A synthetic globotriaosylceramide analogue inhibits HIV-1 infection in vitro by two mechanisms
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Previously, it was shown that the cell-membrane-expressed glycosphingolipid, globotriaosylceramide (Gb3/Pk/CD77), protects against HIV-1 infection and may be a newly described natural resistance factor against HIV infection. We have now investigated the potential of a novel, water soluble, non-toxic and completely synthetic analogue of Gb3/Pk (FSL-Gb3) to inhibit HIV-1 infection in vitro. A uniquely designed analogue, FSL-Gb3, of the natural Gb3/Pk molecule was synthesized. HIV-1IIIB (X4 virus) and HIV-1Ba-L (R5 virus) infection of PHA/interleukin-2-activated, peripheral blood mononuclear cells (PBMCs) and Jurkat T cells in vitro was assessed, as well as infection of U87.CD4.CCR5 by various clinical R5 tropic viruses after treatment with FSL-Gb3. We monitored Gb3, CD4 and CXCR4 expression by fluorescent antibody cell sorting and viral replication by p24 gag ELISA. Total cellular Gb3 was examined by glycosphingolipid extraction and thin layer chromatography. In vivo toxicity was monitored in mice by histological assessment of vital organs and lymphoid tissue. FSL-Gb3 blocked X4 and R5 of both lab and clinical viral strains in activated PBMCs or the U87.CD4.CCR5 cell line with a 50% inhibitory concentration (IC50) of approximately 200–250 μM. FACS and TLC overlay showed that FSL-Gb3 can insert itself into cellular plasma membranes and that cellular membrane-absorbed FSL-Gb3 is able to inhibit subsequent HIV-1 infection. There was no effect of FSL-Gb3 on cell surface levels of CD4 or CXCR4. Thus, FSL-Gb3 can inhibit HIV-1 by two mechanisms: direct inhibition of virus and inhibition of viral entry. Infusion of FSL-Gb3 into laboratory mice at doses well in excess of theoretical therapeutic doses was tolerated with no untoward reactions. Our results demonstrate the potential utility of using a completely synthetic, water soluble globotriaosylceramide analogue, FSL-Gb3, having low toxicity, for possible future use as a novel therapeutic approach for the systemic treatment of HIV/AIDS.
KeywordsGlycosphingolipids Globotriaosylceramide Gb3 Pk blood group antigen HIV HIV infection
This work was funded by the Canadian Blood Services through a graduate fellowship award to Amanda Harrison and operating grants from the Canadian Institutes for Health Research (CIHR), the Ontario HIV Treatment Network (OHTN), and the Canadian Association for HIV Research (CANFAR). Stephen Henry is a founder and shareholder in KODE Biotech Ltd. There are no other author conflicts of interest or financial interest in this work.
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