Hemagglutination Inhibition Antibody Landscapes after Vaccination with
diverse H7 hemagglutinin proteins
Abstract
Background: A systemic evaluation of the antigenic breadth of the H7
influenza hemagglutinin (HA) proteins, especially for the viruses
isolated after 2016, are limited. The purpose of this study was to
investigate the antigenic breadth of major H7 strains with an ultimate
aim to discover H7 HA proteins that can elicit protective
receptor-blocking antibodies against co-circulating H7 influenza
strains. Method: A panel of nine H7 influenza strains were selected from
3,633 H7 HA amino acid sequences identified over the past two decades
(2000-2018). The sequences were expressed on the surface of virus like
particles (VLPs) and used to vaccinate C57BL/6 mice. Serum samples were
collected and tested for hemagglutination-inhibition (HAI) activity. The
vaccinated mice were challenged with lethal dose of H7N9 virus,
A/Anhui/1/2013. Results: VLPs expressing the H7 HA antigens elicited
broadly reactive antibodies each of the other vaccine strains, except
the A/Turkey/Italy/589/2000 (Italy/00) H7 HA. The putative
N-glycosylation site at antigenic site B was identified as a unique
antigenic profile of Italy/00. Introduction of the putative
glycosylation site (H7 HA-A169T) significantly altered the antigenic
profile of HA from the A/Anhui/1/2013 (H7N9) strain. Conclusion: This
study focused the importance of key amino acid mutations that result in
severe vaccine mismatches for future H7 epidemics. Future universal
influenza vaccine candidates will need to focus on viral variants with
these key mutations.