What are the Possible Portals of Entry for HIV into the CNS?
The most widely suspected mechanism by which HIV enters the CNS is with the entry of infected monocytes crossing the vascular barrier. This pathway has recently been thoroughly reviewed in a Science Online NeuroAIDS article (1). But other mechanisms are available. HIV could cross at the choroid plexus, which is infected by HIV (2). HIV also could cross by extracellular pathways (3). Although circulating substances such as serum albumin are largely excluded by the BBB, such exclusion is not absolute since serum-derived albumin can be detected in the CSF. Whether viruses in general or HIV in particular can use these pathways is unknown. Viruses could also enter the brain tissue at the circumventricular organs (CVO), small areas of the brain with an absent or diminished BBB (4). Although these areas are separated from the rest of the brain, they do provide a possible site of CNS infection that does not require penetration of the BBB. This could lead to the disturbance of the CNS functions
