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Since hemagglutinin is the major surface protein of the influenza A virus and is essential to the entry process, it is the primary target of neutralizing antibodies. [citation needed] These antibodies against flu have been found to act by two different mechanisms, mirroring the dual functions of hemagglutinin:
The envelope comprises a lipid bilayer membrane incorporating HA and NA (or HEF [26]) proteins extending outward from its exterior surface. HA and HEF [26] proteins have a distinct "head" and "stalk" structure. M2 proteins form proton channels through the viral envelope that are required for viral entry and exit. Influenza B viruses contain a ...
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 ...
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.
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 ...
3D model of the flu virion. (M2 labeled in white.) The Matrix-2 (M2) protein is a proton-selective viroporin, integral in the viral envelope of the influenza A virus. The channel itself is a homotetramer (consists of four identical M2 units), where the units are helices stabilized by two disulfide bonds, and is activated by low pH.
Ah, January. The season of new beginnings, icy winds, and respiratory infections. With a “quad-demic” of diseases circulating the country—flu, COVID, respiratory syncytial virus (RSV), and ...
The NS1 influenza protein (NS1) is a viral nonstructural protein encoded by the NS gene segments of type A, B and C influenza viruses. Also encoded by this segment is the nuclear export protein (NEP), formerly referred to as NS2 protein, which mediates the export of influenza virus ribonucleoprotein (RNP) complexes from the nucleus into the ...