​Viral Attenuation: The Art of Confusing a Virus


Viruses are tricky; they sneak into the bodies of human beings unnoticed. While some viruses are merciful, lasting for only a couple of days and leaving the body without lasting damage, other viruses are deadly. Yet, no matter how tricky viruses are, human beings are trickier; they have come up with ingenious solutions to protect the human race from deadly viruses.

First, let us find out how a virus sneaks into the body of a human being. Viruses are simple in their structure; however, their danger lies in their ability to trick the body. They can easily get into the cells, because they are disguised as nutrients that the cells desperately need; once it enters, it transfers its genome into the cell. This is the method through which an infected cell follows the instructions of a virus. A virus does not have the mechanism to duplicate itself; yet, through transferring its data to the cell, it reproduces itself.

Despite sneaking into human cells, the cells do not stand helpless in the face of viruses. The immune system is designed to recognize our own cells from other invaders; once an invader is detected, our white blood cells rise to defend the body. T-lymphocytes and B-lymphocytes (white cells) play an important role in attacking the virus and in stopping it from replicating.

Those white cells unite to defend the body against viruses; either by raising the alarm, stopping the virus from making copies of itself, or simply by creating antibodies. Antibodies mark the virus so that other cells know that these are infected cells that they must attack. Our immune system has a memory; once a virus is destroyed, B and T cells retain a memory of the virus so that they can recognize it easily and not be deceived by it again. This means that the immune system can easily prevent another infection from the same virus.

However, with deadly viruses, human beings do not live to retain a memory of the virus; hence, the importance of vaccination. Vaccinations are intended to give our immune system a memory of a virus so that it can recognize and have a lifelong immunity against it without suffering its consequences. There are different methods in creating such vaccinations, but here, we will only focus on viral attenuation, which is the art of weakening a virus so that it can be safely given to human beings, incurring the same immune response expected from the immune system but without causing lasting damage.

Viral attenuation differs from the process of killing a virus completely. Vaccination against diseases such as measles, mumps, rubella, and chickenpox are based on viral attenuation. Weakening a virus happens when the virus is placed in a different host; a virus that attacks human beings is inserted into animals, normally animal embryos. The virus is not inserted once; it is passed from an animal embryo into another several times. With each time it is transferred into the animal embryo, it gets better at replicating itself in animals’ cells, but at the same time, loses its ability to replicate in human cells. What comes out after inserting the virus into different hosts is a weakened version of it that the human cells can recognize. When human beings are vaccinated with an attenuated virus, their bodies receive lifelong immunity without suffering the devastating consequences of the disease itself.

Viruses in the past have claimed the lives of billions of people. Thankfully, with the help of “viral attenuation” vaccination, most of the deadly viruses have been successfully kept in check, if not fully eradicated. It is important to note we owe the disappearance of many deadly viruses to Edward Jenner, known as the “Father of Immunology”. Jenner observed that milkmaids, who were infected by cowpox, were immune to smallpox; thus, he exposed people to cowpox and then to smallpox, and noticed that they were not affected. He repeated the same experience over and over again until he was positively sure that one of the two viruses actually makes people immune to the deadly other. His observations saved people from smallpox, and paved the way for many breakthroughs in vaccinations and immunology. 

Since then, research has been ongoing and we have a better understanding now of the art of vaccinations than Jenner’s basic observations. However, with his help, human lives have been preserved. Thanks to Jenner, and to many scientists who came after him, our world is safe. Stay vaccinated and stay safe.

*Published in SCIplanet printed magazine, Summer 2017 Issue.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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