Academic literature on the topic 'Toll-like receptor 7 a 9 (TLR7'

Objective. The study aimed at locating and quantifying Toll Like Receptor (TLR) 3, 7, 8, and 9 expression in kidney of patients with lupus nephritis (LN) and correlating them with clinicopathological features.Methods. Kidney sections from 26 LN patients and 4 controls were analyzed by immunohistochemistry using anti-human TLR3, TLR7, TLR8, and TLR9 polyclonal antibodies; the number of TLR-positive nuclei/mm2was evaluated on digitalized images.Results. Compared to controls, LN showed a significantly higher amount of glomerular and tubulointerstitial TLR9 (p=0.003andp=0.007), whole and tubulointerstitial TLR3 (p=0.026andp=0.031), and a higher tubulointerstitial TLR7 (p=0.022). TLR9 positively correlated with activity index (p=0.0063) and tubular TLR7 with chronicity index (p=0.026). TLR9 positively correlated with Renal-SLEDAI (p=0.01).Conclusions. This is the first study quantifying kidney expressions of TLRs in LN patients; the results show an overexpression of TLR3, TLR7, and TLR9 and demonstrate a correlation with clinicopathological indices supporting a role of these mediators in the pathogenesis of LN.

TLRs (Toll-like receptors) are a family of innate immune receptors that induce protective immune responses against infections. Single-stranded viral RNA and bacterial DNA containing unmethylated CpG motifs are the ligands for TLR7 and TLR8 and 9 respectively. We have carried out extensive structure–activity relationship studies of DNA- and RNA-based compounds to elucidate the impact of nucleotide motifs and structures on these TLR-mediated immune responses. These studies have led us to design novel DNA- and RNA-based compounds, which act as potent agonists of TLR9 and TLR7 and 8 respectively. These novel synthetic agonists produce different immune response profiles depending on the structures and nucleotide motifs present in them. The ability to modulate TLR-mediated immune responses with these novel DNA- and RNA-based agonists in a desired fashion may allow targeting a broad range of diseases, including cancers, asthma, allergies and infections, alone or in combination with other therapeutic agents, and their use as adjuvants with vaccines. IMO-2055, our first lead candidate, is a TLR9 agonist that is currently in clinical evaluation in oncology patients. A second candidate, IMO-2125, is also a TLR9 agonist that has been shown to induce high and sustained levels of IFN (interferon) in non-human primates and is being evaluated in HepC-infected human subjects.

Recognition of pathogens by the innate immune system requires proteins that detect conserved molecular patterns. Nucleic acids are recognized by cytoplasmic sensors as well as by endosomal Toll-like receptors (TLRs). It has become evident that TLRs require additional proteins to be activated by their respective ligands. In this study, we show that CD14 (cluster of differentiation 14) constitutively interacts with the MyD88-dependent TLR7 and TLR9. CD14 was necessary for TLR7- and TLR9-dependent induction of proinflammatory cytokines in vitro and for TLR9-dependent innate immune responses in mice. CD14 associated with TLR9 stimulatory DNA in precipitation experiments and confocal imaging. The absence of CD14 led to reduced nucleic acid uptake in macrophages. Additionally, CD14 played a role in the stimulation of TLRs by viruses. Using various types of vesicular stomatitis virus, we showed that CD14 is dispensable for viral uptake but is required for the triggering of TLR-dependent cytokine responses. These data show that CD14 has a dual role in nucleic acid–mediated TLR activation: it promotes the selective uptake of nucleic acids, and it acts as a coreceptor for endosomal TLR activation.

Toll-like receptors (TLRs) 3, 7, and 9 recognize microbial nucleic acids in endolysosomes and initiate innate and adaptive immune responses. TLR7/9 in dendritic cells (DCs) also respond to self-derived RNA/DNA, respectively, and drive autoantibody production. Remarkably, TLR7 and 9 appear to have mutually opposing, pathogenic or protective, impacts on lupus nephritis in MRL/lpr mice. Little is known, however, about the contrasting relationship between TLR7 and 9. We show that TLR7 and 9 are inversely linked by Unc93B1, a multiple membrane-spanning endoplasmic reticulum (ER) protein. Complementation cloning with a TLR7-unresponsive but TLR9-responsive cell line revealed that amino acid D34 in Unc93B1 repressed TLR7-mediated responses. D34A mutation rendered Unc93B1-deficient DCs hyperresponsive to TLR7 ligand but hyporesponsive to TLR9 ligand, with TLR3 responses unaltered. Unc93B1 associates with and delivers TLR7/9 from the ER to endolysosomes for ligand recognition. The D34A mutation up-regulates Unc93B1 association with endogenous TLR7 in DCs, whereas Unc93B1 association with TLR9 was down-regulated by the D34A mutation. Consistently, the D34A mutation up-regulated ligand-induced trafficking of TLR7 but down-regulated that of TLR9. Collectively, TLR response to nucleic acids in DCs is biased toward DNA-sensing by Unc93B1.

ObjectiveHuman papillomavirus oncoproteins E6 and E7 down modulate Toll-like receptor (TLR) 9 expression in infected keratinocytes. We explored the status of expression and function of TLR7, TLR8, and TLR9 in primary human Langerhans cells (LCs) isolated from cervical tumors.MethodologySingle-cell suspensions were made from fresh tissues of squamous cell carcinoma (International Federation of Gynecology and Obstetrics stage IB2); myeloid dendritic cells were purified using CD1c magnetic activated cell separation kits. Langerhans cells were further flow sorted into CD1a+CD207+cells. Acute monocytic leukemia cell line THP-1–derived LCs (moLCs) formed the controls. mRNA from flow-sorted LCs was reverse transcribed to cDNA and TLR7, TLR8, and TLR9 amplified. Monocyte-derived Langerhans cells and cervical tumor LCs were stimulated with TLR7, TLR8, and TLR9 ligands. Culture supernatants were assayed for interleukin (IL) 1β, IL-6, IL-10, IL-12p70, interferon (IFN) α, interferon γ, and tumor necrosis factor (TNF) α by Luminex multiplex bead array. Human papillomavirus was genotyped.ResultsWe have for the first time demonstrated that the acute monocytic leukemia cell line THP-1 can be differentiated into LCs in vitro. Although these moLCs expressed all the 3 TLRs, tumor LCs expressed TLR7 and TLR8, but uniformly lacked TLR9. Also, moLCs secreted IL-6, IL-1β, and tumor necrosis factor α to TLR8 ligand and interferon α in response to TLR9 ligand; in contrast, tumor LCs did not express any cytokine to any of the 3 TLR ligands. Human papillomavirus type 16 was one of the common human papillomavirus types in all cases.ConclusionsCervical tumor LCs lacked TLR9 expression and were functionally anergic to all the 3: TLR7, TLR8, and TLR9 ligands, which may play a crucial role in immune tolerance. The exact location of block(s) in TLR7 and TLR8 signaling needs to be investigated, which would have important immunotherapeutic implications.

Toll-like receptors (TLRs) play a fundamental role in the inflammatory response against invading pathogens. However, the dysregulation of TLR-signaling pathways is implicated in several autoimmune/inflammatory diseases. Here, we show that a novel small molecule TLR-inhibitor (TAC5) and its derivatives TAC5-a, TAC5-c, TAC5-d, and TAC5-e predominantly antagonized poly(I:C) (TLR3)-, imiquimod (TLR7)-, TL8-506 (TLR8)-, and CpG-oligodeoxynucleotide (TLR9)-induced signaling pathways. TAC5 and TAC5-a significantly hindered the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), reduced the phosphorylation of mitogen-activated protein kinases, and inhibited the secretion of tumor necrosis factor-α (TNF-α) and interleukin-6. Besides, TAC5-a prevented the progression of psoriasis and systemic lupus erythematosus (SLE) in mice. Interestingly, TAC5 and TAC5-a did not affect Pam3CSK4 (TLR1/2)-, FSL-1 (TLR2/6)-, or lipopolysaccharide (TLR4)-induced TNF-α secretion, indicating their specificity towards endosomal TLRs (TLR3/7/8/9). Collectively, our data suggest that the TAC5 series of compounds are potential candidates for treating autoimmune diseases such as psoriasis or SLE.

Abstract Abstract 4071 Introduction. Emerging trends emphasize the importance of both innate and adaptive immune system in the response against infections, and in the pathogenesis of autoimmune and graft-versus-host (GVHD) diseases. Pattern recognition receptors such as Toll-like receptors (TLRs) play a key role in the cross-talk between innate and adaptive immune system. TLRs belong to type I transmembrane glycoprotein receptor family and recognize pathogen-associated molecular patterns (PAMPs), such as common protein, carbohydrate or DNA/RNA pattern motifs. TLRs are also receptors for endogenous ligands and damaged tissue, suggesting that both pathogen-derived molecules and products of damaged tissue can trigger signals which are responsible for the regulation of innate and adaptive immune responses. Extracellular ligands are recognized by surface TLRs (TLR1,TLR2,TLR4,TLR5, and TLR6). Intracellular TLRs (TLR3,TLR7,TLR8 and TLR9) bind mainly to foreign nucleic acids and sometimes detect self DNA/RNA. Aim of the study. Very little is known about expression and function of TLRs in vivo in patients who underwent allogeneic stem cell transplantation (SCT). The aim of this study was to evaluate the expression of TLRs on lymphocytes and monocytes in relation to the onset of acute GVHD. Methods. The expression of TLRs on lymphocytes and monocytes was analysed by flow cytometry as mean fluorescence intensity at day +30 and at the onset of GVHD. Functional data were obtained by ELISA assay after TLRs activation. The cell supernatants were collected and assayed for TNF-alpha, IFN-gamma and MCP-1. Relative induction of these cytokines was calculated in relation with unstimulated controls. Results. We analyzed 17 healthy donors and 34 patients. Median age was 46 years (range, 22–64) and 22 patients were male. Acute GVHD developed in 19 patients (12 with grade >=2). Clinical and transplant characteristics did not differ in patients with and without GVHD. Lymphocytes and monocytes of patients with acute GVHD showed higher levels of TLR5 (3,5±2,3 vs1,9±1,6 p=0,03; 25,8±25,9 vs 9,0±5,0 p=0,02) and a decreased expression of TLR1 (2,5±2,8 vs 4,3±2,8 p=0,02; 21,4±21,9 vs 54,9±37,4 p=0,005) and TLR9 (63,8±30,4 vs 111,1±62,9 p=0,03; 85,3±73,9 vs 164,2±90,6 p=0,01). IFN-gamma relative induction post-stimulation of TLR2,3,4 and 9 was significantly decreased in patients with acute GVHD (p< 0,04). Conclusions. TLRs show a different profile of expression in patients with acute GVHD in comparison with patients without it. These results suggest that the innate immune response via TLRs activation could be involved in the development of GVHD. In particular, a decreased expression of TLR-9 (receptor of hypomethylated DNA) on lymphocytes and monocytes can promote TLR-7 activation, inducing type I interferons and other pro-inflammatory cytokines. TLR-1 and −5, which are ligands for bacterial cell wall, could also be involved in the pathogenesis of GVHD. Moreover, acute GVHD negatively correlates with IFN-gamma production upon TLR2,3,4 and 9 activation. The assessment of a larger number of patients could be useful to understand the complex interplay among pathogens, self or non-self DNA and RNA, and the immune system. Disclosures: No relevant conflicts of interest to declare.

ABSTRACT Toll-like receptors (TLRs) are key mediators of innate immunity, and their activation by microbial components leads to the production of cytokines and interferons. Recombinant alpha interferon has been used to treat several viral diseases and is the current standard of care for hepatitis C virus (HCV) infection. Recently, agonists of TLR7 and TLR9 have been shown to have clinical efficacy in HCV patients, and this is correlated with their ability to induce endogenous type I interferon production. We have carried out a comprehensive study of agonists of TLRs 1 to 9 to determine if any additional TLRs can induce antiviral molecules from human peripheral blood mononuclear cells (PBMCs). The agonists were incubated with PBMCs, and the supernatant was then removed and added to HCV replicon cells to assess antiviral activity. Agonists of TLRs 3, 4, 7, 8, and 9 were found to be potent inducers of antiviral activity in PBMC supernatants, and the activity correlated with the induction of alpha interferon and the interferon-induced antiviral biomarker 2′,5′-oligoadenylate synthase. Antiviral activity of TLR7 and TLR8 agonists was blocked by an antibody that binds to the type I interferon receptor, confirming that the antiviral activity results from type I interferon induction. TLR4 and TLR8 agonists were found to strongly induce the proinflammatory cytokines interleukin 1β and tumor necrosis factor alpha at concentrations similar to those inducing antiviral activity. This raises concerns about adverse side effects if these were to be used as antiviral agents. We therefore conclude that TLRs 3, 7, and 9 represent the most attractive targets for the development of new HCV therapies.

Abstract Acute myeloid leukemia (AML) is a common form of acute leukemia and remains a difficult disease with poor survival in patients who have failed standard therapy. New therapeutic strategies are needed to achieve longer survival and improve cure rates in AML patients. Toll-like receptor (TLR) agonists have been shown to elicit anti-leukemia effects in murine AML models. However, TLR expression profile of human AML cells is unknown. We analyzed TLR1-10 mRNA expression in purified AML cells from 41 patients with different AML subtypes (M0, M1, M2, M3, M4, or M5; n &gt; 5 per group) by real-time RT-PCR. The majority of AML samples expressed high level of TLR2, 4, 7, 8, low level of TLR1, 5, 9, 10, and undetectable level of TLR3. Significant higher TLR4 and TLR7 expressions were detected on M4 and M5 subtypes of AML cells. Triggering TLR4 or TLR7 with specific TLR agonists (Monophosphoryl Lipid A or Imiquimod) significantly increased the surface expression of molecules essential for T cell activation (CD54, CD80, CD86) on AML M4/M5 cells and enhanced T-cell mediated proliferative responses against AML cells. Thus, TLR signaling enhances the immunogenicity of AML M4/M5 cells and makes them more suitable targets for T cell mediated attack. Most importantly, TLR7 agonist strongly induced apoptotic death of primary AML M4/M5 cells and inhibited the growth of TLR7-expressing AML cell lines (U937, HL-60, KG-1) in culture in a drug dose dependent manner. The addition of TLR7 agonist at 10 ug/ml fully induced apoptosis of AML cells and inhibited the growth of AML cell lines, as confirmed by viable cell counts and TMRE staining. Intracellular staining demonstrated that TLR7 agonist treatment significantly down-regulated the signal transducer and activator of transcription (STAT)3 and STAT5 protein expression in AML cells. These results suggest that TLR7 agonist-induced apoptosis of AML cells is likely via inhibition of STAT3 and/or STAT5 signaling pathway. To study the in vivo effects of TLR7 agonist against human AML cells, primary AML M4/M5 cells or a monocytic AML cell line (U937) were injected i.p. into NOD-SCID IL2Rgamma&lt;null&gt; mice with or without subsequent TLR7 agonist treatment. Mice receiving TLR7 agonist treatment (1 mg/kg daily i.p. infusion for 5 days) significantly reduced tumor burden with substantially lower numbers of engrafted leukemia cells detected in these xenograft mice. Flow cytometry results confirmed that residual AML cells recovered from mice treated with TLR7 agonist were apoptotic with down-regulated expression of TMRE and STAT3/STAT5, confirming previous in vitro findings that TLR7 agonist-treated AML cells are programmed to die. The antitumor efficacy of systemic administration of TLR7 agonist in NOD/SCID mice with established human AML is being investigated using these xenograft mouse models. In summary, our results provide the first report of TLR expression profile of human AML cells and demonstrate that TLR targeting of AML cells can increase the immunogeneicity of leukemia cells and directly induce AML apoptosis in vitro and in vivo, providing new insights into the biology and therapy of AML.

ABSTRACTInnate immune recognition of malaria parasites is the critical first step in the development of the host response. At present, Toll-like receptor 9 (TLR9) is thought to play a central role in sensing malaria infection. However, we and others have observed thatTlr9−/−mice, in contrast to mice deficient in the downstream adaptor, Myeloid differentiation primary response gene 88 (MYD88), exhibit few deficiencies in immune function during early infection with the malaria parasitePlasmodium chabaudi, implying that another MYD88-dependent receptor also contributes to the antimalarial response. Here we use candidate-based screening to identify TLR7 as a key sensor of earlyP. chabaudiinfection. We show that TLR7 mediates a rapid systemic response to infection through induction of cytokines such as type I interferons (IFN-I), interleukin 12, and gamma interferon. TLR7 is also required for induction of IFN-I by other species and strains ofPlasmodium, including an etiological agent of human disease,P. falciparum, suggesting that malaria parasites harbor a common pathogen-associated molecular pattern (PAMP) recognized by TLR7. In contrast to the nonredundant requirement for TLR7 in early immune activation, sensing through both TLR7 and TLR9 was required for proinflammatory cytokine production and immune cell activation during the peak of parasitemia. Our findings indicate that TLR7 plays a central role in early immune activation during malaria infection, whereas TLR7 and TLR9 contribute combinatorially to immune responses as infection progresses.

Les pDC représentent la première ligne de défense de l’organisme contre les pathogènes et établissent le lien essentiel entre l’immunité innée et adaptative. Les pDC endocytent et détruisent les particules virales et ainsi détectent leur matériel génétique grâce à des senseurs antiviraux de la famille des Toll-Like Receptors (TLR). L’activation des TLR7/9 induit la production massive d’interféron de type I (IFN-I), un antiviral puissant indispensable au contrôle de la propagation virale lors des phases aigues de l’infection. Cependant, l’IFN-I peut s’avérer avoir des effets délétères dans un grand nombre d’infections chroniques et de maladies auto-immunes. Ainsi, il semble indispensable de découvrir les mécanismes régulateurs des pDC ainsi que des modulateurs de l’activation des pDC. Nous avons ainsi montré que les monoamines (histamine, dopamine, sérotonine) et les polyamines (spermine et spermidine) inhibent l’activation complète des pDC stimulées par divers virus. Par la suite, nous avons identifié CXCR4 comme étant le récepteur des amines sur les pDC. Ainsi nous avons pu montrer que les amines pouvaient réguler les pDC en passant par CXCR4 et que ce récepteur était un interrupteur d’activation potentiel des pDC lors des infections virales. Afin de comprendre le mécanisme des amines, nous avons développé une nouvelle technologie : la transfection de siRNA dans les pDC primaires humaines. D’autre part, nous avons détecté des cellules géantes multinucléées en forme de roue de bicyclette lorsque les pDC sont cultivées in vitro avec de grandes quantités de virus VIH. Ainsi, comme les monocytes et les macrophages, les pDC peuvent former in vitro des cellules géantes multinucléées exprimant de hauts niveaux de protéines virales p24 de VIH-1. Cependant, les pDC ne sont que très peu infectées (moins de 5%). Nous nous sommes alors demandé si le corécepteur CXCR4 du virus VIH était aussi important que le récepteur CD4 pour la reconnaissance de ce dernier lors de l’activation des pDC
PDC are the first line of defense of our organism against pathogens and establish the essential link between the innate and adaptive immunity. pDC endocyte and destroy the viral particles and thus, detect the genetic material with their antiviral sensors from the Toll-Like Family (TLR). The activation of TLR7/9 induces massive production of type I interferon (IFN-I), a powerful antiviral molecule, essential to control viral propagation during the acute phases of the infection. However, type I IFN can have deleterious effects in a large number of chronic infections and autoimmune diseases. Thus, it seems essential to discover the regulatory mechanism of pDC as well as pDC activation modulators. We showed that monoamines (histamine, dopamine and serotonin) and polyamines (spermine and spermidine) inhibit completely the activation of virus-stimulated pDC. Thus, we showed that amines regulated pDC activation through CXCR4 engagement and that this receptor was a potential switch "on-off" for pDC during viral infections. To better understand the mechanism of action by which amines inhibit pDC activation, we developed a new technology: siRNA transfection in human primary pDC. Furthermore, we detected multinuclear giant cells bearing the shape of a bicycle wheel when pDC are cultured in vitro with high quantities of HIV virus. Thus, on top of monocytes and macrophages, pDC can form in vitro multinuclear giant cells with high levels of p24 viral protein of HIV-1. However, pDC barely get infected (less than 5%). We then wondered if the receptors and co-receptors of the virus were important for the viral recognition during HIV-activation of pDC

Los receptores Toll-like (TLRs), en particular los que se encuentran en vesículas intracelulares de origen endosomal (TLR3, TLR7 y TLR9), están involucrados en la respuesta innata antivírica. La unión a sus respectivos ligandos conduce a la activación de cascadas intracelulares que resultan en una producción de citoquinas pro-inflamatorias (TNF-α) y antivirales (interferones de tipo I). Existe muy poca información sobre la distribución celular y tisular de estos receptores en la especie porcina así como su regulación en condiciones normales o de infección. En el primer estudio de la presente tesis se valoró la distribución tisular de los TLRs endosomales en pulmón y tejidos linfoides primarios y secundarios de cerdos sanos de distintas edades. El marcaje del TLR9 se realizó con un anticuerpo comercial con reactividad específica para el porcino. En cambio, en el caso de TLR3 y TLR7 los anticuerpos se dirigían a las moléculas humanas pero, supuestamente, poseían reactividad cruzada con las moléculas de origen porcino. Los resultados obtenidos permitieron valorar la distribución del TLR9 en los distintos tejidos examinados, pero no la de los TLR3 y TLR7 ya que el uso de los anticuerpos dirigidos frente a estos dos últimos receptores no produjo resultados satisfactorios. Así, el marcaje obtenido con el anticuerpo anti-TLR3 fue muy variable en función del tejido utilizado; es decir, en algunos órganos como el pulmón, tonsila o linfonodos parecía ser específico, pero en otros como en el hígado, producía un intenso color de fondo inespecífico. Por el contrario, sí hubo un marcaje específico para el TLR9 que reveló una expresión constitutiva de dicho receptor en células de la periferia de los folículos linfoides de los linfonodos, la tonsila y las placas de Peyer, (células de tipo epitelial, dendríticas, macrófagos o linfocitos) un hecho que sugería que este receptor probablemente puede jugar un papel importante en la activación el sistema inmunitario de los cerdos a partir de las 3 semanas de vida. El segundo estudio de esta tesis consistió en determinar la variación de la expresión de TLR3, TLR7 y TLR9 a lo largo del tiempo en una población de células presentadoras de antígeno. La población de estudio elegida fue la de macrófagos alveolares porcinos (PAMs). Los resultados de la cinética de expresión mediante citometría de flujo nos mostró que estas células presentaban una expresión basal elevada de TLR3 y TLR9 pero no de TLR7. Una de las explicaciones posibles para este marcaje basal señalaría a la necesaria manipulación de estas células antes de ser congeladas como responsable de esta expresión. Por otra parte, es difícil conocer con exactitud el ambiente en el cual se encontraban los PAMs en el pulmón antes de ser recogidos (concentración de interleuquinas, quimioquinas, otras moléculas, etc). Dado que los animales donantes estaban sanos, no presentaban ningún tipo de lesión pulmonar y eran libres de los patógenos víricos comunes del cerdo (circovirus porcino de tipo 2, influenza A y virus del PRRS entre otros) la causa de esta elevada expresión no está clara. En cuanto a la expresión de TLR7, apenas se pudo detectar una expresión basal en los PAMs utilizados. Para el tercer estudio de esta tesis se buscó un modelo de infección con un virus RNA que pudiera influir en la regulación de estos TLRs y además pudiera añadir nuevos conocimientos respecto a la inmunopatogenia de dicha infección. En el campo de las enfermedades infecciosas del porcino, una de las mayores incógnitas inmunológicas del momento la encontramos en la infección con el virus del PRRS. Los resultados de este estudio demostraron que dos cepas del mismo genotipo del virus del PRRS causaban una regulación diferente del TLR3 y del patrón de citoquinas pro-inflamatorias. En concreto, en los estudios de citometría de flujo, la cepa 3262 al inducir la expresión de TLR3 en PAMs, sobre todo a dosis elevadas (m.o.i=1), activaría la producción de TNF-α+; en cambio, la cepa 3267 o la cepa vacunal DV activaron TLR3 con menor intensidad y no inducirían TNF-α; sugiriendo en definitiva, que la regulación del patrón de citoquinas antivirales o pro-inflamatorias en los macrófagos dependería del tipo de cepa utilizada. Resulta interesante señalar que a pesar de las diferencias observadas en la citometría de flujo respecto el porcentaje de células que expresaban TLR3 y en la intensidad de su expresión según el tipo de virus utilizado, la expresión relativa del mRNA no parecía modificarse. Estas diferencias resultan interesantes y apuntan a que distintas cepas de campo de genotipo europeo podrían ejercer un efecto regulador de diferente intensidad sobre moléculas inhibitorias de la cascada de señalización de los TLRs. Además esta regulación parece depender de diferentes factores tales como: la cepa vírica, el tiempo de infección y la dosis infectiva inicial. Nuestros resultados pueden ser útiles para abrir y conducir una nueva línea de investigaciones orientadas hacia el área de la inmunidad innata frente al virus del PRRS.
Toll-like receptors (TLRs), particularly those found within intracellular vesicles of endosomal origin (TLR3, TLR7 and TLR9), are involved in the innate antiviral responses. Binding of those receptors to their respective ligands leads to the activation of intracellular cascades resulting in the release of pro-inflammatory cytokines (TNF-α) and antiviral (type I) interferons. The knowledge on the distribution of those receptors in porcine organs, tissues and cells and its regulation in physiological states or in infection is scarce. In the first study of the present thesis the distribution of endosomal TLRs in lung and primary and secondary lymphoid tissues of healthy pigs of different ages was assessed. Labeling of TLR9 was performed using a commercial antibody with specific reactivity for the porcine TLR9. For TLR3 and TLR7 the antibodies used in the study were directed to human molecules but they were supposed to cross-react with the porcine counterpart molecules. The results allowed the assessment of the distribution of TLR9 in the different tissues examined, but not that of TLR3 and TLR7 since the use of antibodies directed against the latter two receptors did not yield satisfactory results. Thus, labeling obtained with the anti-TLR3 antibody was highly variable depending on the tissue examined, that is, in some organs such as lungs, tonsils or lymph nodes labeling was apparently specific but in others, as in the liver, the se of that antibody resulted in an intense non-specific background. By contrast, TLR9 labeling was specific and revealed a constitutive expression of this receptor in cells of the periphery of lymphoid follicles of lymph nodes, tonsils and Peyer's patches (epithelial cells, dendritic cells, macrophages or lymphocytes) a fact suggesting that this receptor can probably play an important role in activating the immune system of pigs of 3 week-old piglets. The second study of this thesis was aimed to determine the variation of the expression of TLR3, TLR7 and TLR9 over time in a population of antigen-presenting cells. Porcine alveolar macrophages (PAMs) were used for this purpose. The results of the kinetics of expression as assessed by flow cytometry showed that PAMs had a high basal expression of TLR3 and TLR9 but not of TLR7. A possible explanation for this basal labeling could point to the unavoidable manipulation of PAMs needed for their collection. Moreover, it is difficult to know precisely the environmental conditions in which PAMs were in the lungs before being collected (concentration of interleukins, chemokines, presence of other molecules, etc.). Since PAM donors were healthy, showed no lung lesions and were demonstrated to be free of common viral pathogens of pigs (porcine circovirus type 2, influenza A and PRRS virus among others) the cause of this elevated expression remains unclear. As for TLR7, basal expression in the PAMs used was low or nil. The third study of the present thesis aimed to a model of infection with an RNA virus that might influence the regulation of these TLRs and also could add new knowledge regarding the pathogenesis of the infection. In the field of infectious diseases of swine, one of most interesting models of RNA virus infections is PRRS virus for which immunopathogenesis is largely understood. The results of this study showed that two strains of the same genotype of PRRS virus resulted in a different regulation of TLR3 and in a different pattern of pro-inflammatory cytokines. Specifically, in flow cytometry experiments, strain 3262, induced the expression of TLR3 in PAMs, particularly at high multiplicities of infection (m.o.i = 1) and triggered the production of TNF-α+ whereas strain 3267 or the vaccine strain DV resulted in lower TLR3 expression and did not induce TNF-α, suggesting ultimately that the regulation of the antiviral or pro-inflammatory cytokine patterns in macrophages depends on the strain used. Interestingly, despite the differences observed in flow cytometry for TLR3, the relative mRNA expression did not apparently change under different circumstances. This was an interesting observation that suggests that different field strains of genotype I PRRSV might exert a regulatory effect of different intensity on inhibitory molecules of the signaling cascade of TLRs. Furthermore, this regulation seems to depend on various factors such as the viral strain, the time of infection and the multiplicity of infection. Our results may be useful as a basis for further studies in the area of innate immunity against PRRS virus.

Les récepteurs Toll-like 7 et 8 jouent un rôle important dans l’activation de la réponse immunitaire innée et adaptative. Leur stimulation conduit à la production des cytokines pro-inflammatoires et d’interférons de type I. L’imiquimod et son dérivé le résiquimod sont les premières molécules de faible poids moléculaire décrites comme agonistes du TLR7 et TLR8. Ces deux molécules ont montré des activités anticancéreuses et adjuvantes très importantes. Récemment, les TLR 7 et 8 ont fait l’objet de plusieurs publications visant à développer de nouveaux agonistes TLR7 et/ou TLR8 dans la perspective d’être utilisés comme adjuvants vaccinaux. Malgré les rôles essentiels de TLR7 et TLR8 dans la stimulation du système immunitaire, une activation immunitaire chronique peut être responsable de plusieurs maladies infectieuses et auto-immunes. D’où l’importance de développer également des antagonistes TLR7 et/ou TLR8.Ce travail de thèse est consacré à la synthèse et le développement de nouvelles molécules hétérocycliques, analogues de l’imiquimod et de résiquimod, dans le but d’identifier de nouveaux ligands TLR7 et/ou TLR8. Des voies de synthèse innovantes, permettant une modulation chimique importante grâce à des couplages croisés pallado-catalysés, ont été mises au point et ont permis d’obtenir une cinquantaine de molécules appartenant à trois séries chimiques différentes de type imidazo[1,2-a]pyrazine, imidazo[1,5-a]quinoxaline et pyrazolo[1,5-a]quinoxaline. De nombreux essais d’alkylation ont été tentés sur ces trois séries chimiques afin d’introduire une large variété de substituants sur le cycle à cinq sommets. L’application du couplage croisé de Sonogashira nous a permis d’établir une liaison C-C et introduire diverses chaines alkyles. Ces composés ont été testés pour leur activité agoniste et antagoniste TLR7 et 8. Aucun des composés cibles n'a présenté d’activité agoniste TLR7 et TLR8, dans l'intervalle des concentrations testées. Par contre, tous les composés ont montré une activité antagoniste sélective du TLR7. Les composés les plus actifs, 5.35a et 5.35b, membres de la série pyrazolo[1,5-a]quinoxaline ont montré des IC50 de l’ordre de 10 μM. Ces résultats prometteurs nous ont permis la découverte d’une activité antagoniste TLR7 importante pour la série pyrazolo[1,5-a]quinoxaline, une série très peu développée dans la littérature. La modulation chimique des molécules actives nous permet de donner naissance à de nouveaux leaders, qui peuvent jouer un rôle important dans la thérapie de plusieurs maladies infectieuses et auto-immunes
Toll-like receptors 7 and 8 play an important role in immune system activation. Their stimulation leads to the production of pro-inflammatory cytokines and type I interferons. Both receptors recognize viral ssRNA, as well as synthetic tricyclic imidazoquinoline derivatives such as imiquimod (TLR7 agonist) and resiquimod (TLR7/8 agonist). These two molecules showed significative anti-cancer and adjuvant activities. Many reports in the literature have been focused on the development of new TLR7/8 agonists belonging to different chemical series. These agonists strongly induce the production of T helper 1-polarizing cytokines and may therefore serve as promising candidate vaccine adjuvants. Despite the essential roles of TLR7 and TLR8 in the immune system stimulation, chronic immune activation may be responsible for several infectious and autoimmune diseases. Consequently, the development of TLR7 inhibitors may play an important role in the therapy of these diseases.In this study, we are interested in the synthesis and development of new heterocyclic molecules, analogs of imiquimod and resiquimod, in order to identify new TLR7 and/or TLR8 ligands. Different synthetic pathways have been developed, using cross coupling reactions, in order to obtain a wide variety of molecules belonging to three chemical series: imidazo[1,2-a]pyrazine, imidazo[1,5-a]quinoxaline et pyrazolo[1,5-a]quinoxaline. Various alkylation reactions were attempted on these three chemical series in order to introduce a wide variety of substituents on the five-membered ring. The application of Sonogashira's cross-coupling allowed us to establish a C-C bond and introduce various alkyl chains. All compounds have been tested for their TLR7/8 agonistic and antagonistic activity using HEK-Blue™-hTLR7/8 cells. The synthesized compounds are completely inactive as TLR7/8 agonists and are selective TLR7 antagonists. Two compounds of the pyrazolo[1,5-a]quinoxaline series, compound 5.35a and 5.35b, bearing butyl and isobutyl chain respectively, are potent and selective TLR7 antagonists with low micromolar IC50. Results allowed us to discover significative activity for the pyrazolo[1,5-a]quinoxaline series as selective TLR7 antagonists, which may therefore play an important role in the therapy of several infectious or autoimmune diseases

Les interférons de type I (IFN-I) peuvent être produits par toutes les cellules mais les rares cellules dendritiques plasmacytoïdes en sont les principales cellules productrices. L’IFNa orchestre de nombreux mécanismes pathogéniques dans l’infection par le virus de l’immunodéficience humaine de type 1 (VIH-1). L’étude de modèles physiologiques et pathophysiologiques peut fournir des informations cruciales sur les moyens d’exploiter la signalisation de l’IFNa dans un but thérapeutique. Les pDCs de femmes produisent plus d’IFNa en réponse à la stimulation du récepteur Toll-like 7 (TLR7) que les pDCs d’hommes. Les mécanismes impliqués dans cette différence n’ont été que partiellement identifiés. Nous démontrons ici un mécanisme par lequel la plus forte expression d’IRF5 dans les pDCs chez les sujets sains féminins, sous le contrôle d’ERa, participe à leur production plus élevée d’IFNa en réponse à TLR7. La co-infection par le virus de l’hépatite C (VHC) est aujourd’hui l’une des principales causes de mortalité parmi les individus infectés par le VIH-1. Nous avons émis l’hypothèse que l’activation immunitaire chronique plus élevée rapportée chez des individus co-infectés par le VIH-1 et VHC pourrait être due à un dysfonctionnement de la voie de TLR7/IFN-I dans les pDCs. Nos données montrent que le VHC entraîne, chez des individus infectés par le VIH-1, des altérations associées aux pDCs et à l’IFNa, qui sont associées ˆ la sévérité de la maladie hépatique. Nos résultats suggèrent que les patients co-infectés par le VIH-1 et le VHC, même à fibrose minime, pourraient bénéficier d’un traitement plus précoce
Type I interferons (IFN) can be produce by any cell type but plasmacytoid dendritic cells (pDC) are the main producers. IFNa orchestrates multiple pathogenic mechanisms in human immunodeficiency virus 1 (HIV-1). Studying physiological and pathophysiological model scan provide critical informations on how to harness IFNa signaling for therapeutic purposes. pDCs from females produce more IFNa upon Toll-like receptor (TLR) 7 stimulation than pDCs from males. The mechanisms underlying such difference have only been partially identified. We demonstrate here a mechanism by which increased IRF5 expression in females, under the control of the esrogen receptor a, contribute to increased IFN? production upon TLR7 stimulation. HCV co-infection is one of the major cause of mortality among HIV-1 infected individuals. We hypothesized that increased chronic immune activation observed in HCV-HIV-1 co-infected individuals may be related to altered TLR7/IFNa signaling in pDCs. Our data show that HCV triggers alterations in pDCs and IFNa signaling in HIV-1 co-infected individuals, which are associated to hepatic disease severity. Our results suggest that HCV-HIV-1 co-infected individuals, even with minimal fibrosis, may benefit from ealier treatment initiation

Albert Font Haro ABSTRACT Modulation of plasmacytoid dendritic cell function: role of immunoreceptors TIM-3 and BDCA-2 Plasmacytoid dendritic cells (pDCs) are key players in the antiviral response as well as in linking innate and adaptive immune response. They express endosomal toll-like receptors 7 and 9, which can detect ssRNA and unmethylated CpG DNA, respectively. Due to the constitutive expression of the transcription factor IRF7, pDCs are able to rapidly produce massive quantities of type I (α, β, ω) and type III (1, 2, 3, 4) interferons (IFN-I and IFN-III) as well as pro- inflammatory cytokines such as IL-1, IL-6 and TNF-α. After maturation, they also function as antigen-presenting cells. Despite intense research, the mechanisms of IFN and pro-inflammatory cytokines production and regulation are still poorly understood. Using the pDC cell line GEN2.2 and also primary human pDCs, we shed light on the role of kinases MEK and SYK in IFN-I production and regulation. We found that SYK is not only involved in the regulatory receptor (RR)-mediated BCR-like pathway that represents the negative regulation of IFN-I and IFN-III secretion but also in the positive TLR7/9-mediated signal transduction pathway that leads to IFN-I production, representing the immunogenic function. We also found that MEK plays a...