title: Polyethylene glycol modification of adenovirus reduces platelet activation, endothelial cell activation, and thrombocytopenia.
abstract: Thrombocytopenia is one of the complications for in vivo administration of adenovirus serotype 5 (Ad5) vectors after intravenous injection. In this paper, we investigated the mechanism of Ad5-induced thrombocytopenia and how these effects are attenuated by polyethylene glycol (PEG) modification of Ad5 (Ad-PEG). After intravenous injection, accelerated platelet loss was observed in Ad-injected mice but not in their Ad-PEG-injected counterparts. This platelet loss induced by Ad5 corresponded with increases in coagulation D-dimer levels, splenomegaly, and, later, production of megakaryocytes in the bone marrow. In contrast, these responses were blunted or ablated after injection of Ad-PEG. Ad5 activated both platelets and endothelial cells directly in vitro as evidenced by induction of P-selectin and the formation of von Willebrand factor-platelet strings and in vivo as evidenced by the induction of E-selectin messenger RNA. PEGylation blunted these observed activations. These data suggest that Ad5 may induce thrombocytopenia by direct activation of endothelial cells in addition to its direct effects on platelets. This link provides an important clue for the understanding of the mechanisms of thrombocytopenia associated with Ad5. Given that PEGylation blunted interactions of Ad with platelets and endothelial cells, reduced D-dimer formation, reduced thrombocytopenia, and reduced splenomegaly, these data suggest that this simple vector modification may have utility to improve the safety of Ad vectors for human gene therapy.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Sean E
authors.initials: SE
authors.lastname: Hofherr
authors.forename: Hoyin
authors.initials: H
authors.lastname: Mok
authors.forename: Francisca C
authors.initials: FC
authors.lastname: Gushiken
authors.forename: Jose A
authors.initials: JA
authors.lastname: Lopez
authors.forename: Michael A
authors.initials: MA
authors.lastname: Barry
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D021461:Animals, Outbred Strains; D001792:Blood Platelets / Q000378:metabolism*; D002452:Cell Count; D002478:Cells, Cultured; D019040:E-Selectin / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis / Q000096:biosynthesis; D017930:Genes, Reporter; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006384:Hemagglutination; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D015539:Platelet Activation; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013921:Thrombocytopenia / Q000097:blood* / Q000209:etiology; D019076:Transgenes; D014471:Umbilical Veins / Q000166:cytology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D019040:E-Selectin; D005338:Fibrin Fibrinogen Degradation Products; D012333:RNA, Messenger; D019010:Vascular Cell Adhesion Molecule-1; C036309:fibrin fragment D; D049452:Green Fluorescent Proteins; D011092:Polyethylene Glycols; D008156:Luciferases