Whilst it is clear that gp120 is clearly a major pathophysiological mediator of HAND, we cannot rule out potential effects of other HIV components, such as Tat (‘trans-activator of transcription’) and Nef (‘negative factor’), with which excitotoxic effects have also been reported [5,13,18,38,41-43]. The gene discussed is S100B; the disease is HIV-associated neurocognitive disorder.