Identification and characterization of a human monoclonal antagonistic antibody AL-57 that preferentially binds the high-affinity form of lymphocyte function-associated antigen-1.
LFA-1 (alpha(L)beta(2)) mediates cell-cell and cell-extracellular matrix adhesions essential for immune and inflammatory responses. One critical mechanism regulating LFA-1 activity is the conformational change of the ligand-binding alpha(L) I domain from low-affinity (LA), closed form, to the high-affinity (HA), open form. Most known integrin antagonists bind both forms. Antagonists specific for the HA alpha(L) I domain have not been described. Here, we report the identification and characterization of a human antibody AL-57, which binds to the alpha(L) I domain in a HA but not LA conformation. AL-57 was discovered by selection from a human Fab-displaying library using a locked-open HA I domain as target. AL-57 Fab-phage bound HA I domain-expressing K562 cells (HA cells) in a Mg(2+)-dependent manner. AL-57 IgG also bound HA cells and PBMCs, activated by Mg(2+)/EGTA, PMA, or DTT. The binding profile of AL-57 IgG on PBMCs was the same as that of ICAM-1, the main ligand of LFA-1. In contrast, an anti-alpha(L) murine mAb MHM24 did not distinguish between the HA and LA forms. Moreover, AL-57 IgG blocked ICAM-1 binding to HA cells with a potency greater than MHM24. It also inhibited ICAM-1 binding to PBMCs, blocked adhesion of HA cells to keratinocytes, and inhibited PHA-induced lymphocyte proliferation with potencies comparable with MHM24. These results indicate that specifically targeting the HA I domain is sufficient to inhibit LFA-1-mediated, adhesive functions. AL-57 represents a therapeutic candidate for treatment of inflammatory and autoimmune diseases.
Huang
Lili
L
Dyax Corporation, Cambridge, MA 02139, USA. lhuang@dyax.com
Shimaoka
Motomu
M
Rondon
Isaac J
IJ
Roy
Illa
I
Chang
Qing
Q
Po
Melody
M
Dransfield
Daniel T
DT
Ladner
Robert C
RC
Edge
Albert S B
AS
Salas
Azucena
A
Wood
Clive R
CR
Springer
Timothy A
TA
Cohen
Edward H
EH
D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000494:pharmacology*; D000937:Antigen-Antibody Reactions; D001665:Binding Sites; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000187:drug effects; D015603:Keratinocytes / Q000187:drug effects; D007963:Leukocytes, Mononuclear / Q000187:drug effects*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000187:drug effects* / Q000276:immunology; D008969:Molecular Sequence Data; D010835:Phytohemagglutinins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013329:Structure-Activity Relationship
D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D016169:Lymphocyte Function-Associated Antigen-1; D010835:Phytohemagglutinins; D018799:Intercellular Adhesion Molecule-1