1. Ir-CPI, a coagulation contact phase inhibitor from the tick Ixodes ricinus, inhibits thrombus formation without impairing hemostasis
Blood coagulation starts immediately after damage to the vascular endothelium. This system is essential for minimizing blood loss from an injured blood vessel but also contributes to vascular thrombosis. Although it has long been thought that the intrinsic coagulation pathway is not important for clotting in vivo, recent data obtained with genetically altered mice indicate that contact phase proteins seem to be essential for thrombus formation. We show that recombinant Ixodes ricinus contact phase inhibitor (Ir-CPI), a Kunitz-type protein expressed by the salivary glands of the tick Ixodes ricinus, specifically interacts with activated human contact phase factors (FXIIa, FXIa, and kallikrein) and prolongs the activated partial thromboplastin time (aPTT) in vitro. The effects of Ir-CPI were also examined in vivo using both venous and arterial thrombosis models. Intravenous administration of Ir-CPI in rats and mice caused a dose-dependent reduction in venous thrombus formation and revealed a defect in the formation of arterial occlusive thrombi. Moreover, mice injected with Ir-CPI are protected against collagen- and epinephrine-induced thromboembolism. Remarkably, the effective antithrombotic dose of Ir-CPI did not promote bleeding or impair blood coagulation parameters. To conclude, our results show that a contact phase inhibitor is an effective and safe antithrombotic agent in vivo.
Yves Decrem,1 Géraldine Rath,2 Virginie Blasioli,1 Philippe Cauchie,3 Séverine Robert,4 Jérôme Beaufays,1 Jean-Marie Frère,5 Olivier Feron,2 Jean-Michel Dogné,4 Chantal Dessy,2 Luc Vanhamme,1,6 and Edmond Godfroid1. J. Exp. Med. Vol. 206 No. 11 2381-2395. 2009.
1 Service de Biologie Moléculaire des Ectoparasites, Institut de Biologie et Médecine Moléculaires, Université Libre de Bruxelles, Gosselies B-6041, Belgium
2 Unit of Pharmacology and Therapeutics (FATH 5349), Université Catholique de Louvain, Brussels B-1200, Belgium
3 Experimental Medecine Laboratory, Université de Bruxelles, Montigny-Le-Tilleul B-6110, Belgium
4 Department of Pharmacy, Facultés Universitaires Notre Dame de la Paix Namur, B-5000, Belgium
5 Centre d’Ingénierie des Protéines, Institut de Chimie B6a, Université de Liège, B-4000 Liège, Belgium
6 Service de Parasitologie Moléculaire, Institut de Biologie et Médecine Moléculaires, Université Libre de Bruxelles, Gosselies B-6041, Belgium.
Link : www.jem.org/cgi/doi/10.1084/jem.20091007
2. Variability and Action Mechanism of a Family of Anticomplement Proteins in Ixodes ricinus.
Background. Ticks are blood feeding arachnids that characteristically take a long blood meal. They must therefore counteract host defence mechanisms such as hemostasis, inflammation and the immune response. This is achieved by expressing batteries of salivary proteins coded by multigene families. Methodology/Principal Findings. We report the in-depth analysis of a tick multigene family and describe five new anticomplement proteins in Ixodes ricinus. Compared to previously described Ixodes anticomplement proteins, these segregated into a new phylogenetic group or subfamily. These proteins have a novel action mechanism as they specifically bind to properdin, leading to the inhibition of C3 convertase and the alternative complement pathway. An excess of non-synonymous over synonymous changes indicated that coding sequences had undergone diversifying selection. Diversification was not associated with structural, biochemical or functional diversity, adaptation to host species or stage specificity but rather to differences in antigenicity. Conclusions/Significance. Anticomplement proteins from I. ricinus are the first inhibitors that specifically target a positive regulator of complement, properdin. They may provide new tools for the investigation of role of properdin in physiological and pathophysiological mechanisms. They may also be useful in disorders affecting the alternative complement pathway. Looking for and detecting the different selection pressures involved will help in understanding the evolution of multigene families and hematophagy in arthropods.
Bernard Couvreur1, Jérôme Beaufays1, Cédric Charon1, Kathia Lahaye1, François Gensale1, Valérie Denis1, Benoît Charloteaux2, Yves Decrem1, Pierre-Paul Prévot1, Michel Brossard3, Luc Vanhamme1,4, Edmond Godfroid1. PLoS ONE 3(1): e1400, 2008. doi:10.1371/journal.pone.0001400.
1 Laboratory for Molecular Biology of Ectoparasites, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Gosselies, Belgium,
2 Centre de Biophysique Moléculaire Numérique, Gembloux Agricultural University, Gembloux, Belgium,
3 Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
4 Laboratory of Molecular Parasitology, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Gosselies, Belgium
Link : http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0001400
3. Ir-LBP, an Ixodes ricinus Tick Salivary LTB4-Binding Lipocalin, Interferes with Host Neutrophil Function
Background. During their blood meal, ticks secrete a wide variety of proteins that can interfere with their host’s defense mechanisms. Among these proteins, lipocalins play a major role in the modulation of the inflammatory response. Methodology/Principal Findings. We previously identified 14 new lipocalin genes in the tick Ixodes ricinus. One of them codes for a protein that specifically binds leukotriene B4 with a very high affinity (Kd: 61 nM), similar to that of the neutrophil transmembrane receptor BLT1. By in silico approaches, we modeled the 3D structure of the protein and the binding of LTB4 into the ligand pocket. This protein, called Ir-LBP, inhibits neutrophil chemotaxis in vitro and delays LTB4-induced apoptosis. Ir-LBP also inhibits the host inflammatory response in vivo by decreasing the number and activation of neutrophils located at the tick bite site. Thus, Ir-LBP participates in the tick’s ability to interfere with proper neutrophil function in inflammation. Conclusions/Significance. These elements suggest that Ir-LBP is a ‘‘scavenger’’ of LTB4, which, in combination with other factors, such as histamine-binding proteins or proteins inhibiting the classical or alternative complement pathways, permits the tick to properly manage its blood meal. Moreover, with regard to its properties, Ir-LBP could possibly be used as a therapeutic tool for illnesses associated with an increased LTB4 production.
Jérôme Beaufays1, Benoît Adam2, Catherine Menten-Dedoyart3, Laurence Fievez4, Amélie Grosjean5, Yves Decrem1, Pierre-Paul Prévôt1, Sébastien Santini2, Robert Brasseur2, Michel Brossard6, Michel Vanhaeverbeek5, Fabrice Bureau4, Ernst Heinen3, Laurence Lins2, Luc Vanhamme1,7, Edmond Godfroid1. PLoS ONE 3(12): e3987 (2008). doi:10.1371/journal.pone.0003987
1 Laboratory for Molecular Biology of Ectoparasites, IBMM, Université Libre de Bruxelles, Gosselies, Belgium,
2 Centre de Biophysique Moléculaire Numérique, Gembloux Agricultural University, Gembloux, Belgium,
3 Institute of Human Histology, Department of Morphology and Immunology, Faculty of Medicine, University of Liège, Liège, Belgium,
4 Laboratory of Cellular and Molecular Physiology, GIGA-Research, University of Liège, Liège, Belgium,
5 Laboratoire de Médecine Expérimentale (ULB 222 Unit), ISPPC Hopital André Vesale, Montigny-Le-Tilleul, Belgium,
6 Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland,
7 Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, Gosselies, Belgium
Link : http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0003987