HIV infection of the central nervous system is characterized by rapid turnover of viral RNA in cerebrospinal fluid.

To assess the kinetics of viral replication and decay in cerebrospinal fluid (CSF), we studied the short-term effects of highly active antiretroviral therapy (HAART) on CSF HIV-1 RNA concentrations. In 15 HIV-positive patients, HIV RNA concentrations were measured in paired CSF and plasma/serum samples. Samples were obtained prior to and 5 to 24 days after initiation or change of HAART. The short-term effects of interruption of HAART were tested in 2 patients. Viral load was measured by the Roche Amplicor assay. During HAART, in 12 of 15 patients a significant reduction of CSF HIV RNA concentration was observed, ranging from 0.55 to 2.77 log10 (median, 1.37 log10). This was paralleled by a reduction of blood viremia ranging from 0.12 to 3.0 log10 (median, 1.65 log10). The median half-life, as calculated from the slopes of the two time-point measurements, for CSF and blood viral load was 2.66 and 2.36 days, respectively. In 2 patients, CSF viral load remained essentially unchanged despite substantial reduction of plasma viral load. In 1 patient, after interruption of HAART, a rapid increase of HIV RNA in the CSF and blood was seen. No correlation was found between the CSF:blood albumin ratio as a measure of the functional integrity of the blood-CSF barrier and the ratio of CSF:blood RNA concentration, which suggests that no major passive influx of HIV RNA moves from the blood into the CSF compartment. However, a correlation existed between the CSF cell count and the CSF viral load (r = 0.74; p < .003). We conclude that, in most HIV-infected individuals, the decay of viral load in the CSF is similarly rapid as that seen in plasma. The rapid kinetics of virus found in the CSF suggest that it may be produced by rapidly proliferating cells, such as lymphocytes.