Search

International audience; Systemic lupus erythematosus (SLE) is a heterogeneous disease in which excessive inflammation, autoantibodies and complement activation lead to multisystem tissue damage. The contribution of the individual genetic composition has been extensively studied, and several susceptibility genes related to immune pathways that participate in SLE pathogenesis have been identified. It has been proposed that SLE takes place when susceptibility factors interact with environmental stimuli leading to a deregulated immune response. Experimental evidence suggests that such events are related to the failure of T-cell and B-cell suppression mediated by defects in cell signalling, immune tolerance and apoptotic mechanism promoting autoimmunity. In addition, it has been reported that dendritic cells (DCs) from SLE patients, which are crucial in the modulation of peripheral tolerance to self-antigens, show an increased ratio of activating/inhibitory receptors on their surfaces. This phenotype and an augmented expression of co-stimulatory molecules is thought to be critical for disease pathogen-esis. Accordingly, tolerogenic DCs can be a potential strategy for developing antigen-specific therapies to reduce detrimental inflammation without causing systemic immunosuppression. In this review article we discuss the most relevant data relative to the contribution of DCs to the triggering of SLE.

Dendritic cells (DCs) play a key role in the activation of the immune response against pathogens, as well as in the modulation of peripheral tolerance to self-antigens (Ags). Furthermore, an imbalance in the activating/inhibitory receptors expressed on the surface of DCs has been linked to increased susceptibility to develop autoimmune diseases underscoring their immunogenicity potential. It has been described that modulation of activating or inhibitory molecules expressed by DCs, such as CD86, TLRs, PDL-1 and FcγRs, can define the immunogenic phenotype. On the other hand, T cell tolerance can be achieved by tolerogenic DCs, which have the capacity of blocking undesired autoimmune responses in several experimental models, mainly by inducing T cell anergy, expansion of regulatory T cells and limiting B cell responses. Due to the lack of specific therapies to treat autoimmune disorders and the tolerogenic capacity of DCs shown in experimental autoimmune disease models, autologous tolDCs are a potential therapeutic strategy for fine-tuning the immune system and reestablishing tolerance in human autoimmune diseases. New advances in the role of DCs in systemic lupus erythematosus (SLE) pathogenesis and the identification of pathogenic self-Ags may favor the development of novel tolDC based therapies with a major clinical impact. In this review, we discuss recent data relative to the role of DCs in systemic autoimmune pathogenesis and their use as a therapy to restore tolerance. Fil: Mackern Oberti, Juan Pablo. Pontificia Universidad Católica de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; Argentina Fil: Llanos, Carolina. Pontificia Universidad Católica de Chile; Chile Fil: Vega, Fabián. Pontificia Universidad Católica de Chile; Chile Fil: Salazar-Onfray, Flavio. Universidad de Chile; Chile Fil: Riedel, Claudia A.. Universidad Andrés Bello; Chile. Inserm; Francia Fil: Bueno, Mirian Susana. Pontificia Universidad Católica de Chile; Chile. Inserm; Francia Fil: Kalergis, Alexis. Pontificia Universidad Católica de Chile; Chile. Inserm; Francia

International audience; Thyroid hormones (THs) during pregnancy contribute significantly to cellular differentiation and development in several tissues of the offspring, principally the central nervous system (CNS). TH deficiencies, such as hypothyroidism or hypothyroxinemia, are highly frequent during pregnancy worldwide and known to be detrimental for the development of the fetus. The function of CNS in the offspring gestated under TH deficiency will be irreversible impaired, causing low intellectual quotient, attention deficit, and mental retardation. On the other hand, little is known about the effects of TH deficiency in the offspring immune system, being the prevalent notion that the effects are reversible and only for a while will affect the number of B and T cells. Recent studies have shown that maternal hypothyroidism can altered the function of immune system in the offspring, rendering the female offspring more susceptible to suffer autoimmune-inflammatory diseases, such as experimental autoimmune encephalomyelitis (EAE) and to be more resistant to a bacterial infection. In this article we discuss these recent findings, as well as the possible mechanisms underlying these effects and the potential implications for human health.

International audience; Human respiratory syncytial virus (hRSV) is the leading cause of infant hospitalization related to respiratory disease. Infection with hRSV produces abundant infiltration of immune cells into the airways, which combined with an exacerbated pro-inflammatory immune response can lead to significant damage to the lungs. Human RSV re-infection is extremely frequent, suggesting that this virus may have evolved molecular mechanisms that interfere with host adaptive immunity. Infection with hRSV can be reduced by administering a humanized neutralizing antibody against the virus fusion protein in high-risk infants. Although neutralizing antibodies against hRSV effectively block the infection of airway epithelial cells, here we show that both, bone marrow-derived dendritic cells (DCs) and lung DCs undergo infection with IgG-coated virus (hRSV-IC), albeit abortive. Yet, this is enough to negatively modulate DC function. We observed that such a process is mediated by Fcc receptors (FcγRs) expressed on the surface of DCs. Remarkably, we also observed that in the absence of hRSV-specific antibodies FcγRIII knockout mice displayed significantly less cellular infiltration in the lungs after hRSV infection, compared with wild-type mice, suggesting a potentially harmful, IgG-independent role for this receptor in hRSV disease. Our findings support the notion that FcγRs can contribute significantly to the modulation of DC function by hRSV and hRSV-IC. Further, we provide evidence for an involvement of FcγRIII in the development of hRSV pathogenesis.

International audience; Respiratory Syncytial Virus (RSV) is the first cause of hospitalization due to bronchiolitis in infants. RSV bronchiolitis has been linked to asthma and recurrent wheezing, however the mechanisms behind this association have not been elucidated. Here, we evaluated the cytokine and chemokine profiles in the airways in infants with RSV bronchiolitis. Nasopharyngeal Aspirates (NPA) and Bronchoalveolar Lavage Fluids (BALF) from infants hospitalized due to RSV bronchiolitis and healthy controls were analyzed for cytokine and chemokine production. We observed elevated levels of Th2 cytokines (IL-3, IL-4, IL-10 and IL-13), pro-inflammatory cytokines and chemokines (IL-1β, IL-6, TNF-β, MCP-1/CCL2, MIP-1α/CCL3 and IL-8/CXCL8) in BALF from infants with RSV bronchiolitis, as compared to controls. We found a direct correlation of IL-3 and IL-12p40 levels with the development of recurrent wheezing later in life. These results suggest that IL-3 and IL-12p40 could be considered as molecular predictors for recurrent wheezing due to RSV infection.

International audience; Besides overcoming physical constraints, such as extreme temperatures, reduced humidity, elevated pressure, and natural predators, human pathogens further need to overcome an arsenal of antimicrobial components evolved by the host to limit infection, replication and optimally, reinfection. Herpes simplex virus-1 (HSV-1) and herpes simplex virus-2 (HSV-2) infect humans at a high frequency and persist within the host for life by establishing latency in neurons. To gain access to these cells, herpes simplex viruses (HSVs) must replicate and block immediate host antiviral responses elicited by epithelial cells and innate immune components early after infection. During these processes, infected and noninfected neighboring cells, as well as tissue-resident and patrolling immune cells, will sense viral components and cell-associated danger signals and secrete soluble mediators. While type-I interferons aim at limiting virus spread, cytokines and chemokines will modulate resident and incoming immune cells. In this paper, we discuss recent findings relative to the early steps taking place during HSV infection and replication. Further, we discuss how HSVs evade detection by host cells and the molecular mechanisms evolved by these viruses to circumvent early antiviral mechanisms, ultimately leading to neuron infection and the establishment of latency.

International audience; Human metapneumovirus (hMPV) is a leading cause of acute respiratory tract infections in children and the elderly. The mechanism by which this virus triggers an inflammatory response still remains unknown. Here, we evaluated whether the thymic stromal lymphopoietin (TSLP) pathway contributes to lung inflammation upon hMPV infection. We found that hMPV infection promotes TSLP expression both in human airway epithelial cells and in the mouse lung. hMPV infection induced lung infiltration of OX40L + CD11b + DCs. Mice lacking the TSLP receptor deficient mice (tslpr −/−) showed reduced lung inflammation and hMPV replication. These mice displayed a decreased number of neutrophils as well a reduction in levels of thymus and activation-regulated chemokine/CCL17, IL-5, IL-13, and TNF-α in the airways upon hMPV infection. Furthermore , a higher frequency of CD4 + and CD8 + T cells was found in tslpr −/− mice compared to WT mice, which could contribute to controlling viral spread. Depletion of neutrophils in WT and tslpr −/− mice decreased inflammation and hMPV replication. Remarkably, blockage of TSLP or OX40L with specific Abs reduced lung inflammation and viral replication following hMPV challenge in mice. Altogether, these results suggest that activation of the TSLP pathway is pivotal in the development of pulmonary pathology and pulmonary hMPV replication. Keywords: Dendritic cells r hMPV r Inflammation r Neutrophils r OX40L r TSLP r Viral replication.

International audience; Acute respiratory infections caused by the respiratory syncytial virus (RSV) are important health burdens that affect infants worldwide. RSV is also an important cause of morbidity and disease in adults, which causes enormous economic losses. At the present time, RSV infection is diagnosed by immunofluorescence, test pack and/or PCR, obtaining better results with PCR than with any other technique. The production of new monoclonal antibodies (mAbs) capable of detecting RSV in clinical samples is necessary to generate better and faster diagnosis tools for RSV. In this study, three new mAbs, directed against the RSV N and M2-1 proteins, were evaluated for the detection of RSV in clinical samples. Nasopha-ryngeal swabs were obtained from: 27 RSV-positive patients; 15 human metapneumovirus (hMPV)-positive patients; and 6 healthy controls. To evaluate RSV presence in these samples , clinical samples and RSV-infected cells were tested by Enzyme-Linked ImmunoSorbent Assay (ELISA), flow cytometry, immunofluores-cence, and dot-blot assays. Specificity and sensitivity were determined for each mAb by using purified RSV antigens and antigens from different viruses. Infected cells and clinical samples tested with the three new mAbs resulted positive by immunofluorescence, ELISA, flow cytometry, and dot blot. No false positives were obtained in samples infected with other respiratory virus (hMPV) or from healthy controls. These results suggest that these new anti-RSV mAbs can be considered for the rapid and reliable detection of RSV on infected cells and clinical specimens by multiple immunological approaches.

International audience; Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple alterations affecting the normal function of immune cells, such as lymphocytes, dendritic cells (DCs) and monocytes. Although the understanding of autoimmunity has significantly increased, the breakthrough in effective therapies has been modest, making necessary the development of new therapeutic strategies. Here we propose that a new potential target for therapy is haem oxygenase-1 (HO-1), an enzyme that catalyses the degradation of the haem group into biliverdin, carbon monoxide (CO) and Fe 2+. These products exhibit immunosuppressive and anti-inflammatory effects, which can contribute to improving tolerance during organ transplantation. Because HO-1 is highly expressed by immune cells involved in SLE pathogenesis, such as monocytes and DCs, we evaluated whether induction of HO-1 expression or the administration of CO could ameliorate disease in the FccRIIb knockout (KO) mouse model for SLE. We found that CO administration decreased the expansion of CD11b + cells, prevented the decline of regulatory T cells and reduced anti-histone antibodies observed in untreated FccRIIb KO mice. Furthermore, CO-treated animals and HO-1 induction showed less kidney damage compared with untreated mice. These data suggest that HO-1 modulation and CO administration can ameliorate autoimmunity and prevent the lupus symptoms shown by FccRIIb KO mice, highlighting HO-1 as a potential new target for autoimmune therapy.

International audience; Although identified in the 1960's, interest in autophagy has significantly increased in the past decade with notable research efforts oriented at understanding as to how this multi-protein complex operates and is regulated. Autophagy is commonly defined as a ''self-eating" process evolved by eukaryotic cells to recycle senescent organelles and expired proteins, which is significantly increased during cellular stress responses. In addition, autophagy can also play important roles during human diseases, such as cancer, neurodegenerative and autoimmune disorders. Furthermore, novel findings suggest that autophagy contributes to the host defense against microbial infections. In this article, we review the role of macroautophagy in antiviral immune responses and discuss molecular mechanisms evolved by viral pathogens to evade this process. A role for autophagy as an effector mechanism used both, by innate and adaptive immunity is also discussed.