Kinetics of cytokine profile during intraperitoneal inoculation of Japanese encephalitis virus in BALB/c mice model

Infection with Japanese encephalitis virus (JEV) is mostly asymptomatic/subclinical in 90% of the individuals. Host immune response during subclinical JEV infection is poorly understood. We assessed iNOS, IFN-γ, TNF-α, IL-10 and IL-4 production in spleen, brain and sera of intraperitoneally challenged BALB/c mice by RT-PCR and ELISA along with brain histopathology at different days post inoculation (d.p.i.). In spleen of virus infected mice, expression of all cytokines including iNOS mRNA were upregulated till 5 d.p.i. followed by decline. At 5 d.p.i., IL-10 expression outcompeted TNF-α, IFN-γ and IL-4. However, in the virus infected mice sera, IL-4 production predominated over TNF-α and IL-10 at 5 d.p.i. Conversely, cytokines expression and iNOS mRNA remained unchanged in the brain of virus infected mice from 1 to 7 d.p.i. A significant increase in the cytokine expression was observed at 11 d.p.i. (P < 0.05) in virus infected mice brain, with the predominance of IL-10 along with the presence of meningeal inflammation and viral RNA by histology and RT-PCR, respectively. We report a biased pattern of cytokine production in sera, brain and spleen of mice intraperitoneally challenged with JEV. IL-10 exerts neuroprotective function during JEV and regulates deleterious effects of proinflammatory cytokines; however, its mechanism needs further investigation