Cytokine responses play an important role in the pathogenesis of influenza infection. Previous studies found that cytokine expressions in patients infected with the novel A (H1N1) influenza virus (nvA (H1N1)) could reflect the severity of the disease. But the patterns of cytokine response in patients infected with seasonal influenza virus and the correlations between cytokine responses and clinical data are still unknown. Seventy-two outpatients for laboratory-confirmed seasonal influenza infection were studied: twenty-four seasonal influenza A patients and forty-eight seasonal influenza B patients. Thirty healthy volunteers were enrolled as a control group. Serum samples from influenza patients obtained on the admission day and 6 days later were measured for eight cytokines using enzyme-linked immunosorbent assay (ELISA). The clinical variables were recorded prospectively. The levels of interleukin (IL)-6, IL-33 and tumor necrosis factor (TNF)-α were significantly higher in influenza A patients than those in the control group while IL-6, IL-17A, IL-29, interferon (IFN)-γ and interferon gamma-induced protein (IP)-10 were significantly higher in influenza B patients than those in the control group. Furthermore, IL-17A, IL-29 and IP-10 were increased in seasonal influenza B patients when comparing with those in the seasonal influenza A patients. A positive correlation of IL-29 levels with fever (Spearman's rho, P-values < 0.05) and a negative correlation of IFN-γ and IP-10 levels with lymphocyte count (Spearman's rho, P-values < 0.05) were found in seasonal influenza infection. While a hyperactivated proinflammatory cytokine responses were found in seasonal influenza infection, a higher elevation of cytokines (IL-17A, IL-29 and IP-10) were found in seasonal influenza B infection versus influenza A. IL-29, IFN-γ and IP-10 were important hallmarks in seasonal influenza infection, which can help clinicians make timely treatment decision for severe patients.
Keywords: Adults; clinical aspects; cytokine; immunity; seasonal influenza A; seasonal influenza B.