IRF8 and viral infectious disease: Using the Irf8−/− mice, we demonstrated (i) the effect of IRF8 modulation on JEV replication in the brain, (ii) that the absence of the Irf8 function in Irf8−/− mice did not protect against JEV infection, (iii) that susceptibility to viral infection is also associated with the level of Ifnγ; and (iv) that the lack of Ifnγ or Irf8 alters immune cell abundance in circulation and in the infected brain.