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. 2013 May 10;288(19):13799-807.
doi: 10.1074/jbc.M112.433961. Epub 2013 Mar 15.

Structural basis for treating tumor necrosis factor α (TNFα)-associated diseases with the therapeutic antibody infliximab

Shuaiyi Liang  1 , Jianxin Dai, Sheng Hou, Lishu Su, Dapeng Zhang, Huaizu Guo, Shi Hu, Hao Wang, Zihe Rao, Yajun Guo, Zhiyong Lou
Affiliations

Structural basis for treating tumor necrosis factor α (TNFα)-associated diseases with the therapeutic antibody infliximab

Shuaiyi Liang et al. J Biol Chem. .

Abstract

Background: Although infliximab has high efficacy in treating TNFα-associated diseases, the epitope on TNFα remains unclear.

Results: The crystal structure of the TNFα in complex with the infliximab Fab is reported at a resolution of 2.6 Å.

Conclusion: TNFα E-F loop plays a crucial role in the interaction.

Significance: The structure may lead to understanding the mechanism of mAb anti-TNFα Monoclonal antibody (mAb) drugs have been widely used for treating tumor necrosis factor α (TNFα)-related diseases for over 10 years. Although their action has been hypothesized to depend in part on their ability to bind precursor cell surface TNFα, the precise mechanism and the epitope bound on TNFα remain unclear. In the present work, we report the crystal structure of the infliximab Fab fragment in complex with TNFα at a resolution of 2.6 Å. The key features of the TNFα E-F loop region in this complex distinguish the interaction between infliximab and TNFα from other TNF-receptor structures, revealing the mechanism of TNFα inhibition by overlapping with the TNFα-receptor interface and indicating the crucial role of the E-F loop in the action of this therapeutic antibody. This structure also indicates the formation of an aggregated network for the activation of complement-dependent cytolysis and antibody-dependent cell-mediated cytotoxicity, which result in development of granulomatous infections through TNFα blockage. These results provide the first experimental model for the interaction of TNFα with therapeutic antibodies and offer useful information for antibody optimization by understanding the precise molecular mechanism of TNFα inhibition.

Keywords: Antibodies; Antibody Therapy; Arthritis; Crystal Structure; Drug Action; Infliximab; Mechanism; Tumor Necrosis Factor (TNF).

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Figures

FIGURE 1.
FIGURE 1.
Overall structure of the TNFα-infliximab Fab complex. The TNFα-infliximab Fab complex is shown as a ribbon diagram in two orientations: top view looking down the crystallographic 3-fold symmetry axis (left), and side view with the crystallographic 3-fold axis vertical (right, middle). The molecules in one TNFα trimer are colored green, light blue, and cyan, respectively. The light chain and heavy chain of infliximab Fab are colored gold and purple, respectively.
FIGURE 2.
FIGURE 2.
Comparison of the interface between TNFα and receptors and infliximab Fab. A, TNFα from the complex structures is represented as a colored surface with TNFR2 and the infliximab Fab interface highlighted in red at one of three interfaces on the TNFα trimer. The E-F loop region, which is missing in the TNFα-TNFR2 complex because of the lack of interaction, is labeled. The TNFβ from the TNFβ-TNFR1 complex structure is shown as a colored surface with one of the TNFR1-binding sites highlighted in red. All TNF molecules are superposed and presented in the same orientation. B, the amino acid sequence alignment of TNFα and TNFβ. The E-F loop, which may play a central role in antibody-antigen interaction, is framed. The numbering of residues (top) refers to that in TNFα.
FIGURE 3.
FIGURE 3.
Detailed TNFα-infliximab Fab interface. A, surface representations and ribbon diagrams of infliximab Fab (left) and the TNFα-infliximab Fab complex (right). The light chain and heavy chain of infliximab Fab are colored gold and magenta, respectively. The TNFα trimer is colored cyan. The contact surfaces (≤3.6 Å) are highlighted in blue on infliximab Fab and red on TNFα. Ribbon diagrams corresponding to the surfaces shown above with the same color scheme. B, stereoview of the TNFα-infliximab Fab interface. The residues that are involved in the intermolecular interaction are shown as colored sticks with the same scheme as the surface representation above. Infliximab Fab and TNFα molecules are presented as ribbon diagrams.
FIGURE 4.
FIGURE 4.
Structural variety of TNFα in free form and TNFα-TNFR2 and TNFα-infliximab Fab complexes. The free state of the molecule is colored gray. TNFα molecules in the TNFα-TNFR2 and TNFα-infliximab Fab complex structures are colored red and cyan, respectively. The variant parts of the C-D and E-F loops of TNFα are framed.
See this image and copyright information in PMC

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