Location: Foreign Animal Disease Research2012 Annual Report
1a. Objectives (from AD-416):
1. Develop recombinant African Swine Fever Virus (ASFV) strains by deletion of one or more viral genes already described as responsible for inducting attenuation of highly virulent ASF strains. 2. Test attenuated ASFV strains for their ability to induce protection against challenge with homologous, well-characterized, virulent ASFV isolates. 3. Evaluate patterns of heterologous protection among genetically heterogeneous ASFV strains.
1b. Approach (from AD-416):
1. Develop recombinant African Swine Fever Virus (ASFV) strains by deletion of one or more viral genes already described as responsible for inducting attenuation of highly virulent ASF strains. Critical ASFV genes that are responsible for inducing attenuation of highly virulent ASF strains will be deleted individually or as a group. This deletion should confer virus replication but not disease production. 2. Test attenuated ASFV strains for their ability to induce protection against challenge with homologous, well-characterized, virulent ASFV isolates. This will be done through: Testing strains for in vivo attenuation, testing for efficacy against homologous challenge, determination of minim protective dose response, evaluation of protection profile for at least one attenuated ASFV vaccine candidate, and the evaluation of lead vaccine candidate to induce sterile immunity. 3. Evaluate and confirm cross-protection conferred by lead vaccine candidate (obj. 2) by using genetically diverse ASFV strains.
3. Progress Report:
African Swine Fever (ASF) is a devastating disease. Although historically restricted to Africa, the disease is currently spreading in the Caucasus and Russia, menacing to enter Easter Europe in the near future. No vaccine is available, therefore the only tool to restrict the diffusion of the disease outbreak in a disease free area is by massive destruction of affected animals as well as the preventive elimination of the nearby susceptible ones. There is a need to develop a proof-of-concept, rationally designed, live attenuated ASF vaccine and to produce a vaccine with the ability to confer cross-protection for genetically diverse strains of the virus. During FY 2012, DNA constructs containing reporter gene (b-gus) under the ASFV p72 promoter along with flanking regions corresponding to the ASFV genes to be deleted has been designed and constructed. These plasmids were used to produce recombinant viruses by homologous recombination. Transfection/infection were successfully performed with genetic constructs designed to delete ASFV genes 8-DR, 9GL and NL in the ASFV isolate Georgia. Blue plaques were identified in all three cases. The deliverables of this collaborative agreement compliment ARS in-house research project 1940-32000-056-00D, Countermeasures to Control Foreign Animal Diseases of Swine, objective 2, Develop intervention strategies to control African Swine Fever virus by identifying virus-host determinants of virulence and transmission and by developing technologies to enable the development of ASF vaccines that are efficacious against the most prevalent ASFV strains.