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Life Cycle of the Polio Virus

Poliovirus is a virus that infects cells of the throat and intestines and then enters the bloodstream to invade other cells, including motor neurons, nerve cells that are responsible for a number of important bodily functions, according to the Smithsonian National Museum of American History. Poliovirus infection is triggered when an individual breathes in poliovirus particles, called virions.

  1. Poliovirus Receptor

    • A number of cells throughout the body have on their surface a poliovirus receptor (PVR). This receptor is composed of protein called immunoglobulin and is the site where poliovirus binds to host cells; the natural function of PVR is not known, according to the Polio Information Center Online (PICO). PVR has three different loops, and poliovirus binds to the first of these; the virus is then brought into the cell by the natural cell process of endocytosis (literally, bringing into the cell), according to PICO.

    Uncoating

    • As poliovirus is brought into a host cell through endocytosis, the process of uncoating begins. While the polio virion is in the initial dimple, called an invagination, created by endocytosis, a hole begins to form through the virion and the invagination that allows the contents of the poliovirus to enter the cytoplasm of the host cell, according to the Smithsonian. This is the beginning of the virus' replication process.

    Replication

    • Once uncoated, the viral RNA begins to produce copies of parts of the virus, including its proteins and RNA. This is contrast to some other viruses, which must enter the nucleus of a host cell and interact with the host cell's DNA in order to make copies of itself. Every cell infected by poliovirus can release many copies of poliovirus.

    Packaging

    • New virions are made by the process of packaging, which brings the components made by polio virus RNA together into new capsids, according to PICO. The virus' RNA enters the capsid last and edits the components of the new virion through the process of cleavage (cutting).

    Infection

    • After new virions are packaged, the host cell is destroyed through the process of lysis, which means bursting. The new polio virions enter the bloodstream and go on to infect motor neurons. These cells, according to the Smithsonian, are responsible for functions like swallowing, the circulation of blood, breathing and motion.

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