Herpes simplex virus type 1 (HSV-1), another alphaherpesvirus, can also productively infect human fetal cortical astrocytes without production of cytokines; however, HSV-1 infection of microglia in the same study led to upregulation of TNF-α, IL-1β, IP-10, and RANTES, along with lower amounts of IL-6, IL-8, and macrophage inflammatory protein (MIP)-1α [22], indicating cell type-specific responses to virus infection among CNS cells. This evidence concerns the gene IL1B and viral infectious disease.