|  | Conditions Treatments | Viruses

Structure of Polio Virus

Poliovirus is a fairly simple RNA virus of the viral family Picornaviridae. A poliovirus particle (virion) is essentially an RNA strand surrounded by a capsid. The capsid has on its surface receptors that help the virus recognize and bind to target motor neurons in the host's body. The structure of poliovirus--first discovered in 1985--was among the first viral structures ever discovered.

  1. Genome

    • Polio's genome (genetic information) is contained on a single strand of RNA (ribonucleic acid). This it shares in common with many other viruses, although some viruses, such as herpes, carry their genetic information in DNA (deoxyribonucleic acid). Poliovirus RNA codes for invading the ribosomes of target cells.

    Capsid

    • The capsid of poliovirus surrounds, delivers and protects the RNA. It is composed of proteins and has on its surface receptors that sense nerve cells, thus allowing the poliovirus to bind to these cells.

    Receptors

    • The receptors on poliovirus, made of proteins, sense target nerve cells. Poliovirus targets motor neurons. Many cells in the human body have the same receptor site that poliovirus targets, but it is not understood why poliovirus only invades certain nerve cells. Antibodies produced by the immune system bind to these receptors to help prevent polio from invading cells.

    Infection

    • Once polio has bound to its target nerve cell, the capsid opens and the virus's genetic information is released into the cell. While some viruses deliver their information into the nucleus of the cell, poliovirus targets ribosomes (located in the cytoplasm) directly. The ribosome is responsible for producing proteins within the cell. The ribosomes of a cell infected with polio produce both poliovirus RNA and capsids instead of proteins for the host cell itself.

    Assembly

    • Within the cytoplasm, newly formed capsids and poliovirus RNA join together to form new virions. The cell then undergoes lysis (breaking open), and the new virus particles are released, going on to infect other host cells.

Viruses - Related Articles