title: A BIR motif containing gene of African swine fever virus, 4CL, is nonessential for growth in vitro and viral virulence.
abstract: An African swine fever virus (ASFV) gene with similarity to viral and cellular inhibitor of apoptosis genes (iap) has been described in the African isolate Malawi Lil-20/1 (ORF 4CL) and a cell-culture-adapted European virus, BA71V (ORF A224L). The similarity of the ASFV gene to genes involved in inhibiting cellular apoptosis suggested the gene may regulate apoptosis in ASFV-infected cells and thus may function in ASFV virulence and/or host range. Sequence analysis of additional African and European pathogenic isolates demonstrates that this gene is highly conserved among both pig and tick ASFV isolates and that its similarity to iap genes is limited to the presence of a single IAP repeat motif (BIR motif) in the ASFV gene. To study gene function, a 4CL gene deletion mutant, delta 4CL, was constructed from the pathogenic Malawi Lil-20/1 isolate. Growth characteristics of delta 4CL in swine macrophage cell cultures were indistinguishable from those of parental virus. Infected macrophage survival time and the induction and magnitude of apoptosis in virus-infected macrophages were comparable for cells infected with either delta 4CL or parental virus. In infected swine, delta 4CL exhibited an unaltered Malawi Lil-20/1 virulence phenotype. These data indicate that, although highly conserved among ASFV isolates, the 4CL gene is nonessential for growth in macrophage cell cultures in vitro and for pig virulence. Additionally, despite its limited similarity to JAP genes, 4CL exhibits no anti-apoptotic function in infected macrophage cell cultures. The high degree of gene conservation among ASFV isolates, together with the apparent lack of function in the swine host, suggests 4CL may be a host range gene involved in aspects of infection in the arthropod host, ticks of the genus Ornithodoros.
authors.affiliation: Plum Island Animal Disease Center, U.S. Department of Agriculture, Greenport, New York 11944-0848, USA.
authors.forename: J G
authors.initials: JG
authors.lastname: Neilan
authors.forename: Z
authors.initials: Z
authors.lastname: Lu
authors.forename: G F
authors.initials: GF
authors.lastname: Kutish
authors.forename: L
authors.initials: L
authors.lastname: Zsak
authors.forename: T G
authors.initials: TG
authors.lastname: Burrage
authors.forename: M V
authors.initials: MV
authors.lastname: Borca
authors.forename: C
authors.initials: C
authors.lastname: Carrillo
authors.forename: D L
authors.initials: DL
authors.lastname: Rock
mesh_terms: D000357:African Swine Fever / Q000821:virology*; D000358:African Swine Fever Virus / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity*; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D017124:Conserved Sequence; D004279:DNA, Viral; D017353:Gene Deletion; D005814:Genes, Viral; D007739:L Cells; D008264:Macrophages / Q000166:cytology / Q000821:virology; D051379:Mice; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D013552:Swine; D014407:Tumor Cells, Cultured; D014709:Vero Cells; D015678:Viral Structural Proteins / Q000235:genetics*; D014774:Virulence
chemical_list: C097626:A224L protein, African swine fever virus; D004279:DNA, Viral; D015678:Viral Structural Proteins