Crystal structure of CD27 in complex with a neutralizing noncompeting antibody.

Alexey Teplyakov,Gary L Gilliland,Galina Obmolova,Thomas J Malia

doi:10.1107/s2053230x17005957

Abstract

CD27 is a T-cell and B-cell co-stimulatory glycoprotein of the tumor necrosis factor (TNF) receptor superfamily that is dependent on the availability of the TNF-like ligand CD70. Therapeutic approaches to treating autoimmune diseases and cancers with antagonistic and agonistic anti-CD27 monoclonal antibodies (mAbs), respectively, have recently been developed. Mouse anti-human CD27 mAb 2177 shows potency in neutralizing CD70-induced signaling; however, it does not block the binding of soluble CD70. To provide insight into the mechanism of action of the mAb, the crystal structure of the CD27 extracellular domain in complex with the Fab fragment of mAb 2177 was determined at 1.8 Å resolution. CD27 exhibits the assembly of cysteine-rich domains characteristic of the TNF receptor superfamily. The structure reveals a unique binding site of mAb 2177 at the edge of the receptor molecule, which allows the mAb to sterically block the cell-bound form of CD70 from reaching CD27 while leaving the ligand epitope clear. This mode of action suggests a potential dual use of mAb 2177 either as an antagonist or as an agonist.

Highlights

CD27 is a type I transmembrane glycoprotein expressed as a surface antigen on T cells, natural killer cells and antibodysecreting plasma and memory B cells (Borst et al, 2005)
CD27 belongs to the tumor necrosis factor (TNF) receptor superfamily, which includes OX40, CD40, CD30, receptors of nerve growth factor, lymphotoxin beta and Fas, and a number of death receptors (Camerini et al, 1991)
Identification of the monoclonal antibodies (mAbs) epitope adds to the continued discussion on the structurally distinct epitopes in the TNF receptor (TNFR) superfamily and their possible relationship to different biological outcomes

Summary

Introduction

CD27 is a type I transmembrane glycoprotein expressed as a surface antigen on T cells, natural killer cells and antibodysecreting plasma and memory B cells (Borst et al, 2005). A number of open questions regarding the structure–function relationship of agonistic and antagonistic antibodies and the importance of the epitope and affinity in their biological potency remain. Identification of the mAb epitope adds to the continued discussion on the structurally distinct epitopes in the TNF receptor (TNFR) superfamily and their possible relationship to different biological outcomes. This 1.8 Aresolution structure of CD27 in complex with Fab 2177 is more complete and more accurate than that in a ternary complex with Fabs 2177 and 2191 which was determined previously at. The structure allowed a mapping of the pathological mutations in CD27 related to immunodeficiency

Proteins

Crystallization

X-ray data collection and structure determination

CD27 structure

CD27–Fab 2177 complex