Department of Biology
Date Submitted: 5-2-12
Course: Biology- 162
Instructor: Prof. Estelle
The poliovirus is one of the most transmittable and most contagious viruses that the human population has come in contact with. The structure of the poliovirus allows it to be able to bind to motor neuron cells within a host’s body and reproduce quickly. Like all virus’s, the poliovirus requires a host to survive. Humans are the primary hosts for the virus and the virus is extremely transmittable by way of person-person contact (most commonly fecal-oral contact). Although the virus is extremely contagious, the human immune response can be considered a very worthy advisory in fighting polio. Most of those infected will not experience any symptoms, and only a very small percentage of those who do will develop paralysis from the virus. There are three known strands of the poliovirus, commonly referred to as PV1, PV2, and PV3. Brilliant research and modern science have since almost eradicated the virus through the development of vaccines and a global eradication plan. Despite the success of scientists, containing the virus still remains pertinent due to the virus’s ability to mutate. The virus’s ability to “drift” and mutate has led to many polio cases caused by the vaccinations themselves.
The study of the poliovirus has led to a better understanding of all viruses, as well as a worldwide polio eradication goal that is considered extremely successful. Today the U.S. sees approximately eight paralytic polio cases a year; a suburb achievement considering that 21,000 cases of paralytic polio were reported only sixty years ago. Although the virus is considered mostly eradicated, the virus’s ability to mutate requires further attention be paid to keep it under control. Many aspects contributed to the understanding of the poliovirus and this study will attempt to explain how polio went from a feared viral disease, to becoming regarded as a scientific success. This study will attempt to shed light on how intricate and complicated a small virus can be, as well as how efficient the human immune response is in fighting off the virus. Perhaps the only thing more impressive than the inner workings of the poliovirus is the time and research done by those before us that led to its understanding. Results
A. Poliovirus Structure: One of the first viral structures ever discovered, the poliovirus is a relatively simple, small, icosahedral, nonenveloped, RNA virus of the viral family Picornaviridae. A virion, or particle, of the poliovirus is essentially an RNA strand surrounded by a capsid. Receptors are on the surface of the capsid that help the virus identify and bind to motor neurons in the host’s body. The capsid is composed of proteins, and its main function is to surround and protect the RNA. Polio's genetic information is contained on a single strand of RNA which codes for invading the ribosomes of target cells. Understanding the structure of the poliovirus has not only led to a vaccine for the virus, but has also contributed to understanding the replication of animal RNA virus’s in general. A noteworthy step in understanding the disease was the recognition that there are immunologically distinct strains of the virus. Another major breakthrough occurred in 1985, where Jim Hogle and his collaborators solved the structure of poliovirus to a resolution of 2.9 angstroms (Hogle, Chow and Filman, Science 229: 1358-1365). Holk and his team noted that the virus had a pattern of interlocking N-terminal arms of subunits; these...