Function-blocking Integrin αvβ6 Monoclonal Antibodies

• Published in: The Journal of biological chemistry 2004-04, Vol.279 (17), p.17875
• Main Authors: Paul H. Weinreb, Kenneth J. Simon, Paul Rayhorn, William J. Yang, Diane R. Leone, Brian M. Dolinski, Bradley R. Pearse, Yukako Yokota, Hisaaki Kawakatsu, Amha Atakilit, Dean Sheppard, Shelia M. Violette
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M312103200

We have generated a panel of potent, selective monoclonal antibodies that bind human and mouse α v β 6 integrin with high affinity (up to 15 p m ). A subset of these antibodies blocked the binding of α v β 6 to the transforming growth factor-β1 latency-associated peptide with IC 50 values as low as 18 p m , and prevented the subsequent α v β 6 -mediated activation of transforming growth factor-β1. The antibodies also inhibited α v β 6 binding to fibronectin. The blocking antibodies form two biochemical classes. One class, exemplified by the ligand-mimetic antibody 6.8G6, bound to the integrin in a divalent cation-dependent manner, contained an RGD motif or a related sequence in CDR3 of the heavy chain, was blocked by RGD-containing peptides, and was internalized by α v β 6 -expressing cells. Despite containing an RGD sequence, 6.8G6 was specific for α v β 6 and showed no cross-reactivity with the RGD-binding integrins α v β 3 , α v β 8 ,or α IIb β 3 . The nonligand-mimetic blocking antibodies, exemplified by 6.3G9, were cation-independent, were not blocked by RGD-containing peptides, were not internalized, and did not contain RGD or related sequences. These two classes of antibody were unable to bind simultaneously to α v β 6 , suggesting that they may bind overlapping epitopes. The “ligand-mimetic” antibodies are the first to be described for α v β 6 and resemble those described for α IIb β 3 . We also report for the first time the relative abilities of divalent cations to promote α v β 6 binding to latency-associated peptide and to the ligand-mimetic antibodies. These antibodies should provide valuable tools to study the ligand-receptor interactions of α v β 6 as well as the role of α v β 6 in vivo .