H9N2 avian influenza virus in Bangladesh: three genetically distinct co-circulating subgroups retain a largely conserved antigenic phenotype

In Bangladesh poultry, 219 H9N2 HA sequences form three genetically distinct monophyletic HA G-lineage subgroups, yet antigenic phenotypes remain largely conserved across them.

• Why it matters: Genetic surveillance shows ongoing evolution, but it is unclear how HA/NA diversification and reassortment translate into antigenic change that affects vaccine relevance and zoonotic risk.
• What they did: Phylogenetic analysis of 219 sampled sequences identified three HA subgroups and similar NA diversity, with dual-metric pairing of HA and NA phylogenies flagging 20 putative reassortant viruses.
• The result: Hemagglutination inhibition and virus neutralisation assays showed antigenic similarity despite reassortment and diversity, though one subgroup’s representative induced significantly lower homologous and heterologous antibody titres.

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