#16-177

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Date Full Report Received

Date Abstract Report Received

Investigation

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Classical swine fever (CSF) is a highly infectious viral disease found in domestic pigs and wild boar populations. Outbreaks have a large economic cost for the swine industry and cause significant morbidity and mortality in pigs. Only one compatible vaccine that allows the differentiation between infected and vaccinated animals (DIVA), Suvaxyn® CSF Marker vaccine, is commercially available. However, this vaccine is not used prophylactically and is only used in emergency situations to prevent spread of CSFV to wider areas. An urgent need exists for development of a safe, effective, DIVA compatible vaccine. This study set out to address this need by taking steps towards developing porcine cytomegalovirus (PCMV) as a vaccine platform, both as a conventional vaccine as well as a scalable, self-disseminating vaccine. Species-specific CMV-based vaccines have been shown to induce strong, durable immune responses against heterologous antigens in a variety of animals. Herpesvirus-based vaccines also have the potential to be used in a self-disseminating format, which enables vaccination of inaccessible animal populations such as wild boar. An initial important aim of the present study was to characterize the in vitro growth characteristics of a recent PCMV isolate, which is key for development of the virus as a vaccine vector platform. In terms of subcellular distribution, our results showed that PCMV was primarily released into the supernatant from infected cells. Subsequent studies showed the virus to have a slow growth, low titer phenotype when grown in permissive porcine cells. A second key aim was to use this information towards construction of a prototype PCMV-based vaccine against CSFV. Recombinant shuttle cloning vectors expressing a target antigen (called E2) from border disease virus (BDV) – a virus that is closely related to CSFV, but does not impact current commercial serology-based methods for identification of CSFV-infected animals ¬- were designed, constructed and characterized. Multiple attempts using these shuttle vectors to clone a BDV E2-expressing PCMV vaccine proved unsuccessful. This appears, in large part, to result from the unique growth characteristics of PCMV. In light of these findings, future work using these shuttle vectors will further optimize the cloning strategy for PCMV with the aim of translating the CMV-based vaccine system into a vector platform suitable for use to control infectious disease in domestic pigs and wild boar.