The impact of HIV-1 on neurogenesis: implications for HAND.

HIV-1 infection, in addition to its destructive effects on the immune system, plays a role in the development of neurocognitive deficits. Indeed up to 50% of long-term HIV infected patients suffer from HIV-associated neurocognitive disorders (HAND). These deficits have been well characterized and defined clinically according to a number of cognitive parameters. HAND is often accompanied by atrophy of the brain including inhibition of neurogenesis, especially in the hippocampus. Many mechanisms have been proposed as contributing factors to HAND including induction of oxidative stress in the central nervous system (CNS), chronic microglial-mediated neuroinflammation, amyloid-beta (Aβ) deposition, hyperphosphorylated tau protein, and toxic effects of combination antiretroviral therapy (cART). In these review we focus solely on recent experimental evidence suggesting that disturbance by HIV-1 results in impairment of neurogenesis as one contributing factor to HAND. Impaired neurogenesis has been linked to cognitive deficits and other neurodegenerative disorders. This article will highlight recently identified pathological mechanisms which potentially contribute to the development of impaired neurogenesis by HIV-1 or HIV-1-associated proteins from both animal and human studies.