Genetically engineered deglycosylation of the variable domain increases the affinity of an anti-CD33 monoclonal antibody.

Abstract	M195 is a murine monoclonal antibody that binds to the CD33 antigen and is being tested for the treatment of myeloid leukemia. Surprisingly, a complementarity determining region (CDR)-grafted, humanized M195 antibody displayed a several-fold higher binding affinity for the CD33 antigen than the original murine antibody. Here we show that the increase in binding affinity resulted from eliminating an N-linked glycosylation site at residue 73 in the heavy chain variable region in the course of humanization. Re-introducing the glycosylation site in the humanized antibody reduces its binding affinity to that of the murine antibody, while removing the glycosylation site from the murine M195 variable domain increases its affinity. The removal of variable region carbohydrates may provide a method for increasing the affinity of certain monoclonal antibodies with diagnostic and therapeutic potential.
Authors	M S Co, D A Scheinberg, N M Avdalovic, K McGraw, M Vasquez, P C Caron, C Queen
Journal	Molecular immunology (Mol Immunol) Vol. 30 Issue 15 Pg. 1361-7 (Oct 1993) ISSN: 0161-5890 [Print] England
PMID	8232322 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References	Antibodies, Monoclonal Antigens, CD Antigens, Differentiation, Myelomonocytic Glycoproteins Immunoglobulin Variable Region Recombinant Fusion Proteins Sialic Acid Binding Ig-like Lectin 3
Topics	Amino Acid Sequence Antibodies, Monoclonal (chemistry, immunology) Antibody Affinity Antigens, CD (immunology) Antigens, Differentiation, Myelomonocytic (immunology) Binding Sites, Antibody Glycoproteins (immunology) Immunoglobulin Variable Region (chemistry) Models, Molecular Molecular Sequence Data Protein Structure, Tertiary Recombinant Fusion Proteins (immunology) Sialic Acid Binding Ig-like Lectin 3 Structure-Activity Relationship

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