eritoran and Acute-Lung-Injury

We previously reported that TLR4(-/-) mice are refractory to mouse-adapted A/PR/8/34 (PR8) influenza-induced lethality and that therapeutic administration of the TLR4 antagonist Eritoran blocked PR8-induced lethality and acute lung injury (ALI) when given starting 2 days post infection. Herein we extend these findings: anti-TLR4- or -TLR2-specific IgG therapy also conferred significant protection of wild-type (WT) mice from lethal PR8 infection. If treatment is initiated 3 h before PR8 infection and continued daily for 4 days, Eritoran failed to protect WT and TLR4(-/-) mice, implying that Eritoran must block a virus-induced, non-TLR4 signal that is required for protection. Mechanistically, we determined that (i) Eritoran blocks high-mobility group B1 (HMGB1)-mediated, TLR4-dependent signaling in vitro and circulating HMGB1 in vivo, and an HMGB1 inhibitor protects against PR8; (ii) Eritoran inhibits pulmonary lung edema associated with ALI; (iii) interleukin (IL)-1β contributes significantly to PR8-induced lethality, as evidenced by partial protection by IL-1 receptor antagonist (IL-1Ra) therapy. Synergistic protection against PR8-induced lethality was achieved when Eritoran and the antiviral drug oseltamivir were administered starting 4 days post infection. Eritoran treatment does not prevent development of an adaptive immune response to subsequent PR8 challenge. Overall, our data support the potential of a host-targeted therapeutic approach to influenza infection.

Topics: Acute Lung Injury; Animals; Antiviral Agents; Disaccharides; Drug Synergism; Female; Gene Expression Regulation; HMGB1 Protein; Immunity, Innate; Immunoglobulin G; Interleukin-1 Receptor Accessory Protein; Lung; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Molecular Targeted Therapy; Orthomyxoviridae; Orthomyxoviridae Infections; Oseltamivir; Signal Transduction; Sugar Phosphates; Survival Analysis; Toll-Like Receptor 2; Toll-Like Receptor 4

There is a pressing need to develop alternatives to annual influenza vaccines and antiviral agents licensed for mitigating influenza infection. Previous studies reported that acute lung injury caused by chemical or microbial insults is secondary to the generation of host-derived, oxidized phospholipid that potently stimulates Toll-like receptor 4 (TLR4)-dependent inflammation. Subsequently, we reported that Tlr4(-/-) mice are highly refractory to influenza-induced lethality, and proposed that therapeutic antagonism of TLR4 signalling would protect against influenza-induced acute lung injury. Here we report that therapeutic administration of Eritoran (also known as E5564)-a potent, well-tolerated, synthetic TLR4 antagonist-blocks influenza-induced lethality in mice, as well as lung pathology, clinical symptoms, cytokine and oxidized phospholipid expression, and decreases viral titres. CD14 and TLR2 are also required for Eritoran-mediated protection, and CD14 directly binds Eritoran and inhibits ligand binding to MD2. Thus, Eritoran blockade of TLR signalling represents a novel therapeutic approach for inflammation associated with influenza, and possibly other infections.

Topics: Acute Lung Injury; Animals; Antiviral Agents; Cytokines; Disaccharides; Female; Influenza A Virus, H1N1 Subtype; Ligands; Lipopolysaccharide Receptors; Lymphocyte Antigen 96; Mice; Mice, Inbred C57BL; Orthomyxoviridae Infections; Sugar Phosphates; Survival Analysis; Time Factors; Toll-Like Receptor 2; Toll-Like Receptor 4