BRD4 and viral infectious disease: In summary, we report that BRD4 is increased in COPD patients with viral exacerbation and its expression is correlated with IL-6 and IL-8 expression; Inflammatory cells, IL-6, KC and BRD4 are synergistically induced in the lung of mice by viral infection and CS exposure, and the former three are decreased by JQ1 treatment; IL-6, IL-8 and BRD4 are significantly induced by CSE and influenza virus in bronchial epithelial cells, and this upregulation is suppressed by BRD4 knockdown.