Influenza hemagglutinin

Definition

Influenza hemagglutinin is a glycoprotein found on the surface of the influenza virus that plays a crucial role in viral entry into host cells. It binds to sialic acid residues on the surface of respiratory epithelial cells, facilitating the fusion of the viral envelope with the host cell membrane. This binding is essential for the virus to infect host cells and initiate the replication process, making hemagglutinin a key target for both immune response and vaccine development.

5 Must Know Facts For Your Next Test

1. Influenza hemagglutinin is responsible for the initial attachment of the virus to host cells, which is a critical step in the infection process.
2. The hemagglutinin protein undergoes periodic mutations, leading to antigenic drift and shift, which complicates vaccine development.
3. Hemagglutinin is often used as a marker in diagnostic tests for influenza, helping to identify specific strains of the virus.
4. In addition to its role in infection, hemagglutinin is a major target for neutralizing antibodies produced by the immune system during an influenza infection.
5. The structure of hemagglutinin can be modified through post-translational modifications, which can affect its function and interaction with host cell receptors.

Review Questions

• How does influenza hemagglutinin facilitate viral entry into host cells?
  • Influenza hemagglutinin facilitates viral entry by specifically binding to sialic acid residues present on the surface of respiratory epithelial cells. This binding triggers conformational changes in hemagglutinin that enable the fusion of the viral envelope with the host cell membrane. This process is essential for allowing the viral genome to enter the host cell and begin replication.
• Discuss the implications of hemagglutinin mutations on influenza vaccine effectiveness.
  • Hemagglutinin mutations can lead to antigenic drift and shift, which results in changes to its structure that may prevent existing antibodies from recognizing and neutralizing the virus effectively. As a consequence, vaccines based on previous strains may become less effective against newly emerged strains. This necessitates regular updates to influenza vaccines to match circulating strains and highlights the challenges in controlling influenza outbreaks through vaccination.
• Evaluate the role of hemagglutinin in the development of therapeutic strategies against influenza infections.
  • The role of hemagglutinin in viral entry makes it a prime target for developing therapeutic strategies against influenza. Researchers are investigating ways to design inhibitors that can block hemagglutinin's ability to bind to sialic acid or interfere with its fusion capabilities. Additionally, understanding how hemagglutinin interacts with immune responses can lead to improved vaccine formulations and adjuvants that enhance protection against various influenza strains, ultimately aiming to reduce morbidity and mortality associated with influenza infections.

Related terms

Neuraminidase: A viral glycoprotein that cleaves sialic acid residues from host cell surfaces, aiding in the release of newly formed influenza viruses from infected cells.

Sialic Acid: A sugar molecule present on the surface of host cells that hemagglutinin specifically recognizes and binds to, initiating viral entry.

Viral Antigens: Substances that are recognized by the immune system as foreign, including proteins like hemagglutinin that can elicit an immune response.