ABSTRACT
Infusion reactions are a major side effect of the administration of therapeutic Abs and are the result of a complex immune reaction. In this study, we report that substitutions of Fc amino acids in the anti-HLA-DR Ab HD8 reduce its ability to induce infusion reactions in rats and monkeys. We first showed that i.v. administration of IgG1- and IgG2-subclass HD8 Abs induces severe infusion reactions in monkeys. These Abs express strong complement-dependent cytotoxicity (CDC), and in vivo depletion of complement in rats by pretreatment with cobra venom factor abrogated the lethal infusion reactions generated by HD8-IgG1. Thus, the infusion reactions appear to be largely driven by the complement system. To reduce the CDC function of HD8-IgG1, its Fc region was modified by two amino acid substitutions at Pro(331)Ser and Lys(322)Ala. The modified Ab was incapable of expressing CDC in vitro and did not induce severe infusion reactions in rats and monkeys, even at extremely high doses. The modified Ab retained its Ab-dependent cellular cytotoxicity function as well as its antitumor activity in a tumor-bearing mouse model. In summary, complement appears to drive infusion reactions, and modifications that eliminate the CDC activity of an Ab also reduce its ability to induce infusion reactions.
Subject(s)
Antibody-Dependent Cell Cytotoxicity/immunology , Complement Activation/immunology , Isoantibodies/toxicity , Animals , Animals, Congenic , Antineoplastic Agents/administration & dosage , Antineoplastic Agents/therapeutic use , CHO Cells , Cell Line , Cell Line, Tumor , Complement System Proteins/toxicity , Cricetinae , Cricetulus , HLA-DR Antigens/immunology , HLA-DR Antigens/metabolism , Humans , Immunoglobulin Fc Fragments/administration & dosage , Immunoglobulin Fc Fragments/genetics , Immunoglobulin Fc Fragments/metabolism , Infusions, Intravenous/adverse effects , Isoantibodies/administration & dosage , Isoantibodies/therapeutic use , Lymphoma/immunology , Lymphoma/mortality , Lymphoma/therapy , Macaca fascicularis , Male , Mice , Mice, SCID , Rats , Transplantation, HeterologousABSTRACT
HD8, a fully human monoclonal antibody specific for human leukocyte antigen-DR (HLA-DR), was generated by using the transchromosome mouse that bears the human immunoglobulin genes. HD8 could bind to all 13 tested HLA-DR-positive cell lines and 35 B-cells from healthy donors. Epitope mapping revealed that while the antibody recognizes the most polymorphic region of the HLA-DRB chain, its critical epitope residues are conserved in the major alleles. Indeed, HD8 could recognize 99.2% of HLA-DRB alleles. Since its essential epitope residues are also largely conserved in HLA-DP and HLA-DQ, HD8 could recognize 100% and 66% of the HLA-DP and HLA-DQ alleles tested, respectively. HD8 exerted strong antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in vitro, and significantly extended the life span of immunocompromised mice inoculated with non-Hodgkin lymphoma cell lines. The HD8 antibody may be highly useful in HLA-DR-targeted immunotherapy as it is likely to evoke similarly strong responses in individuals carrying different HLA-DR alleles.
