#Molecular basis of a protective/neutralizing #monoclonal #antibody targeting envelope proteins of both #tick-borne #encephalitis virus and louping ill virus (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

Molecular basis of a protective/neutralizing monoclonal antibody targeting envelope proteins of both tick-borne encephalitis virus and louping ill virus

Xu Yang, Jianxun Qi, Ruchao Peng, Lianpan Dai, Ernest A. Gould, George F. Gao, Po Tien

DOI: 10.1128/JVI.02132-18



Tick-borne encephalitis virus (TBEV) and louping ill virus (LIV) are members of the tick-borne flaviviruses (TBFVs) in the family Flaviviridae, which cause encephalomeningitis and encephalitis in humans and other animals. Although vaccines against TBEV and LIV are available, infection rates are rising due to the low vaccination coverage. To date, no specific therapeutics have been licensed. Several neutralizing monoclonal antibodies (MAbs) show promising effectiveness in the control of TBFVs, but the underlying molecular mechanisms are yet to be characterized. Here, we determined the crystal structures of LIV envelope protein (E) and report the comparative structural analysis of a TBFV broadly neutralizing murine MAb (MAb 4.2) in complex with either LIV or TBEV E proteins. The structures reveal that MAb 4.2 binds to the lateral ridge of Domain III (EDIII) of LIV-E or TBEV-E, an epitope also reported for other potently neutralizing MAbs against mosquito-borne flaviviruses (MBFVs), but adopts a unique binding orientation. Further structural analysis suggested that MAb 4.2 may neutralize flavivirus infection by preventing the structural rearrangement required for membrane fusion during virus entry. These findings extend our understanding of the vulnerability of TBFVs and other flaviviruses (including MBFVs) and provide an avenue for antibody-based TBFVs antiviral development.



Understanding the mechanism of antibody neutralization/protection against a virus is crucial for antiviral counter-measures development. Tick-borne encephalitis virus (TBEV) and louping ill virus (LIV) are tick-borne flaviviruses (TBFVs) in the family Flaviviridae. They cause encephalomeningitis and encephalitis in humans and other animals. Although vaccines for both viruses are available, infection rates are rising due to the low vaccination coverage. In this study, we solved the crystal structures of LIV envelope protein (E) and a broadly-neutralizing/protective TBFV MAb, MAb 4.2, in complex with E from either TBEV or LIV. Key structural features shared by TBFV E proteins were analyzed. Structures of E-antibody complexes show that MAb 4.2 targets the lateral ridge of both TBEV and LIV E proteins, a vulnerable site in flaviviruses for other potent neutralizing MAbs. Thus, this site represents a promising target for TBFV antiviral development. Further, these structures provide important information for understanding TBFV antigenicity.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Flavivirus; Tick-borne encephalitis virus; Louping ill virus; Monoclonal antibodies.



Early #human B cell response to #Ebola virus in four #US #survivors of #infection (J Virol., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

J Virol. 2019 Feb 6. pii: JVI.01439-18. doi: 10.1128/JVI.01439-18. [Epub ahead of print]

Early human B cell response to Ebola virus in four U.S. survivors of infection.

Williamson L1, Flyak AI1, Kose N1, Bombardi R1, Branchizio A1, Reddy S2, Davidson E2, Doranz B2, Fusco ML3, Saphire EO3, Halfmann PJ4, Kawaoka Y4, Piper AE5, Glass PJ5, Crowe JE Jr6,1,1.

Author information: 1 Departments of Pathology, Microbiology, and Immunology Pediatrics, and The Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Vanderbilt University, Nashville, TN 37232, USA. 2 Integral Molecular, Philadelphia, PA, 19104, USA. 3 Departments of Immunology and Microbial Science, The Scripps Research Institute La Jolla, CA 92037, USA. 4 Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI, USA. 5 Virology Division, US Army Medical Research Institute of Infectious Diseases, MD 21702, USA. 6 Departments of Pathology, Microbiology, and Immunology Pediatrics, and The Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Vanderbilt University, Nashville, TN 37232, USA james.crowe@vanderbilt.edu.



The human B cell response to natural filovirus infections early after recovery is poorly understood. Previous serologic studies suggest that some Ebola virus survivors exhibit delayed antibody responses with low magnitude and quality. Here, we sought to study the population of individual memory B cells induced early in convalescence. We isolated monoclonal antibodies (mAbs) from memory B cells from four survivors treated for Ebola virus disease (EVD) one or three-months after discharge from hospital. At the early time points post-recovery, the frequency of Ebola-specific B cells was low and dominated by clones that were cross-reactive with both Ebola glycoprotein (GP) and with the secreted form (sGP). Of 25 mAbs isolated from four donors, only one exhibited neutralization activity. This neutralizing mAb, designated mAb EBOV237, recognizes an epitope in the glycan cap of the surface glycoprotein. In vivo murine lethal challenge studies showed that EBOV237 conferred protection when given prophylactically at a level similar to that of the ZMapp component mAb 13C6. The results suggest that the human B cell response to EVD one to three months post-discharge is characterized by a paucity of broad or potent neutralizing clones. However, the neutralizing epitope in the glycan cap recognized by EBOV237 may play a role in the early human antibody response to EVD and should be considered in rational design strategies for new Ebola virus vaccine candidates.



The pathogenesis of Ebola virus disease (EVD) in humans is complex, and the mechanisms contributing to immunity are poorly understood. In particular, it appears that the quality and magnitude of the human B cell response early after recovery from EVD may be reduced compared to most viral infections. Here we isolated human monoclonal antibodies from B cells of four survivors of EVD at one or three months after hospital discharge. Ebola-specific memory B cells early in convalescence were low in frequency, and the antibodies they encoded demonstrated poor neutralizing potencies. One neutralizing antibody that protected mice from lethal infection, EBOV237, was identified in the panel of 25 human antibodies isolated. Recognition of the glycan cap epitope recognized by EBOV237 suggests this antigenic site should be considered in vaccine design and treatment strategies for EVD.

Copyright © 2019 American Society for Microbiology.

PMID: 30728263 DOI: 10.1128/JVI.01439-18

Keywords: Ebola; Monoclonal antibodies.


Potent anti- #influenza #H7 human #monoclonal #antibody induces separation of #hemagglutinin receptor-binding head domains (PLoS Biology, abstract)

[Source: PLoS Biology, full page: (LINK). Abstract, edited.]


Potent anti-influenza H7 human monoclonal antibody induces separation of hemagglutinin receptor-binding head domains

Hannah L. Turner , Jesper Pallesen , Shanshan Lang, Sandhya Bangaru, Sarah Urata, Sheng Li, Christopher A. Cottrell, Charles A. Bowman, James E. Crowe Jr., Ian A. Wilson, Andrew B. Ward

Published: February 4, 2019 / DOI: https://doi.org/10.1371/journal.pbio.3000139 / This is an uncorrected proof.



Seasonal influenza virus infections can cause significant morbidity and mortality, but the threat from the emergence of a new pandemic influenza strain might have potentially even more devastating consequences. As such, there is intense interest in isolating and characterizing potent neutralizing antibodies that target the hemagglutinin (HA) viral surface glycoprotein. Here, we use cryo-electron microscopy (cryoEM) to decipher the mechanism of action of a potent HA head-directed monoclonal antibody (mAb) bound to an influenza H7 HA. The epitope of the antibody is not solvent accessible in the compact, prefusion conformation that typifies all HA structures to date. Instead, the antibody binds between HA head protomers to an epitope that must be partly or transiently exposed in the prefusion conformation. The “breathing” of the HA protomers is implied by the exposure of this epitope, which is consistent with metastability of class I fusion proteins. This structure likely therefore represents an early structural intermediate in the viral fusion process. Understanding the extent of transient exposure of conserved neutralizing epitopes also may lead to new opportunities to combat influenza that have not been appreciated previously.


Author summary

Influenza viruses cause severe respiratory infections on a global scale annually. Vaccine efforts are hampered by the virus’s naturally high mutation rate, which results in wide variation between influenza strains of the antigens that are produced and recognized by antibodies, particularly in the surface glycoprotein hemagglutinin (HA). However, broadly neutralizing antibodies (bnAbs) are a class of antibodies that develop during natural infections that are capable of inhibiting infection across multiple strains. In this study, we structurally characterized one such bnAb, H7.5, which targets a unique semioccluded yet highly conserved region on the HA head. We showed, using both negative-stain and high-resolution cryo-electron microscopy (cryoEM), that after a short incubation, H7.5 fragment antigen binding (Fab) induces HA to fall apart, effectively preventing infection. We found that H7.5 binds to an epitope only accessible through transient “breathing” of the HA head, and this observation provides insight into the conformational transitions necessary for viral fusion as well as key information about a unique vaccine target.


Citation: Turner HL, Pallesen J, Lang S, Bangaru S, Urata S, Li S, et al. (2019) Potent anti-influenza H7 human monoclonal antibody induces separation of hemagglutinin receptor-binding head domains. PLoS Biol 17(2): e3000139. https://doi.org/10.1371/journal.pbio.3000139

Academic Editor: James Conway, University of Pittsburgh, UNITED STATES

Received: September 28, 2018; Accepted: January 18, 2019; Published: February 4, 2019

Copyright: © 2019 Turner et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The final coordinates for the H7.5 Fab structure have been deposited to the RCSB database with the accession code PDB 6BTJ. The nsEM map of H7 NY HA1/2 complexed with 3 H7.5 Fabs bound, and the cryo-EM maps of H7 NL HA1/2 with 3 H7.5 Fabs bound, the H7 NL HA1/2 with 2 H7.5 Fabs bound, and the H7 Sh2 HA1/2 with 3 H7.5 Fabs bound were deposited to the Electron Microscopy Databank with the accession codes EMD-9144, EMD-9143, EMD-9145 EMD-9142, respectively. The cryo-EM map and fitted coordinates for H7 NY HA with 3 H7.7 Fabs bound has been deposited to the RCSB database with accession numbers EMD-9139/PDB 6MLM.

Funding: National Institutes of Health grant U19 AI117905 and National Institutes Health contract HHSN272201400024C. Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIAID, DOE, or NIH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: bnAb, broadly neutralizing antibody; CDRH3, complementary determining region heavy chain 3; cryoEM, cryo-electron microscopy; Fab, fragment antigen binding; FSC, Fourier shell correlation; HA, hemagglutinin; HDX-MS, hydrogen–deuterium exchange mass spectrometry; H-FR3, heavy-chain framework region 3; mAb, monoclonal antibody; NA, neuraminidase; nsEM, negative-stain electron microscopy; PDB, Protein Data Bank; RBS, receptor-binding site; smFRET, single molecule Forster resonance energy transfer

Keywords: Influenza A; H7; Monoclonal antibodies.


#Prophylactic efficacy of a #human #mAb against #MERS #Coronavirus in the common marmoset (Antiviral Res., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Antiviral Res. 2019 Jan 23. pii: S0166-3542(19)30036-1. doi: 10.1016/j.antiviral.2019.01.016. [Epub ahead of print]

Prophylactic efficacy of a human monoclonal antibody against MERS-CoV in the common marmoset.

de Wit E1, Feldmann F2, Horne E1, Okumura A3, Cameroni E4, Haddock E1, Saturday G2, Scott D2, Gopal R5, Zambon M5, Corti D4, Feldmann H6.

Author information: 1 Laboratory of Virology, Hamilton, MT, USA. 2 Rocky Mountain Veterinary Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA. 3 Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY, USA. 4 Humabs BioMed SA, A Subsidiary of Vir Biotechnology, 6500, Bellinzona, Switzerland. 5 National Infection Service, Public Health England (PHE), London, NW9 5EQ, United Kingdom. 6 Laboratory of Virology, Hamilton, MT, USA. Electronic address: feldmannh@niaid.nih.gov.



Effective antiviral treatments for MERS-CoV are urgently needed. LCA60 is a MERS-CoV-neutralizing monoclonal antibody isolated from a convalescent MERS patient. Previously, it was shown that treatment with LCA60 resulted in reduced disease and virus titers in mouse models of MERS-CoV infection. Here, we tested the prophylactic efficacy of LCA60 in the common marmoset model of MERS-CoV infection. Intravenous administration of LCA60 one day before virus challenge resulted in high levels of MERS-CoV-neutralizing activity in circulating blood. Clinically, there was a moderate benefit of treatment with LCA60 including reduced respiratory involvement. Although viral lung loads were not reduced in LCA60-treated animals as compared to controls, there were fewer pathological changes in the lungs. Thus, prophylactic LCA60 treatment could be implemented to reduce disease burden in contacts of confirmed MERS-CoV patients.

Copyright © 2019. Published by Elsevier B.V.

KEYWORDS: Common marmoset; LCA60; MERS-CoV; Neutralizing monoclonal antibody; Prophylaxis; Treatment

PMID: 30684561 DOI: 10.1016/j.antiviral.2019.01.016

Keywords: MERS-CoV; Monoclonal antibodies; Animal models.


#Neuraminidase #inhibition contributes to #influenza A virus #neutralization by anti-hemagglutinin stem #antibodies (J Exp Med., abstract)

[Source: Journal of Experimental Medicine, full page: (LINK). Abstract, edited.]

Neuraminidase inhibition contributes to influenza A virus neutralization by anti-hemagglutinin stem antibodies

Ivan Kosik,  Davide Angeletti, James S. Gibbs, Matthew Angel, Kazuyo Takeda, Martina Kosikova, Vinod Nair,  Heather D. Hickman, Hang Xie, Christopher B. Brooke,  Jonathan W. Yewdell

DOI: 10.1084/jem.20181624 | Published January 25, 2019



Broadly neutralizing antibodies (Abs) that bind the influenza virus hemagglutinin (HA) stem may enable universal influenza vaccination. Here, we show that anti-stem Abs sterically inhibit viral neuraminidase (NA) activity against large substrates, with activity inversely proportional to the length of the fibrous NA stalk that supports the enzymatic domain. By modulating NA stalk length in recombinant IAVs, we show that anti-stem Abs inhibit virus release from infected cells by blocking NA, accounting for their in vitro neutralization activity. NA inhibition contributes to anti-stem Ab protection in influenza-infected mice, likely due at least in part to NA-mediated inhibition of FcγR-dependent activation of innate immune cells by Ab bound to virions. Food and Drug Administration–approved NA inhibitors enhance anti-stem–based Fc-dependent immune cell activation, raising the possibility of therapeutic synergy between NA inhibitors and anti-stem mAb treatment in humans.

Keywords: Influenza A; Antivirals; Monoclonal antibodies.


#Ebola #therapies: an unconventionally calculated #risk (Lancet, summary)

[Source: The Lancet, full page: (LINK). Summary, edited.]

Ebola therapies: an unconventionally calculated risk

Mosoka P Fallah, Laura A Skrip

Published: January 24, 2019 / DOI: https://doi.org/10.1016/S0140-6736(19)30160-6


The current outbreak of Ebola virus disease in the Democratic Republic of the Congo, uninterrupted since August, 2018, is the largest to date in a country that has had nine outbreaks since 1976 and contained the virus each time.1 Ongoing transmission2 has shown the difficulties of outbreak response in an area that is vulnerable to Ebola virus disease and that has violent conflict, food insecurity, and a lack of functional health infrastructure;3  yet the response to ongoing transmission has also highlighted commitment among humanitarian and scientific actors to containing the virus. The actions taken by these groups have included administration of multiple novel therapies under a WHO protocol of Monitored Emergency Use of Unregistered and Investigational Interventions (MEURI).4


Keywords: Ebola; Antivirals; Monoclonal antibodies.


Safety, tolerability, pharmacokinetics, and #immunogenicity of the #therapeutic monoclonal #antibody #mAb114 targeting #Ebola virus glycoprotein (VRC 608): an open-label phase 1 study (Lancet, abstract)

[Source: The Lancet, full page: (LINK). Abstract, edited.]

Safety, tolerability, pharmacokinetics, and immunogenicity of the therapeutic monoclonal antibody mAb114 targeting Ebola virus glycoprotein (VRC 608): an open-label phase 1 study

Martin R Gaudinski, MD, Emily E Coates, PhD, Laura Novik, MA, Alicia Widge, MD, Katherine V Houser, PhD, Eugeania Burch, MPH, LaSonji A Holman, FNP, Ingelise J Gordon, RN, Grace L Chen, MD, Cristina Carter, MD, Martha Nason, PhD, Sandra Sitar, MS, Galina Yamshchikov, MS, Nina Berkowitz, MPH, Charla Andrews, MS, Sandra Vazquez, MS, Carolyn Laurencot, PhD, John Misasi, MD, Frank Arnold, PhD, Kevin Carlton, MBA, Heather Lawlor, MS, Jason Gall, PhD, Robert T Bailer, PhD, Prof Adrian McDermott, PhD, Prof Edmund Capparelli, PharmD, Prof Richard A Koup, MD, Prof John R Mascola, MD, Prof Barney S Graham, MD, Prof Nancy J Sullivan, PhD, Prof Julie E Ledgerwood, DO on behalf of theVRC 608 Study team †

Published: January 24, 2019 / DOI: https://doi.org/10.1016/S0140-6736(19)30036-4




mAb114 is a single monoclonal antibody that targets the receptor-binding domain of Ebola virus glycoprotein, which prevents mortality in rhesus macaques treated after lethal challenge with Zaire ebolavirus. Here we present expedited data from VRC 608, a phase 1 study to evaluate mAb114 safety, tolerability, pharmacokinetics, and immunogenicity.


In this phase 1, dose-escalation study (VRC 608), conducted at the US National Institutes of Health (NIH) Clinical Center (Bethesda, MD, USA), healthy adults aged 18–60 years were sequentially enrolled into three mAb114 dose groups of 5 mg/kg, 25 mg/kg, and 50 mg/kg. The drug was given to participants intravenously over 30 min, and participants were followed for 24 weeks. Participants were only enrolled into increased dosing groups after interim safety assessments. Our primary endpoints were safety and tolerability, with pharmacokinetic and anti-drug antibody assessments as secondary endpoints. We assessed safety and tolerability in all participants who received study drug by monitoring clinical laboratory data and self-report and direct clinician assessment of prespecified infusion-site symptoms 3 days after infusion and systemic symptoms 7 days after infusion. Unsolicited adverse events were recorded for 28 days. Pharmacokinetic and anti-drug antibody assessments were completed in participants with at least 56 days of data. This trial is registered with ClinicalTrials.gov, number NCT03478891, and is active but no longer recruiting.


Between May 16, and Sept 27, 2018, 19 eligible individuals were enrolled. One (5%) participant was not infused because intravenous access was not adequate. Of 18 (95%) remaining participants, three (17%) were assigned to the 5 mg/kg group, five (28%) to the 25 mg/kg group, and ten (55%) to the 50 mg/kg group, each of whom received a single infusion of mAb114 at their assigned dose. All infusions were well tolerated and completed over 30–37 min with no infusion reactions or rate adjustments. All participants who received the study drug completed the safety assessment of local and systemic reactogenicity. No participants reported infusion-site symptoms. Systemic symptoms were all mild and present only in four (22%) of 18 participants across all dosing groups. No unsolicited adverse events occurred related to mAb114 and one serious adverse event occurred that was unrelated to mAb114. mAb114 has linear pharmacokinetics and a half-life of 24·2 days (standard error of measurement 0·2) with no evidence of anti-drug antibody development.


mAb114 was well tolerated, showed linear pharmacokinetics, and was easily and rapidly infused, making it an attractive and deployable option for treatment in outbreak settings.


Vaccine Research Center, US National Institute of Allergy and Infectious Diseases, and NIH.

Keywords: Ebola; Monoclonal antibodies.