Influenza A virus H5N1 hemagglutinin (HA) (HA)

Influenza A virus H5N1 hemagglutinin (HA) is the primary surface glycoprotein of the highly pathogenic avian influenza virus, serving as the essential mediator for viral entry into host cells [1]. It functions as a trimeric class I fusion protein that recognizes and binds to alpha-2,3-linked sialic acid receptors, which are prevalent in the avian respiratory tract and the human lower respiratory tract [2][3]. Following receptor-mediated endocytosis, the acidic environment of the endosome triggers a massive structural rearrangement in the HA2 subunit, facilitating the fusion of viral and host membranes [3]. In the context of public health and vaccinology, H5 HA is the critical antigen used in prepandemic vaccines to elicit neutralizing antibodies, primarily targeting the immunodominant globular head to block receptor binding [4]. While it is not a traditional pharmacologic target for small molecules, its high rate of antigenic drift necessitates constant surveillance and the development of next-generation vaccines, including those targeting the more conserved stem region [5][6].

Other names

H5 HAHemagglutininHA1/HA2H5N1 HA antigenH5 antigen

Induction of neutralizing antibodies that bind to the HA protein, thereby preventing viral attachment to host sialic acid receptors or inhibiting the pH-dependent membrane fusion process.