In contrast, primary CTL responses induced in noninfectious conditions by minor Ags, and cell-associated and protein-triggered immunizations [9], [10], and also CTL responses in infectious diseases, such as Herpes simplex (HSV), Viral encephalitis and Vaccinia virus [4], [11]–[13], heavily depend on CD4+ T cell signals. Here, CD4 is linked to viral encephalitis.