Experiments indicate that CCL2 is an essential chemokine for monocyte transmigration into the brain parenchyma (Fuentes et al., 1995; Gonzalez et al., 2002) and elevated levels of CCL2 have been detected in the CSF and sera of HIV-1 infected individuals with HAND (Conant et al., 1998; Kelder et al., 1998). This evidence concerns the gene CCL2 and HIV-associated neurocognitive disorder.