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.

Deciphering the role of DC subsets in MCMV infection to better understand immune protection against viral infections

“…Little is known about the role of viral immune evasion genes in modulating DC cytokine responses. A study on infected macrophages showed that the viral ie1 gene blocks their capacity to produce TNF through a pathway independent of NFKB (Rodriguez-Martin et al, 2012 ). The viral m45 gene blocks the NFKB pathway in infected fibroblast, resulting in a loss of TNF production (Mack et al, 2008 ).…”

Bile Acids Act as Soluble Host Restriction Factors Limiting Cytomegalovirus Replication in Hepatocytes

“…5C), indicating that at this time point the translation but not the transcription of virus-encoded ie1 mRNAs was negatively affected by bile acids. The in vivo replication of an MCMV mutant lacking ie1 coding capacity was shown be significantly reduced (ϳ1 log 10 ) in the liver (54,55). However, we observed neither altered replication competence nor different TCDC susceptibility of an ie1-deficient MCMV in primary hepatocytes ex vivo (Fig.…”

Mechanism of curcumin resistance to human cytomegalovirus in HELF cells

“…HCMV infection provokes a proinflammatory response characterized by an increased expression of chemokines, adhesion molecules, and modulation of angiogenesis, which in turn promotes progressive HCMV infection. IL-6 drives reactivation of latent HCMV infection by transcriptional upregulation of IE genes [ 26 ]; HCMV IE and late proteins play important roles in immune evasion such as TNF-mediated death receptor signaling pathway, TNF-α release, IL-6 production [ 27 , 28 ].We deduce that curcuminreduces HCMV IE and UL83 expression, which in turn decreases inflammatory factor secretion and recovers host cell cycle to normal status. In fact, viral IE and UL83 expression play a key role in the pathogenesis of HCMV infection [ 29 , 30 ].…”