As to the inflammatory response caused by the viral infection, DEGs analysis showed that the proinflammatory cytokine genes including CCL7, IL-6, CXCL2, CCR4, CXCR2 and TNF in H1N1-infected P815 cells were significantly up-regulated while the expression of these up-regulated genes were markedly suppressed by melatonin treatment (Fig 4F). Here, CCR4 is linked to viral infectious disease.