HSV-1 AMPLICON VECTORS DIRECT THE IN SITU PRODUCTION OF FOOT-AND-MOUTH DISEASE VIRUS-LIKE PARTICLES IN MAMMALIAN CELLS

D'ANTUONO A; LAIMBACHER A; LA TORRE J; TRIBULATTI V; ROMANUTTI C; ZAMORANO P; QUATTROCCHI V; SCHRANER EM; ACKERMAN M; FRAEFEL C; MATTION N

Viena

Simposio; EUFMD - FMD week 2010; 2010

European Comission for the control of FMD

Introduction: Herpes simplex virus type 1 (HSV-1) based vectors have been shown to be very useful and safe in human gene therapy, and are considered promising vehicles to deliver antigens and immune-modulators for prophylactic and therapeutic vaccination. Materials and Methods: HSV-1 amplicon vectors encoding foot-and-mouth disease virus (FMDV) structural proteins and the 3C protease from O1 Campos strain, were generated and packaged using a helper virus-free system. The HSV-1 genome was provided in trans by a bacterial artificial chromosome (BAC) deleted in the essential ICP27 gene and packaging (pac) signals.  The amplicons carried approximately 15 copies of a cassette of FMDV sequences inserted after the IE4/5 promoter plus a picornavirus IRES preceding the reporter EGFP gene, and flanked by specific pac signals. Results: HSV-1 amplicon vectors were capable to mediate in situ generation of VLPs and other subunits in mammalian cells, which could be fractionated in sucrose gradients and were recognized by O1 specific monoclonal antibodies.  Inoculation of mice with 5 x 105 transducing units of amplicon vectors in the absence of adjuvant, resulted in a FMDV-specific humoral response. Challenge of vaccinated mice with 104.5 TCID50 of live O1/Campos FMD virus, resulted in a significant reduction of viremia. FMDV-specific immune responses depended on the in situ de novo production of the vector-encoded antigens.  Discussion: The HSV-1 amplicon vectors have been designed to provide a highly safety profile, as they do not express any HSV-1 genes when packaged using a helper virus-free system, are able to encapsidate several copies of the transgene or allow the simultaneous expression of different genes (up to 150Kb).  They combine the high immunogenicity of modified live virus vaccines with the safety and simplicity of DNA vaccines, were able to induce both humoral and cellular immune responses in preliminary experiments.