[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

Identification of human neutralizing antibodies against MERS-CoV and their role in virus adaptive evolution

Xian-Chun Tang<SUP>a</SUP>,<SUP>1</SUP>, Sudhakar S. Agnihothram<SUP>b</SUP>,<SUP>1</SUP>, Yongjun Jiao<SUP>a</SUP>, Jeremy Stanhope<SUP>a</SUP>, Rachel L. Graham<SUP>b</SUP>, Eric C. Peterson<SUP>a</SUP>, Yuval Avnir<SUP>a</SUP>, Aimee St. Clair Tallarico<SUP>a</SUP>, Jared Sheehan<SUP>a</SUP>, Quan Zhu<SUP>a</SUP>, Ralph S. Baric<SUP>b</SUP>,<SUP>c</SUP>,<SUP>2</SUP>, and Wayne A. Marasco<SUP>a</SUP>,<SUP>2</SUP>
Author Affiliations: <SUP>a</SUP>Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215; and Departments of <SUP>b</SUP>Microbiology and Immunology and <SUP>c</SUP>Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599

Edited by Linda J. Saif, The Ohio State University, Wooster, OH, and approved April 3, 2014 (received for review February 3, 2014)

Published online before print April 28, 2014, doi: 10.1073/pnas.1402074111 - <ABBR>PNAS</ABBR> May 13, 2014 vol. 111 no. 19 E2018-E2026


The recently emerged Middle East Respiratory Syndrome coronavirus (MERS-CoV) causes severe respiratory disease with ∼43% mortality. There is no licensed vaccine or antiviral for MERS. Here we identified seven human neutralizing Abs (nAbs) against MERS-CoV. These nAbs bind to three epitope groups in the viral Spike protein?receptor interface, blocking virus attachment. Five residues in the viral receptor-binding domain critical for neutralization escape were identified. Further study indicated that four of five mutations not only confer neutralization resistance but also impair receptor binding and viral fitness. This panel of nAbs offers the possibility of developing human mAb-based immunotherapy.


The newly emerging Middle East Respiratory Syndrome coronavirus (MERS-CoV) causes a Severe Acute Respiratory Syndrome-like disease with ∼43% mortality. Given the recent detection of virus in dromedary camels, zoonotic transfer of MERS-CoV to humans is suspected. In addition, little is known about the role of human neutralizing Ab (nAb) pressure as a driving force in MERS-CoV adaptive evolution. Here, we used a well-characterized nonimmune human Ab-phage library and a panning strategy with proteoliposomes and cells to identify seven human nAbs against the receptor-binding domain (RBD) of the MERS-CoV Spike protein. These nAbs bind to three different epitopes in the RBD and human dipeptidyl peptidase 4 (hDPP4) interface with subnanomolar/nanomolar binding affinities and block the binding of MERS-CoV Spike protein with its hDPP4 receptor. Escape mutant assays identified five amino acid residues that are critical for neutralization escape. Despite the close proximity of the three epitopes on the RBD interface, escape from one epitope did not have a major impact on neutralization with Abs directed to a different epitope. Importantly, the majority of escape mutations had negative impacts on hDPP4 receptor binding and viral fitness. To our knowledge, these results provide the first report on human nAbs against MERS-CoV that may contribute to MERS-CoV clearance and evolution. Moreover, in the absence of a licensed vaccine or antiviral for MERS, this panel of nAbs offers the possibility of developing human mAb-based immunotherapy, especially for health-care workers.

IGHV1?69 ? biodefense - emerging pathogen ? zoonosis - humoral immunity


<SUP>1</SUP>X.-C.T. and S.S.A. contributed equally to this work.

<SUP>2</SUP>To whom correspondence may be addressed. E-mail: rbaric@ad.unc.edu or wayne_marasco@dfci.harvard.edu.

Author contributions: X.-C.T., S.S.A., Q.Z., R.S.B., and W.A.M. designed research; X.-C.T., S.S.A., Y.J., J. Stanhope, R.L.G., E.C.P., Y.A., and J. Sheehan performed research; X.-C.T., S.S.A., and A.S.C.T. analyzed data; and X.-C.T., S.S.A., Q.Z., and W.A.M. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1402074111/-/DCSupplemental.