Showing papers by "Benoit Barbeau published in 2001"

Negative regulation of the NFAT1 factor by CD45: implication in HIV-1 long terminal repeat activation.

Abstract: HIV-1 gene regulation is greatly dependent on the presence of the -104/-81 enhancer region which is regulated by both NF-kappaB and NFAT transcription factors. We have found that a greater induction in HIV-1 long terminal repeat-driven gene expression was observed upon PMA/ionomycin (Iono) stimulation of a CD45-deficient cell line (J45.01) in comparison to the parental Jurkat cells. Unlike NF-kappaB which was not affected by the absence of CD45, NFAT showed a much greater augmentation in nuclear translocation and transcriptional activity in J45.01 cells upon PMA/Iono stimulation. PMA/Iono-induced NFAT activation, NFAT translocation and calcium influx peaked at similar time points for both Jurkat and J45.01 cell lines. The NFAT-dependent promoters from the IL-2 and TNF-alpha genes were also more potently activated by PMA/Iono in J45.01 cells. Interestingly, higher levels of intracellular calcium were consistently demonstrated in PMA/Iono-induced CD45-deficient cell lines (J45.01 and HPB45.0). Furthermore, PMA/Iono induction of calcium mobilization in both Jurkat and J45.01 cell lines was observed to be EGTA-sensitive. Mechanistic studies revealed that CD3zeta and ZAP-70 were more heavily tyrosine phosphorylated in J45.01 cells than Jurkat cells. Analysis of the HIV-1 enhancer by EMSAs demonstrated that the bound NFAT complex was present at higher levels in J45.01 nuclear extracts and that the NFAT1 member was predominant. In conclusion, our results indicate that NFAT activation by stimuli acting in a more distal fashion from the TCR-mediated signaling pathway can be down-regulated by CD45 and that this CD45-dependent regulation in turn affects HIV-1 long terminal repeat activation.

Inhibition of HIV-1-mediated syncytium formation and virus replication by the lipophosphoglycan from Leishmania donovani is due to an effect on early events in the virus life cycle.

Abstract: Previous findings have indicated that the major surface molecule of Leishmania, lipophosphoglycan (LPG), could abrogate HIV-1-induced syncytium formation and virus replication In the present work, we were interested in characterizing this inhibitory process Data from a new luciferase-based semiquantitative assay for syncytium formation, relying on the coincubation of a T-cell line containing an HIV-1 LTR-driven luciferase construct with a cell line chronically infected with HIV-1, confirmed that LPG was indeed a strong inhibitor of HIV-1-dependent syncytium formation and that this inhibition was dose-dependent As determined by flow cytometric analyses, this inhibition was not apparently due to downregulation of CD4, CXCR4 or LFA-1, three distinct surface glycoproteins known to be important in HIV-1 mediated syncytium formation Furthermore, LPG did not seem to affect signal transduction pathways in T cells as judged by measurement of HIV-1 LTR-driven reporter gene activity upon treatment with different stimuli However, pretreatment of either of the cell lines used in the assay with LPG led to a significant decrease of virus-mediated syncytium formation, which was further accentuated when both cell lines were pretreated LPG inhibition of HIV-1 replication was next assessed When measuring either infection with luciferase-encoding recombinant HIV-1 particles or multinucleated giant cell formation following an acute virus infection, we again observed that LPG was efficient at blocking HIV-1 replication Specific assays probing different steps of viral entry demonstrated that attachment was not hindered by LPG but that viral entry was modulated, suggesting that LPG targets a postbinding step Hence, incorporation of LPG into a target cell membrane could influence its fluidity and diminish both the virus-cell and cell-to-cell fusion processes initiated by HIV-1

Use of a phosphotyrosyl phosphatase inhibitor for the treatment of immunosuppressed patients

Abstract: The present invention provides a method for restoring the immune functions and the overall immune response by administration of a bis-peroxovanadium (bpV) compound, a potent class of phosphotyrosyl phosphatase inhibitors. The method can be utilized in treating individuals afflicted with immune disorders or for the treatment of patients suffering from infections caused by viruses that destroy the natural immune response, such as the human immunodeficiency virus (HIV). The bpV compound may be used in combination with various immunomodulators and/or antiviral agents. The present invention also relates to the use of such bpV compound for restoring the immune functions and the overall immune response in a patient in need of such a treatment.