herpes simplex virus-1 (hsv-1) is a pathogen that may cause severe encephalitis in humans. in this study, we aimed to investigate the role of interleukin-4 (il-4) in a model of hsv-1 brain infection. il-4 knockout (il-4-/-) and wild type (wt) c57bl/6 mice were inoculated with 104 plaque-forming units of hsv-1 by the intracranial route. histopathologic analysis revealed a distinct profile of infiltrating cells at 3 days post-infection (dpi). infected wt mice presented mononuclear inflammatory cells while il-4-/- mice developed meningoencephalitis with predominance of neutrophils. il-4-/- mice had diminished leukocyte adhesion at 3 dpi when compared to infected wt animals in intravital microscopy study. conversely no differences were found in cerebral levels of cxcl1, cxcl9, ccl3, ccl5 and tnf-α between wt and il-4-/- infected mice. il-4 may play a role in the recruitment of cells into central nervous system in this acute model of severe encephalitis caused by hsv-1.