Isolation of human Fab antibodies specific for the low-affinity IgE receptor (CD23) by selecting a hierarchical antibody library system against B lymphoblastic IM-9 cells.

Abstract

The development of human antibodies specific for certain B cell markers is required to generate therapeutic antibody leads with improved therapeutic indices against B-cell lymphomas. To meet this demand, we selected a primary human antibody library, HuDVFab-8L, against human B lymphoblastic IM-9 cells via a 'Biopanning and Rapid Analysis of Selective Interactive Ligands (BRASIL)' cell panning approach. Six Fab clones that specifically bound to IM-9 cells were successfully isolated. Among these clones, two clones (IM-L6-E and IM-L8-G), were found to be specific for CD23 (FcɛRII). Affinity maturation of these Fab clones was then performed in a hierarchical manner by constructing secondary antibody libraries through combining heavy (H) chains of two Fabs with the human kappa L chain sublibrary HuNL-D3 followed by biopanning against the CD23 antigen. Clone IM-L6-5, one of the affinity maturated Fab derivatives from IM-L6-E, has a binding affinity of k(D)≈30 nM to soluble CD23. In addition, IM-L6-5 Fab is able to bind to an inducible form of CD23 expressed on U937 cells upon IL-4 stimulation, and inhibits binding of human IgE to CD23. Since the Fab IM-L6-5 is derived from a fully human naïve origin, we believe that IM-L6-5 can be utilized for the development of a therapeutic mAb which may have an improved therapeutic index over lumiliximab, a primatized anti-CD23 mAb, for the treatment of CLL or allergic diseases.

• Authors: Hyo-jung Choi, Suk-yoon Song, Jae-bong Yoon, Li-kun Liu, Kristine Kim, Sang-hoon Cha
• Journal: Immunology letters (Immunol Lett) Vol. 136 Issue 2 Pg. 213-20 (May 2011) ISSN: 1879-0542 [Electronic] Netherlands
• PMID: 21277901 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 Elsevier B.V. All rights reserved.

Chemical References

• Immunoglobulin Fab Fragments
• Immunoglobulin Light Chains
• Peptide Library
• Receptors, IgE

Topics

• Antibody Affinity (immunology)
• Antibody Specificity (immunology)
• Cell Line, Tumor
• Humans
• Immunoglobulin Fab Fragments (immunology, isolation & purification)
• Immunoglobulin Light Chains (immunology, metabolism)
• Lymphoma, B-Cell (metabolism)
• Peptide Library
• Protein Binding (immunology)
• Receptors, IgE (immunology, metabolism)
• U937 Cells