The vaccinia virus C12L protein inhibits mouse IL-18 and promotes virus virulence in the murine intranasal model.
A bioassay that measured the interleukin (IL)-12-induced production of interferon (IFN)-gamma from mouse splenocytes was used to identify a soluble factor in the supernatants of vaccinia virus (VV)-infected cells that inhibited the production of IFN-gamma. This soluble factor was expressed by 14 out of 16 VV strains including the Western Reserve (WR) strain, but strains Copenhagen and Tashkent and a mutant of strain WR called 6/2 lacked this activity. The gene encoding this activity was identified as C12L by transferring DNA present in VV WR but missing in VV WR 6/2 into VV Copenhagen and testing for expression of the soluble factor. The C12L protein shows amino acid similarity to IL-18 binding proteins that are encoded by poxviruses, mice and humans, and C12L protein produced from VV or baculovirus inhibited the biological activity of mouse IL-18 in vitro. Thus the inhibition of IL-12-induced IFN-gamma production was due to indirect effects of C12L on IL-18, illustrating the synergistic action of these pro-inflammatory cytokines. To study the role of the C12L protein in the virus life-cycle, we constructed a deletion mutant lacking the C12L gene and a revertant virus in which the gene was reinserted into the deletion mutant. In vitro the replication and plaque size of these viruses were indistinguishable. However, infection of BALB/c mice by the intranasal route showed that the deletion mutant was attenuated and induced lower weight loss and signs of illness compared to controls.
Symons
Julian A
JA
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK1.
Adams
Elizabeth
E
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK1.
Tscharke
David C
DC
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK1.
Reading
Patrick C
PC
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK1.
Waldmann
Herman
H
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK1.
Smith
Geoffrey L
GL
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK1.
D000281:Administration, Intranasal; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D002874:Chromosome Mapping; D004279:DNA, Viral; D004195:Disease Models, Animal; D015870:Gene Expression; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000494:pharmacology; D020382:Interleukin-18 / Q000037:antagonists & inhibitors*; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D011212:Poxviridae / Q000276:immunology / Q000502:physiology; D013154:Spleen / Q000166:cytology; D013997:Time Factors; D014615:Vaccinia; D014616:Vaccinia virus / Q000276:immunology / Q000472:pathogenicity*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D014779:Virus Replication
C469545:C12L protein, vaccinia virus; D004279:DNA, Viral; D020382:Interleukin-18; D014764:Viral Proteins; D018664:Interleukin-12; D007371:Interferon-gamma