Induction of HIV-1 resistance: cell susceptibility to infection is an inverse function of globotriaosyl ceramide levels

Abstract

To examine the role of the glycosphingolipid (GSL), globotriaosylceramide (Gb₃, CD77, p^k blood group antigen) in HIV-1 infection, we have pharmacologically modulated Gb₃ metabolism in an X4 HIV-1 infectable monocytic cell line (THP-1) that naturally expresses Gb₃ and in a Gb₃-expressing glioblastoma cell line (U87) transfected to express both CD4 and CCR5 to permit R5 HIV-1 infection. THP-1 and U87 cells were treated with either a competitive inhibitor of α-galactosidase A, 1-deoxygalactonojirimycin (DGJ) to induce Gb₃ accumulation, or a glucosylceramide synthase inhibitor, phenyl-2-palmitylamino-3-pyrrolidino-1-propanol (P4) to deplete cells of Gb₃. HIV susceptibility was determined via measurement of p24^gag antigen production by ELISA. In addition, total cellular Gb₃ content was determined using thin layer chromatography followed by Verotoxin1 overlay binding. The cell surface expression of Gb₃ was verified by FACS analysis. We found that DGJ significantly decreased THP-1 and U87 cell susceptibility to HIV-1_IIIB and HIV-1_BaL infection, respectively, at a concentration of approximately 100 μM. In contrast, P4 (2 μM) substantially increased cellular susceptibility to HIV-1 infection. Total cellular GSL analysis verified increased Gb₃ expression in cells treated with DGJ and considerable reduction of Gb₃ in P4-treated cells as compared to controls. These results show a reciprocal relationship between Gb₃ expression and infection with either X4 HIV-1_IIIB or R5 HIV-1_Ba-L. These results support previous studies that Gb₃ provides resistance to HIV infection. Variable Gb₃ expression may provide a natural HIV resistance factor in the general population, and pharmacological manipulation of Gb₃ levels may provide an approach to induction of HIV resistance.

glycosphingolipids, gp120, lipid rafts, p^k blood group antigen

© Oxford University Press 2008