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United States Department of Agriculture

Agricultural Research Service

Project Type: Appropriated

Start Date: Mar 28, 2007
End Date: Oct 10, 2011

Objectives of research: 1. Develop effective Classical Swine Fever Virus (CSFV) marker vaccines and companion diagnostic tests capable of differentiating vaccinated from infected animals. 2. Examine innate local immune mechanisms mediating early protection in vaccinated pigs and mechanisms of delivery for rapid mucosal immunity. 3. Develop a DNA recombinant technology approach to enable the development of an African Swine Fever (ASF) vaccine that is efficacious against the ASF strain circulating in Caucasus.

Development of a novel live-attenuated CSF marker vaccine requires knowledge of the genetic basis of viral virulence. Using reverse genetics, it is possible to systematically evaluate the role of specific viral proteins or virus virulence, and use this information to engineer recombinant LAVs. Our strategy is to introduce modifications in our CSFV infectious clone. The first objective will be achieved by introducing specific mutations on the CSFV envelope glycoprotein and determine their effect on virus virulence. We hypothesize that positive and negative virus antigenic markers will induce unique antibody responses in vaccinated animals, thus showing differentiation in ELISA tests. Serological tests will be developed to differentiate experimentally vaccinated from CSFV wildtype infected animals. The approach to achieving the second objective consists in identifying and characterizing the tissues and cells infected with attenuated and virulent strains. This will provide information on the mechanisms inducing early protection after LAV administration. A comparison will be conducted of the tissue and cell types affected during early stages of infection with attenuated and virulent strains. Analysis will be done on the profiles of locally produced pro-inflammatory chemical mediators and host gene activation during infection with attenuated and virulent strains. We also postulate that oral administration of the candidate LAV strains will lead to effective protective response in domestic pigs. The third objective is to develop a DNA recombinant technology approach to enable the development of an ASF vaccine that is efficacious against the ASF strain circulating in Caucasus. The main goal is the development of attenuated strains of the Georgian ASFV (ASFV-G) isolate. The approach will be based in the deletion of specific virus genes which were previously identified as critical factors of virulence during the infection in pigs. The selected genes will be individually deleted from the genome of the ASFV-G and the effect in virus virulence of the resulting viruses in swine will be assessed. ASFV-G "delta" mutant strains presenting completely attenuated phenotype in swine will be selected to their further assessment as putative live attenuated vaccine strains. Protection induced by these selected strains will be evaluated against both homologous as well as heterologous virulent viruses.

Last Modified: 6/1/2015
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