Isotype choice for chimeric antibodies affects binding properties.
Construction of a series of chimeric antibodies (murine variable region and human constant region) derived from the murine antibody BIRR1, which recognizes intercellular adhesion molecule 1 (ICAM-1), has revealed differences in the relative binding abilities of the chimeric antibody to antigen. The chimeric antibodies show a ranking of their ability to compete with BIRR1 for antigen on the surface of cells with the order BIRR1 = cIgG1 (100%) > cIgG4 (30%) > cIgG2 (10%) as demonstrated by solid-phase competitive enzyme-linked immunosorbent assay. Papain digestion yielded Fab fragments that were purified to homogeneity. Competitive enzyme-linked immunosorbent assay showed that the chimeric and murine Fab binding constants were equivalent. A solution-phase binding assay (analyzed by size exclusion high performance liquid chromatography) between the intact mAbs and recombinant soluble ICAM-1 further established that the binding constants involving the Fab arms of the two antibodies were equivalent. In summary, the murine and chimeric anti-ICAM-1 antibodies bind cellular ICAM-1 with equivalent affinities but with differing avidities.
Morelock
M M
MM
Department of Biochemistry, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877-0368.
Rothlein
R
R
Bright
S M
SM
Robinson
M K
MK
Graham
E T
ET
Sabo
J P
JP
Owens
R
R
King
D J
DJ
Norris
S H
SH
Scher
D S
DS
D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D001483:Base Sequence; D001666:Binding Sites, Antibody; D016466:CHO Cells; D015815:Cell Adhesion Molecules / Q000276:immunology; D006224:Cricetinae; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D018799:Intercellular Adhesion Molecule-1; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D007140:Immunoglobulin Fab Fragments; D007132:Immunoglobulin Isotypes; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D018799:Intercellular Adhesion Molecule-1