The TGF-β inhibitory activity of antibody 37E1B5 depends on its H-CDR2 glycan.

Excessive transforming growth factor (TGF)-beta is associated with pro-fibrotic responses in lung disease, yet it also plays essential roles in tissue homeostasis and autoimmunity. Therefore, selective inhibition of excessive and aberrant integrin-mediated TGF-beta activation via targeting the alpha-v family of integrins is being pursued as a therapeutic strategy for chronic lung diseases, to mitigate any potential safety concerns with global TGF-beta inhibition. In this work, we reveal a novel mechanism of inhibiting TGF-beta activation utilized by an alpha v beta 8 targeting antibody, 37E1B5. This antibody blocks TGF-beta activation while not inhibiting cell adhesion. We show that an N-linked complex-type Fab glycan in H-CDR2 of 37E1B5 is directly involved in the inhibition of latent TGF-beta activation. Removal of the Fab N-glycosylation site by single amino acid substitution, or removal of N-linked glycans by enzymatic digestion, drastically reduced the antibody's ability to inhibit latency-associated peptide (LAP) and alpha v beta 8 association, and TGF-beta activation in an alpha v beta 8-mediated TGF-beta signaling reporter assay. Our results indicate a non-competitive, allosteric inhibition of 37E1B5 on alpha v beta 8-mediated TGF-beta activation. This unique, H-CDR2 glycan-mediated mechanism may account for the potent but tolerable TGF-beta activation inhibition and lack of an effect on cellular adhesion by the antibody.