globotriaosylceramide and HIV-Infections

We propose that the fatty acid heterogeneity of glycosphingolipids may compensate for the relative few and simple glycosphingolipid structures found in mammalian cells. Variation in GSL fatty acid composition may mediate aglycone regulation of GSL membrane receptor function by a differential interaction with cholesterol and other membrane components which may be differentially organized within plasma membrane lipid domains. These concepts are specifically illustrated in model membrane studies and in relation to the role of the glycolipid, globotriaosyl ceramide (Gb(3)) in verotoxin-induced renal pathology and gp120 binding in HIV infection.

Topics: Cholesterol; Drug Resistance, Viral; Glycosphingolipids; HIV Envelope Protein gp120; HIV Infections; Humans; Receptors, Cell Surface; Shiga Toxins; Trihexosylceramides

The glycosphingolipid globotriaosyl ceramide, (Galalpha1-4Galss1-4 glucosyl ceramide-Gb(3)) also known as CD77 and the P(k) blood group antigen, is bound by both verotoxins and by the HIV adhesin, gp120. Gb(3) plays an important receptor role in VT induced hemolytic uremic syndrome (HUS) and HIV infection. The organization of glycolipids, including Gb(3), into lipid rafts is central to both pathologies. The fatty acid heterogeneity within the Gb(3) lipid moiety plays a central role in assembly within such ordered domains. Differential binding of verotoxins and gp120 to such Gb(3) isoforms in model and cell membranes indicates a significant role in the eventual pathogenic outcome. HUS may provide the first example whereby membrane Gb(3) organization provides a predictor for tissue selective in vivo pathology.

Topics: Animals; Cell Membrane Structures; Glycosphingolipids; Hemolytic-Uremic Syndrome; HIV Envelope Protein gp120; HIV Infections; Humans; Membrane Microdomains; Receptors, Cell Surface; Shiga Toxins; Trihexosylceramides

Globotriaosylceramide (Gb(3)) is a cell surface-expressed natural resistance factor for HIV infection, but, its expression in human T-cells remains unknown. Therefore, Gb(3) in resting or activated CD4(+) T-cells was assessed by flow cytometry and thin layer chromatography of cell extracts. We found the majority of CD4(+) T-cells, whether resting or activated, do not express Gb(3) at significant levels (<2% positive cells). Thus, HIV treatment or prevention strategies must focus on development of soluble Gb(3) analogues for inhibition of HIV infection.

Topics: CD4-Positive T-Lymphocytes; Chromatography, Thin Layer; Flow Cytometry; HIV Infections; Humans; Immunity, Innate; Trihexosylceramides

Several human histo-blood groups are glycosphingolipids, including P/P1/P(k). Glycosphingolipids are implicated in HIV-host-cell-fusion and some bind to HIV-gp120 in vitro. Based on our previous studies on Fabry disease, where P(k) accumulates and reduces infection, and a soluble P(k) analog that inhibits infection, we investigated cell surface-expressed P(k) in HIV infection. HIV-1 infection of peripheral blood-derived mononuclear cells (PBMCs) from otherwise healthy persons, with blood group P(1)(k), where P(k) is overexpressed, or blood group p, that completely lacks P(k), were compared with draw date-matched controls. Fluorescence-activated cell sorter analysis and/or thin layer chromatography were used to verify P(k) levels. P(1)(k) PBMCs were highly resistant to R5 and X4 HIV-1 infection. In contrast, p PBMCs showed 10- to 1000-fold increased susceptibility to HIV-1 infection. Surface and total cell expression of P(k), but not CD4 or chemokine coreceptor expression, correlated with infection. P(k) liposome-fused cells and CD4(+) HeLa cells manipulated to express high or low P(k) levels confirmed a protective effect of P(k). We conclude that P(k) expression strongly influences susceptibility to HIV-1 infection, which implicates P(k) as a new endogenous cell-surface factor that may provide protection against HIV-1 infection.

Topics: CD4 Antigens; Cells, Cultured; Cytoprotection; Galactosyltransferases; Gene Expression Regulation, Enzymologic; Genetic Predisposition to Disease; HeLa Cells; HIV Infections; HIV-1; Humans; Immunity, Innate; Jurkat Cells; Receptors, CCR5; Receptors, CXCR4; RNA, Small Interfering; Transfection; Trihexosylceramides

To determine the effect of a gp120 binding, non-cytotoxic soluble analogue of the glycosphingolipid (GSL), globotriaosyl ceramide (Gb3) on HIV infection in vitro.. HIV-1(IIIB) (X4 virus) infection in Jurkat and phytohaemagglutinin (PHA)/interleukin-2 (IL2) activated, peripheral blood mononuclear cells (PBMC), and HIV-1(Ba-L) (R5 virus) infection of PHA activated PBMC in vitro were assessed. We monitored cell surface markers, cell viability, and viral/host cell morphology to eliminate pleiotropic effects. Viral-host cell fusion was measured to further address any inhibitory mechanism.. HIV infection was monitored by p24(gag) ELISA. CD4, CCR5, CXCR4 and apoptosis were determined by fluorescent antibody cell sorting. A model fusion system comprising a cell line transfected with either CD4 and CXCR4 or CCR5, cocultured with a cell line expressing gp120 from either X4-, R5-tropic HIV-1 or HIV-2 virions, was used. PHA/IL2 activated PBMC GSL synthesis was monitored by metabolic radiolabelling.. AdamantylGb3 blocked X4 and R5 virus infection with a 50% inhibitory concentration of approximately 150 microM. A reverse transcriptase and a protease-resistant X4 HIV-1 strain retained adamantylGb3 sensitivity. AdamantylGb3 had minimal effect on cell viability. Treated Jurkat cells showed a small increase in CCR5/CXCR4 expression and a slight, transient CD4 down-regulation, which was probably not related to the mechanism of inhibition. Electron microscopy showed normal viral and host cell morphology following adamantylGb3 treatment, and viral entry was blocked. AdamantylGb3 was able to prevent virus-host cell fusion irrespective of HIV strain or chemokine receptor preference.. These results suggest that adamantylGb3 may provide a new basis for blocking HIV infections, irrespective of HIV envelope/chemokine co-receptor preference or resistance to other therapeutics.

Topics: Adamantane; Antiviral Agents; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Glycolipids; HIV Infections; HIV-1; Humans; Inhibitory Concentration 50; Jurkat Cells; Leukocytes, Mononuclear; Microscopy, Electron; Trihexosylceramides

A lack of viral replication after HIV-1Ba-L (R5) but not HIV-1IIIB (X4) infection was found using in-vitro activated peripheral blood-derived mononuclear cells from patients with Fabry disease, who have a defect in the catabolism of globotriaosylceramide. CCR5, but not CD4 or CXCR4 expression levels, were lower and the surface expression of globotriaosylceramide was negligible on activated patients' cells. Our findings suggest a novel resistance mechanism to productive infection with R5 HIV-1 that potentially involves abnormal globotriaosylceramide catabolism.

Topics: Case-Control Studies; CD4 Antigens; Fabry Disease; HIV Infections; HIV-1; Humans; Leukocytes, Mononuclear; Lymphocyte Activation; Receptors, CCR5; Receptors, CXCR4; Trihexosylceramides; Virus Replication

To better understand the pathophysiology of B cell populations-the precursors of antibody secreting cells-during chronic human immunodeficiency virus (HIV) infection, we examined the phenotype of circulating B cells in newly diagnosed Africans. We found that all African individuals displayed low levels of naive B cells and of memory-type CD27+ B cells, and high levels of differentiated B cells. On the other hand, HIV-infected African patients had a population of germinal center B cells (i.e. CD20+, sIgM-, sIgD+, CD77+, CD138(+/-)), which are generally restricted to lymph nodes and do not circulate unless the lymph node architecture is altered. The first observations could be linked to the tropical environment whereas the presence of germinal center B cells may be attributable to chronic exposure to HIV as it is not observed in HIV-negative African controls and HAART treated HIV-infected Europeans. It may impact the management of HIV infection in countries with limited access to HIV drugs and urges consideration for implementation of therapeutic vaccines.

Topics: Adult; Antigens, CD20; B-Lymphocytes; Blood Donors; Female; Germinal Center; HIV Infections; Humans; Immunophenotyping; Lymph Nodes; Male; Middle Aged; Trihexosylceramides; Tumor Necrosis Factor Receptor Superfamily, Member 7

The metabolism of glycosphingolipids (GSL) has been investigated in peripheral blood mononuclear cells (PBMC) from 8 patients at an early stage of HIV-1 infection. Following metabolic labeling of these cells with [14C]galactose, the GSL were purified and the radioactivity incorporated into each individual GSL quantitated by phosphoimaging. Compared with PBMC from seronegative donors, the GSL metabolism in PBMC from HIV-1-infected individuals was characterized by an increased synthesis of two GSL: the B-lymphocyte differentiation antigen globotriaosylceramide (Gb3, also referred to as CD77), and the monosialoganglioside GM3, a marker of T-lymphocytes and macrophages. The accumulation of Gb3 and GM3 in PBMC from HIV-1-infected patients was associated with the appearance of anti-Gb3 and anti-GM3 antibodies. Because these GSL are involved in the control of cell proliferation and signal transduction, such anti-GSL autoantibodies may contribute to the immune suppression during the course of HIV-1 infection. Studies on purified cell populations showed that GM3 accumulation occurred preferentially in HIV-1-infected monocytes/macrophages, whereas the synthesis glucosylceramide, the common precursor of complex GSL, was enhanced in both macrophages and CD4+ lymphocytes. Taken together, our data suggest that the dysregulation of GSL metabolism is an early event of HIV-1 pathogenesis that can induce important effects on immune cells homeostasis.

Topics: CD4-Positive T-Lymphocytes; Cells, Cultured; Chromatography, Thin Layer; Female; G(M3) Ganglioside; Glycosphingolipids; HIV Infections; HIV-1; Humans; Leukocytes, Mononuclear; Macrophages; Male; Trihexosylceramides