title: Controlling complement resistance in cancer by using human monoclonal antibodies that neutralize complement-regulatory proteins CD55 and CD59.
abstract: Expression of the complement-regulatory proteins (CRP) CD46, CD55 and CD59 represents a strategy used by tumor cells to evade complement-dependent cell cytoxicity stimulated by monoclonal antibodies. We have isolated two single-chain variable fragments (scFv) to CD55 and CD59 from a human phage-display library and from these scFv we have produced two miniantibodies (MB), MB-55 (against CD55) and MB-59 (against CD59), containing the human hinge-CH2-CH3 domains of IgG1. The specificity of the two MB for the corresponding CRP was assessed by ELISA using purified CD46, CD55 and CD59. MB-55 and MB-59 neutralized the inhibitory activity of CD55 and CD59, respectively, restoring the complement-mediated lysis of sheep and guinea pig erythrocytes that was otherwise inhibited by the two CRP. FACS analysis revealed binding of MB-55 and MB-59 to the lymphoma cell line Karpas 422. The two MB induced a two-fold increase in the complement-dependent killing of these cells stimulated by Rituximab, a chimeric anti-CD20 monoclonal antibody. Transfection of HEK293T cells with vectors encoding MB-55 or MB-59 markedly reduced the expression of CD55 and CD59. We conclude that the human antibodies MB-55 and MB-59 may represent a therapeutic tool to increase the complement-dependent killing activity of Rituximab in the treatment of non-Hodgkin's lymphoma.
authors.affiliation: Department of Biology, University of Trieste, Trieste, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Ziller
authors.forename: Paolo
authors.initials: P
authors.lastname: Macor
authors.forename: Roberta
authors.initials: R
authors.lastname: Bulla
authors.forename: Daniele
authors.initials: D
authors.lastname: Sblattero
authors.forename: Roberto
authors.initials: R
authors.lastname: Marzari
authors.forename: Francesco
authors.initials: F
authors.lastname: Tedesco
mesh_terms: D000911:Antibodies, Monoclonal / Q000235:genetics / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents / Q000494:pharmacology; D018958:CD55 Antigens / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D018957:CD59 Antigens / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D003169:Complement Inactivator Proteins / Q000276:immunology* / Q000378:metabolism* / Q000502:physiology; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D016393:Lymphoma, B-Cell / Q000188:drug therapy / Q000276:immunology; D009369:Neoplasms / Q000276:immunology* / Q000378:metabolism; D000069283:Rituximab; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents; D018958:CD55 Antigens; D018957:CD59 Antigens; D003169:Complement Inactivator Proteins; D007128:Immunoglobulin Fragments; D007135:Immunoglobulin Variable Region; D000069283:Rituximab