PubMed Health⌕ Search

Biomedical subjects

Yves Levy

Publications and source records attributed to Yves Levy.

9 recordsLinked to original sources
PubMed2006

CD4 regulation in human lymphoid non-T-cells: a role for the silencer element.

In humans, the CD4 molecule is expressed on a subset of T-cells and at various levels on myeloid and lymphoid cells. The mechanisms regulating human CD4 gene expression are yet poorly understood. We speculated that the CD4 silencer, which operates in CD8+ T-cells to repress CD4 expression, could be responsible for CD4 repression in human lymphoid non-T-cells. To test this possibility, we used lentiviral vectors carrying CD4 regulatory sequences, with or without the silencer element, to express an eGFP reporter gene. We observed that (i) in the absence of the silencer element, eGFP expression was detected in CD34+-derived B- and NK-cells that otherwise lacked endogenous CD4 mRNA, indicating active repression of the CD4 regulatory sequences and (ii) the addition of the CD4 silencer could repress eGFP expression in these same cells, as well as in human B-cells generated in vivo in NOD/SCID mice. Collectively, our results suggest that beyond its well-characterized function in T-cells, the CD4 silencer also regulates CD4 gene expression in human lymphoid non-T-cells.

CD4 Antigens↗
PubMed2005

A polypyrrole protein microarray for antibody-antigen interaction studies using a label-free detection process.

Protein microarray is a promising technology that should combine rapidity and easy use with high throughput and versatility. This article describes a method in which an electrocopolymerization process is employed to graft biological molecules on to a chip so that surface plasmon resonance imaging may be used to detect molecular interactions. Copolymerization of pyrrole-modified protein and pyrrole is an efficient grafting process which immobilizes molecules at defined positions on a gold surface. Surface plasmon resonance imaging is an optical technique that allows real-time simultaneous detection of molecular interactions on a large number of spots without labeling. This method was successfully used to analyze antibody-antigen interactions. This illustrates its high specificity and good sensitivity and demonstrates its suitability for biological studies.

Animals↗
PubMed2004

Human immunodeficiency virus-driven expansion of CD4+CD25+ regulatory T cells, which suppress HIV-specific CD4 T-cell responses in HIV-infected patients.

The present study demonstrates that CD4(+)CD25(+) T cells, expanded in peripheral blood of HIV-infected patients receiving highly active antiretroviral therapy (HAART), exhibit phenotypic, molecular, and functional characteristics of regulatory T cells. The majority of peripheral CD4(+)CD25(+) T cells from HIV-infected patients expressed a memory phenotype. They were found to constitutively express transcription factor forkhead box P3 (Foxp3) messengers. CD4(+)CD25(+) T cells weakly proliferated to immobilized anti-CD3 monoclonal antibody (mAb) and addition of soluble anti-CD28 mAb significantly increased proliferation. In contrast to CD4(+)CD25(-) T cells, CD4(+)CD25(+) T cells from HIV-infected patients did not proliferate in response to recall antigens and to p24 protein. The proliferative capacity of CD4 T cells to tuberculin, cytomegalovirus (CMV), and p24 significantly increased following depletion of CD4(+)CD25(+) T cells. Furthermore, addition of increasing numbers of CD4(+)CD25(+) T cells resulted in a dose-dependent inhibition of CD4(+)CD25(-) T-cell proliferation to tuberculin and p24. CD4(+)CD25(+) T cells responded specifically to p24 antigen stimulation by expressing transforming growth factor beta (TGF-beta) and interleukin 10 (IL-10), thus indicating the presence of p24-specific CD4(+) T cells among the CD4(+)CD25(+) T-cell subset. Suppressive activity was not dependent on the secretion of TGF-beta or IL-10. Taken together, our results suggest that persistence of HIV antigens might trigger the expansion of CD4(+)CD25(+) regulatory T cells, which might induce a tolerance to HIV in vivo.

Antiretroviral Therapy, Highly Active↗
PubMed2004

Versatile analysis of multiple macromolecular interactions by SPR imaging: application to p53 and DNA interaction.

The greatest challenge in the postgenomic era is the description of proteome interactions, such as protein-protein or protein-DNA interactions. Surface plasmon resonance (SPR) is an optical technique in which binding of an analyte to the surface changes the refractive index at the surface/solution interface. Molecular interactions are analysed in real time without a labeling step. Currently, the limit to SPR imaging is the small number of reactions that can be simultaneously analysed. Using a novel grafting technology and a new imaging system, we increased the throughput of SPR imaging. The interaction between p53 and DNA was chosen as a paradigm for validation of this assay. Using a tagged DNA methodology, we simultaneously targeted multiple DNA sequences on a single chip. The interaction between p53 and these DNA sequences was monitored by SPR imaging. Qualitative and quantitative analysis provides results similar to those obtained with conventional technologies.

DNA↗
PubMed2004

Autoimmune thrombocytopenic purpura and common variable immunodeficiency: analysis of 21 cases and review of the literature.

To describe the main characteristics and outcome of autoimmune thrombocytopenic purpura (AITP) in patients with common variable immunodeficiency (CVID), we analyzed data from 21 patients and reviewed additional cases from the literature. To be included in this study, patients had to have CVID and a previous history of AITP with a platelet count < or = 50 x 10(9)/L at onset. A complete response to treatment was defined by a platelet count > or = 150 x 10(9)/L, and a partial response by a platelet count >>50 x 10(9)/L with an increase of at least twofold the initial level. The median platelet count at AITP diagnosis was 20 x 10(9)/L (range, 2-50 x 10(9)/L). The median age at AITP diagnosis was 23 years (range, 1-51 yr), whereas the median age at CVID diagnosis was 27 years (range, 10-74 yr). CVID was diagnosed before the onset of AITP in only 4 patients (19%), 3 of whom were being treated with intravenous immunoglobulin (i.v.Ig) replacement therapy. CVID was diagnosed more than 6 months after AITP in 13 cases (62%), and the 2 conditions were diagnosed concomitantly in 4 cases. Eleven patients (52%) had at least 1 autoimmune manifestation other than AITP, among which autoimmune hemolytic anemia (7 cases) and autoimmune neutropenia (5 cases) were preeminent. Seventeen of the 21 patients (80%) received at least 1 treatment for AITP; 13 patients received corticosteroids alone and 7 (54%) achieved at least a partial response; 8 patients received i.v.Ig at 1-2 g/kg alone or in combination with steroids, leading to a short-term response rate of 50%. Four patients underwent a splenectomy (2 complete responses, 2 failures); 2 additional splenectomies were performed for associated autoimmune hemolytic anemia. With a mean follow-up of 5.6 years after the surgical procedure, none of the 6 splenectomized patients had a life-threatening infection. With a median follow-up after AITP onset of 12 years, 13/21 patients (62%) were in treatment-free remission (7 complete responses, 6 partial responses), 7 patients (23%) were in remission while on prednisone < or = 20 mg/day with or without azathioprine, and only 1 patient still had a platelet count <50 x 10(9)/L. Five patients had died at the time of the analysis; none of the deaths was related to a hemorrhage. Severe infections including 3 fatal bacterial infections and 2 opportunistic infections occurred in 6 patients during or after treatment of AITP. In conclusion, AITP, alone or in combination with autoimmune hemolytic anemia (Evans syndrome) and/or autoimmune neutropenia, is frequent in patients with CVID, and is not prevented by i.v.Ig substitutive therapy. Since AITP frequently precedes the diagnosis of CVID, testing for immunoglobulin levels should be performed in every patient diagnosed with AITP. Steroids and splenectomy seem to have the same efficacy as in idiopathic AITP, but the increased risk of severe infections must be taken into consideration.

Adolescent↗
PubMed2003

Polypyrrole based DNA hybridization assays: study of label free detection processes versus fluorescence on microchips.

In this paper, we present different ways to detect DNA hybridization on a solid support. The grafting chemistry is based on the electro-controlled copolymerization of a pyrrole-modified oligonucleotide and pyrrole. This process allows an easy functionalization of conducting materials. Three kind of devices were studied: silicon chips bearing an array of addressable 50 or 4 microm microelectrodes, quartz crystal microbalance (QCM) and a non patterned gold/glass slide bearing 500 microm spots. Each device is compatible with a specific detection process: a classical indirect fluorescence detection for the microchips, a microgravimetric measurement for the QCM and a surface plasmon resonance imaging process (SPRi) for the gold slides. Both QCM and SPRi are a label-free real time detection process whereas the fluorescence methodology gives end-point data but only the fluorescence and the SPRi give multiparametric results. Although the hybridization experiments show that the detection limit for an oligonucleotide is better for the fluorescence (1-10 pM) than that found for SPRi (10 nM) and QCM (250 nM), the information content of real time measurement techniques such as SPRi is of interest for many biological studies.

DNA↗
PubMed2003

Effects of interleukin-2 therapy combined with highly active antiretroviral therapy on immune restoration in HIV-1 infection: a randomized controlled trial.

BACKGROUND: Intermittent interleukin-2 (IL-2) therapy leads to a sustained increase of CD4 T cells in HIV-1-infected patients. METHODS: Symptom-free HIV-1-infected patients who were naive to all antiretroviral drugs (n = 68) and/or to protease inhibitors (n = 50) and had a CD4 cell count of 200-550 x 10(6) cells/l were randomly assigned to start lamivudine/stavudine/indinavir alone (controls) or combined from week 4 with subcutaneous IL-2 (5 x 10(6) IU twice daily for 5 days: every 4 weeks for three cycles, then every 8 weeks for seven cycles). Immunological and virological results were monitored until week 74. RESULTS: CD4 T cell counts increased more in the IL-2 group than in the controls (median increases 865 and 262 x 10(6) cells/l, respectively; P < 0.0001); an 80% increase in CD4 T cells was achieving by 89% of the IL-2 group and by 47% of the controls (P < 0.0001). Decrease of plasma viral loads was similar in both groups. Compared with controls, IL-2 induced a greater increase of naive and memory CD4 T cells, lymphocyte expression of CD28 and CD25 (P < 0.0001) and natural killer cells (P < 0.001). In a logistic regression analysis, odds of being responders to recall antigens was 8.5-fold higher in IL-2 recipients (P = 0.002) than in controls. The former experienced a higher level of antibody response to tetanus vaccination at week 64 than controls (32 and 8 haemagglutinating units/ml, respectively; P = 0.01). CONCLUSIONS: The combination of antiviral drugs and IL-2 induced a greater expansion and function of CD4 T cells than antiretroviral drugs alone.

Adjuvants, Immunologic↗
PubMed2003

In vitro identification of human pro-B cells that give rise to macrophages, natural killer cells, and T cells.

In this study we report the molecular and functional characterization of very early interleukin 7 receptor alpha (IL-7Ralpha)+-CD79a+CD19- B-cell progenitors, produced by human CD34+CD19-CD10- cord blood cells grown in the presence of stromal cells and cytokines. Purified IL-7Ralpha+CD79a+CD19- cells transcribed the B-lymphoid specific genes E2A, EBF, TdT, Rag-1, had initiated DJH rearrangements, but almost lacked Pax-5 mRNA. When exposed to appropriate environmental conditions, these cells repressed B-cell genes and completely differentiated into CD14+ macrophages, CD56+ natural killer cells, and CD4high T cells. Retention of the DJH rearranged genes in both CD14+ and CD56+ cells unambiguously demonstrates that early B-cell genes, expressed prior to Pax-5, can be activated in a multipotent human progenitor cell whose final fate, including in non-B lineages, is determined by external signals.

Antigens, CD↗