In brains of infected mice, the levels of activated microglia were low in the early stage of infection (on day 3 p.i.)and increased on day 5 p.i. Because HSV-1 infection increased microglia activation in mouse brains on day 5 p.i. as demonstrated by makers of CD68 and Iba1 as well as the amoeboid shape, we examined the antiviral activity of brain microglia by adding virus to microglia harvested from brains of mice mock-infected or infected with virus for 5 days. Here, AIF1 is linked to infection.