IL-17 Level in Patients with Dengue Virus Infection & its Association with Severity of Illness

Background Clinical symptoms of Dengue vary from mild febrile illness to severe infection. A potent proinflammatory cytokine, IL-17, secreted by mainly Th17 cells mediate inflammation and autoimmune diseases. Role of IL-17 in pathogenesis of dengue virus (DV) infection is not clear. Methods Total 211 dengue patients and 70 healthy controls were enrolled. IL-17 level was tested in serum samples from all cases and controls. Cases were grouped as either dengue or severe dengue; based on WHO (2009) classification. Anti DV IgG antibody detection and DV serotype specific PCR were also done. Levels of IL-17 in dengue and severe dengue patients, primary and secondary DV infection were compared. Association of DV serotypes with severity of illness and various clinical and laboratory features with IL-17 levels were analyzed. Results Of total 211cases, 90 and 121cases were presenting as dengue and severe dengue illness, respectively. Levels of IL-17 were significantly higher in dengue patients as compared to control. Mean level of IL-17 was higher in severe cases than non severe cases; however difference was not statistically significant. Stratified analysis of IL-17 level in different age group showed significantly high IL-17 levels in children with severe dengue. Mean level of IL-17 was also significantly higher in cases with secondary DV infection in comparison to primary DV infection. Levels of IL-17 were higher in patients with DV-2 infection in comparison to cases with DV-1 and DV-3 infection. Significant positive association of high IL-17 levels was seen with pleural effusion and respiratory distress. Conclusion IL-17 appears to be associated with severe DV infection. It is very important to understand the exact role of IL-17 in the pathogenesis of severe DV infection.