Thus owing to the fact that many studies are beginning to implicate the immune response to HSV-1 and its various cell populations (e.g. microglia, CD8+ T cells) in causing widespread CNS pathology such as acute encephalitis, our finding of a higher frequency of some KIR haplotype (AA haplotype) and of some HLA allele such as HLA-C2 or HLA-A-BW4 may represent, to the best of our knowledge, the first report offering promising information about the immunologic background of patients with acute viral encephalitis. This evidence concerns the gene KIR3DL1 and viral encephalitis.