title: The effect of aglycosylation on the immunogenicity of a humanized therapeutic CD3 monoclonal antibody.
abstract: The factors affecting the immunogenicity of a humanized gamma 1 CD3 monoclonal antibody (mAb) were investigated in transgenic mice that express the human CD3 antigen epsilon polypeptide (the mAb target antigen). Two derivatives of the mAb were employed, one with a normal, glycosylated Fc region (gamma 1 CD3 mAb), and the other with an aglycosylated Fc region (aglycosyl gamma 1 CD3 mAb). Comparisons of the antiglobulin responses elicited by the two derivatives in transgenic and nontransgenic mice demonstrated that Fab-mediated cell binding activity, dependent on target antigen expression, was a major positive determinant of CD3 mAb immunogenicity. A second positive factor was mAb Fc region glycosylation. At low dose levels the gamma 1 CD3 mAb consistently produced a higher antiglobulin response than the aglycosyl gamma 1 CD3 mAb. This was probably a result of the nonspecific, in vivo T cell activating property of the gamma 1 CD3 mAb, a consequence of its ability to cross-link T cells to Fc gamma receptor-bearing cells. (The aglycosyl gamma 1 CD3 mAb has a reduced Fc binding affinity for Fc gamma receptors and so does not activate T cells in vivo.) In support of this hypothesis, the gamma 1 CD3 mAb was able to nonspecifically enhance humoral immunity to an unrelated, coadministered antigen, whereas the aglycosyl gamma 1 CD3 mAb was not. The lower immunogenicity of the aglycosyl gamma 1 CD3 mAb correlated with a longer in vivo half-life and an improved capacity to block the target CD3 antigen. These results suggest that, as well as reducing the cytokine-induced side effects normally associated with CD3 mAb therapy, the nonactivating aglycosyl gamma 1 CD3 mAb will be less likely than the activating gamma 1 CD3 mAb to stimulate a neutralizing antiglobulin response.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000276:immunology* / Q000627:therapeutic use; D017252:CD3 Complex / Q000276:immunology*; D015195:Drug Design; D006031:Glycosylation; D006801:Humans; D007109:Immunity; D007141:Immunoglobulin Fc Fragments / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic
chemical_list: D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D007141:Immunoglobulin Fc Fragments