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The serotype of IAV is determined by the HA and neuraminidase (NA) proteins expressed on its surface. [12] Neuraminidase has 11 known subtypes; hence, influenza viruses are named according to the combinations of HA and NA proteins expressed (e.g., H1N1 and H5N2). [7] Structure of influenza, showing neuraminidase marked as NA and hemagglutinin ...
Hemagglutinins are small proteins that extend from the surface of the virus membrane as spikes that are 135 Angstroms (Å) in length and 30-50 Å in diameter. [19] Each spike is composed of three identical monomer subunits, making the protein a homotrimer.
Viral neuraminidase cleaves terminal sialic acid residues from glycan structures on the surface of the infected cell. This promotes the release of progeny viruses and the spread of the virus from the host cell to uninfected surrounding cells. Neuraminidase also cleaves sialic acid residues from viral proteins, preventing aggregation of viruses.
Two viral proteins; hemagglutinin (HA) and neuraminidase (NA), are inserted into the envelope and are exposed as spikes on the surface of the virion. Both proteins are antigenic; a host's immune system can react to them and produce antibodies in response. The M2 protein forms an ion channel in the envelope and is responsible for uncoating the ...
This attachment is required for efficient transfer of flu virus genes into cells, a process that can be blocked by antibodies that bind to the hemagglutinin proteins. One genetic factor in distinguishing between human flu viruses and avian flu viruses is that avian influenza HA bind to alpha 2-3 sialic acid receptors while human influenza HA ...
Influenza A viruses are further classified, based on the viral surface proteins hemagglutinin (HA or H) and neuraminidase (NA or N). 18 HA subtypes (or serotypes) and 11 NA subtypes of influenza A virus have been isolated in nature. Among these, the HA subtype 1-16 and NA subtype 1-9 are found in wild waterfowl and shorebirds and the HA ...
Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes the disease avian influenza (often referred to as "bird flu"). It is enzootic (maintained in the population) in many bird populations, and also panzootic (affecting animals of many species over a wide area). [ 1 ]
Figure 3 showed the structure of an influenza virus. The hemagglutinin (HA) surface proteins feature the influenza virus. The HA antigens of seasonal virus strains are the target for the influenza vaccines to trigger an immune response in the human body. During the manufacturing process, the virus’ gene is first obtained.