The influenza virus, also called "the flu," is a contagious respiratory infection. Most people who come down with the flu will have a fever, cough, sore throat and muscle aches for a few days, but some may have a serious enough infection that they will have to be hospitalized.
Influenza A Virus Defined
The influenza A, B and C viruses are all members of a family of viruses called the orthomyxovirus family. A virus is type A, B or C, based upon the kind of protein it has. Influenza A virus has several strains. Each strain is based upon the type of protein it has, where the virus started and when it was separated in a lab, explains Raphael Dolin, M.D., professor of medicine at the Harvard Medical School in "Harrison's Principles of Internal Medicine."
Structure
The influenza A virus has a fairly round shape. The outside surface is made of lipids, but there are substances called glycoproteins, hemagglutinin and neuraminidase that stick out from the surface. On each virus, there are two glycoproteins, or proteins with attached sugars. The virus uses the hemagglutinin to attach to a cell, while neuraminidase helps release the viruses after they duplicate inside the infected human cell, as explained by Dolin. The outer surface of the virus, called the lipid envelope, also contains the M1 protein and the M2 protein.
M2 Protein
In the January 2008 issue of "Nature," Jason Schnell of the University of Oxford writes about the function of the M2 protein. This protein is called an ion channel protein because it allows hydrogen ions to pass through an ion channel, or opening, to enter the virus. As a result, the inside of the virus becomes more acidic, which in turn helps the M1 protein to break away. The virus can then get rid of its lipid envelope and cause an infection.
Treatment and the M2 Protein
Amantadine and rimantadine are two medications used to treat influenza A, although rimantadine is approximately four to 10 times more powerful than amantadine, according to Frederick Hayden, M.D., professor of clinical virology at the University of Virginia School of Medicine in "Goodman & Gilman's The Pharmacological Basis of Therapeutics." The two medications interfere with the duplication of the virus and may affect hemagglutinin, but their main target is the M2 protein. Because they interfere with this protein, the virus does not become acidic, and it cannot get rid of its lipid envelope to become infectious.
References
- "Goodman & Gilman's The Pharmacological Basis of Therapeutics"; Laurence Brunton, Ph.D.; 2006
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., et al; 2008
- "Nature"; Structure and Mechanism of the M2 Proton Channel of Influenza A Virus; Jason Schnell, et al; January 2008
