Attenuated pseudorabies virus-evoked rapid innate immune response in the rat brain

Ba-DupGreen (BDG) is a highly attenuated, Bartha-derived pseudorabies virus (PRV) expressing green fluorescent protein (GFP) with immediate-early kinetics. Innate immune mechanisms underlying the low infectivity of the virus and the disappearance of infected neurons from the brain were studied at cellular level following injection of BDG into the spleen. The temporal shift in the expression between GFP and viral structural proteins allowed us to discriminate three stages of viral infection in the compromised neurons in correlation with the ongoing local inflammatory response. Iba1/lectin/OX42-positive microglia were recruited to infected neurons within 4-6 h following the initiation of virus replication, incorporated BrdU, isolated the infected cells before the disintegration of their membranes and phagocytosed collapsed neurons. Ex vivo-labeled blood and bone marrow-derived leukocytes, including ED-1-positive macrophages were involved in the immune cell assembly around compromised neurons, which resulted in the complete clearance of infected neurons from the early-infected brain regions.