title: The complement receptor 2/factor H fusion protein TT30 protects paroxysmal nocturnal hemoglobinuria erythrocytes from complement-mediated hemolysis and C3 fragment.
abstract: Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated intravascular hemolysis because of the lack from erythrocyte surface of the complement regulators CD55 and CD59, with subsequent uncontrolled continuous spontaneous activation of the complement alternative pathway (CAP), and at times of the complement classic pathway. Here we investigate in an in vitro model the effect on PNH erythrocytes of a novel therapeutic strategy for membrane-targeted delivery of a CAP inhibitor. TT30 is a 65 kDa recombinant human fusion protein consisting of the iC3b/C3d-binding region of complement receptor 2 (CR2) and the inhibitory domain of the CAP regulator factor H (fH). TT30 completely inhibits in a dose-dependent manner hemolysis of PNH erythrocytes in a modified extended acidified serum assay, and also prevents C3 fragment deposition on surviving PNH erythrocytes. The efficacy of TT30 derives from its direct binding to PNH erythrocytes; if binding to the erythrocytes is disrupted, only partial inhibition of hemolysis is mediated by TT30 in solution, which is similar to that produced by the fH moiety of TT30 alone, or by intact human fH. TT30 is a membrane-targeted selective CAP inhibitor that may prevent both intravascular and C3-mediated extravascular hemolysis of PNH erythrocytes and warrants consideration for the treatment of PNH patients.
authors.affiliation: Hematology, Department of Biochemistry and Medical Biotechnologies, Federico II University, Naples, Italy. amrisita@unina.it
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Risitano
authors.forename: Rosario
authors.initials: R
authors.lastname: Notaro
authors.forename: Caterina
authors.initials: C
authors.lastname: Pascariello
authors.forename: Michela
authors.initials: M
authors.lastname: Sica
authors.forename: Luigi
authors.initials: L
authors.lastname: del Vecchio
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Horvath
authors.forename: Masha
authors.initials: M
authors.lastname: Fridkis-Hareli
authors.forename: Carmine
authors.initials: C
authors.lastname: Selleri
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Lindorfer
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Taylor
authors.forename: Lucio
authors.initials: L
authors.lastname: Luzzatto
authors.forename: V Michael
authors.initials: VM
authors.lastname: Holers
mesh_terms: D016022:Case-Control Studies; D002478:Cells, Cultured; D003176:Complement C3 / Q000009:adverse effects / Q000037:antagonists & inhibitors / Q000494:pharmacology; D017242:Complement Factor H / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D003165:Complement System Proteins / Q000009:adverse effects / Q000502:physiology; D019610:Cytoprotection / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004912:Erythrocytes / Q000187:drug effects* / Q000502:physiology; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood* / Q000473:pathology; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D015514:Oncogene Proteins, Fusion / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D017464:Receptors, Complement 3d / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D003176:Complement C3; D015514:Oncogene Proteins, Fusion; D017464:Receptors, Complement 3d; D011993:Recombinant Fusion Proteins; C574810:TT30 fusion protein, human; D017242:Complement Factor H; D003165:Complement System Proteins