Influenza A H7N9 hemagglutinin (H7N9 HA)

The **Influenza A H7N9 hemagglutinin** is a trimeric surface glycoprotein and the principal antigen on the Influenza A H7N9 virus envelope, responsible for **binding host cell sialic acid receptors** and mediating the fusion of viral and host cell membranes, thereby enabling viral entry[1][3][7]. This HA subtype—part of a broader family of hemagglutinins that define influenza A strain tropism and antigenicity—is a key determinant of host range and a critical target for neutralizing antibodies and vaccine development[3][5][7]. Molecular studies show H7N9 HA has a **weak baseline affinity for human cell receptors** but can acquire mutations increasing human transmissibility and pandemic potential[5][6][7]. There are currently **no approved drugs that directly target HA**, but various neutralizing monoclonal antibodies are in research and clinical development; HA is also used as a **biomarker for serological surveillance and vaccine efficacy**[9]. Major safety and therapeutic challenges relate to its high mutation rate, potential for immune escape, and ability to drive zoonotic and pandemic outbreaks with variable pathogenicity (low or high pathogenic avian influenza; LPAI and HPAI)[5][7][8].

Other names

Hemagglutinin (HA) protein of Influenza A H7N9H7 hemagglutininInfluenza A virus subtype H7N9 hemagglutinin

Neutralizing antibodies: Bind to the HA globular head or stem, block receptor binding or membrane fusion, prevent viral entry into human cells. Small molecules (experimental): Inhibit conformational changes or binding/fusion (no approved direct-acting HA inhibitors).