Infection with recombinant orf viruses demonstrates that the viral interleukin-10 is a virulence factor.
Orf virus is the prototype parapoxvirus that causes the contagious skin disease orf. It encodes an orthologue of the cytokine interleukin (IL)-10. Recombinant orf viruses were constructed in which the viral interleukin-10 (vorfIL-10) was disabled (vorfIL-10ko) and reinserted (vorfrevIL-10) at the same locus and compared to wild-type virus for their ability to induce skin lesions in sheep. After either primary infection or reinfection, smaller less severe lesions were recorded in the vorfIL-10ko-infected animals compared with either of the vorfIL-10-intact virus-infected animals. Thus, the vorfIL-10ko virus was attenuated compared with the vorfIL-10 intact viruses, demonstrating that orf virus IL-10 is a virulence factor. The virus IL-10 is one of several virulence or immuno-modulatory factors expressed by orf virus. Removal of any one of these genes would be expected to have only a partial effect on virulence, which is what was observed in this study with vorfIL-10.
Fleming
Stephen B
SB
Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
Anderson
Ian E
IE
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, UK.
Thomson
Jackie
J
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, UK.
Deane
David L
DL
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, UK.
McInnes
Colin J
CJ
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, UK.
McCaughan
Catherine A
CA
Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
Mercer
Andrew A
AA
Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand.
Haig
David M
DM
Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik EH26 0PZ, UK.
D000818:Animals; D002478:Cells, Cultured; D004474:Ecthyma, Contagious / Q000276:immunology / Q000473:pathology / Q000821:virology; D017353:Gene Deletion; D005814:Genes, Viral; D016753:Interleukin-10 / Q000096:biosynthesis / Q000235:genetics*; D009923:Orf virus / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D011995:Recombination, Genetic; D012756:Sheep; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology*; D014774:Virulence / Q000235:genetics / Q000276:immunology
D014764:Viral Proteins; D016753:Interleukin-10