Higher order structures of Adalimumab, Infliximab and their complexes with TNF? revealed by electron microscopy.

ABSTRACT: Adalimumab and Infliximab are recombinant IgG1 monoclonal antibodies (mAbs) that bind and neutralize human tumor necrosis factor alpha (TNF?). TNF? forms a stable homotrimer with unique surface-exposed sites for Adalimumab, Infliximab, and TNF receptor binding. Here, we report the structures of Adalimumab-TNF? and Infliximab-TNF? complexes modeled from negative stain EM and cryo-EM images. EM images reveal complex structures consisting of 1:1, 1:2, 2:2, and 3:2 complexes of Adalimumab-TNF? and Infliximab-TNF?. The 2:2 complex structures of Adalimumab-TNF? and Infliximab-TNF? show diamond-shaped profiles and the 2D class averages reveal distinct orientations of the Fab domains, indicating different binding modes by Adalimumab and Infliximab to TNF?. After separation by size exclusion chromatography and analysis by negative stain EM, the 3:2 complexes of Adalimumab-TNF? or Infliximab-TNF? complexes are more complicated but retain features recognized in the 2:2 complexes. Preliminary cryo-EM analysis of 3:2 Adalimumab-TNF? complex generated a low-resolution density consistent with a TNF? trimer bound with three Fab domains from three individual antibody molecules, while each antibody molecule binds to two molecules of TNF? trimer. The Fc domains are not visible in the reconstruction. These results show the two mAbs form structurally distinct complexes with TNF?.

SUBMITTER: Tran BN 

PROVIDER: S-EPMC5699491 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature