Soon We Can Say Goodbye to Polio

Genomics Revolution

Genomics Revolution

Kiyana Caver & Brittany Weaver

Genetics Podcast Transcript

Episode 44: Poliovirus

Script:

Hello, I am Kiyana & I am Brittany and we will discuss the virus poliovirus which causes polio. Polio can also be known as poliomyelitis. It stems from the Greek meaning of an inflammation of the gray matter. In the early 20thcentury there weren’t many diseases that had parents worried about the health and wellbeing for their children. However, poliomyelitis is something that parents were fearful of their children getting. Poliomyelitis was a disease that was more common to catch during the summer as that is when polio was more likely to come about, in warmer weather. This disease is very contagious and it is caused by a virus that attacks the nervous system, it also can lead to spinal cord and or brain stem paralysis if it is not treated soon. The people that are mostly affected by it are younger children, usually children become affected with the disease before they turn 5 years old (7 & 6). Polio was most likely spread through contact between people by nasal and oral secretions and by coming into contact with contaminated feces. Polio enters through the mouth, multiplies through the digestive tract where it continues to multiply. Polio was discovered in 1908 by Karl Landsteiner and Erwin Popper. Poliovirus was discovered as scientists were proving that it was not a bacterium that had been causing paralysis, but instead it was a virus (5). Despite it being discovered it the early 1900’s, poliovirus did not peak in the United States until around 1952 when almost 60,00 cases had sparked throughout the United States.

Poliovirus is a RNA genome with a protein capsid made up of one single RNA positive sense stand, that is about 7500 nucleotides long. There is one primary RNA molecule in the genome, which has been shown to have 8 unused start codon sites that are in front of the active AUG start codon. The molecule also has 23 RNA hairpin secondary structures (3). Poliovirus has one main cleavage of a precursor polypeptide called NCVP 1 which encodes for proteins VP 1, 2, 3, and 4 (1). Poliovirus originated from a single precursor molecule called NCVPOO [noncapsid viral protein (NCVP] (2). Poliovirus is a well known and studied virus because between the period of the 1940’s-1950’s the virus was at its most epidemic (8). Polio had crippled around 35,000 people every year in the US alone. A study was preformed in 1994-1995 that showed over 1 million people had survived poliovirus but, over 443,000 people reported having been paralyzed, as it affects a persons nervous system. During the epidemic when it was at its highest affect there were reports of about 27,000 people reporting paralyzation and about 6,000 deaths. When poliovirus was sequenced it led to many discoveries that affected the treatment and prevention of polio in the world. Research found that there were 3 serotypes of poliovirus that caused paralysis in diffferent ratios, type 1 was the most paralytic and accounted for about 80% of paralyzation, type 2 had 8% and type 3 had 13%. This finding was important because it allowed for more focus to be pulled onto why one type was more paralytic than others. Another key finding was that of inactivated poliovirus also known as IPV being introduced for polio in 1955 and oral poliovirus also known as OPV in 1961. These were both used to protect immunized patients and it was found that OPV could spread from the vaccinated to close companions when in contact, increasing the immunity in the US, which was seen when the number of annual inciddences fell drastically. Knowing that OPV was a good way of immunization it was studied along with the wild poliovirus sequence to see how many doses of OPV was approximately needed to eradicate wild poliovirus. The US and other countries tested the possibility of eradicating the wild poliovirus and was first succesful in Cuba through the eradication of wild poliovirus. It was found that if a child by the age of 12 months had 3 doses of OPV that percentage of cases of wild poliovirus decreases. The eradication of all indigenous wild poliovirus occurred in 1991 (4).

This is Brad Goodner and I need to step in with an add-on to Brittany’s last sentence. After success in Cuba, the eradication of wild poliovirus in 1991 was from the entire Western Hemisphere through an organized immunization effort using the oral poliovirus vaccine. Since then, efforts have continued worldwide and we are so close to complete eradication of polio that immunization programs have switched from the oral vaccine to the inactivated vaccine to prevent OPV-derived shedding of live virus that might cause rare infections on non-immunized individuals. Hopefully, we are only a few years away from saying goodbye to this small but devasting virus.

This has been our genomic podcast on poliovirus, thank you for listening and we hope you now know more about poliovirus.

References:

1. Rekosh, David. “Gene Order of the Poliovirus Capsid Proteins.” Journal of Virology, vol. 9, no. 3, Mar. 1972, pp. 479–487., doi:10.1128/jvi.9.3.479-487.1972.

2. Nomoto, A., et al. “Complete Nucleotide Sequence of the Attenuated Poliovirus Sabin 1 Strain Genome.” Proceedings of the National Academy of Sciences, vol. 79, no. 19, Jan. 1982, pp. 5793–5797., doi:10.1073/pnas.79.19.5793.

3. Simoes, E A, and P Sarnow. “An RNA Hairpin at the Extreme 5 End of the Poliovirus RNA Genome Modulates Viral Translation in Human Cells.” Journal of Virology, vol. 65, no. 2, Feb. 1991, pp. 913–921., doi:10.1128/jvi.65.2.913-921.1991.

4. Nathanson, N., and O. M. Kew. “From Emergence to Eradication: The Epidemiology of Poliomyelitis Deconstructed.” American Journal of Epidemiology, vol. 172, no. 11, 26 Oct. 2010, pp. 1213–1229., doi:10.1093/aje/kwq320.

5. “NMAH: Polio: The Polio Genome.” NMAH | Polio: The Polio Genome, 1 Feb. 2005, https://amhistory.si.edu/polio/virusvaccine/livingchem.htm

6. “Polio.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 9 Dec. 2017, www.mayoclinic.org/diseases-conditions/polio/symptoms-causes/syc-20376512.

7. “Poliomyelitis.” World Health Organization, World Health Organization, www.who.int/news-room/fact-sheets/detail/poliomyelitis.

8. “Post-Polio Syndrome Fact Sheet.” National Institute of Neurological Disorders and Stroke, U.S. Department of Health and Human Services, www.ninds.nih.gov/disorders/patient-caregiver-education/fact-sheets/post-polio-syndrome-fact-sheet.