Brigitte Solhonne

A loss-of-function variant of the antiviral molecule MAVS is associated with a subset of systemic lupus patients.

Dysregulation of the antiviral immune response may contribute to autoimmune diseases. Here, we hypothesized that altered expression or function of MAVS, a key molecule downstream of the viral sensors RIG‐I and MDA‐5, may impair antiviral cell signalling and thereby influence the risk for systemic lupus erythematosus (SLE), the prototype autoimmune disease. We used molecular techniques to screen non‐synonymous single nucleotide polymorphisms (SNPs) in the MAVS gene for functional significance in human cell lines and identified one critical loss‐of‐function variant (C79F, rs11905552). This SNP substantially reduced expression of type I interferon (IFN) and other proinflammatory mediators and was found almost exclusively in the African‐American population. Importantly, in African‐American SLE patients, the C79F allele was associated with low type I IFN production and absence of anti‐RNA‐binding protein autoantibodies. These serologic associations were not related to a distinct, functionally neutral, MAVS SNP Q198K. Hence, this is the first demonstration that an uncommon genetic variant in the MAVS gene has a functional impact upon the anti‐viral IFN pathway in vivo in humans and is associated with a novel sub‐phenotype in SLE. This study demonstrates the utility of functional data in selecting rare variants for genetic association studies, allowing for fewer comparisons requiring statistical correction and for alternate lines of evidence implicating the particular variant in disease.

Study of human RIG-I polymorphisms identifies two variants with an opposite impact on the antiviral immune response.

Background RIG-I is a pivotal receptor that detects numerous RNA and DNA viruses. Thus, its defectiveness may strongly impair the host antiviral immunity. Remarkably, very little information is available on RIG-I single-nucleotide polymorphisms (SNPs) presenting a functional impact on the host response. Methodology/Principal Findings Here, we studied all non-synonymous SNPs of RIG-I using biochemical and structural modeling approaches. We identified two important variants: (i) a frameshift mutation (P229fs) that generates a truncated, constitutively active receptor and (ii) a serine to isoleucine mutation (S183I), which drastically inhibits antiviral signaling and exerts a down-regulatory effect, due to unintended stable complexes of RIG-I with itself and with MAVS, a key downstream adapter protein. Conclusions/Significance Hence, this study characterized P229fs and S183I SNPs as major functional RIG-I variants and potential genetic determinants of viral susceptibility. This work also demonstrated that serine 183 is a residue that critically regulates RIG-I-induced antiviral signaling.

Acute exposure to silica nanoparticles enhances mortality and increases lung permeability in a mouse model of Pseudomonas aeruginosa pneumonia.

BackgroundThe lung epithelium constitutes the first barrier against invading pathogens and also a major surface potentially exposed to nanoparticles. In order to ensure and preserve lung epithelial barrier function, the alveolar compartment possesses local defence mechanisms that are able to control bacterial infection. For instance, alveolar macrophages are professional phagocytic cells that engulf bacteria and environmental contaminants (including nanoparticles) and secrete pro-inflammatory cytokines to effectively eliminate the invading bacteria/contaminants. The consequences of nanoparticle exposure in the context of lung infection have not been studied in detail. Previous reports have shown that sequential lung exposure to nanoparticles and bacteria may impair bacterial clearance resulting in increased lung bacterial loads, associated with a reduction in the phagocytic capacity of alveolar macrophages.ResultsHere we have studied the consequences of SiO2 nanoparticle exposure on Pseudomonas aeruginosa clearance, Pseudomonas aeruginosa-induced inflammation and lung injury in a mouse model of acute pneumonia. We observed that pre-exposure to SiO2 nanoparticles increased mice susceptibility to lethal pneumonia but did not modify lung clearance of a bioluminescent Pseudomonas aeruginosa strain. Furthermore, internalisation of SiO2 nanoparticles by primary alveolar macrophages did not reduce the capacity of the cells to clear Pseudomonas aeruginosa. In our murine model, SiO2 nanoparticle pre-exposure preferentially enhanced Pseudomonas aeruginosa-induced lung permeability (the latter assessed by the measurement of alveolar albumin and IgM concentrations) rather than contributing to Pseudomonas aeruginosa-induced lung inflammation (as measured by leukocyte recruitment and cytokine concentration in the alveolar compartment).ConclusionsWe show that pre-exposure to SiO2 nanoparticles increases mice susceptibility to lethal pneumonia but independently of macrophage phagocytic function. The deleterious effects of SiO2 nanoparticle exposure during Pseudomonas aeruginosa-induced pneumonia are related to alterations of the alveolar-capillary barrier rather than to modulation of the inflammatory responses.

Silver Nanoparticles Impair Retinoic Acid-Inducible Gene I Mediated Mitochondrial Anti-Viral Immunity by Blocking the Autophagic Flux in Lung Epithelial Cells

Silver nanoparticles (AgNPs) are microbicidal agents which could be potentially used as an alternative to antivirals to treat human infectious diseases, especially influenza virus infections where antivirals have generally proven unsuccessful. However, concerns about the use of AgNPs on humans arise from their potential toxicity, although mechanisms are not well-understood. We show here, in the context of an influenza virus infection of lung epithelial cells, that AgNPs down-regulated influenza induced CCL-5 and -IFN-β release (two cytokines important in antiviral immunity) through RIG-I inhibition, while enhancing IL-8 production, a cytokine important for mobilizing host antibacterial responses. AgNPs activity was independent of coating and was not observed with gold nanoparticles. Down-stream analysis indicated that AgNPs disorganized the mitochondrial network and prevented the antiviral IRF-7 transcription factor influx into the nucleus. Importantly, we showed that the modulation of RIG-I-IRF-7 pathway was concomitant with inhibition of either classical or alternative autophagy (ATG-5- and Rab-9 dependent, respectively), depending on the epithelial cell type used. Altogether, this demonstration of a AgNPs-mediated functional dichotomy (down-regulation of IFN-dependent antiviral responses and up-regulation of IL-8-dependent antibacterial responses) may have practical implications for their use in the clinic.

The antimicrobial molecule trappin-2/elafin has anti-parasitic properties and is protective in vivo in a murine model of cerebral malaria

According to the WHO, and despite reduction in mortality rates, there were an estimated 438 000 malaria deaths in 2015. Therefore new antimalarials capable of limiting organ damage are still required. We show that systemic and lung adenovirus (Ad)-mediated over-expression of trappin-2 (T-2) an antibacterial molecule with anti-inflammatory activity, increased mice survival following infection with the cerebral malaria-inducing Plasmodium berghei ANKA (PbANKA) strain. Systemically, T-2 reduced PbANKA sequestration in spleen, lung, liver and brain, associated with a decrease in pro-inflammatory cytokines (eg TNF-α in spleen and lung) and an increase in IL-10 production in the lung. Similarly, local lung instillation of Ad-T-2 resulted in a reduced organ parasite sequestration and a shift towards an anti-inflammatory/repair response, potentially implicating monocytes in the protective phenotype. Relatedly, we demonstrated in vitro that human monocytes incubated with Plasmodium falciparum-infected red blood cells (Pf-iRBCs) and IgGs from hyper-immune African human sera produced T-2 and that the latter colocalized with merozoites and inhibited Pf multiplication. This array of data argues for the first time for the potential therapeutic usefulness of this host defense peptide in human malaria patients, with the aim to limit acute lung injury and respiratory distress syndrom often observed during malaria episodes.

Human airway trypsin-like protease exerts potent, antifibrotic action in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by the deposition of excessive extracellular matrix and the destruction of lung parenchyma, resulting from an aberrant wound‐healing response. Although IPF is often associated with an imbalance in protease activity, the mechanisms underlying the sustained repair mechanisms are not fully understood. Here, we addressed the role of the recently identified, membrane‐anchored serine protease human airway trypsin‐like protease (HAT). In the present study, we show that both HAT expression and activity were up‐regulated in human IPF specimens. Next, adenoviral overexpression of HAT before bleomycin challenge attenuated lung injury as well as extracellular matrix deposition in the bleomycin‐induced pulmonary fibrosis model. In vitro, HAT prevented specific fibrosis‐associated responses in primary human pulmonary fibroblasts and induced the expression of mediators associated with the prostaglandin E2 pathway. Altogether, our findings suggested that HAT could have a protective role in IPF and other fibrotic lung disorders.—Menou, A., Flajolet, P., Duitmen, J., Justet, A., Moog, S., Jaillet, M., Tabèze, L., Solhonne, B., Garnier, M., Mal, H., Mordant, P., Castier, Y., Cazes, A., Sallenave, J.‐M., Mailleux, A. A., Crestani, B. Human airway trypsin‐like protease exerts potent, anti‐fibrotic action in pulmonary fibrosis. FASEB J. 32, 1250‐1264 (2018). www.fasebj.org

FGF9 prevents pleural fibrosis induced by intrapleural adenovirus injection in mice

Fibroblast growth factor 9 (FGF9) is necessary for fetal lung development and is expressed by epithelium and mesothelium. We evaluated the role of FGF9 overexpression on adenoviral-induced pleural injury in vivo and determined the biological effects of FGF9 on mesothelial cells in vitro. We assessed the expression of FGF9 and FGF receptors by mesothelial cells in both human and mouse lungs. Intrapleural injection of an adenovirus expressing human FGF9 (AdFGF9) or a control adenovirus (AdCont) was performed. Mice were euthanized at days 3, 5, and 14 Expression of FGF9 and markers of inflammation and myofibroblastic differentiation was studied by qPCR and immunohistochemistry. In vitro, rat mesothelial cells were stimulated with FGF9 (20 ng/ml), and we assessed its effect on proliferation, survival, migration, and differentiation. FGF9 was expressed by mesothelial cells in human idiopathic pulmonary fibrosis. FGF receptors, mainly FGFR3, were expressed by mesothelial cells in vivo in humans and mice. AdCont instillation induced diffuse pleural thickening appearing at day 5, maximal at day 14 The altered pleura cells strongly expressed α-smooth muscle actin and collagen. AdFGF9 injection induced maximal FGF9 expression at day 5 that lasted until day 14 FGF9 overexpression prevented pleural thickening, collagen and fibronectin accumulation, and myofibroblastic differentiation of mesothelial cells. In vitro, FGF9 decreased mesothelial cell migration and inhibited the differentiating effect of transforming growth factor-β1. We conclude that FGF9 has a potential antifibrotic effect on mesothelial cells.