title: African Swine Fever Virus Georgia 2007 with a Deletion of Virulence-Associated Gene 9GL (B119L), when Administered at Low Doses, Leads to Virus Attenuation in Swine and Induces an Effective Protection against Homologous Challenge.
abstract: African swine fever virus (ASFV) is the etiological agent of an often lethal disease of domestic pigs. Disease control strategies have been hampered by the unavailability of vaccines against ASFV. Since its introduction in the Republic of Georgia, a highly virulent virus, ASFV Georgia 2007 (ASFV-G), has caused an epizootic that spread rapidly into Eastern European countries. Currently no vaccines are available or under development to control ASFV-G. In the past, genetically modified ASFVs harboring deletions of virulence-associated genes have proven attenuated in swine, inducing protective immunity against challenge with homologous parental viruses. Deletion of the gene 9GL (open reading frame [ORF] B119L) in highly virulent ASFV Malawi-Lil-20/1 produced an attenuated phenotype even when administered to pigs at 10(6) 50% hemadsorption doses (HAD50). Here we report the construction of a genetically modified ASFV-G strain (ASFV-G-Δ9GLv) harboring a deletion of the 9GL (B119L) gene. Like Malawi-Lil-20/1-Δ9GL, ASFV-G-Δ9GL showed limited replication in primary swine macrophages. However, intramuscular inoculation of swine with 10(4) HAD50 of ASFV-G-Δ9GL produced a virulent phenotype that, unlike Malawi-Lil-20/1-Δ9GL, induced a lethal disease in swine like parental ASFV-G. Interestingly, lower doses (10(2) to 10(3) HAD50) of ASFV-G-Δ9GL did not induce a virulent phenotype in swine and when challenged protected pigs against disease. A dose of 10(2) HAD50 of ASFV-G-Δ9GLv conferred partial protection when pigs were challenged at either 21 or 28 days postinfection (dpi). An ASFV-G-Δ9GL HAD50 of 10(3) conferred partial and complete protection at 21 and 28 dpi, respectively. The information provided here adds to our recent report on the first attempts toward experimental vaccines against ASFV-G.
  
  
  OBJECTIVE
  The main problem for controlling ASF is the lack of vaccines. Studies on ASFV virulence lead to the production of genetically modified attenuated viruses that induce protection in pigs but only against homologous virus challenges. Here we produced a recombinant ASFV lacking virulence-associated gene 9GL in an attempt to produce a vaccine against virulent ASFV-G, a highly virulent virus isolate detected in the Caucasus region in 2007 and now spreading though the Caucasus region and Eastern Europe. Deletion of 9GL, unlike with other ASFV isolates, did not attenuate completely ASFV-G. However, when delivered once at low dosages, recombinant ASFV-G-Δ9GL induces protection in swine against parental ASFV-G. The protection against ASFV-G is highly effective after 28 days postvaccination, whereas at 21 days postvaccination, animals survived the lethal challenge but showed signs of ASF. Here we report the design and development of an experimental vaccine that induces protection against virulent ASFV-G.
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA Department of Pathobiology and Veterinary Science, CAHNR, University of Connecticut, Storrs, Connecticut, USA.
authors.forename: Vivian
authors.initials: V
authors.lastname: O'Donnell
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Holinka
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Krug
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA Department of Pathobiology and Veterinary Science, CAHNR, University of Connecticut, Storrs, Connecticut, USA.
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Gladue
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Jolene
authors.initials: J
authors.lastname: Carlson
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Brenton
authors.initials: B
authors.lastname: Sanford
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Marialexia
authors.initials: M
authors.lastname: Alfano
authors.affiliation: U.S. Department of Homeland Security, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Kramer
authors.affiliation: U.S. Department of Homeland Security, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Lu
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Arzt
authors.affiliation: Center for Genome Innovation, University of Connecticut, Storrs, Connecticut, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Reese
authors.affiliation: APHIS, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Carrillo
authors.affiliation: Department of Pathobiology and Veterinary Science, CAHNR, University of Connecticut, Storrs, Connecticut, USA.
authors.forename: Guillermo R
authors.initials: GR
authors.lastname: Risatti
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Plum Island Animal Disease Center, Greenport, New York, USA manuel.borca@ars.usda.gov.
authors.forename: Manuel V
authors.initials: MV
authors.lastname: Borca
mesh_terms: D000357:African Swine Fever / Q000517:prevention & control*; D000358:African Swine Fever Virus / Q000235:genetics* / Q000276:immunology*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D017353:Gene Deletion; D005818:Genetic Engineering / Q000379:methods; D059014:High-Throughput Nucleotide Sequencing; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics; D016133:Polymerase Chain Reaction; D013552:Swine; D014764:Viral Proteins / Q000235:genetics*; D014765:Viral Vaccines / Q000235:genetics / Q000494:pharmacology*; D037521:Virulence Factors / Q000235:genetics*
chemical_list: C403418:9GL protein, African swine fever virus; D017931:DNA Primers; D014764:Viral Proteins; D014765:Viral Vaccines; D037521:Virulence Factors