Biomedical subjects

Georges Herbein

Publications and source records attributed to Georges Herbein.

9 recordsLinked to original sources

PubMed2006

Development and characterization of ten monoclonal anti-Vpr antibodies.

HIV-1 Vpr is a 96-amino acid auxiliary protein that performs numerous activities during viral infection. In the present study, 10 antibodies were generated after mice immunization with either the N- or the C-terminus domain of Vpr, respectively, Vpr(1-51) and Vpr(52-96). ELISA and immunoblot experiments using pure synthetic overlapping Vpr peptides suggested that these anti-Vpr antibodies could be classified into five groups and that they recognized conformational or linear Vpr epitopes. Further analysis revealed the effect of C-terminal arginine mutations on the antibody binding. Two of the antibodies precipitated Vpr expressed after transfection of a Vpr-encoding vector in human cells. More importantly, one of them was able to detect Vpr in HIV-1-infected U1 cells and in HIV-1-infected human PBMC. Surface plasmon resonance experiments demonstrated that some of these antibodies prevented the interaction between Vpr and one of its cellular partners, the adenine nucleotide translocator. Thus, these anti-Vpr monoclonal antibodies may be useful to any laboratory working on the molecular mechanism of HIV-1 infection.

Animals↗

PubMed2005

Synthetic Vpr protein activates activator protein-1, c-Jun N-terminal kinase, and NF-kappaB and stimulates HIV-1 transcription in promonocytic cells and primary macrophages.

The human immunodeficiency virus (HIV) Vpr protein plays a critical role in AIDS pathogenesis, especially by allowing viral replication within nondividing cells such as mononuclear phagocytes. Most of the data obtained so far have been in experiments with endogenous Vpr protein; therefore the effects of extracellular Vpr protein remain largely unknown. We used synthetic Vpr protein to activate nuclear transcription factors activator protein-1 (AP-1) and NF-kappaB in the promonocytic cell line U937 and in primary macrophages. Synthetic HIV-1 Vpr protein activated AP-1, c-Jun N-terminal kinase, and MKK7 in both U937 cells and primary macrophages. Synthetic Vpr activated NF-kappaB in primary macrophages and to a lesser extent in U937 cells. Because synthetic Vpr activated AP-1 and NF-kappaB, which bind to the HIV-1 long terminal repeat, we investigated the effect of synthetic Vpr on HIV-1 replication. We observed that synthetic Vpr stimulated HIV-1 long terminal repeat in U937 cells and enhanced viral replication in chronically infected U1 promonocytic cells. Similarly, synthetic Vpr stimulated HIV-1 replication in acutely infected primary macrophages. Activation of transcription factors and enhancement of viral replication in U937 cells and primary macrophages were mediated by both the N-terminal and the C-terminal moieties of synthetic Vpr. Therefore, our results suggest that extracellular Vpr could fuel the progression of AIDS via stimulation of HIV-1 provirus present in such cellular reservoirs as mononuclear phagocytes in HIV-infected patients.

Acquired Immunodeficiency Syndrome↗

PubMed2005

HIV and inflammation.

A main feature of HIV infection is the expression of several proinflammatory cytokines. Proinflammatory cytokines expressed as soluble factors or membrane-bound molecules regulate both HIV replication and T cell apoptosis. Proinflammatory cytokines have key roles in the HIV lifecycle, especially at the level of transcription, favouring the ability of HIV to establish latent reservoirs. In addition, proinflammatory cytokines are involved in both CD4+ T cell and CD8+ T cell apoptosis, resulting in immune suppression. Moreover, several HIV proteins such as Nef, Tat, and Vpr hijack proinflammatory cytokine signaling, further underlining the potential importance of inflammation in HIV pathogenesis. In vivo chronic inflammatory conditions have been correlated to increased levels of viremia and accelerated disease progression. This article raises the possibility that inflammation plays a crucial role in both immune suppression and the formation of viral reservoirs during HIV infection. Understanding the role of inflammation in HIV infection could lead to new therapeutic strategies that could ultimately enhance immune restoration and limit the formation of viral reservoirs in HIV-infected patients.

Apoptosis↗

PubMed2004

Histone deacetylase 3, a class I histone deacetylase, suppresses MAPK11-mediated activating transcription factor-2 activation and represses TNF gene expression.

During inflammatory events, the induction of immediate-early genes, such as TNF-alpha, is regulated by signaling cascades including the JAK/STAT, NF-kappaB, and the p38 MAPK pathways, which result in phosphorylation-dependent activation of transcription factors. We observed the direct interaction of histone deacetylase (HDAC) 3, a class I histone deacetylase, with MAPK11 (p38 beta isoform) by West-Western-based screening analysis, pull-down assay, and two-hybrid system analysis. Results further indicated that HDAC3 decreases the MAPK11 phosphorylation state and inhibits the activity of the MAPK11-dependent transcription factor, activating transcription factor-2 (ATF-2). LPS-mediated activation of ATF-2 was inhibited by HDAC3 in a time- and dose-dependent manner. Inhibition of HDAC3 expression by RNA interference resulted in increased ATF-2 activation in response to LPS stimulation. In agreement with decreased ATF-2 transcriptional activity by HDAC3, HDAC3-repressed TNF gene expression, and TNF protein production observed in response to LPS stimulation. Therefore, our results indicate that HDAC3 interacts directly and selectively with MAPK11, represses ATF-2 transcriptional activity, and acts as a regulator of TNF gene expression in LPS-stimulated cells, especially in mononuclear phagocytes.

Activating Transcription Factor 2↗

PubMed2004

Mixed cytomegalovirus glycoprotein B genotypes in immunocompromised patients.

On the basis of sequence variation in the UL55 gene that encodes glycoprotein B (gB), human cytomegalovirus (CMV) can be classified into 4 gB genotypes. The goal of the present study was to determine the distribution of CMV gB genotypes and the effect of gB type on clinical outcomes in a cohort of immunocompromised patients, including both transplant recipients and nonrecipients. The distribution of gB genotypes was as follows: gB1, 28.9% of patients; gB2, 19.6%; gB3, 23.7%; gB4, 2.0%; and mixed infection, 25.8%. In contrast to patients infected with a single gB genotype, patients infected with multiple gB genotypes developed progression to CMV disease, had an increased rate of graft rejection, had higher CMV loads, and were significantly more often infected with other herpesviruses. The presence of multiple gB genotypes, rather than the presence of a single gB genotype, could be a critical factor associated with severe clinical manifestations in immunocompromised patients.

Adult↗

PubMed2004

CXCR4-mediated T cell apoptosis in human immunodeficiency virus infection.

Mechanisms of CXCR4-mediated T lymphocyte apoptosis in human immunodeficiency virus (HIV) infection are poorly understood. The authors used peripheral blood mononuclear cells isolated from HIV type 1-infected subjects and assessed both CD4(+) and CD8(+) T cell apoptosis in the presence and absence of CXCR4 blockade by AMD3100. Both CD4(+) and CD8(+) T cell apoptosis could be inhibited by CXCR4 blockade, mostly in acquired immunodeficiency syndrome subjects and more weakly in asymptomatic HIV-positive subjects, and depended only partially on the syncytium-inducing/non-syncytium-inducing viral envelope phenotype. Immune activation of CD8(+), but not CD4(+), T cells was CXCR4-dependent, resulting in increased T cell apoptosis. In the presence of monocyte-derived macrophages, CXCR4-mediated apoptosis targeted mostly CD8(+) T cells, with CD4(+) T cells being more weakly affected. Several immune and viral factors thus play a role in CXCR4-mediated T cell apoptosis in HIV infection: CD4/CD8 phenotype, viral envelope phenotype, T cell activation and T cell-macrophage intercellular contacts.

Adult↗

PubMed2003

Potential role for CD63 in CCR5-mediated human immunodeficiency virus type 1 infection of macrophages.

Macrophages and CD4(+) lymphocytes are the principal target cells for human immunodeficiency virus type 1 (HIV-1) infection, but the molecular details of infection may differ between these cell types. During studies to identify cellular molecules that could be involved in macrophage infection, we observed inhibition of HIV-1 infection of macrophages by monoclonal antibody (MAb) to the tetraspan transmembrane glycoprotein CD63. Pretreatment of primary macrophages with anti-CD63 MAb, but not MAbs to other macrophage cell surface tetraspanins (CD9, CD81, and CD82), was shown to inhibit infection by several R5 and dualtropic strains, but not by X4 isolates. The block to productive infection was postfusion, as assessed by macrophage cell-cell fusion assays, but was prior to reverse transcription, as determined by quantitative PCR assay for new viral DNA formation. The inhibitory effects of anti-CD63 in primary macrophages could not be explained by changes in the levels of CD4, CCR5, or beta-chemokines. Infections of peripheral blood lymphocytes and certain cell lines were unaffected by treatment with anti-CD63, suggesting that the role of CD63 in HIV-1 infection may be specific for macrophages.

Antibodies, Monoclonal↗

PubMed2002

Exogenous Nef protein activates NF-kappa B, AP-1, and c-Jun N-terminal kinase and stimulates HIV transcription in promonocytic cells. Role in AIDS pathogenesis.

The human immunodeficiency virus (HIV) Nef protein plays a critical role in AIDS pathogenesis by enhancing replication and survival of the virus within infected cells and by facilitating its spread in vivo. Most of the data obtained so far have been in experiments with endogenous Nef protein, so far overlooking the effects of exogenous soluble Nef protein. We used recombinant exogenous Nef proteins to activate nuclear transcription factors NF-kappaB and AP-1 in the promonocytic cell line U937. Exogenous SIV and HIV-1 Nef proteins activated NF-kappaB and AP-1 in a dose- and time-dependent manner. Activation of NF-kappaB by exogenous Nef was concomitant to the degradation of the inhibitor of NF-kappaB, IkappaBalpha. In agreement with increased AP-1 activation, a time- and dose-dependent increase in JNK activation was observed following treatment of U937 cells with exogenous Nef. Since exogenous Nef activates the transcription factors NF-kappaB and AP-1, which bind to the HIV-1 long terminal repeat (LTR), we investigated the effect of exogenous Nef on HIV-1 replication. We observed that exogenous Nef stimulated HIV-1 LTR via NF-kappaB activation in U937 cells and enhanced viral replication in the chronically infected promonocytic cells U1. Therefore, our results suggest that exogenous Nef could fuel the progression of the disease via stimulation of HIV-1 provirus present in such cellular reservoirs as mononuclear phagocytes in HIV-infected patients.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

NF-kappaB, AP-1, Zinc-deficiency and aging.

Zinc (Zn) deficiency, a frequent condition in human population especially in aged persons, induces oxidative stress and subsequently activates/inhibits oxidant-sensitive transcription factors that can affect cell function, proliferation and survival leading to disease. Zn deficiency-triggered oxidative stress could affect cell signalling, including transcription factors containing Zn finger motifs and other oxidant-sensitive transcription factors such as nuclear factor kappa B (NF-kappaB) and activator protein-1 (AP-1). AP-1 can be activated in Zn deficiency that can occur secondary to an increase in cellular H(2)O(2), followed by activation of MAPKs p38 and JNK. Similarly, the cytosolic steps of the NF-kappaB cascade are activated by oxidants in Zn deficiency. However, an impaired nuclear transport of the active transcription factor leads to a low expression of NF-kappaB-dependent genes that could be involved in multiple steps of Zn deficiency associated pathology. We present here evidence that, following experimental depletion of Zn, both NF-kappaB and AP-1 signallings are altered in primary T cells isolated from young and elderly healthy individuals under CD3/CD28 costimulation. A supplementation of Zn restored both NF-kappaB and AP-1 activation in CD3/CD28 costimulated T cells from young, but not from elderly, healthy individuals, indicating that the Zn deficiency is only one component of a more complex mechanism involved in immunosenescence. In this review we summarize our present knowledge on NF-kappaB and AP-1 activation and underline the role of Zn in this process, especially in the context of Zn deficiency observed in aged persons leading to immunosenescence.

Aging↗