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    Throwback Thursday: Science Edition: Battling Polio

    It’s that time of the week again – Throwback Thursday! As vaccines are currently at the forefront of conversation, we thought it would be appropriate to take a look at another world-changing vaccination breakthrough from history. This week’s edition delves into the work behind the polio vaccine and how it saved the lives of children everywhere. Let’s find out more…

    Poliovirus is the causative agent of poliomyelitis, otherwise known as polio. The disease mostly affects children under the age of five and has been active since the 1800s, although at that time it was not considered a widespread problem. Fast forward several decades, and polio had managed to grow into a pandemic across multiple countries during the 1910s through to the 1960s, sickening and even killing tens of thousands of children at its peak. The push by scientists to develop a vaccine was an intense effort, and it was Jonas Salk who was finally credited with developing the first effective vaccine in 1953.

    Up until the 1940s, the general consensus was that polio, because of its paralysis symptoms, could only impact the nervous system. A scientist called John Enders and his team of researchers dedicated themselves to demonstrating that the virus can grow in places besides the nervous system, such as the intestines, which some patient data suggested. To develop a vaccine, it’s important to know where the virus can attack and where it can thrive, since you need to be able to grow the virus in the lab. This is not as easy as it sounds, nor does it draw parallel to growing a plant or bacteria. In order to grow, viruses need to be able to infect living cells. The technique used in labs to grow a virus is called Mammalian Tissue Culture, which uses real mammal cells that make up organs of, well, a mammal!

    In previous experiments, polio was only ever shown to grow in brain and nerve cells, despite efforts to grow the virus in liver, kidney, spleen and lung cells. Enders decided to take a different approach; his aim was to grow the virus in human muscle, skin, tissue and intestinal cells. He and his colleagues used the bodies of deceased human embryos and a deceased premature infant and, borrowing a technique used with the mumps virus, suspended the cells in a mix of salt, buffers and a protein solution. They varied their efforts from previous attempts by changing the nutrient solution regularly (cells will die in their own waste without fresh nutrients) and growing fresh subcultures, otherwise known as passaging.

    To figure out the amount of virus that had been produced, the team took infected fluids from the cells and infected lab mice and monkeys with the product. For comparison, they also infected different mice and monkeys with the original virus sample. The results showed that the virus had successfully grown at a very high rate – the levels were actually higher in intestinal cells than in nerve cells. This proved that it was possible for the poliovirus to grow outside of the brain and nervous cells, which was the breakthrough the science community had desperately needed. This allowed Jonas Salk to grow the poliovirus in large enough quantity to develop that life-changing vaccine!

    Polio isn’t completely eradicated; the disease is still active in a few countries including Afghanistan, Nigeria, and Pakistan. However, the world has mostly seen it die out. John Enders and colleagues Robbins and Weller were awarded the Nobel Prize in Medicine in 1954 for their groundbreaking and innovative work.

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