Evolutionary dynamic of antigenic residues on influenza B hemagglutinin

Abstract

Hemagglutinin (HA) of seasonal influenza virus evolves under positive selection pressure exerted by host immunity. It was previously shown that antigenic drift in different influenza B sublineages during different time periods distributed unevenly among different epitopes, and that more recent viruses up to 2007 might have their antigenic drift more focused on certain epitope. We further analyzed whether more recent influenza B viruses up to 2016 followed that same pattern of antigenic evolution. By using Shannon entropy and relative entropy to characterize HA antigenic epitopes, the most recent viruses of both Victoria and Yamagata lineages had residues with high relative entropy located most frequently on the 120-loop region. In addition to residues in the known epitopes, possible antigenic residues were also identified outside of the known epitope regions. The data provide an insight into the antigenic evolution of current influenza B viruses and expand our knowledge on their antigenic sites.

Influenza B virus infections in Western Saxony, Germany in three consecutive seasons between 2015 and 2018: Analysis of molecular and clinical features

“…In contrast to the Victoria lineage, which has a faster evolution with nearly each season representing a phylogenetic bottleneck, the biology of the Yamagata lineage is different. In long term studies of the HA of the Yamagata lineage a long co-circulation of Yamagata variants was observed [3,13,29]. In accordance with these observations the analyzed strains of this study were phylogenetically closely related.…”

“…The key component of the vaccine is the viral hemagglutinin (HA) that covers the viral surface in a trimeric form. The major antigenic regions are the 120-loop, 150-loop, 160-loop, and 190helix [13] and are located on the HA1 subunit which forms the globular head domain. It is responsible for recognition and binding of sialic acids on the surface of the target cells.…”

Genetic characterization of influenza B virus in Cameroon and high frequency of reassortant strains

“…Four antigenic epitopes have been described on the HA gene of influenza B viruses: the 120 loop (position 116‐137 as well as residues 48, 56, 75,177, 179‐181), the 150 loop (position 141‐150), the 160 loop (position 162‐167), and the 190 helix (position 194‐202) . We analyzed mutations in these epitopes by comparing Cameroonian strains with the reference strains B/Brisbane/60/2008, B/Massachusetts/02/2012, and B/Phuket/3073/2013, vaccine strains recommended during the 2014 to 2017 influenza seasons .…”

Influenza B viruses in pigs, Taiwan

“…Compared with B/Brisbane/60/2008, amino acid sequence variations relevant to antigenicity, evolutionary signatures, and biological characteristics were examined. In IBV HA protein, 4 antigenic sites were identified: 120‐loop (positions 116‐137), 150‐loop (positions 141‐150), 160‐loop (positions 162‐167), and 190‐helix (positions 194‐202), respectively . Diversity in the 120‐loop was frequently found in recent IBVs during 2010‐15 in Italy, Malaysia, China, and Thailand .…”

“…The 190‐helix comprising amino acid residue 194‐202 contains a glycosylation site . The N‐linked glycosylation plays a major role in stabilizing the HA structure, to protect the HA protein from being hydrolyzed by the enzyme and to evade antibody recognition.…”