The Experts below are selected from a list of 17115 Experts worldwide ranked by ideXlab platform
Ivan Peyron - One of the best experts on this subject based on the ideXlab platform.
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the c1 and c2 domains of Blood Coagulation Factor viii mediate its endocytosis by dendritic cells
Haematologica, 2017Co-Authors: Bagirath Gangadharan, Mathieu Ing, Sandrine Delignat, Ivan PeyronAbstract:The development of inhibitory antibodies to therapeutic Factor VIII is the major complication of replacement therapy in patients with hemophilia A. The first step in the initiation of the anti-Factor VIII immune response is Factor VIII interaction with receptor(s) on antigen-presenting cells, followed by endocytosis and presentation to naive CD4+ T cells. Recent studies indicate a role for the C1 domain in Factor VIII uptake. We investigated whether charged residues in the C2 domain participate in immunogenic Factor VIII uptake. Co-incubation of Factor VIII with BO2C11, a monoclonal C2-specific immunoglobulin G, reduced Factor VIII endocytosis by dendritic cells and presentation to CD4+ T cells, and diminished Factor VIII immunogenicity in Factor VIII-deficient mice. The mutation of basic residues within the BO2C11 epitope of C2 replicated reduced in vitro immunogenic uptake, but failed to prevent Factor VIII immunogenicity in mice. BO2C11 prevents Factor VIII binding to von Willebrand Factor, thus potentially biasing Factor VIII immunogenicity by perturbing its half-life. Interestingly, a Factor VIIIY1680C mutant, that does not bind von Willebrand Factor, demonstrated unaltered endocytosis by dendritic cells as well as immunogenicity in Factor VIII-deficient mice. Co-incubation of Factor VIIIY1680C with BO2C11, however, resulted in decreased Factor VIII immunogenicity in vivo. In addition, a previously described triple C1 mutant showed decreased uptake in vitro, and reduced immunogenicity in vivo, but only in the absence of endogenous von Willebrand Factor. Taken together, the results indicate that residues in the C1 and/or C2 domains of Factor VIII are implicated in immunogenic Factor VIII uptake, at least in vitro. Conversely, in vivo, the binding to endogenous von Willebrand Factor masks the reducing effect of mutations in the C domains on Factor VIII immunogenicity.
Koen Mertens - One of the best experts on this subject based on the ideXlab platform.
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hla dr presented peptide repertoires derived from human monocyte derived dendritic cells pulsed with Blood Coagulation Factor viii
Molecular & Cellular Proteomics, 2011Co-Authors: Simon D. Van Haren, Jan Voorberg, Eszter Herczenik, Anja Ten Brinke, Koen Mertens, Alexander B. MeijerAbstract:Activation of T-helper cells is dependent upon the appropriate presentation of antigen-derived peptides on MHC class II molecules expressed on antigen presenting cells. In the current study we explored the repertoire of peptides presented on MHC class II molecules on human monocyte derived dendritic cells (moDCs) from four HLA-typed healthy donors. MHC class II-bound peptides could be routinely recovered from small cultures containing 5 × 106 cells. A fraction of the identified peptides were derived from proteins localized in the plasma membrane, endosomes, and lysosomes, but the majority of peptides that were presented on MHC class II originate from other organelles. Subsequently, we studied the antigen-specific peptide repertoire after endocytosis of a soluble antigen. Blood Coagulation Factor VIII (FVIII) was chosen as the antigen since our current knowledge on MHC class II presented peptides derived from this immunogenic therapeutic protein is limited. Analysis of the total repertoire of MHC class II-associated peptides revealed that per individual sample 20–50 FVIII-derived peptides were presented on FVIII-pulsed moDCs. Repertoires of FVIII-derived peptides eluted from moDCs derived from a panel of four HLA typed donors revealed that some MHC class II-presented FVIII peptides were presented by multiple donors, whereas the presentation of other FVIII peptides was donor-specific. In total 32 different core peptides were presented on FVIII-pulsed moDCs from four HLA-typed donors. Together our findings provide an unbiased approach to identify peptides that are presented by MHC class II on antigen-loaded moDCs from individual donors.
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the sequence glu1811 lys1818 of human Blood Coagulation Factor viii comprises a binding site for activated Factor ix
Journal of Biological Chemistry, 1996Co-Authors: Peter J Lenting, J A Van Mourik, M J S H Donath, J W H P Van De Loo, Koen MertensAbstract:In previous studies have shown that the interaction between Factor IXa and VIII involves the light chain of Factor VIII and that this interaction inhibited by the monoclonal antibody CLB-CAg A against the Factor VIII region Gln1778-Asp1840 (Lenting, P.J., Donath, M.J.S.H., van Mourik, J.A., and Mertens, K. (1994) J. Biol. Chem. 269, 7150-7155). Employing distinct recombinant Factor VIII fragments, we now have localized the epitope of this antibody more precisely between the A3 domain residues Glu1801 and Met1823. Hydropathy analysis indicated that this region is part of a major hydrophilic exosite within the A3 domain. The interaction of Factor IXa with this exosite was studied by employing overlapping synthetic peptides encompassing the Factor VII region Tyr1786-Ala1834. Factor IXa binding was found to be particularly efficient to peptide corresponding to the Factor VIII sequences Lys1804-Lys1818 and Glu1811-Gln1820. The same peptides proved effective in binding antibody CLB-CAg A. Further analysis revealed that peptides Lys1804-Lys1818 and Glu1811-Gln1820 interfere with binding of Factor IXa to immobilized Factor VIII light chain (Ki approximately 0.2 mM and 0.3 mM, respectively). Moreover, these peptides inhibit Factor X activation by Factor IXa in the presence of Factor VIIIa (Ki approximately 0.2 mM and 0.3 mM, respectively) but not in its absence. Equilibrium binding studies revealed that these two peptides bind to the Factor IX zymogen and its activated form, Factor IXa, with the same affinity (apparent Kd approximately 0.2 mM), whereas the complete Factor VIII light chain displays preferential binding to Factor IXa. In conclusion, our results demonstrate that peptides consisting of the Factor VIII light chain residues Lys1804-Lys1818 and Glu1811-Gln1820 share a Factor IXa binding site that is essential for the assembly of the Factor X-activating Factor IXa-Factor VIIIa complex. We propose that the overlapping sequence Glu1811-Lys1818 comprises the minimal requirements for binding to activated Factor IX.
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association of idiopathic venous thromboembolism with single point mutation at arg506 of Factor v
The Lancet, 1994Co-Authors: Jan Voorberg, Koen Mertens, J C Roelse, J A Van Mourik, R Koopman, H R Buller, F Berends, J Ten W CateAbstract:Abnormal Coagulation Factor V may underlie the thrombotic events associated with resistance to activated protein C (APC). We analysed 27 consecutive patients with documented idiopathic (recurrent) thromboembolism for the occurrence of point mutations within the APC sensitive regions of Blood Coagulation Factor V. In 10 patients we observed a single basepair mutation resulting in a substitution of Arg506 to Gln. This mutation was significantly linked to in-vitro resistance to APC in these subjects. This mutation at Arg506 of Factor V may form the molecular basis for the thrombotic events associated with APC resistance.
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identification of a binding site for Blood Coagulation Factor ixa on the light chain of human Factor viii
Journal of Biological Chemistry, 1994Co-Authors: Peter J Lenting, J A Van Mourik, M J S H Donath, Koen MertensAbstract:The interaction between human Factor IXa and Factor VIII or its constituent units was investigated. Equilibrium binding studies were performed employing Factor VIII light chain that was immobilized on a monoclonal antibody. Factor VIII light chain was observed to bind Factor IXa with high affinity (Kd = 14.8 +/- 3.2 nM) and approximately 1:1 stoichiometry. Optimal interaction required NaCl concentrations below 0.2 M and the presence of Ca2+ ions. Factor VIII light chain in solution effectively inhibited binding of Factor IXa to the immobilized light chain (Ki = 10.9 +/- 1.9 nM). The isolated Factor VIII light chain and the Factor VIII heterodimer were equally effective in Factor IXa binding, demonstrating that this interaction did not require the Factor VIII heavy chain. Factor Xa and activated Protein C were found to be inefficient (Ki > or = 1.2 microM) in competing with Factor IXa, indicating that the high affinity for Factor VIII light chain was unique for Factor IXa. The Factor IXa-Factor VIII light chain interaction was inhibited by von Willebrand Factor, but this effect was abolished by cleavage of the Factor VIII light chain by thrombin. An antibody that inhibits von Willebrand Factor-Factor VIII complex formation did not compete for Factor IXa binding. In contrast, association of Factor IXa with the Factor VIII light chain was inhibited by an antibody directed against the Factor VIII region Gln1778-Asp1840. We propose that this sequence provides a Factor IXa binding site and that its exposure requires dissociation of the Factor VIII-von Willebrand Factor complex.
Mathieu Ing - One of the best experts on this subject based on the ideXlab platform.
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the c1 and c2 domains of Blood Coagulation Factor viii mediate its endocytosis by dendritic cells
Haematologica, 2017Co-Authors: Bagirath Gangadharan, Mathieu Ing, Sandrine Delignat, Ivan PeyronAbstract:The development of inhibitory antibodies to therapeutic Factor VIII is the major complication of replacement therapy in patients with hemophilia A. The first step in the initiation of the anti-Factor VIII immune response is Factor VIII interaction with receptor(s) on antigen-presenting cells, followed by endocytosis and presentation to naive CD4+ T cells. Recent studies indicate a role for the C1 domain in Factor VIII uptake. We investigated whether charged residues in the C2 domain participate in immunogenic Factor VIII uptake. Co-incubation of Factor VIII with BO2C11, a monoclonal C2-specific immunoglobulin G, reduced Factor VIII endocytosis by dendritic cells and presentation to CD4+ T cells, and diminished Factor VIII immunogenicity in Factor VIII-deficient mice. The mutation of basic residues within the BO2C11 epitope of C2 replicated reduced in vitro immunogenic uptake, but failed to prevent Factor VIII immunogenicity in mice. BO2C11 prevents Factor VIII binding to von Willebrand Factor, thus potentially biasing Factor VIII immunogenicity by perturbing its half-life. Interestingly, a Factor VIIIY1680C mutant, that does not bind von Willebrand Factor, demonstrated unaltered endocytosis by dendritic cells as well as immunogenicity in Factor VIII-deficient mice. Co-incubation of Factor VIIIY1680C with BO2C11, however, resulted in decreased Factor VIII immunogenicity in vivo. In addition, a previously described triple C1 mutant showed decreased uptake in vitro, and reduced immunogenicity in vivo, but only in the absence of endogenous von Willebrand Factor. Taken together, the results indicate that residues in the C1 and/or C2 domains of Factor VIII are implicated in immunogenic Factor VIII uptake, at least in vitro. Conversely, in vivo, the binding to endogenous von Willebrand Factor masks the reducing effect of mutations in the C domains on Factor VIII immunogenicity.
Sandrine Delignat - One of the best experts on this subject based on the ideXlab platform.
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the c1 and c2 domains of Blood Coagulation Factor viii mediate its endocytosis by dendritic cells
Haematologica, 2017Co-Authors: Bagirath Gangadharan, Mathieu Ing, Sandrine Delignat, Ivan PeyronAbstract:The development of inhibitory antibodies to therapeutic Factor VIII is the major complication of replacement therapy in patients with hemophilia A. The first step in the initiation of the anti-Factor VIII immune response is Factor VIII interaction with receptor(s) on antigen-presenting cells, followed by endocytosis and presentation to naive CD4+ T cells. Recent studies indicate a role for the C1 domain in Factor VIII uptake. We investigated whether charged residues in the C2 domain participate in immunogenic Factor VIII uptake. Co-incubation of Factor VIII with BO2C11, a monoclonal C2-specific immunoglobulin G, reduced Factor VIII endocytosis by dendritic cells and presentation to CD4+ T cells, and diminished Factor VIII immunogenicity in Factor VIII-deficient mice. The mutation of basic residues within the BO2C11 epitope of C2 replicated reduced in vitro immunogenic uptake, but failed to prevent Factor VIII immunogenicity in mice. BO2C11 prevents Factor VIII binding to von Willebrand Factor, thus potentially biasing Factor VIII immunogenicity by perturbing its half-life. Interestingly, a Factor VIIIY1680C mutant, that does not bind von Willebrand Factor, demonstrated unaltered endocytosis by dendritic cells as well as immunogenicity in Factor VIII-deficient mice. Co-incubation of Factor VIIIY1680C with BO2C11, however, resulted in decreased Factor VIII immunogenicity in vivo. In addition, a previously described triple C1 mutant showed decreased uptake in vitro, and reduced immunogenicity in vivo, but only in the absence of endogenous von Willebrand Factor. Taken together, the results indicate that residues in the C1 and/or C2 domains of Factor VIII are implicated in immunogenic Factor VIII uptake, at least in vitro. Conversely, in vivo, the binding to endogenous von Willebrand Factor masks the reducing effect of mutations in the C domains on Factor VIII immunogenicity.
Christos Tsaklakidis - One of the best experts on this subject based on the ideXlab platform.
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chlorothiophenecarboxamides as p1 surrogates of inhibitors of Blood Coagulation Factor xa
Bioorganic & Medicinal Chemistry Letters, 2004Co-Authors: Werner Mederski, Bertram Cezanne, Christoph Van Amsterdam, Karlulrich Buhring, Dieter Dorsch, Johannes Gleitz, Joachim Marz, Christos TsaklakidisAbstract:Neutral chlorothiophenecarboxamides bearing an amino acid and a substituted aniline were synthesized and investigated for their Factor Xa inhibitory activity in vitro. From selected 2-methylphenyl morpholinones the solution properties were determined. The most soluble and active compounds were then investigated in different animal species to compare the pharmacokinetic parameters. This led to a potent, water soluble and orally bioavailable candidate for further development: EMD 495235.
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chlorothiophenecarboxamides as p1 surrogates of inhibitors of Blood Coagulation Factor xa
Bioorganic & Medicinal Chemistry Letters, 2004Co-Authors: Werner Mederski, Bertram Cezanne, Karlulrich Buhring, Dieter Dorsch, Johannes Gleitz, Joachim Marz, Christoph Van Amsterdam, Christos TsaklakidisAbstract:Neutral chlorothiophenecarboxamides bearing an amino acid and a substituted aniline were synthesized and investigated for their Factor Xa inhibitory activity in vitro. From selected 2-methylphenyl morpholinones the solution properties were determined. The most soluble and active compounds were then investigated in different animal species to compare the pharmacokinetic parameters. This led to a potent, water soluble and orally bioavailable candidate for further development: EMD 495235.
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halothiophene benzimidazoles as p1 surrogates of inhibitors of Blood Coagulation Factor xa
Bioorganic & Medicinal Chemistry Letters, 2004Co-Authors: Werner Mederski, Bertram Cezanne, Dieter Dorsch, Johannes Gleitz, Soheila Anzali, Christos TsaklakidisAbstract:Neutral weak halothiophene benzimidazole inhibitors of the serine protease Factor Xa were identified via screening of a compound library. The X-ray crystal structure of representative 3a bound to human fXa confirmed the S1 binding mode. Starting from 3a a series of halothiophene benzimidazoles was synthesized and investigated for their Factor Xa inhibitory activity. This led to potent and selective achiral inhibitors against fXa such as compounds 9k and 9w.