Identification of their epitope reveals the structural basis for the mechanism of action of the immunosuppressive antibodies basiliximab and daclizumab

TY - JOUR

T1 - Identification of their epitope reveals the structural basis for the mechanism of action of the immunosuppressive antibodies basiliximab and daclizumab

AU - Binder, Mascha

AU - Vögtle, Friederike-Nora

AU - Michelfelder, Stefan

AU - Müller, Fabian

AU - Illerhaus, Gerald

AU - Sundararajan, Sangeeth

AU - Mertelsmann, Roland

AU - Trepel, Martin

PY - 2007/4/15

Y1 - 2007/4/15

N2 - Interleukin-2 (IL-2) and its receptor (IL-2R) play a major role in cellular immunity. The monoclonal antibodies basiliximab and daclizumab directed against the IL-2R subunit CD25 are widely used to prevent graft or host rejection after allogeneic tissue transplantation. Although these antibodies have been used for this purpose for many years, their common epitope within the CD25 protein is unknown. We screened a random phage display library to isolate peptides specifically binding to basiliximab. A striking amino acid sequence motif was enriched. This motif is homologous to the peptide ERIYHFV comprising amino acid positions 116 to 122 within the extracellular domain of CD25, suggesting that this is the basiliximab epitope. Basiliximab and daclizumab binding of selected phage was specific, as no binding was observed to isotype antibody controls. Phage binding could be inhibited by the cognate peptide. In cells expressing mutant CD25, binding of basiliximab was abolished when two or more amino acids of the suspected epitope were changed. In contrast, basiliximab binding remained unaffected in cells expressing CD25 versions with mutations outside this epitope. We therefore conclude that the (116)ERIYHFV(122) string within CD25 is the epitope recognized by basiliximab and daclizumab. This epitope overlaps with the interaction site of CD25 and IL-2, thus revealing the structural basis for the inhibition of IL-2R binding by this class of immunosuppressive antibodies.

AB - Interleukin-2 (IL-2) and its receptor (IL-2R) play a major role in cellular immunity. The monoclonal antibodies basiliximab and daclizumab directed against the IL-2R subunit CD25 are widely used to prevent graft or host rejection after allogeneic tissue transplantation. Although these antibodies have been used for this purpose for many years, their common epitope within the CD25 protein is unknown. We screened a random phage display library to isolate peptides specifically binding to basiliximab. A striking amino acid sequence motif was enriched. This motif is homologous to the peptide ERIYHFV comprising amino acid positions 116 to 122 within the extracellular domain of CD25, suggesting that this is the basiliximab epitope. Basiliximab and daclizumab binding of selected phage was specific, as no binding was observed to isotype antibody controls. Phage binding could be inhibited by the cognate peptide. In cells expressing mutant CD25, binding of basiliximab was abolished when two or more amino acids of the suspected epitope were changed. In contrast, basiliximab binding remained unaffected in cells expressing CD25 versions with mutations outside this epitope. We therefore conclude that the (116)ERIYHFV(122) string within CD25 is the epitope recognized by basiliximab and daclizumab. This epitope overlaps with the interaction site of CD25 and IL-2, thus revealing the structural basis for the inhibition of IL-2R binding by this class of immunosuppressive antibodies.

KW - Amino Acid Motifs

KW - Amino Acid Sequence

KW - Antibodies, Monoclonal

KW - Antibodies, Monoclonal, Humanized

KW - Binding Sites

KW - Cell Line

KW - Epitopes

KW - Humans

KW - Immunoglobulin G

KW - Immunosuppressive Agents

KW - Interleukin-2

KW - Interleukin-2 Receptor alpha Subunit

KW - Models, Molecular

KW - Molecular Sequence Data

KW - Peptide Library

KW - Peptides

KW - Protein Conformation

KW - Receptors, Interleukin-2

KW - Recombinant Fusion Proteins

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1158/0008-5472.CAN-06-3919

DO - 10.1158/0008-5472.CAN-06-3919

M3 - SCORING: Journal article

C2 - 17440057

VL - 67

SP - 3518

EP - 3523

JO - CANCER RES

JF - CANCER RES

SN - 0008-5472

IS - 8

ER -