The Role of Hemagglutinin in Influenza Virus Transmission

Abstract

Influenza is a rapidly mutating RNA virus causing mortality and morbidity in humans.The three different strains of influenza are characterized by different surface glycoproteins. Hemagglutinin (HA) is one of the primary binding proteins of Influenza A, the most prevalent strain of the virus. HA is a trimer, with each macromolecule consisting of a head and stalk region. The head region recognizes sialic acid on the host cell surface, initiating viral infection. The sialic acid binding site is highly susceptible to antigenic drift, and is the primary target of current vaccine development. The binding site consists of a loop‐helix‐loop region that allows for the attachment between HA and sialic acid. Because this region is both constantly mutating and strain specific, new vaccines need to be developed annually. Most antigenic drift is located within two antigenic sites. The Marshfield High School SMART (Students Modeling A Research Topic) Team will be modeling the sialic acid binding site on HA to demonstrate how the protein triggers viral infection. The stalk domain functions to mediate fusion of the viral and endosomal membranes. During this process, the domain undergoes extensive structural rearrangement. As such, the stalk domain is a more suitable vaccine target because it is conserved across strains and is not as susceptible to genetic drift. Therefore, emerging research has focused on the stalk region for more promising vaccinations, and maybe an eventual elimination of the need to develop a new vaccine every year. The Marshfield Research Foundation is currently studying influenza vaccine effectiveness and safety including the effects of repeated vaccination on immunity.