702 The Choroid Plexus is a Potential Site of HIV Entry into the CNS E. Burkala*1, J. He1, J. T. West1, C. Wood1, C. Petito2 1Univ of Nebraska, Lincoln and 2Univ of Miami, FL
Background: The mechanism and route of HIV entry into the brain is often considered to be primarily through the endothelial blood-brain barrier. The choroid plexus, however, consists of leaky ependymal layer of epithelial cells that can be infected by HIV. We propose that the choroid plexus is both a site of HIV entry into the CNS and a latent reservoir for viral infection.
Methods: Immunohistochemistry for HIV gp41 was performed on sections of choroid plexus to identify infected cell types within the tissue. Virus was isolated by co-culture of brain, choroid plexus, and spleen tissues with PHA-stimulated PBMC. Isolated virus was characterized by determination of co-receptor usage, syncytium induction, productive macrophage infection, and sequence analysis. The heteroduplex mobility analysis (HMA) was used to determine viral variation in the env gene and major variants were sequenced.
Results: Immunohistochemistry for HIV gp41 indicated that the choroid plexus is present within the ependymal region and surrounding dendritic cells. Virus isolated from autopsy tissues showed exclusive CCR5 co-receptor usage in brain and choroid plexus isolates, whereas spleen isolates displayed CCR5 and CXCR4 usages. No difference was observed in the ability of isolates from these tissues to productively infect macrophages or the ability to form syncytia in MT-2 cells. Of the 56 tissues investigated from 19 individuals, 46 had detectable HIV nucleic acid by nested PCR. The choroid plexus showed the greatest number of variants analyzed by HMA and displayed some similarity to both the brain and spleen isolates. The V1-V5 sequence and phylogenetic analysis of the choroid plexus viral sequences displayed elements found in both the spleen- and brain-derived sequences.
Conclusions: The choroid plexus contains a mixture of viruses with both phenotypic and genotypic similarities to those found in the brain and periphery. Although this may not be the only mechanism of neuro-invasion, the choroid plexus could play an important role in the trafficking of virus or virus-infected cells both into and out of the CNS compartment.
