title: Protective immunization of horses with a recombinant canarypox virus vectored vaccine co-expressing genes encoding the outer capsid proteins of African horse sickness virus.
abstract: We describe the development and preliminary characterization of a recombinant canarypox virus vectored (ALVAC) vaccine for protective immunization of equids against African horse sickness virus (AHSV) infection. Horses (n=8) immunized with either of two concentrations of recombinant canarypox virus vector (ALVAC-AHSV) co-expressing synthetic genes encoding the outer capsid proteins (VP2 and VP5) of AHSV serotype 4 (AHSV-4) developed variable titres (<10-80) of virus-specific neutralizing antibodies and were completely resistant to challenge infection with a virulent strain of AHSV-4. In contrast, a horse immunized with a commercial recombinant canarypox virus vectored vaccine expressing the haemagglutinin genes of two equine influenza H3N8 viruses was seronegative to AHSV and following infection with virulent AHSV-4 developed pyrexia, thrombocytopenia and marked oedema of the supraorbital fossae typical of the "dikkop" or cardiac form of African horse sickness. AHSV was detected by virus isolation and quantitative reverse transcriptase polymerase chain reaction in the blood of the control horse from 8 days onwards after challenge infection whereas AHSV was not detected at any time in the blood of the ALVAC-AHSV vaccinated horses. The control horse seroconverted to AHSV by 2 weeks after challenge infection as determined by both virus neutralization and ELISA assays, whereas six of eight of the ALVAC-AHSV vaccinated horses did not seroconvert by either assay following challenge infection with virulent AHSV-4. These data confirm that the ALVAC-AHSV vaccine will be useful for the protective immunization of equids against African horse sickness, and avoids many of the problems inherent to live-attenuated AHSV vaccines.
authors.affiliation: Equine Research Centre, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa. alan.guthrie@up.ac.za
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Guthrie
authors.forename: Melvyn
authors.initials: M
authors.lastname: Quan
authors.forename: Carina W
authors.initials: CW
authors.lastname: Lourens
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Audonnet
authors.forename: Jules M
authors.initials: JM
authors.lastname: Minke
authors.forename: Jiansheng
authors.initials: J
authors.lastname: Yao
authors.forename: Ling
authors.initials: L
authors.lastname: He
authors.forename: Robert
authors.initials: R
authors.lastname: Nordgren
authors.forename: Ian A
authors.initials: IA
authors.lastname: Gardner
authors.forename: N James
authors.initials: NJ
authors.lastname: Maclachlan
mesh_terms: D000355:African Horse Sickness / Q000276:immunology / Q000517:prevention & control*; D000356:African Horse Sickness Virus / Q000276:immunology / Q000302:isolation & purification; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D028121:Canarypox virus / Q000276:immunology; D036022:Capsid Proteins / Q000276:immunology*; D002478:Cells, Cultured; D006224:Cricetinae; D005260:Female; D006736:Horses / Q000276:immunology*; D008297:Male; D014613:Vaccines, Attenuated / Q000276:immunology; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: C078788:ALVAC vaccine; D000914:Antibodies, Viral; D036022:Capsid Proteins; C442519:VP2 protein, African horse sickness virus; C442560:VP5 protein, African horse sickness virus; D014613:Vaccines, Attenuated; D014765:Viral Vaccines