Hemagglutinin (HA) of G4 Eurasian avian-like H1N1 influenza A virus (G4 EA H1N1 HA)

The G4 Eurasian avian-like (EA) H1N1 hemagglutinin (HA) is the primary surface glycoprotein of a reassortant influenza A virus genotype that has become predominant in swine populations in China since 2016 (Sun et al., 2020, PNAS). This HA protein is a critical target for the immune system and therapeutic intervention because it mediates viral entry by binding to sialic acid receptors on host respiratory cells (CDC, 2020). Specifically, the G4 HA has evolved to preferentially bind to alpha 2,6-linked sialic acids, which are prevalent in the human upper respiratory tract, increasing its zoonotic potential (WHO, 2020). As a major antigen, it is the focus of pandemic preparedness efforts, including the development of candidate vaccine viruses (CVVs) and neutralizing antibodies. Because current seasonal influenza vaccines provide little to no cross-protection against G4 EA H1N1, this HA antigen represents a significant public health concern and a high-priority target for novel vaccine development (Sun et al., 2020).

Other names

G4 EA H1N1 HemagglutininEurasian avian-like H1N1 HAG4 genotype H1N1 HA antigenSwine influenza A virus G4 HA

Binding to the hemagglutinin protein prevents the virus from attaching to host cell sialic acid receptors or inhibits the pH-dependent conformational change required for membrane fusion, thereby neutralizing viral infectivity.