MAPPIT analysis of the early events in Toll-Like receptor signalling

Vertebraten bezitten een ingenieus verdedigingssysteem waarmee ze zich wapenen tegen het constante gevaar van invasieve pathogenen. Het immuunsysteem bij zoogdieren kan onderverdeeld worden in een adaptieve en een aangeboren respons. De adaptieve immuniteit is gebaseerd op clonale expansie van T and B lymphocyten die antigen-specifieke receptoren expresseren. Door deze clonale selectie en expansie is de adaptieve respons pas volledig operationeel drie tot vijf dagen na infectie. De aangeboren respons daarentegen vormt de eerstelijnsdefensie tegen pathogenen en is daarom essentieel om de infectie onder controle te houden tot de adaptieve respons geactiveerd wordt. De aangeboren immuniteit maakt gebruik van een gelimiteerde set aan pathogeen-herkennende receptoren waarvan de familie van de Toll-Like receptoren (TLRs) de belangrijkste zijn. TLRs herkennen een brede waaier aan bacteriële en virale structuren zoals lipopolysaccharide, dsRNA of bacterieel DNA. Deze structuren worden vaak pathogeen-geassocieerde moleculaire patronen of PAMPs genoemd. PAMPs zijn essentieel voor het overleven en de replicatie van deze pathogenen en zijn daarom onveranderd gebleven doorheen de evolutie. Herkenning van een pathogen door TLRs leidt tot de productie van pro-inflammatoire cytokines. Deze cytokines activeren de aangeboren immuuncellen zoals macrofagen en neutrofielen. De TLRs zijn bovendien ook betrokken bij de activatie en modulatie van de daaropvolgende adaptieve immuunrespons. Echter, ongepaste en overmatige activatie van de TLR signaalweg leidt tot excessieve inflammatie wat vaak enorm schadelijk is. Daarom is de TLR signaalweg strikt gereguleerd. Verscheidene modulatoren zijn beschreven die ofwel interfereren in ligand binding, ofwel de receptorexpressie beïnvloeden ofwel de intracellulaire signaalweg moduleren. Dit werk richt zich voornamelijk op de initiële stappen van de TLR signaalweg. Daarbij zijn vier adaptor molecules betrokken: MyD88, Mal, Trif and Tram. Verschillende TLRs gebruiken verschillende combinaties van adaptoren, wat gedeeltelijk de ligand specifieke respons kan verklaren. Door gebruik te maken van MAPPIT (Mammalian Protein-Protein Interaction Trap), een twee-hybride methode die in ons laboratorium werd ontwikkeld, creëerden we een TLR-adaptor interactiemap. Bovendien toonden we aan dat Mal een brugfunctie vervult in TLR2 en TLR4 signalisatie, door MyD88 naar de geactiveerde receptor te derigeren. We identificeerden CIS, een lid van de SOCS proteïne familie, als een mogelijke regulator van de MyD88-afhankelijke signaalweg en toonden aan dat de bindingsmodaliteiten van CIS verschilden tussen receptor en MyD88 interactie

IgG regulation through FcRn blocking: A novel mechanism for the treatment of myasthenia gravis

The neonatal Fc receptor (FcRn) is an MHC class I–like molecule that is widely distributed in mammalian organs, tissues, and cells. FcRn is critical to maintaining immunoglobulin G (IgG) and albumin levels through rescuing these molecules from lysosomal degradation. IgG autoantibodies are associated with many autoimmune diseases, including myasthenia gravis (MG), a rare neuromuscular autoimmune disease that causes debilitating and, in its generalized form (gMG), potentially life-threatening muscle weakness. IgG autoantibodies are directly pathogenic in MG and target neuromuscular junction proteins, causing neuromuscular transmission failure. Treatment approaches that reduce autoantibody levels, such as therapeutic plasma exchange and intravenous immunoglobulin, have been shown to be effective for gMG patients but are not indicated as ongoing maintenance therapies and can be associated with burdensome side effects. Agents that block FcRn-mediated recycling of IgG represent a rational and promising approach for the treatment of gMG. Blocking FcRn allows targeted reduction of all IgG subtypes without decreasing concentrations of other Ig isotypes; therefore, FcRn blocking could be a safe and effective treatment strategy for a broad population of gMG patients. Several FcRn-blocking antibodies and one antibody Fc fragment have been developed and are currently in various stages of clinical development. This article describes the mechanism of FcRn blockade as a novel approach for IgG-mediated disease therapy and reviews promising clinical data using such FcRn blockers for the treatment of gMG

Combining transplant professional's psychosocial donor evaluation and donor self-report measures to optimise the prediction of HRQoL after kidney donation:an observational prospective multicentre study

OBJECTIVES: Living donor kidney transplantation is currently the preferred treatment for patients with end-stage renal disease. The psychosocial evaluation of kidney donor candidates relies mostly on the clinical viewpoint of transplant professionals because evidence-based guidelines for psychosocial donor eligibility are currently lacking. However, the accuracy of these clinical risk judgements and the potential added value of a systematic self-reported screening procedure are as yet unknown. The current study examined the effectiveness of the psychosocial evaluation by transplant professionals and the potential value of donor self-report measures in optimising the donor evaluation. Based on the stress-vulnerability model, the predictive value of predonation, intradonation and postdonation factors to impaired longer term health-related quality of life (HRQoL) of kidney donors was studied. DESIGN: An observational prospective multicentre study. SETTING: Seven Dutch transplantation centres. PARTICIPANTS: 588 potential donors participated, of whom 361 donated. Complete prospective data of 230 donors were available. Also, 1048 risk estimation questionnaires were completed by healthcare professionals. METHODS: Transplant professionals (nephrologists, coordinating nurses, social workers and psychologists) filled in risk estimation questionnaires on kidney donor candidates. Furthermore, 230 kidney donors completed questionnaires (eg, on HRQoL) before and 6 and 12 months after donation. PRIMARY AND SECONDARY OUTCOME MEASURES: HRQoL, demographic and preoperative, intraoperative and postoperative health characteristics, perceived support, donor cognitions, recipient functioning and professionals risk estimation questionnaires. RESULTS: On top of other predictors, such as the transplant professionals’ risk assessments, donor self-report measures significantly predicted impaired longer term HRQoL after donation, particularly by poorer predonation physical (17%–28% explained variance) and psychological functioning (23%). CONCLUSIONS: The current study endorses the effectiveness of the psychosocial donor evaluation by professionals and the additional value of donor self-report measures in optimising the psychosocial evaluation. Consequently, systematic screening of donors based on the most prominent risk factors provide ground for tailored interventions for donors at risk

Visualization of Allostery in P-Selectin Lectin Domain Using MD Simulations

Allostery of P-selectin lectin (Lec) domain followed by an epithelial growth factor (EGF)-like domain is essential for its biological functionality, but the underlying pathways have not been well understood. Here the molecular dynamics simulations were performed on the crystallized structures to visualize the dynamic conformational change for state 1 (S1) or state 2 (S2) Lec domain with respective bent (B) or extended (E) EGF orientation. Simulations illustrated that both S1 and S2 conformations were unable to switch from one to another directly. Instead, a novel S1' conformation was observed from S1 when crystallized B-S1 or reconstructed “E-S1” structure was employed, which was superposed well with that of equilibrated S1 Lec domain alone. It was also indicated that the corresponding allosteric pathway from S1 to S1' conformation started with the separation between residues Q30 and K67 and terminated with the release of residue N87 from residue C109. These results provided an insight into understanding the structural transition and the structure-function relationship of P-selectin allostery

The calcium activated nucleotidases: A diverse family of soluble and membrane associated nucleotide hydrolyzing enzymes

It has long been known that the salivary glands of hematophagous (blood-feeding) arthropods secrete soluble apyrases, which are potent nucleotide hydrolyzing enzymes capable of hydrolyzing extracellular ATP and ADP, the latter being a major agonist contributing to platelet aggregation. Only recently, however, has the identification of proteins homologous to these apyrases been reported in non-blood-feeding organisms such as rodents and humans. In this review, we present an overview of the diverse family of apyrases first described in the blood-feeding arthropods, including the identification and characterization of the soluble and membrane-bound vertebrate enzymes homologous to these arthropod apyrases. We also describe the enzymatic properties and nucleotide specificities of the expressed enzymes, and insights gained into the structure and function of this calcium activated nucleotidase (CAN) family from biophysical, mutagenesis and crystallography studies. The potential therapeutic value of these proteins is also discussed

In Vivo Analysis of the Role of O-Glycosylations of Von Willebrand Factor

The objective of this project was to study the function of O-glycosylations in von Willebrand factor (VWF) life cycle. In total, 14 different murine Vwf cDNAs mutated on one or several O-glycosylations sites were generated: 9 individual mutants, 2 doublets, 2 clusters and 1 mutant with all 9 murine glycosylation sites mutated (Del-O-Gly). We expressed each mutated cDNA in VWF deficient-mice by hydrodynamic injection. An immunosorbent assay with Peanut Agglutinin (PNA) was used to verify the O-glycosylation status. Wild-type (WT) VWF expressed by hepatocytes after hydrodynamic injection was able to bind PNA with slightly higher affinity than endothelial-derived VWF. In contrast, the Del-O-Gly VWF mutant did not bind PNA, demonstrating removal of O-linked glycans. All mutants displayed a normal multimeric pattern. Two mutants, Del-O-Gly and T1255A/T1256A, led to expression levels 50% lower than those induced by WT VWF and their half-life in vivo was significantly reduced. When testing the capacity of each mutant to correct the bleeding time of VWF-deficient mice, we found that S1486A, T1255A, T1256A and the doublet T1255A/T1256A were unable to do so. In conclusion we have shown that O-glycosylations are dispensable for normal VWF multimerization and biosynthesis. It also appears that some O-glycosylation sites, particularly the T1255 and T1256 residues, are involved in the maintenance of VWF plasma levels and are essential for normal haemostasis. As for the S1486 residue, it seems to be important for platelet binding as demonstrated in vitro using perfusion experiments

Cleavage of von Willebrand Factor by Granzyme M Destroys Its Factor VIII Binding Capacity

Von Willebrand factor (VWF) is a pro-hemostatic multimeric plasma protein that promotes platelet aggregation and stabilizes coagulation factor VIII (FVIII) in plasma. The metalloproteinase ADAMTS13 regulates the platelet aggregation function of VWF via proteolysis. Severe deficiency of ADAMTS13 is associated with thrombotic thrombocytopenic purpura, but does not always correlate with its clinical course. Therefore, other proteases could also be important in regulating VWF activity. In the present study, we demonstrate that VWF is cleaved by the cytotoxic lymphocyte granule component granzyme M (GrM). GrM cleaved both denaturated and soluble plasma-derived VWF after Leu at position 276 in the D3 domain. GrM is unique in that it did not affect the multimeric size and pro-hemostatic platelet aggregation ability of VWF, but instead destroyed the binding of VWF to FVIII in vitro. In meningococcal sepsis patients, we found increased plasma GrM levels that positively correlated with an increased plasma VWF/FVIII ratio in vivo. We conclude that, next to its intracellular role in triggering apoptosis, GrM also exists extracellularly in plasma where it could play a physiological role in controlling blood coagulation by determining plasma FVIII levels via proteolytic processing of its carrier VWF

The preclinical pharmacology of the high affinity anti-IL-6R Nanobody (R) ALX-0061 supports its clinical development in rheumatoid arthritis

Introduction: The pleiotropic cytokine interleukin-6 (IL-6) plays an important role in the pathogenesis of different diseases, including rheumatoid arthritis (RA). ALX-0061 is a bispecific Nanobody (R) with a high affinity and potency for IL-6 receptor (IL-6R), combined with an extended half-life by targeting human serum albumin. We describe here the relevant aspects of its in vitro and in vivo pharmacology. Methods: ALX-0061 is composed of an affinity-matured IL-6R-targeting domain fused to an albumin-binding domain representing a minimized two-domain structure. A panel of different in vitro assays was used to characterize the biological activities of ALX-0061. The pharmacological properties of ALX-0061 were examined in cynomolgus monkeys, using plasma levels of total soluble (s)IL-6R as pharmacodynamic marker. Therapeutic effect was evaluated in a human IL-6-induced acute phase response model in the same species, and in a collagen-induced arthritis (CIA) model in rhesus monkeys, using tocilizumab as positive control. Results: ALX-0061 was designed to confer the desired pharmacological properties. A 200-fold increase of target affinity was obtained through affinity maturation of the parental domain. The high affinity for sIL-6R (0.19 pM) translated to a concentration-dependent and complete neutralization of sIL-6R in vitro. In cynomolgus monkeys, ALX-0061 showed a dose-dependent and complete inhibition of hIL-6-induced inflammatory parameters, including plasma levels of C-reactive protein (CRP), fibrinogen and platelets. An apparent plasma half-life of 6.6 days was observed after a single intravenous administration of 10 mg/kg ALX-0061 in cynomolgus monkeys, similar to the estimated expected half-life of serum albumin. ALX-0061 and tocilizumab demonstrated a marked decrease in serum CRP levels in a non-human primate CIA model. Clinical effect was confirmed in animals with active drug exposure throughout the study duration. Conclusions: ALX-0061 represents a minimized bispecific biotherapeutic of 26 kDa, nearly six times smaller than monoclonal antibodies. High in vitro affinity and potency was demonstrated. Albumin binding as a half-life extension technology resulted in describable and expected pharmacokinetics. Strong IL-6R engagement was shown to translate to in vivo effect in non-human primates, demonstrated via biomarker deregulation as well as clinical effect. Presented results on preclinical pharmacological properties of ALX-0061 are supportive of clinical development in RA