Human immunodeficiency virus type 1 enters primary human brain microvascular endothelial cells by a mechanism involving cell surface proteoglycans independent of lipid rafts

Several studies have reported a crucial role for cholesterol-enriched membrane lipid rafts and cell-associatedheparan sulfate proteoglycans (HSPGs), a class of molecules that can localize in lipid rafts, in the entryof human immunodeficiency virus type 1 (HIV-1) into permissive cells. For the present study, we examined therole of these cell surface moieties in HIV-1 entry into primary human brain microvascular endothelial cells(BMVECs), which represent an important HIV-1 central nervous system-based cell reservoir and a portal forneuroinvasion. Cellular cholesterol was depleted by exposure to -cyclodextrins and 3-hydroxy-3-methylglutaryl(HMG)-coenzyme A reductase inhibitors (statins), the loss of cholesterol was quantitated, and disruptionof membrane rafts was verified by immunofluorescence. Nevertheless, these treatments did not affect bindingof several strains of HIV-1 virions to BMVECs at 4°C or their infectivities at 37°C. In contrast, we confirmedthat cholesterol depletion and raft disruption strongly inhibited HIV-1 binding and infection of Jurkat T cells.Enzymatic digestion of cell-associated HSPGs on human BMVECs dramatically inhibited HIV-1 infection, andour data from quantitative HIV-1 DNA PCR analysis strongly suggest that cell-associated chondroitin sulfateproteoglycans greatly facilitate infective entry of HIV-1 into human BMVECs. These findings, in combinationwith our earlier work showing that human BMVECs lack CD4, indicate that the molecular mechanisms forHIV-1 entry into BMVECs are fundamentally different from that of viral entry into T cells, in which lipid rafts,CD4, and probably HSPGs play important roles.