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Biomedical subjects

A M Quero

Publications and source records attributed to A M Quero.

At least 19 recordsLinked to original sources
PubMed2000

Human cytomegalovirus infects Caco-2 intestinal epithelial cells basolaterally regardless of the differentiation state.

Human cytomegalovirus (CMV) causes severe disease in immunosuppressed patients and notably infects the gastrointestinal tract. To understand the interaction of CMV with intestinal epithelial cells, which are highly susceptible to CMV infection in vivo, we used the intestinal epithelial cell line Caco-2 and demonstrated that CMV enters predominantly through the basolateral surface of polarized Caco-2 cells. As shown by expression of all three classes of CMV proteins and by visualization of nucleocapsids by transmission electron microscopy, both poorly and fully differentiated Caco-2 cells were permissive to CMV replication. However, infection failed to produce infectious particles in Caco-2 cells, irrespective of the state of differentiation.

Antigens, Viral↗
PubMed2000

Rotavirus infection induces an increase in intracellular calcium concentration in human intestinal epithelial cells: role in microvillar actin alteration.

Rotaviruses, which infect mature enterocytes of the small intestine, are recognized as the most important cause of viral gastroenteritis in young children. We have previously reported that rotavirus infection induces microvillar F-actin disassembly in human intestinal epithelial Caco-2 cells (N. Jourdan, J. P. Brunet, C. Sapin, A. Blais, J. Cotte-Laffitte, F. Forestier, A. M. Quero, G. Trugnan, and A. L. Servin, J. Virol. 72:7228-7236, 1998). In this study, to determine the mechanism responsible for rotavirus-induced F-actin alteration, we investigated the effect of infection on intracellular calcium concentration ([Ca(2+)](i)) in Caco-2 cells, since Ca(2+) is known to be a determinant factor for actin cytoskeleton regulation. As measured by quin2 fluorescence, viral replication induced a progressive increase in [Ca(2+)](i) from 7 h postinfection, which was shown to be necessary and sufficient for microvillar F-actin disassembly. During the first hours of infection, the increase in [Ca(2+)](i) was related only to an increase in Ca(2+) permeability of plasmalemma. At a late stage of infection, [Ca(2+)](i) elevation was due to both extracellular Ca(2+) influx and Ca(2+) release from the intracellular organelles, mainly the endoplasmic reticulum (ER). We noted that at this time the [Ca(2+)](i) increase was partially related to a phospholipase C (PLC)-dependent mechanism, which probably explains the Ca(2+) release from the ER. We also demonstrated for the first time that viral proteins or peptides, released into culture supernatants of rotavirus-infected Caco-2 cells, induced a transient increase in [Ca(2+)](i) of uninfected Caco-2 cells, by a PLC-dependent efflux of Ca(2+) from the ER and by extracellular Ca(2+) influx. These supernatants induced a Ca(2+)-dependent microvillar F-actin alteration in uninfected Caco-2 cells, thus participating in rotavirus pathogenesis.

Actins↗
PubMed1999

Inhibitory activity of constitutive nitric oxide on the expression of alpha/beta interferon genes in murine peritoneal macrophages.

We investigated the role of the constitutive nitric oxide (NO) in the expression of interferon (IFN) genes in mouse peritoneal macrophages (PM). The treatment of PM with L-arginine-N(G)-amine (AA), a potent inhibitor of NO-producing enzymes, resulted in a marked accumulation of IFN-alpha4 mRNA and, to a minor extent, of IFN-beta mRNA. In contrast, the expression of IFN-gamma mRNA, as well as tumor necrosis factor alpha and interleukin-6 mRNA, was not affected. Furthermore, a remarkable increase in the expression of the IFN regulating factor 1 (IRF-1), but not of IRF-2, mRNA was detected in AA-treated PM. To investigate whether the AA-induced activation of the IFN system correlates with the production and antiviral activity of IFN, the extent of encephalomyocarditis virus (EMCV) replication was monitored in AA-treated PM with respect to control cultures. AA treatment strongly inhibited, in a dose-dependent manner, EMCV yields in PM. Likewise, similar results were obtained by the addition of the NO-scavenger carboxyphenyl-tetramethylimidazoline-oxyl-oxide. In addition, inhibition of NO synthesis by N(G)-mono-methyl-L-arginine in PM strongly decreased virus replication in coculture of PM and EMCV-infected L929 cells, whereas no antiviral effect was observed in L929 cells alone. Moreover, the AA-mediated antiviral activity was abrogated in the presence of antibody to IFN-alpha/beta, whereas antibody to IFN-gamma was completely ineffective. Taken together, these results indicate that low levels of NO, constitutively released by resting PM, negatively regulate the expression and activity of IFN-alpha/beta in PM. We suggest that NO acts as a homeostatic agent in the regulation of IFN pathway expression in macrophages.

Animals↗
PubMed1998

Influence of intestinal microflora on murine bone marrow and spleen macrophage precursors.

To investigate the adjuvant effect of intestinal flora on macrophage-colony-stimulating factor-responsive macrophage progenitors from spleen and bone marrow, we compared progenitor numbers and phenotypic characteristics of in vitro matured macrophages in germ-free and flora-associated mice (conventional, Escherichia coli-monoassociated and conventionalized mice). The data obtained show that the flora affected differentially bone marrow and spleen progenitors. It increased the numbers of progenitors in the spleen but not in the bone marrow. It did not modify the expression of F4/80, Mac-1 and major histocompatibility complex (MHC) class II on bone-marrow-derived macrophages (BMDM), while it clearly up-regulated MHC class II expression on spleen-derived macrophages (SDM). This effect was more pronounced in flora-associated ex germ-free mice than in conventional mice and it was greatly enhanced in the absence of M-CSF. In vitro stimulation by lipopolysaccharide had no effect on marker expression of BMDM, while it decreased F4/80 and enhanced MHC class II molecules on SDM from germ-free and flora-associated mice. However, the expression of MHC class II remained lower in germ-free mice. Enhancement of MHC class II molecule expression on SDM may contribute to the protective role of flora, because successful immune responses are dependent on the expression of these molecules.

Animals↗
PubMed1998

Rotavirus infection reduces sucrase-isomaltase expression in human intestinal epithelial cells by perturbing protein targeting and organization of microvillar cytoskeleton.

Rotavirus infection is the most common cause of severe infantile gastroenteritis worldwide. These viruses infect mature enterocytes of the small intestine and cause structural and functional damage, including a reduction in disaccharidase activity. It was previously hypothesized that reduced disaccharidase activity resulted from the destruction of rotavirus-infected enterocytes at the villus tips. However, this pathophysiological model cannot explain situations in which low disaccharidase activity is observed when rotavirus-infected intestine exhibits few, if any, histopathologic changes. In a previous study, we demonstrated that the simian rotavirus strain RRV replicated in and was released from human enterocyte-like Caco-2 cells without cell destruction (N. Jourdan, M. Maurice, D. Delautier, A. M. Quero, A. L. Servin, and G. Trugnan, J. Virol. 71:8268-8278, 1997). In the present study, to reinvestigate disaccharidase expression during rotavirus infection, we studied sucrase-isomaltase (SI) in RRV-infected Caco-2 cells. We showed that SI activity and apical expression were specifically and selectively decreased by RRV infection without apparent cell destruction. Using pulse-chase experiments and cell surface biotinylation, we demonstrated that RRV infection did not affect SI biosynthesis, maturation, or stability but induced the blockade of SI transport to the brush border. Using confocal laser scanning microscopy, we showed that RRV infection induces important alterations of the cytoskeleton that correlate with decreased SI apical surface expression. These results lead us to propose an alternate model to explain the pathophysiology associated with rotavirus infection.

Biological Transport↗
PubMed1997

Rotavirus is released from the apical surface of cultured human intestinal cells through nonconventional vesicular transport that bypasses the Golgi apparatus.

Rotaviruses are nonenveloped viruses that infect enterocytes of the small intestine and cause severe infantile gastroenteritis. It was previously thought that rotavirus exits cells by lysis, but this behavior does not match the local pathogenesis of the virus. In this study, we have investigated the release of the simian rotavirus strain (RRV) from the polarized intestinal Caco-2 cells. We found that RRV is released almost exclusively from the apical pole of Caco-2 cells before any cells lyse. Using confocal laser scanning microscopy and drugs that inhibit vesicular transport, we studied the RRV transport route from the endoplasmic reticulum (ER) to the apical side of intestinal cells. We demonstrated that RRV exits from the ER through a carbonyl cyanide m-chlorophenylhydrazone-sensitive vesicular transport. RRV staining was never found within the Golgi apparatus or lysosomes, suggesting that the RRV intracellular pathway does not involve these organelles. This finding was confirmed by treatment with monensin or NH4Cl, which do not affect release of RRV. Electron microscopic analysis revealed RRV containing small smooth vesicles in the apical area and free virions outside the cell in the brush border, consistent with a vesicular vectorial transport of virus. These results may provide, for the first time, a cellular explanation of the pathogenesis of rotavirus.

Biological Transport↗
PubMed1996

Activity of nitric oxide-generating compounds against encephalomyocarditis virus.

Nitric oxide (NO) generated by two NO donors (sodium nitroprusside or S-nitroso-L-glutathione) was shown to exert a dose-dependent inhibition of encephalomyocarditis virus growth in L-929 cells. This activity was not due to the cytotoxic or direct virucidal effects of NO donors. L-929 cells were shown to produce NO endogenously, but this low level of production did not counter encephalomyocarditis virus replication.

Cell Line↗
PubMed1995

The influence of E. coli implantation in axenic mice on cytokine production by peritoneal and bone marrow-derived macrophages.

To assess the involvement of bacterial microflora in the development of host defenses, we compared in vitro LPS-induced cytokine production by macrophages in germ-free and E. coli monoxenic mice. E. coli implantation significantly increased IL-1 and IL-6 and, to a lesser extent, TNF activities of peritoneal and bone marrow-derived macrophages. These results suggest that exposure to microflora primes macrophages for an enhanced cytokine production, which may contribute to the activation of the antiinfectious defense. The priming was not restricted to peritoneal macrophages but was associated with a more general effect of the flora since the enhanced response of bone marrow-derived macrophages indicates an effect on macrophage precursors. Furthermore, a higher ability of peritoneal macrophages to produce IL-1 in axenic and monoxenic mice was observed as compared to bone marrow-derived macrophages. In contrast, bone marrow-derived macrophages demonstrated a higher ability to produce IL-6 and TNF but only 3 weeks after bacterial administration.

Animals↗
PubMed1995

Role of trehalose dimycolate-induced interferon-alpha/beta in the restriction of encephalomyocarditis virus growth in vivo and in peritoneal macrophage cultures.

Preventive intraperitoneal trehalose dimycolate (TDM) treatment of mice, inoculated with encephalomyocarditis (EMC) virus by the same route, caused restriction of virus growth in the peritoneum, which was correlated to IFN production in peritoneal fluids prior to infection. Peritoneal macrophages from TDM-treated mice (TDM-PM) spontaneously secreted IFN-alpha/beta in large amounts. By their supernatants, TDM-PM could transfer an antiviral state against EMC virus to permissive resident peritoneal macrophages from control mice. IFN-alpha/beta produced by TDM-PM was found to be involved in this transfer activity. TDM-PM also exerted a strong antiviral effect on EMC virus-infected L-929 cells, which increased with time and the macrophage-target cell ratio. This activity also occurred by an IFN-alpha/beta-dependent mechanism. These data point to the role of IFN-alpha/beta production prior to EMC virus infection in the antiviral activities of TDM-PM and, more generally, in the outcome of viral infection.

Animals↗
PubMed1993

Effect of acute oral administration of alcohol on superoxide anion production from mouse alveolar macrophages.

The production of superoxide anions (superoxide) from alveolar macrophages stimulated or not with opsonized zymosan was investigated in the mouse after acute oral administration of alcohol (6.5 g/kg). Superoxide production was assayed using a nitroblue tetrazolium (NBT) reduction and chemiluminescence assay. In the absence of opsonized zymosan, superoxide concentration was not affected 1 h after ethanol treatment but was significantly increased 15 and 24 h after treatment. In the presence of opsonized zymosan, a biphasic response was observed. Superoxide production was significantly reduced 1 and 3 h after administration but was increased 15 and 24 h after treatment. One hour after treatment, the percentage of cells that phagocytized opsonized zymosan and reduced NBT was significantly decreased, whereas 24 h after alcohol treatment, phagocytosis was normal and the percentage of cells reducing NBT was significantly increased. The activity of cytosolic superoxide dismutase from alveolar macrophages was not altered 1 h after administration but was significantly reduced 24 h later. Considering the functions of alveolar macrophages in the defense of the lung, these alterations in the production of reactive oxygen species after ingestion of alcohol could explain why alcoholics are more sensitive to pulmonary infections.

Animals↗
PubMed1993

Antiviral action of trehalose dimycolate against EMC virus: role of macrophages and interferon alpha/beta.

Preventive treatment of mice with trehalose 6,6' dimycolate (TDM), an immunomodulator of bacterial origin, enhances their resistance to encephalomyocarditis (EMC) virus infection. The protective effect of TDM is totally abolished by the injection of silica particles in mice, demonstrating the role of macrophages in the antiviral action of TDM. In vitro, peritoneal macrophages from mice treated with TDM (TDM-PM) exhibit an intrinsic antiviral activity against EMC virus, while resident peritoneal macrophages (RES-PM) are permissive to this virus. Greater amounts of interferon are detected in supernatants of cultures of TDM-PM than of RES-PM. Neutralization of interferon (IFN) by addition in vitro of anti-IFN alpha/beta serum markedly reduces the antiviral activity of TDM-PM. These results indicate that interferon alpha/beta is involved in the intrinsic anti-EMC virus activity of peritoneal macrophages from mice treated with TDM.

Animals↗
PubMed1992

Effect of nanoparticle-bound ampicillin on the survival of Listeria monocytogenes in mouse peritoneal macrophages.

The efficacy of ampicillin bound to polyisohexylcyanoacrylate nanoparticles was studied in vitro in mouse peritoneal macrophages infected with Listeria monocytogenes. Nanoparticles containing ampicillin 1 mg/L were more effective after 30 h than free ampicillin at the same concentration, with viable counts of 3.68 and 5.43 log10 cfu/mL, respectively. The nanoparticles acted on the intracellular bacteria after a lag period of 6-9 h; this time was apparently required for the degradation of the polymer. At the doses used in these experiments, empty nanoparticles had neither an anti-listeria nor a cytotoxic effect.

Ampicillin↗
PubMed1990

Production of interleukin 1 and tumour necrosis factor activities in bronchoalveolar washings following infection of mice by influenza virus.

Mice were infected with influenza A virus by aerosol. Bronchoalveolar washings obtained from infected mice contained interleukin 1 (IL-1) and tumour necrosis factor (TNF) activities. IL-1 was present at day 4 post-infection but not at day 7. TNF activity was present at day 4 and day 7 post-infection. The presence of both these monokines was coincident with increased cell populations in the lungs. In vitro studies demonstrated that macrophages from non-infected mice produce IL-1 and TNF activities in response to live influenza A virus stimulation. These results suggest that a direct interaction between virus and alveolar macrophages leads to IL-1 and TNF production during the course of infection and could account for both the immune responses and the pathology that occur during influenza A virus infection.

Animals↗
PubMed1988

Specific binding characteristics of high affinity monoclonal antidigitoxin antibodies.

The specificity of various monoclonal antidigitoxin antibodies was characterized using 6 cardiac glycoside analogs. Spleen cells from BALB/c mice, immunized with BSA- or KLH-digitoxin conjugates, were fused with NS1 myeloma cells, and antibody-producing hybrids were identified by radioimmunoassay. Twenty-one monoclonal antidigitoxin-specific antibodies were obtained, 10 of which were cloned and characterized for affinity and specificity. All the antibodies had a high affinity constant, ranging from 8.10(8) to 2.5.10(10) 1/M. On the basis of their binding specificities, the antibodies could be classified into 3 groups: the first contained 7 antibodies exhibiting high cross reactivity (42-100%) with digitoxigenin, whereas the second and third groups did not recognize this analog (cross-reactivity of 1%). In the former group, the absence of the sugar moiety only slightly affected the binding reaction, although for the two other groups, this structure did appear to be involved in antibody recognition. Changes in the functional groups of the hapten molecule led to considerable changes in the antibody-antigen reaction. For all the antibodies except one, saturation of the lactone ring considerably affected binding. These results demonstrated that monoclonal antibodies of different specificities with respect to both the steroid backbone and the sugar moiety of digitoxin can be induced using a digitoxin-protein conjugate.

Animals↗
PubMed1987

Effects of RU 41740 aerosol treatment on mouse bronchoalveolar cells, and protection afforded against influenza virus infection.

RU 41740, an immunomodulating compound extracted from Klebsiella pneumoniae, was previously shown to enhance mice resistance to bacterial and viral lung infections. To explore lung defense mechanisms, we studied the influence of RU 41740 aerosol treatment on the bronchoalveolar cell populations. Five successive daily RU 41740 aerosol treatments induced a large accumulation of leukocytes in the lungs 4h after the last treatment. Polymorphonuclear leukocytes predominated. The numbers of lymphocytes and monocytes rose significantly. A single RU 41740 aerosol treatment significantly raised the number of polymorphonuclears only. A luminol-dependent chemiluminescence assay was used to test the effect of RU 41740 on the opsonized zymosan induced response of alveolar macrophages. In vitro, addition of RU 41740 enhanced this chemiluminescence. After a single RU 41740 aerosol treatment of mice, the chemiluminescence of purified alveolar macrophages from these mice increased significantly. The protective effect of five daily RU 41740 aerosol treatments against influenza virus infection was believed to be due to the great intensity of the cellular response and the polymorphonuclear influx. The alveolar macrophage activation observed might also explain the enhanced resistance of mice to influenza virus infection.

Adjuvants, Immunologic↗
PubMed1987

Enhancement of bronchoalveolar cell recovery and stimulation of alveolar macrophage chemiluminescence and resistance to influenza virus after treatment with RU 41821 aerosol.

Aerosol treatment with RU 41821, a glycoprotein extract from Klebsiella pneumoniae, was tested in mice for its effect on the kinetics of the induction of bronchoalveolar cells (i.e., alveolar macrophages, monocytes, lymphocytes, and polymorphonuclear leukocytes). RU 41821 led to an increase in the total number of bronchoalveolar cells. The largest increase was observed for polymorphonuclear leukocytes, and more moderate increases occurred in the numbers of alveolar macrophages, monocytes, and lymphocytes. The alveolar macrophages recruited in response to RU 41821 were activated, as indicated by luminol-dependent chemiluminescence in response to stimulation by opsonized zymosan. The effects of five RU 41821 aerosol treatments and those of a single treatment were further examined in vivo by aerosol infection of mice inoculated with a mouse-pathogenic influenza virus. The maximum protective effect was obtained after five once-a-day treatments and was correlated with the largest increase in the total number of bronchoalveolar cells.

Aerosols↗