIRAL VECTOR FOR THE DEVELOPMENT OF SIV/HIV VACCINES
DO Willer1, AP Ambagala1, JK Chan1, H Merks2, J Brooks2, R Pilon2, J Fournier2, PA Sandstrom2, KS MacDonald1
1Toronto, ON; 2Ottawa, ON
Objectives: Varicella-Zoster Virus (VZV), the causative agent of chickenpox and herpes zoster, establishes a life-long latent infection in neural ganglia, with evidence of periodic reactivation even in healthy individuals. In addition to the proven safety and efficacy record of the live-attenuated VZV Oka vaccine strain, the large DNA genome can be readily manipulated for the accommodation of foreign genes. Together with the ability to induce broad-ranging cellular and humoral immune responses, and the key feature of durable immunity, VZV is an attractive candidate for use as a vector in HIV vaccine development.
Methods: Live, parental Oka VZV was assessed for viral "take" and immunogenicity in cynomolgus macaques following intra-tracheal and intravenous inoculations. The ability of the virus to replicate was assessed by quantitative PCR and shell vial/DFA analysis of whole blood, bronchial alveolar lavage and nasopharyngeal samples. Humoral and cellular immune responses to VZV were monitored longitudinally by ELISA and IFN-gamma ELISPOT and/or multi-colour FACS/ICS, respectively.
Results: Following inoculation, a productive infection was detected in at least one animal. Robust antibody responses were readily detected by day 15 post-inoculation in all animals, and assessment of cell-mediated immunity is ongoing. Concurrently, we have generated an extensive panel of recombinant VZV vectors expressing various combinations of SIV genes to be assessed as potential vaccine candidates. These VZV-SIV recombinants demonstrate high-level transgene expression, genome stability, and wild-type growth characteristics in preliminary in vitro testing.
Conclusions: VZV can be readily manipulated to accommodate and stably express SIV transgenes. Our preliminary data suggests that cynomolgus macaques may provide an appropriate setting in which to assess recombinant VZV vectors as SIV/HIV vaccine candidates. Pending the completion of this work, a multi-low dose mucosal challenge trial will be initiated to assess the protective efficacy of various VZV-SIV vectors.