Combined effect of anti‐high‐mobility group box‐1 monoclonal antibody and peramivir against influenza A virus‐induced pneumonia in mice.

Human pandemic H1N1 2009 influenza virus causes significant morbidity and mortality with severe acute lung injury due to the excessive inflammatory reaction, even with neuraminidase inhibitor use. The anti‐inflammatory effect of anti‐high‐mobility group box‐1 (HMGB1) monoclonal antibody (mAb) against influenza pneumonia has been reported. In this study, we evaluated the combined effect of anti‐HMGB1 mAb and peramivir against pneumonia induced by influenza A (H1N1) virus in mice. Nine‐week‐old male C57BL/6 mice were inoculated with H1N1 and treated with intramuscularly administered peramivir at 2 and 3 days post‐infection (dpi). The anti‐HMGB1 mAb or a control mAb was administered at 2, 3, and 4 dpi. Survival rates were assessed, and lung lavage and pathological analyses were conducted at 5 and 7 dpi. The combination of peramivir with the anti‐HMGB1 mAb significantly improved survival rate whereas the anti‐HMGB1 mAb alone did not affect virus proliferation in the lungs. This combination therapy also significantly ameliorated histopathological changes, neutrophil infiltration, and macrophage aggregation by inhibiting HMGB1, inflammatory cytokines, and oxidative stress. Fluorescence immunostaining showed that the anti‐HMGB1 mAb inhibited HMGB1 translocation from type I alveolar epithelial cells. In summary, combining anti‐HMGB1 with conventional anti‐influenza therapy might be useful against severe influenza virus infection. ‐Combined therapy of anti‐HMGB1 monoclonal antibody and peramivir significantly improved the survival rate of influenza‐induced pneumonia model mice.‐Combined therapy of anti‐HMGB1 monoclonal antibody and peramivir also significantly ameliorated histopathological changes, neutrophil infiltration, and macrophage aggregation by inhibiting HMGB1 translocation from type I alveolar epithelial cells, leading to the inhibition of TLR4 signaling, cytokine/chemokine responses, and oxidative stress.‐Anti‐HMGB1 therapy in combination with an anti‐influenza drug may be an option for severe influenza pneumonia. [ABSTRACT FROM AUTHOR]