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Structures of Ebola virus GP and sGP in complex with therapeutic antibodies

Abstract

The Ebola virus (EBOV) GP gene encodes two glycoproteins. The major product is a soluble, dimeric glycoprotein (sGP) that is secreted abundantly. Despite the abundance of sGP during infection, little is known regarding its structure or functional role. A minor product, resulting from transcriptional editing, is the transmembrane-anchored, trimeric viral surface glycoprotein (GP). GP mediates attachment to and entry into host cells, and is the intended target of antibody therapeutics. Because large portions of sequence are shared between GP and sGP, it has been hypothesized that sGP may potentially subvert the immune response or may contribute to pathogenicity. In this study, we present cryo-electron microscopy structures of GP and sGP in complex with GP-specific and GP/sGP cross-reactive antibodies undergoing human clinical trials. The structure of the sGP dimer presented here, in complex with both an sGP-specific antibody and a GP/sGP cross-reactive antibody, permits us to unambiguously assign the oligomeric arrangement of sGP and compare its structure and epitope presentation to those of GP. We also provide biophysical evaluation of naturally occurring GP/sGP mutations that fall within the footprints identified by our high-resolution structures. Taken together, our data provide a detailed and more complete picture of the accessible Ebolavirus glycoprotein landscape and a structural basis to evaluate patient and vaccine antibody responses towards differently structured products of the GP gene.

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Figure 1: Structural analysis of ZMapp–EBOV GP complexes.
Figure 2: Details of the ZMapp antibody epitopes.
Figure 3: Cryo-EM structure of EBOV sGP in complex with c13C6 from ZMapp and BDBV human survivor mAb BDBV91.
Figure 4: Comparison of GP and sGP structures.
Figure 5: Effects of naturally occurring mutations that appeared in the 2014 EBOV outbreak on antibody binding within identified GP and sGP footprints.
Figure 6: Differential presentation of GP/sGP epitopes during Ebolavirus infection.

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Acknowledgements

The authors thank K. Swope and J. Morton of Kentucky Bioprocessing for preparing and sending all ZMapp IgGs. The authors thank T. Nieusma and B. Anderson of TSRI for assistance with loading cryo samples, data collection and running the microscopy facility, and B. Barad for providing the scripts for EMRinger. This work was supported by R01 AI067927 ‘Ebola Viral Glycoproteins: Structural Analysis’, the NIH/National Institute of Allergy and Infectious Diseases Center for Excellence in Translational Research grant no. U19AI109762 ‘Consortium for Immunotherapeutics Against Viral Hemorrhagic Fevers’, and U19AI109711 ‘Advancement of Treatments for Ebola and Marburg Virus Infections’. C.D.M. was supported by a predoctoral fellowship from the National Science Foundation. This is manuscript no. 29260 from The Scripps Research Institute.

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Authors and Affiliations

Authors

Contributions

J.P., C.D.M., E.O.S. and A.B.W. designed the research plan. M.L.F. designed the protein expression constructs for GP and sGP. A.I.F. and J.E.C. isolated and purified BDBV91. L.Z. provided ZMapp antibodies. C.D.M. and H.L.T. expressed and purified proteins. K.M.H. and C.D.M. performed biophysical experiments. J.P., C.D.M. and H.L.T. prepared protein complexes. J.P., C.D.M and N.d.-V. froze grids. J.P. and N.d.-V. collected cryo data. J.P. processed the cryo data. C.D.M. collected and processed negative stain data. C.A.C. performed structure modelling and refinement. J.P., C.D.M., C.A.C., K.M.H., M.L.F., E.O.S. and A.B.W. analysed data. J.P., C.D.M., C.A.C., E.O.S. and A.B.W. wrote the manuscript. K.G.A. provided Makona outbreak sequence information.

Corresponding authors

Correspondence to Erica Ollmann Saphire or Andrew B. Ward.

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Competing interests

Larry Zeitlin is a co-owner of Mapp Biopharmaceutical, Inc. The other authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary Figures 1–16, Supplementary Tables 1–4, 6 and 7, legend of Supplementary Table 5, Supplementary References. (PDF 30079 kb)

Supplementary Table 5

2014 EBOV outbreak GP mutations. (XLSX 42 kb)

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Pallesen, J., Murin, C., de Val, N. et al. Structures of Ebola virus GP and sGP in complex with therapeutic antibodies. Nat Microbiol 1, 16128 (2016). https://doi.org/10.1038/nmicrobiol.2016.128

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