Agonistic activity of a CD40-specific single-chain Fv constructed from the variable regions of mAb G28-5.
A single-chain Fv (sFv) was expressed from the variable regions of the CD40-specific mAb G28-5. The molecule bound CD40 with a high affinity (2.2 nM) and was a monomer in solution. Surprisingly, G28-5 sFv was a potent CD40 agonist that rapidly crosslinked CD40 on the cell surface but did not crosslink CD40-Ig in solution. G28-5 sFv was a more potent agonist than G28-5 IgG and was able to stimulate CD40 responses by B cells and monocytes. G28-5 IgG partially blocked, whereas G28-5 sFv augmented CD40 responses during stimulation with natural ligand (gp39-CD8 fusion protein). These results indicate that the functional activity of ligands built from the binding site of G28-5 is highly dependent upon the size and physical properties of the molecule both in solution and on the cell surfaces.
Ledbetter
J A
JA
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, WA 98121, USA.
Francisco
J A
JA
Siegall
C B
CB
Gilliland
L K
LK
Hollenbaugh
D
D
Aruffo
A
A
Siadak
A W
AW
Mischel-Petty
N
N
Grosmaire
L S
LS
Gordon
M L
ML
Brown
T J
TJ
Moran-Davis
P
P
Mittler
R S
RS
Kiener
P A
PA
Nadler
S G
SG
D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004727:Endothelium / Q000166:cytology; D015870:Gene Expression; D006801:Humans; D007128:Immunoglobulin Fragments / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D009000:Monocytes / Q000276:immunology; D016328:NF-kappa B / Q000276:immunology
D000911:Antibodies, Monoclonal; D019013:CD40 Antigens; D007128:Immunoglobulin Fragments; D007135:Immunoglobulin Variable Region; D016328:NF-kappa B; C055966:immunoglobulin Fv