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J Estaquier

Publications and source records attributed to J Estaquier.

At least 37 records · Page 2Linked to original sources
PubMed1998

The immunomodulating glycoprotein extract from Klebsiella pneumoniae RU 41740 exerts a suppressive effect on human monocyte death by apoptosis.

Programmed cell death or apoptosis is a physiological cell suicide process that can be suppressed by survival factors. Monocytes undergo rapid apoptosis in culture, unless signalled by cytokines or the bacterial lipopolysaccharide LPS. We have investigated the effect on monocyte apoptosis of the immunostimulating agent RU 41740 (Biostim), a glycoprotein extract from the Klebsiella pneumoniae K2O1 strain that is used for the prevention of recurrent infections. RU 41740, as LPS, strongly enhanced monocyte survival in vitro, an effect related to apoptosis suppression. RU 41740 at concentration ranging from 1 ng/ml to 10 microg/ml prevented apoptosis induced both by survival factor deprival and by gamma-irradiation. Our observation suggests that enhancement of monocyte survival may represent a component of the reported immunostimulating effect of this compound.

Adjuvants, Immunologic↗
PubMed1998

Cellular and molecular mechanisms of senescent erythrocyte phagocytosis by macrophages. A review.

Human red blood cells (RBCs) have a life-span of 120 days in circulation, after which they are phagocytized by resident macrophages. Extensive studies have been undertaken by many investigators in order to elucidate the cellular and molecular mechanisms of the erythrophagocytosis. The critical questions addressed by physiologists, clinicians and biochemists are: 'which of the many traumatic blemishes that appear on the erythrocyte surface as it winds its way through the circulation is the primary signal for clearance of the effete RBC from the circulation?', or 'What is the critical signal that it, and it alone, will activate the resident macrophage to adhere to and engulf it?'. Numerous, and often conflicting, hypotheses have been proposed. Each investigator focusing on but one of the many modifications that afflict the cell surface of the ageing erythrocyte, viz changes in either or both the carbohydrate or peptidic moieties of glycoproteins; abolishment of the pre-existing asymmetry in the lipid bilayer with the exposure of phosphatidylserine residues; or alterations in spectrin, to mention but a few. Many of these investigators also have invoked an intermediary role for auto-immune antibodies that recognise the change(s) on the erythrocyte surface and thereby serve as opsonins as a prelude to the erythrophagocytosis. The objective of the present review is to evaluate the data in support of the various hypotheses, and to submit some of our own recent observations involving the use of flow cytometric procedures that: i) provide evidence that the cell surface sialic acid serves as a determinant of the life-span; ii) characterise the senescent erythrocyte population that is specifically captured and phagocytized by macrophages (utilising the rapid and sensitive procedure we developed for quantification of in vitro erythrophagocytosis); and finally iii) provide evidence for the existence of an alternative pathway that is independent of immunoglobulins.

Animals↗
PubMed1998

Molecular and cellular analysis of human immunodeficiency virus-induced apoptosis in lymphoblastoid T-cell-line-expressing wild-type and mutated CD4 receptors.

We have previously shown that the presence of the CD4 cytoplasmic tail is critical for human immunodeficiency virus (HIV)-induced apoptosis (J. Corbeil, M. Tremblay, and D. D. Richman, J. Exp. Med. 183:39-48, 1996). We have pursued our investigation of the role of the CD4 transduction pathway in HIV-induced apoptosis. To do this, wild-type and mutant forms of the CD4 cytoplasmic tail were stably expressed in the lymphoblastoid T-cell line A2.01. Apoptosis was prevented when CD4 truncated at residue 402 was expressed; however, cells expressing mutated receptors that do not associate with p56(lck) (mutated at the dicysteine motif and truncated at residue 418) but which conserved proximal domains of the cytoplasmic tail underwent apoptosis like wild-type CD4. The differences between wild-type and mutated receptors in the induction of apoptosis were not related to levels of p56(lck) or NF-kappaB activation. Initial signaling through the CD4 receptor played a major role in the sensitization of HIV-infected T cells to undergo apoptosis. Incubation of HIV-infected cells with monoclonal antibody (MAb) 13B8-2, which binds to CD4 in a region critical for dimerization of the receptor, prevented apoptosis without inhibiting HIV replication. Moreover, the apoptotic process was not related to Fas-Fas ligand interaction; however, an antagonistic anti-Fas MAb (ZB-4) enhanced apoptosis in HIV-infected cells without inducing apoptosis in uninfected cells. These observations demonstrate that CD4 signaling mediates HIV-induced apoptosis by a mechanism independent of Fas-Fas ligand interaction, does not require p56(lck) signaling, and may involve a critical region for CD4 dimerization.

Amino Acid Sequence↗
PubMed1997

A role for T-helper type-1 and type-2 cytokines in the regulation of human monocyte apoptosis.

T-helper type-1 (Th1) and type-2 (Th2) cytokines, respectively, favor T-cell-mediated immunity and defense against intracellular pathogens or antibody-mediated immunity and defense against extracellular pathogens. Here we report that type-1 and type-2 cytokines also exert a regulatory effect on human monocyte survival. Interleukin-12 (IL-12) enhanced survival in long-term (10 days) cultures of adherent monocytes, whereas IL-10 induced death by apoptosis. In short-term cultures (2 days), the Th2 cytokines, IL-10 and IL-4, enhanced apoptosis; however, the Th1 cytokines, IL-12 and IL-2 only showed a reducing effect on monocyte apoptosis in culture conditions that decreased monocyte adhesion leading to increased levels of spontaneous apoptosis; finally, the Th1 cytokine, interferon-gamma (IFN-gamma), acted in a dose-dependent fashion: At high concentrations, IFN-gamma enhanced apoptosis, which is an effect related to IL-10 secretion and reduced by antibodies to IL-10. Th1 cytokines reduced monocyte apoptosis induced by several stimuli: IL-2 reduced apoptosis induced by either IL-10 or high concentrations of IFN-gamma, IL-12 reduced apoptosis induced by either the ligation of the Fas (CD95) molecule or gamma-irradiation, and IFN-gamma (at low doses that did not trigger apoptosis) reduced apoptosis induced by gamma-irradiation. These findings suggest that the regulatory role of type-1 and type-2 cytokines on the development of immune responses and inflammatory reactions also involves the regulation of monocyte death by apoptosis.

Animals↗
PubMed1997

Mycobacterium bovis Bacillus Calmette Guérin infection prevents apoptosis of resting human monocytes.

Apoptosis plays an essential role in the development and homeostasis of multicellular organisms. Some infectious agents interfere with this programmed cell death to their own benefit. Here, we show that infection of resting human monocytes with Mycobacterium bovis Bacillus Calmette Guérin (BCG) increases monocyte viability by preventing them from undergoing apoptosis. Heat-killed BCG also prevented apoptosis, indicating that replication of BCG is not required to prevent cell death. Analysis of BCG-infected monocytes revealed an up-regulation of the A1 mRNA, whereas the bcl-2 mRNA was not up-regulated. Interestingly, preinfection with BCG renders the cells resistant to interleukin (IL)-10-induced apoptosis which may be one of the mechanisms mycobacteria use to modulate immune responses. BCG infection was also accompanied by an impairment of the capacity of monocytes to secrete IL-10 and by an induction of the capacity to secrete tumor necrosis factor-alpha, two cytokines known to induce and prevent human monocyte apoptosis, respectively. Since it has been reported that apoptosis is involved in killing of intracellular mycobacteria, the prevention of apoptosis may represent a strategy for mycobacterial survival in the infected host.

Apoptosis↗
PubMed1997

Molecular mechanisms of erythrophagocytosis. Characterization of the senescent erythrocytes that are phagocytized by macrophages.

We have recently developed a flow cytometric assay for the quantitation of erythrophagocytosis, using PKH 26-labeled erythrocytes as the target cells. Using this assay we have shown that there is extensive phagocytosis of desialylated erythrocytes. Furthermore, we have demonstrated that it is the densest population of erythrocytes obtained on a self-forming gradient of Percoll that shows the greatest susceptibility to phagocytosis. We designate this population of erythrocytes as fraction X; it is even denser than the fraction 5 found previously. This population of erythrocytes corresponds to zone X previously seen in the dot-plot of the flow cytometric analyses of human erythrocytes. Further scrutiny of this fraction indicates that a) it shows the greatest reactivity with annexin V, which is specific for the detection of phosphatidylserine (PS) exposed on the outer leaflet of the erythrocyte membrane, b) it is the most susceptible to erythrophagocytosis by resident murine peritoneal macrophages, and c) this erythrophagocytosis of PKH 26-labeled erythrocytes can be inhibited by annexin V and by liposomes containing PS. Scanning electron microscopy of fraction X shows two populations of erythrocytes: (A) spheroechinocytes with filipodes and (B) echinocytes without filipods. After a 2-h period of phagocytosis, the cells remaining in fraction X show a decrease in population A, commensurate with a decrease in reactivity with FITC-labeled annexin V from 65.5 to 24%.

Animals↗
PubMed1997

Analysis of the immune response elicited by a multiple antigen peptide (MAP) composed of two distinct protective antigens derived from the parasite Schistosoma mansoni.

In this report we analyse the immune response elicited by a Multiple Antigen Peptide (MAP), containing three peptide sequences derived from two distinct vaccine candidates against schistosomiasis; the Schistosoma mansoni 28 kDa Gluthatione-S-Transferase (Sm28GST) and the Schistosoma mansoni Triose-Phosphate-Isomerase (sTPI). We examined the immunogenicity of this construct, named MAP 'DA', in three distinct mouse strains. The B-cell response, studied by measuring the production of different IgG isotypes, was mainly directed against the peptide derived from the Sm28GST, but also against the whole Sm28GST protein. In contrast, the T-cell response, as assessed by proliferation assay and cytokine mRNA expression, was directed against the MAP construct, the peptides derived from the sTPI protein and the whole sTPI protein. Significantly, T-cells from all MAP 'DA'-immunized mice, restimulated in vitro was the sTPI antigen, expressed IFN-gamma specific messengers. This cytokine has been described to play a major role in the reduction of the Schistosoma mansoni pathology. We thus demonstrate that a single MAP construct, composed of peptides from distinct antigens of Schistosoma mansoni, induced a B- and T-cell response, including production of potentially protective IFN-gamma, irrespective of the MHC background.

Animals↗
PubMed1997

Interleukin-10-mediated T cell apoptosis during the T helper type 2 cytokine response in murine Schistosoma mansoni parasite infection.

The pathogenesis of infection with the helminth parasite Schistosoma (S) mansoni in mice has been reported to involve a T helper (Th)1 to Th2 cytokine switch, associated with a pathogenic granulomatous response to parasite eggs and to a global defect in Th1-cell effector functions. Here we report that the Th2 cytokine response, which begins 6 weeks after infection, at the time of parasite egg laying (i) does not occur in the context of a genuine Th1 to Th2 cytokine switch, but is associated with a persistent capacity of Th1 (or Th0) cells to secrete IL-2 and IFN-gamma in response to T cell receptor (TCR) stimulation; (ii) is associated, in vitro, with spontaneous death by apoptosis of a significant fraction of the CD4 and CD8 T cells, which is greatly enhanced by TCR stimulation; and (iii) is associated, in vivo, with numerous and large clusters of apoptotic cells in the spleen and in the inflammatory infiltrates surrounding the parasite egg deposits in the liver. The in vitro addition of antibodies to the Th2 cytokine IL-10 had both a preventive effect on TCR-induced T cell apoptosis and an enhancing effect on TCR-induced T cell secretion of Th1 cytokines. Taken together, these findings suggest that the downregulation of Th1-cell-mediated effector functions in S. mansoni-infected mice may not be related to a lack of Th1 cell production, but to a process of IL-10-mediated and activation-induced premature T cell death, that include Th1 (or Th0) cells. Further identification of mechanisms involved in the regulation of T cell apoptosis has implications for the understanding of the pathogenesis of immunosuppression associated with chronic infectious diseases.

Animals↗
PubMed1996

Fas-mediated apoptosis of CD4+ and CD8+ T cells from human immunodeficiency virus-infected persons: differential in vitro preventive effect of cytokines and protease antagonists.

Human immunodeficiency syndrome (HIV) infection leads to a progressive loss of T-cell-mediated immunity associated with T-cell apoptosis. We report here that CD4+ and CD8+ T cells from HIV-1-infected persons are sensitive to Fas (CD95/APO-1)-mediated death induced either by an agonistic anti-Fas antibody or by the physiologic soluble Fas ligand, although showing no sensitivity to tumor necrosis factor alpha-induced death. CD4+ and CD8+ T-cell apoptosis induced by Fas ligation was enhanced by inhibitors of protein synthesis and was prevented either by a soluble Fas receptor decoy or an antagonistic anti-Fas antibody. Fas-mediated apoptosis could also be prevented in a CD4+ or CD8+ T-cell-type manner (1) by several protease antagonists, suggesting the involvement of the interleukin-1beta (IL-1beta)-converting enzyme (ICE)-related cysteine protease in CD4+ T-cell death and of both a CPP32-related cysteine protease and a calpain protease in CD8+ T-cell death; and (2) by three cytokines, IL-2, IL-12, and IL-10, that exerted their effects through a mechanism that required de novo protein synthesis. Finally, T-cell receptor (TCR)-induced apoptosis of CD4+ T cells from HIV-infected persons involved a Fas-mediated death process, whereas TCR stimulation of CD8+ T cells led to a different Fas-independent death process. These findings suggest that Fas-mediated T-cell death is involved in acquired immunodeficiency syndrome (AIDS) pathogenesis and that modulation of Fas-mediated signaling may represent a target for new therapeutic strategies aimed at the prevention of CD4+ T-cell death in AIDS.

Animals↗
PubMed1995

T helper type 1/T helper type 2 cytokines and T cell death: preventive effect of interleukin 12 on activation-induced and CD95 (FAS/APO-1)-mediated apoptosis of CD4+ T cells from human immunodeficiency virus-infected persons.

Human immunodeficiency virus (HIV) infection leads to a progressive loss of CD4+ T helper (Th) type 1 cell-mediated immunity that is associated with defective in vitro CD4+ T cell proliferation and abnormal T cell death by apoptosis in response to T cell receptor (TCR) stimulation. Quantification of interleukin (IL)-2, interferon gamma, IL-4, IL-5, and IL-10 secretion by immunoassays, and of interferon gamma, IL-4 and IL-10 messenger RNA expression by competitive reverse transcriptase polymerase chain reaction after in vitro stimulation of the TCR revealed a similar Th1 cytokine profile in T cells from HIV-infected persons and from controls. These data indicated that the loss of CD4+ Th1 cell function in HIV-infected persons is not related to a Th1 to Th2 cytokine switch as previously proposed, but to a process of activation-induced death of CD4+ Th1 cells. Despite the absence of elevated levels of Th2 cytokines, apoptosis of CD4+ T cells, but not of CD8+ T cells, was prevented in vitro by antibodies to IL-10 or IL-4, two Th2 cytokines that downregulate Th1 cell responses, or by the addition of recombinant IL-12, a cytokine that upregulates Th1 functions. TCR-induced apoptosis of T cell hybridomas and preactivated T cells has been shown to involve the CD95 (Fas/Apo-1) molecule. CD4+ and CD8+ T cells from HIV-infected persons expressed high levels of the CD95 molecule, and, in contrast to T cells from controls, were highly sensitive to antibody-mediated CD95 ligation, which induced apoptosis in a percentage of T cells similar to that induced by TCR stimulation. As TCR-induced apoptosis, CD95-mediated apoptosis of CD4+ T cells, but not of CD8+ T cells, was prevented by the addition of recombinant IL-12. Together, these findings suggest that apoptosis of CD4+ T cells from HIV-infected persons involves an abnormal sensitivity to CD95 ligation, and to TCR stimulation in the presence of normal levels of Th2 cytokines. The preventive effect of IL-12 on both mechanisms has potential implications for the design of immunotherapy strategies aimed at the upregulation of CD4+ Th1 cell functions in AIDS.

Apoptosis↗
PubMed1995

YOPRO-1 permits cytofluorometric analysis of programmed cell death (apoptosis) without interfering with cell viability.

In the absence of cell permeabilization, the impermeant nuclear dye YOPRO-1 permits accurate analysis of apoptosis using cytofluorometry or fluorescent microscopy. Several immune cell populations were studied including dexamethasone-treated thymocytes, irradiated peripheral blood mononuclear cells and a growth factor-depleted tumor B cell line. Excellent correlation values were found with acridine orange using cytofluorometry and with eosin-hematoxylin using optical microscopy. Under fluorescent microscopy, YOPRO-1-fluorescent cells demonstrate the morphological features of cells undergoing apoptosis such as nuclear shrinkage and fragmentation. An important characteristic of the dye that differs from all other nuclear dyes previously used for the detection of apoptosis is that it does not label living cells. Cell sorting after flow cytofluorometry analysis confirmed that only the apoptotic cell population was labelled with YOPRO-1. Further studies showed that while incubation of living cells with Hoechst 33342 almost completely abrogated the capacity of T cells to proliferate in response to several stimuli, YOPRO-1 had no inhibitory effect. This new simple, rapid and reproducible use of the YOPRO-1 dye should prove useful in the analysis of apoptotic cells as well as for investigations of the functional properties of living cells in a culture containing apoptotic cells.

Acridine Orange↗
PubMed1995

The relevance of apoptosis to AIDS pathogenesis.

Several recent experimental findings support the hypothesis that apoptosis induced by human immune deficiency virus (HIV) is important in the pathogenesis of acquired immune deficiency syndrome (AIDS). Thus, one potential therapeutic strategy against AIDS may be to block the HIV-mediated apoptosis signal transduction pathway. Induction of apoptosis by HIV infection may prove a useful paradigm for the pathogenesis of a wide range of diseases that involve cell depletion and tissue atrophy.

Journal Article↗
PubMed1995

Green fluorescent protein as a new expression marker in mycobacteria.

This study describes the use and the advantages of the green fluorescent protein (GFP) as a reporter molecule for mycobacteria. The gfp gene from Aequorea victoria was placed under the control of the hsp60 promoter in the shuttle vector pGFM-11. The gfp expression in the recombinant Mycobacterium smegmatis and BCG was readily detected on agar plates by the development of an intense green fluorescence upon irradiation with long-wave u.v. light. In mycobacteria containing a pGFM-11 derivative that lacks the hsp60 promoter, no fluorescence was observed. However, this plasmid was successfully used as a promoter-probe vector to identify BCG promoters. The fluorescence emission of GFP in mycobacteria harbouring pGFM-11 and grown in liquid media could be quantified by spectrofluorimetry. This allowed for easy assessment of drug susceptibility. As GFP does not require the addition of substrates or co-factors, the green fluorescent bacilli could be directly observed within infected macrophages using fluorescence and laser confocal microscopy, or in tissue sections of infected mice. Finally, infected cells or free-living recombinant mycobacteria could also be analysed by flow cytometry. The GFP thus appears to be a convenient reporter for mycobacteria, allowing tracing of recombinant mycobacteria, isolation of promoters with interesting properties, in vivo drug testing and the development of new diagnostic tools.

Amino Acid Sequence↗
PubMed1995

Analysis of the Mycobacterium tuberculosis 85A antigen promoter region.

A mycobacterial expression-secretion vector was constructed in which the Escherichia coli alkaline phosphatase (phoA) reporter gene was placed under the control of the Mycobacterium tuberculosis 85A promoter and secretion signal sequences. In recombinant Mycobacterium smegmatis and Mycobacterium bovis BCG, PhoA activity could readily be detected on the mycobacterial cell surface and in the culture supernatant, indicating that the 85A signals can drive heterologous expression and secretion in both species. In contrast to the mycobacteria, the 85A promoter did not function in E. coli. We mapped the promoter region by progressive deletions using BAL 31 exonuclease and by primer extension analysis. Insertion and deletion mutations within the promoter region indicated that, unlike most E. coli promoters but similar to Streptomyces promoters, the position of the putative -35 region was not critical for efficient promoter activity. In addition, we investigated the ability of the identified signals to drive the production and secretion in BCG of recombinant Schistosoma mansoni glutathione S-transferase (Sm28GST), a protective antigen against schistosomiasis. BALB/c mice immunized with the recombinant BCG by a single dose exhibited a weak but specific T-cell response to Sm28GST.

Alkaline Phosphatase↗
PubMed1994

Programmed cell death and AIDS: significance of T-cell apoptosis in pathogenic and nonpathogenic primate lentiviral infections.

We have proposed that inappropriate induction of programmed cell death (PCD) or apoptosis, a physiological cell-suicide process, may play a role in the pathogenesis of AIDS. This model has been supported by several reports of abnormal levels of PCD in vitro in both CD4+ and CD8+ T cells from human immunodeficiency virus type 1 (HIV-1)-infected persons. To further assess the significance of such a process in AIDS pathogenesis, in vitro PCD was compared in HIV-1-infected persons and in various primate models that allow discrimination between pathogenic chronic lentiviral infection either in the same species, such as rhesus macaques infected with different simian immunodeficiency viruses (SIV), or in different species, such as SIV-infected African green monkeys and HIV-1-infected chimpanzees. Abnormal levels of PCD in CD4(+)-T-cell-depleted peripheral blood mononuclear cells (PBMC), containing the CD8+ T cells, were observed in both pathogenic and nonpathogenic models. However, abnormal levels of PCD in the CD8(+)-T-cell-depleted PBMC, containing the CD4+ T cells, was only observed in the two models leading to AIDS: HIV-1-infected persons and rhesus macaques infected with a pathogenic strain of SIV. This suggests that inappropriate T-cell PCD in HIV-1-infected persons involves two distinct processes: one, concerning CD4+ T cells, is closely related to AIDS pathogenesis; and the other, concerning CD8+ T cells, may be a consequence of immune stimulation with no direct link to AIDS pathogenesis.

Acquired Immunodeficiency Syndrome↗