title: Ablation of the regulatory IE1 protein of murine cytomegalovirus alters in vivo pro-inflammatory TNF-alpha production during acute infection.
abstract: Little is known about the role of viral genes in modulating host cytokine responses. Here we report a new functional role of the viral encoded IE1 protein of the murine cytomegalovirus in sculpting the inflammatory response in an acute infection. In time course experiments of infected primary macrophages (MΦs) measuring cytokine production levels, genetic ablation of the immediate-early 1 (ie1) gene results in a significant increase in TNFα production. Intracellular staining for cytokine production and viral early gene expression shows that TNFα production is highly associated with the productively infected MΦ population of cells. The ie1- dependent phenotype of enhanced MΦ TNFα production occurs at both protein and RNA levels. Noticeably, we show in a series of in vivo infection experiments that in multiple organs the presence of ie1 potently inhibits the pro-inflammatory cytokine response. From these experiments, levels of TNFα, and to a lesser extent IFNβ, but not the anti-inflammatory cytokine IL10, are moderated in the presence of ie1. The ie1- mediated inhibition of TNFα production has a similar quantitative phenotype profile in infection of susceptible (BALB/c) and resistant (C57BL/6) mouse strains as well as in a severe immuno-ablative model of infection. In vitro experiments with infected macrophages reveal that deletion of ie1 results in increased sensitivity of viral replication to TNFα inhibition. However, in vivo infection studies show that genetic ablation of TNFα or TNFRp55 receptor is not sufficient to rescue the restricted replication phenotype of the ie1 mutant virus. These results provide, for the first time, evidence for a role of IE1 as a regulator of the pro-inflammatory response and demonstrate a specific pathogen gene capable of moderating the host production of TNFα in vivo.
authors.affiliation: Division of Pathway Medicine and Centre for Infectious Diseases, University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Sara
authors.initials: S
authors.lastname: Rodríguez-Martín
authors.forename: Kai Alexander
authors.initials: KA
authors.lastname: Kropp
authors.forename: Vanessa
authors.initials: V
authors.lastname: Wilhelmi
authors.forename: Vanda Juranic
authors.initials: VJ
authors.lastname: Lisnic
authors.forename: Wei Yuan
authors.initials: WY
authors.lastname: Hsieh
authors.forename: Mathieu
authors.initials: M
authors.lastname: Blanc
authors.forename: Andrew
authors.initials: A
authors.lastname: Livingston
authors.forename: Andreas
authors.initials: A
authors.lastname: Busche
authors.forename: Hille
authors.initials: H
authors.lastname: Tekotte
authors.forename: Martin
authors.initials: M
authors.lastname: Messerle
authors.forename: Manfred
authors.initials: M
authors.lastname: Auer
authors.forename: Iain
authors.initials: I
authors.lastname: Fraser
authors.forename: Stipan
authors.initials: S
authors.lastname: Jonjic
authors.forename: Ana
authors.initials: A
authors.lastname: Angulo
authors.forename: Matthias J
authors.initials: MJ
authors.lastname: Reddehase
authors.forename: Peter
authors.initials: P
authors.lastname: Ghazal
mesh_terms: D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics; D005260:Female; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D006566:Herpesviridae Infections / Q000276:immunology* / Q000821:virology; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018146:Muromegalovirus / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D010641:Phenotype; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication
chemical_list: D016207:Cytokines; D004279:DNA, Viral; C088645:IE1 protein, cytomegalovirus; D017874:Immediate-Early Proteins; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins