Human antibody recognition of H7N9 influenza virus HA following natural infection
Iuliia M. Gilchuk, Sandhya Bangaru, Nurgun Kose, Robin G. Bombardi, Andrew Trivette, Sheng Li, Hannah L. Turner, Robert H. Carnahan, Andrew B. Ward, James E. Crowe Jr.
Iuliia M. Gilchuk, Sandhya Bangaru, Nurgun Kose, Robin G. Bombardi, Andrew Trivette, Sheng Li, Hannah L. Turner, Robert H. Carnahan, Andrew B. Ward, James E. Crowe Jr.
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Research Article Infectious disease

Human antibody recognition of H7N9 influenza virus HA following natural infection

Abstract

Avian H7N9 influenza viruses cause sporadic outbreaks of human infections and threaten to cause a major pandemic. The breadth of B cell responses to natural infection and the dominant antigenic sites recognized during first exposure to H7 HA following infection are incompletely understood. Here, we studied the B cell response to H7 HA of 2 individuals who had recovered from natural H7N9 virus infection. We used competition binding, hydrogen-deuterium mass spectrometry, and single-particle negative stain electron microscopy to identify the patterns of molecular recognition of the antibody responses to H7 HA. We found that circulating H7-reactive B cells recognized a diverse antigenic landscape on the HA molecule, including HA head domain epitopes in antigenic sites A and B and in the trimer interface-II region and epitopes in the stem region. Most H7 antibodies exhibited little heterosubtypic breadth, but many recognized a wide diversity of unrelated H7 strains. We tested the antibodies for functional activity and identified clones with diverse patterns of inhibition, including neutralizing, hemagglutination- or egress-inhibiting, or HA trimer–disrupting activities. Thus, the human B cell response to primary H7 natural infection is diverse, highly functional, and broad for recognition of diverse H7 strains.

Authors

Iuliia M. Gilchuk, Sandhya Bangaru, Nurgun Kose, Robin G. Bombardi, Andrew Trivette, Sheng Li, Hannah L. Turner, Robert H. Carnahan, Andrew B. Ward, James E. Crowe Jr.

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Figure 3

Natural H7N9 influenza virus infection elicits HA-specific mAbs targeting 3 main regions on H7 head (sites A and B, HA interface) and stem domains.

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Natural H7N9 influenza virus infection elicits HA-specific mAbs targetin...
MAbs were assessed for competition binding by biolayer interferometry (BLI) using a Bio-Rad device with trimeric HA from SH13 H7N9 virus strain. MAbs were judged to compete for the same site if the maximum binding of the second antibody was reduced to no more than 30% of its uncompeted binding (shown in black boxes). The mAbs were considered noncompeting if the maximum binding of the second mAb was at least 70% of its uncompeted binding (shown in white boxes). Gray color indicates an intermediate phenotype (competition between 30% and 70% of uncompeted binding). Orange, red, violet, blue, and green boxes indicate inferred competition-binding groups. Reference mAbs with known epitopes are indicated with colors. (A) BLI raw data; (B) Pearson’s correlation coefficient for BLI data; (C) HDX-MS profiles of H7-243, H7-247, H7-236, H7-197, or H7-238 mAbs were mapped onto the surface of the H7 HA trimer (Protein Data Bank ID 4N5J). The yellow circle indicates the RBS. Amino acid residues within the epitope with decreased deuteration level upon H7-243, H7-247, H7-236, H7-197, or H7-238 mAbs binding are indicated by colors corresponding to competition-binding groups: orange, red, violet, and blue. (D) Two-dimensional (2D) class averages of H7 HA in complex with anti-H7 Fabs. For each complex, 3 different views of the 2D class averages are shown on the left column with corresponding images with the Fabs colored in the right column. rH7-243 caused the HA trimer to fully decompose into HA protomers, while rH7-247 did so only partially under the given experimental conditions. See also Supplemental Figures 4 and 5.