title: A human-mouse chimeric Lym-1 monoclonal antibody with specificity for human lymphomas expressed in a baculovirus system.
abstract: A murine anti-human B-cell monoclonal antibody, Lym-1, has shown considerable promise for the treatment of human malignant lymphomas and has been utilized as a new radioimmunotherapy for refractory lymphoma. In order to enhance its clinical potential, a genetically engineered chimeric Lym-1 (chLym-1) with murine variable regions and human gamma 1 and kappa constant regions was constructed and expressed. The goal of this study was to generate a Lym-1 reagent with decreased immunogenicity and improved effector functions. Murine Lym-1 variable region cDNAs were isolated from the murine Lym-1 hybridoma cell line, fused to gamma 1 and kappa constant region cDNAs, and expressed in an insect cell expression system with the baculovirus transfer vector pAcUW31. The chLym-1 antibody expressed in this system was correctly processed and assembled into the expected immunoglobulin monomer. Chimeric Lym-1 bound to both target antigen-bearing Raji cells and a Lym-1 anti-idiotype antibody and had a similar binding affinity as murine Lym-1. The chimeric and murine versions of Lym-1 were assayed for their ability to mediate antibody-dependent cellular cytotoxicity (ADCC) and to induce complement-mediated cytotoxicity (CMC) against Raji targets. Chimeric Lym-1 mediated a two-fold higher level of ADCC than murine Lym-1 and slightly lower levels of CMC than murine Lym-1. In addition, in Raji lymphoma-bearing nude mice, chLym-1 localized to the tumor with approximately equal uptake at 24 and 72 hours. Chimeric Lym-1, however, cleared from the blood of nontumor-bearing mice approximately 5 times faster than murine Lym-1 (20 h vs. 5 days), as expected for a xenogeneic protein. The improved in vitro and in vivo activities of this genetically engineered monoclonal antibody render it a new potential immunotherapeutic reagent for the treatment of human malignant lymphomas.
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000912:Antibodies, Neoplasm / Q000276:immunology* / Q000378:metabolism; D000915:Antibody Affinity; D000920:Antibody-Dependent Cell Cytotoxicity; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D005822:Genetic Vectors; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000276:immunology; D008223:Lymphoma / Q000276:immunology*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009368:Neoplasm Transplantation; D017924:Nucleopolyhedroviruses / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics; D011994:Recombinant Proteins / Q000493:pharmacokinetics; D018411:Spodoptera
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D000912:Antibodies, Neoplasm; D017931:DNA Primers; D007130:Immunoglobulin Idiotypes; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins