To evaluate serum and cerebrospinal fluid (CSF) levels of interleukin-6 (IL-6), interleukin-10 (IL-10), and RANTES (regulated on activation, normal T-cell expressed and secreted) in AES patients, and to correlate these cytokine levels with clinical features, outcomes, and differences between JE and non-JE cases.

Patients with acute encephalitis syndrome (AES) of less than two weeks’ duration underwent brain imaging followed by cerebrospinal fluid (CSF) analysis for routine parameters and viral studies. Serum levels of interleukin (IL)-6, IL-10, and RANTES (regulated on activation, normal T-cell expressed and secreted) were measured in all patients, and CSF cytokines were analyzed in 50. These results were compared with serum cytokine levels from 64 age- and sex-matched controls.

Among 87 AES patients, 13 were diagnosed with Japanese encephalitis (JE). Serum IL-6, IL-10, and RANTES levels were significantly higher in AES patients compared to controls. Patients who died had significantly lower serum IL-10 and higher RANTES levels. In CSF, IL-6 and IL-10 levels were elevated in non-JE patients compared to JE cases, while RANTES levels were higher in patients who did not experience seizures.

Cytokine elevation reflects marked immune activation in AES. Higher IL-10 levels appear protective and associated with survival, while increased RANTES correlates with poor outcomes. Distinct cytokine patterns in JE and non-JE cases suggest differing immune responses, which may guide future therapeutics.