Proinflammatory chemokines are major mediators of exuberant immune response associated with Influenza A (H1N1) pdm09 virus infection.

In India, the case fatality ratio of the pandemic A (H1N1) pdm09 influenza was relatively higher when compared to seasonal Influenza A infection. Hypercytokinemia or "cytokine storm" has been previously implicated in the pathogenesis of other influenza viruses. The present study was undertaken to compare the cytokine profiles of A (H1N1) pdm09 influenza and seasonal H3 infection in Indian population and to correlate the findings with disease severity. Plasma levels of 18 cytokines/chemokines were measured by flow-cytometry using a bead based assay in patients infected with A (H1N1) pdm09 virus (n = 96) and Influenza A seasonal H3 virus (n = 30) categorised into mild, moderate, and severe groups along with healthy controls (n = 36). There was an overall trend indicating an exuberant cytokine/chemokine response in A (H1N1) pdm09 as compared to seasonal H3 influenza, which was more evident in severe cases, suggesting a role for these cytokines/chemokines in the pathogenesis of A(H1N1) pdm09. Increased levels of CXCL-8/IL-8, IL-10, IL-6, and IL-17A were seen in both A(H1N1) pdm09 influenza and seasonal H3 cases when compared to healthy controls. However, dysregulated production of proinflammatory chemokines was seen more pronounced in A (H1N1) pdm09 influenza cases as compared to seasonal H3 cases. This study has brought forth the potential role of chemokines as prognostic indicators of disease severity and outcome. Further research on modulating the host immune response to limit severity of the disease could help in the treatment and management of influenza.