“…Several studies have validated the use of CSF as a surrogate source of virus from the brain, and CSF viral loads often predict the neurological outcome of HIV-1 infection (8,9,24,46,49). However, although CSF is an integral component of the CNS, in the context of HIV-1 infection it more accurately serves as an intermediate compartment between the brain and the periphery (7,10,13). Unique HIV-1 lineages evolve over time in the brain and peripheral blood, which is most likely a reflection of different selective pressures on viral replication in each compartment, whereas viral populations in the CSF appear to be genetically related to those in both the brain and the periphery (3,48,51).…”