No abstract

The numbers of immune-activated brain mononuclear phagocytes (MPs) affect the progression of human immunodeficiency virus (HIV)-1-associated dementia (HAD). Such MPs originate , in measure , from a pool of circulating monocytes. To address the mechanism(s) for monocyte penetration across the bloodbrain barrier (BBB) , we performed cross-validating laboratory , animal model , and human brain tissue investigations into HAD pathogenesis. First , an artificial BBB was constructed in which human brain microvascular endothelial and glial cells-astrocytes, microglia , and/or monocyte-derived macrophages (MDM)-were placed on opposite sides of a matrixcoated porous membrane. Second , a SCID mouse model of HIV-1 encephalitis (HIVE) was used to determine in vivo monocyte blood-to-brain migration. Third , immunohistochemical analyses of human HIVE tissue defined the relationships between astrogliosis , activation of microglia , virus infection, monocyte brain infiltration , and ␤-chemokine expression. The results , taken together , showed that HIV-1-infected microglia increased monocyte migration through an artificial BBB 2 to 3.5 times more than replicate numbers of MDM. In the HIVE SCID mice, a marked accumulation of murine MDM was found in areas surrounding virus-infected human microglia but not MDM. For human HIVE , microglial activation and virus infection correlated with astrogliosis, monocyte transendothelial migration , and ␤-chemokine expression. Pure cultures of virus-infected and activated microglia or astrocytes exposed to microglial conditioned media produced significant quantities of ␤-chemokines. We conclude that microglial activation alone and/or through its interactions with astrocytes induces ␤-chemokine-mediated monocyte migration in HAD. (Am J Pathol 1999, 155:1599 -1611)

The technique of cortical stimulation to enhance stroke recovery is well tolerated and safe.