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Title: Cryo-EM structures elucidate neutralizing mechanisms of anti-chikungunya human monoclonal antibodies with therapeutic activity

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes severe acute and chronic disease in humans. Although highly inhibitory murine and human monoclonal antibodies (mAbs) have been generated, the structural basis of their neutralizing activity remains poorly characterized. In this paper, we determined the cryo-EM structures of chikungunya virus-like particles complexed with antibody fragments (Fab) of two highly protective human mAbs, 4J21 and 5M16, that block virus fusion with host membranes. Both mAbs bind primarily to sites within the A and B domains, as well as to the B domain’s β-ribbon connector of the viral glycoprotein E2. The footprints of these antibodies on the viral surface were consistent with results from loss-of-binding studies using an alanine scanning mutagenesis-based epitope mapping approach. The Fab fragments stabilized the position of the B domain relative to the virus, particularly for the complex with 5M16. Finally, this finding is consistent with a mechanism of neutralization in which anti-CHIKV mAbs that bridge the A and B domains impede movement of the B domain away from the underlying fusion loop on the E1 glycoprotein and therefore block the requisite pH-dependent fusion of viral and host membranes.
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [4] ;  [5] ;  [2] ;  [6] ;  [3] ;  [1]
  1. Purdue Univ., West Lafayette, IN (United States). Dept. of Biological Sciences
  2. Integral Molecular, Inc., Philadelphia, PA (United States)
  3. Washington Univ., St. Louis, MO (United States). School of Medicine. Dept. of Medicine, Molecular Microbiology, Pathology, and Immunology
  4. Vanderbilt Univ., Nashville, TN (United States). Dept. of Pediatrics
  5. VLP Therapeutics, LLC, Gaithersburg, MD (United States)
  6. Vanderbilt Univ., Nashville, TN (United States). Dept. of Pediatrics. Dept. of Pathology, Microbiology, and Immunology. Vanderbilt Univ. Medical Center. Vanderbilt Vaccine Center
Publication Date:
OSTI Identifier:
1229894
Grant/Contract Number:
AC02-06CH11357; R01 AI095366; R01 AI089591; HHSN272200900055C; R01 AI114816
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 112; Journal Issue: 45; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Purdue Univ., West Lafayette, IN (United States); Vanderbilt Univ., Nashville, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Inst. of Health (NIH) (United States)
Contributing Orgs:
Integral Molecular, Inc., Philadelphia, PA (United States); VLP Therapeutics, LLC, Gaithersburg, MD (United States); Washington Univ., St. Louis, MO (United States)
Country of Publication:
United States
Language:
ENGLISH
Subject:
60 APPLIED LIFE SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; chikungunya virus-antibody complexes; cryo-electron microscopy structure; neutralizing mechanism; viral fusion inhibition