Of these, Tat (the transactivator of transcription) is a viral protein, 101 amino acids in length, known to be made and secreted early and continuously by HIV-1-infected cells in the CNS throughout infection and has been implicated in mediating and altering the functions of several host factors, disrupting the molecular and biochemical balance of numerous pathways, thus contributing to cellular toxicity, dysfunction, and death (Ensoli et al., 1993; Chang et al., 1997; Rappaport et al., 1999; Li et al., 2009). Here, TAT is linked to infection.