Biomedical subjects

Patrice André

Publications and source records attributed to Patrice André.

13 recordsLinked to original sources

PubMed2006

1-Methyl-tryptophan can interfere with TLR signaling in dendritic cells independently of IDO activity.

The compound 1-methyl-tryptophan (1-MT) is a competitive inhibitor of IDO that can break tolerance and induce fetus, graft, and tumor rejection. Because of its broad effect on immune-related mechanisms, the direct action of 1-MT on human monocyte-derived dendritic cells (DC) was analyzed. It is shown here that the effect of 1-MT on DC is dependent on the maturation pathway. Although 1-MT had no effect on DC stimulated by the TLR3 ligand poly(I:C), it strongly enhanced the Th1 profile of DC stimulated with TLR2/1 or TLR2/6 ligands. Drastic changes in the function of DC stimulated by the TLR4 ligand LPS were induced by 1-MT. These cells could still activate allogeneic and syngeneic T cells but stimulation yielded T cells secreting IL-5 and IL-13 rather than IFN-gamma. This action of 1-MT correlated with an increased phosphorylation of p38 and ERK MAPKs and sustained activation of the transcription factor c-Fos. Inhibiting p38 and ERK phosphorylation with synthetic inhibitors blocked the effect of 1-MT on LPS-stimulated DC. Thus, 1-MT can modulate DC function depending on the maturation signal and independently of its action on IDO. This is consistent with previous observations and will help further understanding the mechanisms of DC polarization.

Cell Differentiation↗

PubMed2006

Preferential association of Hepatitis C virus with apolipoprotein B48-containing lipoproteins.

Hepatitis C virus (HCV) in cell culture has a density comparable to that of other members of the family Flaviviridae, whereas in vivo infectious particles are found partially in low-density fractions, associated with triacylglycerol (TG)-rich lipoproteins (TRLs). In the blood of infected patients, HCV circulates as heterogeneous particles, among which are lipo-viroparticles (LVPs), globular particles rich in TG and containing viral capsid and RNA. The dual viral and lipoprotein nature of LVPs was addressed further with respect to apolipoprotein composition and post-prandial dynamic lipid changes. The TRLs exchangeable apoE, -CII and -CIII, but not the high-density lipoprotein apoA-II, were present on LVPs, as well as the viral envelope proteins. apoB100 and -B48, the two isoforms of the non-exchangeable apoB, were represented equally on LVPs, despite the fact that apoB48 was barely detectable in the plasma of these fasting patients. This indicates that a significant fraction of plasma HCV was associated with apoB48-containing LVPs. Furthermore, LVPs were enriched dramatically and rapidly in triglycerides after a fat meal. As apoB48 is synthesized exclusively by the intestine, these data highlight the preferential association of HCV with chylomicrons, the intestine-derived TRLs. These data raise the question of the contribution of the intestine to the viral load and suggest that the virus could take advantage of TRL assembly and secretion for its own production and of TRL fate to be delivered to the liver.

Apolipoprotein B-48↗

PubMed2005

Lysophosphatidylcholine is a natural adjuvant that initiates cellular immune responses.

The discovery of new adjuvants that can stimulate the immune response to protein antigens is a major issue for the development of subunit vaccines. Lipoprotein oxidation occurring during the acute phase response (APR) to aggression of the organism, provides signals of danger that are detected by dendritic cells (DC). Among other instructive molecules generated during the APR, lysophosphatidylcholine (LPC) promotes mature DC generation from differentiating human monocytes in vitro. It is shown here that LPC also controls the initiation of an adaptive immune response in vivo. LPC displays adjuvant properties when injected to mice in mixture with various antigens. Immunizations with LPC induced the production of antigen-specific antibodies with an efficiency similar to Alum, the reference adjuvant for human vaccination. Importantly, LPC also induced cytotoxic T cell responses, opening perspectives for vaccine development. Therefore, LPC is a natural adjuvant for the immune system, inducing humoral and cellular immune responses.

Adjuvants, Immunologic↗

PubMed2005

French national sentinel survey of antiretroviral drug resistance in patients with HIV-1 primary infection and in antiretroviral-naive chronically infected patients in 2001-2002.

OBJECTIVE: To survey the frequency of genotypic antiretroviral resistance and the spread of non-B subtypes in patients with primary HIV-1 infection (2001-2002) and in treatment-naive chronically HIV-1-infected patients (2001). METHODS: Plasma samples from 303 patients with acute HIV-1 infection (Primo study) and 363 treatment-naive patients with chronic HIV-1 infection (Odyssee study) were tested for genotypic resistance. Resistance mutations were identified from the International AIDS Society Resistance Testing-USA panel and resistant viruses were defined according to the French Agence Nationale de Recherches sur le SIDA (ANRS) resistance algorithm. RESULTS: In the Primo study, 14% of the patients had viruses with resistance mutations and 12% of patients had viruses with mutations conferring resistance to least 1 antiretroviral drug. Thirty patients had viruses with mutations to at least 1 antiretroviral drug in a single pharmacologic class. Six patients were infected by viruses resistant to 2 or 3 classes of drugs. In the Odyssee study, the prevalence of reverse transcript (RT) associated and major protease inhibitor-associated mutations was 6.1% (95% CI: 3.6-8.6). Six patients had viruses resistant to at least 1 antiretroviral drug and 3 patients had viruses resistant to 2 classes of antiretroviral drugs. Twenty-four percent of acutely infected patients harbored non-B subtype strains (19% in 1999-2000) and 33.2% of chronically infected patients (10% in 1998; P < 0.0001). CONCLUSION: In France, the frequency of HIV-1 resistance in untreated patients was not significantly higher in 2001-2002 than in previous surveys while the prevalence of non-B subtypes is increasing.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Hepatitis C virus particles and lipoprotein metabolism.

The majority of infectious hepatitis C particles are present in the low-density fractions from plasma of infected patients, suggesting an association of the virus with lipoproteins and the use of lipoprotein receptors for cell entry. Although classical hepatitis C virus (HCV) virions have been reported by some investigators, their role in the HCV life cycle has not been clearly identified. Moreover, two other forms of particles have been characterized: low-density lipo-viro-particles (LVPs) and high-density particles. The latter are nonenveloped nucleocapsids that have immunoglobulin G Fcgamma binding capacity. LVPs are spherical particles enriched in triglycerides. At a minimum, they contain apolipoprotein B, HCV RNA, and core protein. The main source of LVPs is likely to be the enterocytes rather than the hepatocytes, suggesting an interaction between chylomicron and LVP assembly. In experimental systems, HCV core protein inhibits the microsomal triglyceride transfer protein, binds to apolipoprotein AII, and induces accumulation of cytoplasmic lipid droplets. A model of LVP and HCV core-lipid droplet generation is proposed.

Hepacivirus↗

PubMed2004

Strand specific quantitative real-time PCR to study replication of hepatitis C virus genome.

Qualitative detection of negative hepatitis C virus (HCV) RNA has been used widely to demonstrate HCV replication. However, relative quantitation of both positive and negative HCV RNA strands has never been reported for studying viral genome replication. A strand specific real-time PCR carried out in the highly conserved 5'-non-coding region of HCV genome and monitored either by the DNA binding dye SYBR Green I or by molecular beacons is described. Using these techniques, it was found that negative HCV RNA strand was a 100-1000 times less abundant than the positive strand in the liver of HCV infected patients.

5' Untranslated Regions↗

PubMed2004

Sensing environmental lipids by dendritic cell modulates its function.

Because of its oxidative modification during the acute-phase response to an aggression, low density lipoprotein (LDL) can be regarded as a source of lipid mediators that can act both to promote and inhibit inflammation. This can be exemplified by the production of anti-inflammatory oxidized fatty acids and proinflammatory lysophosphatidylcholine (LPC) during LDL oxidation. We have shown previously that oxidized LDL (oxLDL) plays an active role at the interface between innate and adaptive immunity by delivering instructive molecules such as LPC, which promotes mature dendritic cell (DC) generation from differentiating monocytes. It is shown in this study that LPC affects the signaling pathway of peroxisome proliferator-activated receptors (PPARs). LPC-induced DC maturation is associated with complete inhibition of PPARgamma activity and up-regulation of the activity of an uncharacterized nuclear receptor that bind peroxisome proliferator response element. Oxidized fatty acids generated during LDL oxidation are natural ligands for PPARgamma and inhibit oxLDL- and LPC-induced maturation. Inhibition experiments with synthetic PPARgamma ligands suggested a PPARgamma-dependent and independent effect of LPC on DC maturation. Therefore, the relative amount of oxidized fatty acids and LPC influences the immunological functions of oxLDL on DC, in part by regulating the PPAR pathway. By sensing the biochemical composition of lipoprotein particles, the innate immune system may thus identify various endogenous signals that influence the immune response during the acute-phase reaction. The therapeutic emulsion intralipid also blocks LPC action on PPAR activity and DC maturation. Intralipid may thus be an alternative therapeutic strategy for some chronic inflammatory diseases.

Acute-Phase Proteins↗

PubMed2004

Secretory phospholipase A2 induces dendritic cell maturation.

High level of phospholipase A(2) (PLA(2)) activity is found in serum and biological fluids during the acute-phase response (APR). Extracellular PLA(2) in fluids of patients with inflammatory diseases such as sepsis, acute pancreatitis or rheumatoid arthritis is also associated with propagation of inflammation. PLA(2) activity is involved in the release of both pro- and anti-inflammatory lipid mediators from phospholipids of cellular membranes or circulating lipoproteins. PLA(2) may thus generate signals that influence immune responses. Here, group III secretory PLA(2) were tested for their ability to promote generation of functionally mature human dendritic cells (DC). PLA(2) treatment of differentiating monocytes in the presence of granulocyte/macrophage colony-stimulating factor and IL-4 yielded cells with phenotypical and functional characteristics of mature DC. This maturation was dependent on the dose of PLA(2), and PLA(2)-generated DC stimulated IFN-gamma secretion by allogeneic T cells. The effects of PLA(2) on DC maturation was mainly dependent on enzyme activity and correlated with the activation of NF-kappaB, AP-1 and NFAT. The data suggest that transient increase in PLA(2) activity generates signals that promote transition of innate to adaptive immunity during the APR.

Catalytic Domain↗

PubMed2004

Failure and success of HIV tests for the prevention of HIV-1 transmission by blood and tissue donations.

French blood banks recently implemented nucleic acid testing (NAT) of all blood donations to reduce the risk of HIV transmission during the pre-seroconversion period. For tissue donation, HIV infection screening relies on HIV p24 antigen and anti-HIV-1 and 2 antibody detection. In this report, two related cases of infectious donations are described from a cornea donor during the preseroconversion window who was infected by an HIV antibody and NAT negative blood donor. After investigation, the blood donor was found to be herself in the preseroconversion window. Two months after donation, she was found to be HIV positive. The residual risk of HIV infectious blood donations since NAT has been introduced is estimated to be lower than one out of 2.5 millions. Individual NAT instead of minipool testing would not increase significantly the blood transfusion safety. In contrast, introduction of NAT should be considered to increase tissue donation safety as soon as such screening will be possible technically.

Aged↗

PubMed2004

Expression of hepatitis C virus proteins in epithelial intestinal cells in vivo.

Previous work on hepatitis C virus (HCV) led to the discovery of a new form of virus particle associating virus and lipoprotein elements. These hybrid particles (LVP for lipo-viro-particles) are enriched in triglycerides and contain at least apolipoprotein B (apoB), HCV RNA and core protein. These findings suggest that LVP synthesis could occur in liver and intestine, the two main organs specialized in the production of apoB-containing lipoprotein. To identify the site of LVP production, the genetic diversity and phylogenetic relationship of HCV quasispecies from purified LVP, whole serum and liver biopsies from chronically infected patients were studied. HCV quasispecies from LVP and liver differed significantly, suggesting that LVP were not predominantly synthesized in the liver but might also originate in the intestine. The authors therefore searched for the presence of HCV in the small intestine. Paraffin-embedded intestinal biopsies from 10 chronically HCV-infected patients and from 12 HCV RNA-negative controls (10 anti-HCV antibody-negative and two anti-HCV antibody-positive patients) were tested for HCV protein expression. HCV NS3 and NS5A proteins were stained in small intestine epithelial cells in four of the 10 chronically infected patients, and not in controls. Cells expressing HCV proteins were apoB-producing enterocytes but not mucus-secreting cells. These data indicate that the small intestine can be infected by HCV, and identify this organ as a potential reservoir and replication site. This further emphasizes the interaction between lipoprotein metabolism and HCV, and offers new insights into hepatitis C infection and pathophysiology.

Adult↗

PubMed2003

Sensitive and reliable JC-1 and TOTO-3 double staining to assess mitochondrial transmembrane potential and plasma membrane integrity: interest for cell death investigations.

BACKGROUND: Apoptosis is currently studied by flow cytometry with mitochondrial membrane potential (Deltapsimt) and membrane integrity fluorochromes. Rhodamine 123 and DiOC6(3) remain controversial to identify cells displaying a low Deltapsimt. JC-1 constitutes a good Deltapsimt indicator, due to a fluorescence shift from green to orange emission, according to the increase in Deltapsimt. Nevertheless, it is not feasible to analyze it simultaneously with propidium iodide. Among available fluorescent probes, TOTO-3 seems to be a good candidate for double staining with JC-1. METHODS: Cell death of HaCaT cells was induced by H2O2 and FasL. Samples were stained with DiOC6(3)/IP or JC-1/TOTO-3 then analyzed by flow cytometry. Results were supported by confocal microscopy analyses of mitochondrial membrane potential. Moreover, cell morphology was determined on the sorted subpopulations defined on the basis of staining (JC-1 versus TOTO-3). RESULTS: We found that JC-1 is a more efficient mitochondrial probe than DiOC6(3). After stress induction, the fluorescence level of JC-1 and TOTO-3 clearly defined three fluorescent subpopulations, respectively: (1) JC-1high and TOTO-3low, (2) JC-1low and TOTO-3medium, and (3) JC-1low and TOTO-3high. Their morphologic aspects after cell sorting indicated that they corresponded to three functional states (intact, apoptotic, and necrotic cells), and data were supported by caspase activity measurements. CONCLUSIONS: We propose a reliable and efficient staining, with JC-1 and TOTO-3 to discriminate three functional cellular states: intact, apoptotic, and necrotic/late apoptotic cells by flow cytometry.

Apoptosis↗

PubMed2002

Mature dendritic cell generation promoted by lysophosphatidylcholine.

During the acute phase response, the interplay between high density lipoproteins and low density lipoproteins (LDL) favors transient generation of oxidized LDL with proinflammatory activities. We hypothesized that oxidative modification of LDL is an endogenous signal for the immune system, and we have shown that oxidized LDL promotes mature dendritic cell transition from monocyte, therefore linking the nonspecific acute phase response to adaptive immunity. Lysophosphatidylcholine (LPC) is a major lipid component of oxidized LDL with reported proinflammatory activities. We now report that LPC acts through G protein-coupled receptors on differentiating monocytes to generate mature dendritic cells with the ability to stimulate IL-2 and IFN-gamma production by allogeneic T lymphocytes. LPC is most effective in lipoprotein-deprived serum and can be inhibited by an excess of native LDLs reflecting normal plasma conditions. Therefore, by controlling the balance between native and oxidized lipoproteins and the resulting production of LPC, the acute phase reactants may provide a context of Ag presentation that is transiently favorable to immune activation. Intralipid, a therapeutic lipid emulsion for parenteral nutrition with unexplained immunomodulatory properties, also blocked LPC activity. This opens perspectives for the understanding and treatment of acute and chronic inflammatory diseases.

Acute-Phase Reaction↗

PubMedDate not supplied

Skin ageing: clinical and histopathologic study of permanent and reducible wrinkles.

Wrinkles are modifications of the skin associated with cutaneous ageing and develop preferentially on sun-exposed skin. The aim of the study was to analyse the clinicopathological features of wrinkles, among the different types of skin relief modifications. Despite its importance in dermato-cosmetology and skin ageing, few studies have been specifically devoted to wrinkles. In the present study, we analyzed the histological features of the pre-auricular wrinkle compared to retro-auricular skin, obtained from sixteen patients undergoing facial surgery; skin samples were immediately processed for routine histology and histochemical staining. Four types of skin depressions could be defined according to their depth: folds, permanent wrinkles, reducible wrinkles and skin micro-relief. Two different types of pre-auricular wrinkles were observed: (i) permanent wrinkles which were conserved after sampling and, (ii) reducible wrinkles which required in vivo staining to be visible at histology. Histological analysis of the epidermis and dermis of the skin forming the pre-auricular wrinkle revealed a normal skin morphology, identical to that of the skin immediately adjacent to the wrinkle. This was particularly striking for the reducible wrinkles which could not be individualized in the absence of in vivo staining. Both types of wrinkles comprised skin modifications observed in sun-exposed skin, however, in the upper dermis, permanent wrinkles showed a more pronounced accumulation of basophilic fibers, i.e. actinic elastosis, than reducible wrinkles did. These data suggest that the development of wrinkles could be secondary to actinic elastosis and to the disappearance of microfibrils and collagen fibers at the dermal-epidermal junction.

Adult↗