Cellular & molecular basis of HIV-associated neuropathogenesis

Although a plethora of molecules have been implicated in the development of HIV associated dementia (HAD), the identity of the indispensable ones is still elusive. The action of various molecules appears to follow a cascade path with one molecule activating another thereby regulating the expression and modulation of the regulatory machineries. Two pathways have been proposed leading to HIV-induced central nervous system (CNS) injury. First involving neurotoxic effect of viral proteins and second, with immunomodulatory substances secreted by the infected cells playing vital role. The viral transfer from infected cells (for example, cells representing macrophage-microglial lineage) to uninfected cells (such as same cell type or nerve cells) occurring perhaps via virological synapse is also not well documented. While the mechanism underlying transfer of HIV-1 through blood-brain barrier is not clearly understood, macrophage-microglial cell lineages are undisputedly predominant cell types that HIV uses for transmission in CNS. The present review describes existing knowledge of the modus operandi of HIV-induced neuropathogenesis gathered through research evidences. Mechanisms by which regulatory molecules exploit such cell types in promoting neuropathogenesis would provide key insights in intersecting pathway(s) for designing intervention strategies.