CD4 and HIV-1 infection: HIV-1 infects CD4+ T cells first and then proceeds to invade the brain by infiltrating the blood–brain barrier (BBB), and exhibiting its devastating effects at later stages to develop HAND in nearly half of all AIDS patients.14 HIV-1 infection in the brain generally occurs in macrophages and microglia in a receptor-mediated manner, whereas a limited number of astrocytes are infected nonproductively.15 Despite the fact that neurons bear surface receptors, HIV-1 does not infect these cells.