Although the causes of HAND are still unclear, there is a general agreement that the pathogenic mechanisms of HAND are induced by neurotoxic HIV-1 proteins, including Tat, and by pro-inflammatory cytokines and chemokines, as well as NO produced by HIV-1-infected macrophages and glial cells [27-29,34-36,45-47]. This evidence concerns the gene TAT and HIV-associated neurocognitive disorder.