Acute Encephalitic Syndrome in Adults and its Correlation with Cytokine Levels in Serum and Cerebrospinal Fluid

Acute encephalitis syndrome (AES) is a major health problem in developing countries including India. Neuronal injury in encephalitis is attributed to direct toxicity from pathogens and proinflammatory cytokines. In this study, we assessed cytokine levels in serum and cerebrospinal fluid (CSF), and their correlation with clinical symptoms. In our study, patients with AES for a duration of less than 2 weeks underwent brain imaging followed by CSF analysis for routine parameters and viral studies. We assessed interleukin (IL)-6, IL-10, and regulated on activation, normal T cell expressed and secreted (RANTES) levels in the serum samples of all patients and in 50 CSF samples and compared them with serum cytokine levels of 64 age- and sex-matched controls. Of the 87 AES patients, 13 had Japanese encephalitis (JE). Serum IL-6, IL-10, and RANTES levels were significantly elevated in patients with AES compared with that in controls. Serum IL-10 levels were significantly reduced while RANTES levels were significantly elevated in patients who died. CSF IL-6 and IL-10 levels were significantly elevated in the non-JE group compared with that in JE patients. RANTES levels in the CSF were high in patients who had no seizures. IL-10 exerts its anti-inflammatory effect by modulating the innate and adaptive immune response, thus limiting the production of pro-inflammatory cytokines. Higher IL-10 levels were found to be protective in patients with acute encephalitis.