Transcript Polio_virus
Poliovirus By: Connor Nash The Basics • Group: IV; Family: Picornaviridae; Genus: Enterovirus; Species: Poliovirus • There are several types of polio: nonparalytic polio & paralytic polio. Paralytic polio can be divided into: Spinal polio, bulbar polio, and bulbospinal polio. • Post-polio syndrome may also occur in which symptoms ranging form breathing and swallowing problems to joint pain, start many decades after the initial sickenss • Poliovirus causes a disease know as poliomyelitis which is characterized as an infectious viral disease spread mostly through fecal matter entering the mouth of another individual • In 90% of cases no symptoms are exhibited • Symptoms include: flaccid paralysis, muscle weakness, fever, headache, vomiting, diarrhea, fatigue, back pain or stiffness, neck pain or stiffness, pain or stiffness in the arms or legs, muscle spasms or tenderness Basics Cont. • The virus is composed of an RNA genome and a protein capsule. The genome is single-stranded positive-sense RNA genome that is about 7500 nucleotides long • Is often called the simplest significant virus • First isolated in 1909 by Karl Landsteiner and Erwin Popper • Egyptian paintings depicted the effects of polio by showing otherwise healthy individuals with withered limbs • Outbreaks reached pandemic proportions in the early 20th century in Europe, North America, New Zealand and Australia • Accordingly the doctors who worked on finding a cure and a vaccine became famous Virus Infection Process • The polio virus infects human cells by binding to an immunoglobubin-like receptor called CD155 (poliovirus receptor). • The exact mechanism that poliovirus uses for entering the cell is unknown. However, the interaction of poliovirus and CD155 causes a change in the shape of the viral particle that is needed to enter the cell • There are two thesis' for the way the viral nucleic acid to enters the cell. The first thesis is that the RNA of poliovirus is injected into the host cell through a pore in the membrane of the host cell. The second, and the one that is most likely and has the most supporte through research, is that the poliovirus is taken in by the host cell through endocytosis. • Poliovirus has ssRNA. Also known as single-strand RNA. Virus Infection Process cont. • The genome inside poliovirus can be used as mRNA and immediately translated by the host cell • Inside the host cell, the virus then takes over the cell’s translation machinery then causes inhibition of cellular protein synthesis. This favors the virus. • The poliovirus mRNA is then translated into a long polypeptide which is cleaved into 10 individual viral proteins • These proteins range from RNA polymerase to the proteins of the viral capsid • Translation of the viral RNA occurs by an IRES-mediated (internal ribosome entry site) mechanism • The IRES is the extremely long 5’ end of the poliovirus’ mRNA. • The assembly of viral particles is not fully understood. • The particles leave the host cell 4-6 hours after the initial infection. Each dying host cell can release 10,000 polio virions. • This means poliovirus is lytic Treatment • Currently there is no treatment to cure Polio. Treatment is focused on supportive care • Medication and rest to lower the fever • Medication to reduce pain and improve the strength • Breathing assistance with a ventilator • Moderate exercise • A nutritious diet • To Prevent Poliovirus: The most effective and most commonly used is the Polio vaccine. This vaccine is given to young children in specific increments. • Vaccine works by strengthening and preparing the immune system to a future encounter with the Poliovirus. Pictures Genomic structure of type 1 Poliovirus Cellular life cycle of Poliovirus Sources Cited • NAMH. How Polio Works. http://polio.emedtv.com/polio/polio-treatment.html • MayoClinic.com. Infectious Disease. http://www.mayoclinic.com/health/polio/DS00572/DSEC TION=symptoms • Wikipedia. Poliovirus. http://en.wikipedia.org/wiki/Poliovirus • Wikipedia. Poliomyelitis. http://en.wikipedia.org/wiki/Poliomyelitis