Abstract
H9N2 avian influenza virus is a major cause of poultry production loss across Asia leading to the wide use of vaccines. Efficacy of vaccines is often compromised due to the rapid emergence of antigenic variants. To improve the effectiveness of vaccines in the field, a better understanding of the antigenic epitopes of the major antigen, hemagglutinin, is required. To address this, a panel of nine monoclonal antibodies were generated against a contemporary Pakistani H9N2 isolate, which represents a major Asian H9N2 viral lineage. Antibodies were characterized in detail and used to select a total of 26 unique ‘escape’ mutants with substitutions across nine different amino acid residues in hemagglutinin including seven that have not been described as antigenic determinants for H9N2 viruses before. Competition assays and structural mapping revealed two novel, discrete antigenic sites “H9-A” and “H9-B”. Additionally, a second subset of escape mutants contained amino acid deletions within the hemagglutinin receptor binding site. This constitutes a novel method of escape for group 1 hemagglutinins and could represent an alternative means for H9N2 viruses to overcome vaccine induced immunity. These results will guide surveillance efforts for arising antigenic variants as well as evidence based vaccine seed selection and vaccine design.
Highlights
212, in the context of a contemporary G1-like virus[20,21,22]
In addition we present a group of escape mutants with unique deletions within the 220 loop of the receptor binding site which have not been reported before in group 1 hemagglutinins of influenza A33,34
Some of the identified residues had a wide variability, for example 162, 183, 212, 217 whilst other residues were fairly conserved for example at positions 115, 139, 145 and 234. This suggests that viruses with the variations at residues we identified as escape mutations may exist as naturally circulating antigenic variants in the field
Summary
212, in the context of a contemporary G1-like virus[20,21,22]. In addition we present a group of escape mutants with unique deletions within the 220 loop of the receptor binding site which have not been reported before in group 1 hemagglutinins of influenza A33,34. The results indicate a general trend whereby the mAbs displayed higher cross-reactivity with more closely related viruses, as determined phylogenetically (see supplementary Fig. S3 online); there were some exceptions that can be explained by natural variation at antigenic residues deduced in this work to be within the mAb epitopes.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
