title: Inhibition of the inflammatory cytokine tumor necrosis factor-alpha with etanercept provides protection against lethal H1N1 influenza infection in mice.
abstract: BACKGROUND
  Factors implicated in influenza-mediated morbidity and mortality include robust cytokine production (cytokine storm), excessive inflammatory infiltrates, and virus-induced tissue destruction. Tumor necrosis factor-alpha (TNF-α) is an important pro-inflammatory cytokine present during influenza infection, but it is unclear whether direct inhibition of TNF-α can elicit protection against influenza infection.
  
  
  METHODS
  In this study, the commercially available TNF-α inhibitor etanercept was used to inhibit TNF-α induced by lethal A/FM/1/47 (H1N1) influenza virus infection of mice. The effects of TNF-α inhibition on mouse survival, pathologic changes, immune cell infiltration, inflammatory cytokine secretion, Toll-like receptor expression, and activation of the NF-κB (nuclear factor kappa B) signaling pathway were evaluated.
  
  
  RESULTS
  The intranasal delivery of etanercept provided significant protection against mortality (30% of mice survived up to 14 days after infection) in mice treated with etanercept. In contrast, no survivors were found beyond 6 days in mice treated with saline after lethal challenge with H1N1 influenza virus. It was observed that etanercept significantly reduced inflammatory cell infiltration (for example, macrophages and neutrophils), inflammatory cytokine secretion (for example, interleukin-6, TNF-α, and interferon gamma), and expression of Toll-like receptors (TLR-3, TLR-4, and TLR-7). Etanercept also downregulated and inhibited the cascade proteins of the NF-κB signaling pathway (for example, MyD88, TRIF, NF-κB, and p65), as well as enhanced host control of virus replication.
  
  
  CONCLUSIONS
  These findings indicate that etanercept, by blocking TNF-α, can significantly downregulate excessive inflammatory immune responses and provide protection against lethal influenza infection, making its use a novel strategy for controlling severe influenza-induced viral pneumonia.
authors.forename: Xunlong
authors.initials: X
authors.lastname: Shi
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.forename: Hai
authors.initials: H
authors.lastname: Huang
authors.forename: Hongguang
authors.initials: H
authors.lastname: Zhu
authors.forename: Pei
authors.initials: P
authors.lastname: Zhou
authors.forename: Haiyan
authors.initials: H
authors.lastname: Zhu
authors.forename: Dianwen
authors.initials: D
authors.lastname: Ju
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use*; D016207:Cytokines / Q000378:metabolism; D015536:Down-Regulation; D000068800:Etanercept; D007113:Immunity, Innate; D007074:Immunoglobulin G / Q000627:therapeutic use*; D053118:Influenza A Virus, H1N1 Subtype; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism; D009976:Orthomyxoviridae Infections / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D011024:Pneumonia, Viral / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use*; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*; D014779:Virus Replication
chemical_list: D000998:Antiviral Agents; D016207:Cytokines; D007074:Immunoglobulin G; D016328:NF-kappa B; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D000068800:Etanercept