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Title: Deletion of the thymidine kinase gene induces complete attenuation of the Georgia isolate of African swine fever virus

Author
item SANDFORD, BRENTON - Former ARS Employee
item Holinka-Patterson, Lauren
item O'DONNELL, V - University Of Connecticut
item Krug, Peter
item CARLSON, J - Kansas State University
item ALFANO, M - Oak Ridge Institute For Science And Education (ORISE)
item CARRILLO, C - Animal And Plant Health Inspection Service (APHIS)
item WU, PING - Animal And Plant Health Inspection Services (APHIS), National Wildlife Center
item LOWE, ANDRE - Animal And Plant Health Inspection Services (APHIS), National Wildlife Center
item RISATTI, GUILLERMO - University Of Connecticut
item Gladue, Douglas
item Borca, Manuel

Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2015
Publication Date: 12/2/2015
Citation: Sandford, B., Holinka-Patterson, L.G., O'Donnell, V., Krug, P.W., Carlson, J., Alfano, M., Carrillo, C., Wu, P., Lowe, A., Risatti, G.R., Gladue, D.P., Borca, M.V. 2015. Deletion of the thymidine kinase gene induces complete attenuation of the Georgia isolate of African swine fever virus. Virus Research. 213:165-171. doi: 10.1016/j.viruses.2015.12.002.

Interpretive Summary: African swine fever (ASF) is a lethal disease of swine caused by a double-stranded DNA virus, African swine fever virus (ASFV). There is no available vaccine to prevent the disease and current control measures are limited to eliminate susceptible animals and restrict animal movement. Swine infected with experimental live attenuated lacking a viral gene, such as the thymidine kinase gene (TK), have been able to protect swine from lethal challenge. Here we report the deletion of TK in the current outbreak strain in Georgia, ASFV-G. We were able to obtain this deletion virus by delteing the TK gene in a virulent strain of ASFV that had been adapted to grow in Vero cells (ASFV-G/VP30). The resulting delta TK virus demonstrated decreased replication both in primary swine macrophage cell cultures and in Vero cells. Intramuscular administration of up to 10(6) TCID50 of delta TK virus does not result in ASF disease. However, these animals are not protected when challenged with the virulent parental Georgia strain.

Technical Abstract: African swine fever virus (ASFV) is the etiological agent of a contagious and often lethal viral disease of domestic pigs. There are no vaccines to control Africa swine fever (ASF). Experimental vaccines have been developed using genetically modified live attenuated ASFVs obtained by specifically deleting virus genes involved in virulence, including the thymidine kinase (TK) gene. TK has been shown to be involved in the virulence of several viruses, including ASFV. Here we report the construction of a recombinant virus (ASFV-G/V-Delta TK) obtained by deleting the TK gene in a virulent strain of ASFV Georgia adapted to replicate in Vero cells (ASFV-G/VP30). ASFV-G/P-Delta TK demonstrated decreased replication both in primary swine macrophage cell cultures and in Vero cells compared with ASFV-G/VP30. In vivo, intramuscular administration of up to 10 6 TCID 50 of ASFV-G/V-Delta TK does not result in ASF disease. However, these animals are not protected when challenged with the virulent parental Georgia strain.