Vaccinia virus protein C4 inhibits NF-κB activation and promotes virus virulence.
Vaccinia virus (VACV) strain Western Reserve protein C4 has been characterized and its function and contribution to virus virulence assessed. Bioinformatic analysis showed that C4 is conserved in six orthopoxvirus species and shares 43 % amino acid identity with VACV protein C16, a known virulence factor. A recombinant VACV expressing a C-terminally tagged version of C4 showed that, like C16, this 37 kDa protein is expressed early during infection and localizes to both the cytoplasm and the nucleus. Functional assays using a firefly luciferase reporter plasmid under the control of a nuclear factor kappa B (NF-κB)-dependent promoter demonstrated that C4 inhibits NF-κB activation at, or downstream of, the inhibitor of kappa kinase (IKK) complex. Consistent with this, C4 inhibited interleukin-1β-induced translocation of p65 into the nucleus. A VACV lacking the C4L gene (vΔC4) showed no significant differences from wild-type virus in growth kinetics or spread in cell culture, but had reduced virulence in a murine intranasal model of infection. vΔC4-infected mice exhibited fewer symptoms, lost less weight and recovered 7 days earlier than animals infected with control viruses expressing C4. Furthermore, bronchoalveolar lavage fluid from vΔC4-infected mice had increased cell numbers at day 5 post-infection, which correlated with reduced lung virus titres from this time onward. C4 represents the ninth VACV protein to inhibit NF-κB activation and remarkably, in every case examined, loss of each protein individually caused an alteration in virus virulence, despite the presence of other NF-κB inhibitors.
Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK.|Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
Stuart W J
SWJ
Ember
Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK.|Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
Hongwei
H
Ren
Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK.|Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
Brian J
BJ
Ferguson
Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, UK.|Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
Geoffrey L
GL
Smith
D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000821:virology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D019295:Computational Biology; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D008168:Lung / Q000378:metabolism / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D018155:Orthopoxvirus / Q000235:genetics / Q000378:metabolism; D011213:Poxviridae Infections / Q000821:virology; D011401:Promoter Regions, Genetic / Q000235:genetics; D014615:Vaccinia / Q000235:genetics / Q000378:metabolism / Q000821:virology; D014616:Vaccinia virus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D019562:Viral Load; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D014779:Virus Replication / Q000235:genetics
D002352:Carrier Proteins; C484020:HSAJ2425 protein, human; D053583:Interleukin-1beta; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D009363:Neoplasm Proteins; D014764:Viral Proteins