things you need to know about: mRNA vaccines
They are a completely new type of vaccine.
If an mRNA – vaccine for coronavirus is approved, it will be the first of its kind. ‘It’s a very unique way of making a vaccine, and no (such) vaccine has yet been licensed for infectious disease,’ Prof. Bekeredjian-Ding explained.
Vaccines work by teaching the body to recognize and respond to proteins produced by disease-causing organisms like viruses and bacteria. Traditional vaccines are composed of small or inactivated doses of the entire disease-causing organism or the proteins it produces, which are introduced into the body to stimulate the immune system into mounting a response.
Scientists create an mRNA vaccine by creating a synthetic version of the mRNA that a virus uses to build its infectious proteins. This mRNA is delivered into the human body, where cells read it as instructions to build that viral protein, and thus some of the virus’s molecules. Because these proteins are solitary, they do not combine to form a virus. When the immune system detects these viral proteins, it begins to mount a defensive response.
The molecule known as mRNA has been a surprising star of the coronavirus pandemic response. It is a key component of the Pfizer and Moderna COVID-19 vaccines. However, mRNA is not a novel laboratory discovery. It evolved billions of years ago and can be found in every cell of your body. Scientists believe that RNA existed before DNA in the earliest life forms.
Here’s a quick primer on mRNA and the critical role it plays.
Meet the genetic intermediary.
You’ve probably heard of DNA. It’s the molecule that contains all of your genes, which are denoted by a four-letter code – A, C, G, and T.
Every living thing has DNA inside its cells. It is safeguarded in the nucleus of the cell. The genes are the details in the DNA blueprint that account for all of the physical characteristics that distinguish you from others.
However, the information from your genes must travel from the nucleus to the cytoplasm, which is where proteins are assembled. Proteins are used by cells to carry out the numerous processes required for the body to function. That’s where messenger RNA, abbreviated mRNA, comes in.
Sections of the DNA code are transcribed into shortened messages that contain protein-making instructions. These messages, known as mRNA, are carried to the cell’s nucleus. Once the mRNA arrives, the cell can use these instructions to make specific proteins.
The structure of RNA is similar to that of DNA, but there are some significant differences. RNA is made up of a single strand of code letters (nucleotides), whereas DNA is made up of two strands. The RNA code contains a U rather than a T – uracil rather than thymine. Both RNA and DNA have a backbone made of sugar and phosphate molecules, but the sugar in RNA is ribose and the sugar in DNA is deoxyribose. The sugar in DNA contains one less oxygen atom, which is reflected in their names: DNA is short for deoxyribonucleic acid, and RNA is short for ribonucleic acid.
Every cell in an organism contains identical copies of DNA, from a lung cell to a muscle cell to a neuron. RNA is synthesized as needed in response to the dynamic cellular environment and the body’s immediate needs. It is the job of mRNA to help activate the cellular machinery in order to build the proteins encoded by DNA that are appropriate for that time and place.
The process of converting DNA to mRNA and then to protein is the foundation for how the cell works.
As an intermediary messenger, mRNA plays an important role in the cell’s safety mechanism. Because any RNA outside of the cell is instantly targeted for destruction by RNase enzymes, it prevents invaders from hijacking the cellular machinery to produce foreign proteins. When these enzymes recognize the structure and the – U in the RNA code, they erase the message, preventing the cell from receiving incorrect instructions.
The mRNA also allows the cell to regulate the rate of protein production by switching the blueprints “on” or “off” as needed. No cell wishes to produce every protein described in your entire genome at the same time.
Messenger RNA instructions are programmed to self-destruct, much like a text or snapchat message. The mRNA’s structural features – the U in the code, its single-stranded shape, ribose sugar, and specific sequence – ensure that it has a short half-life. These characteristics work together to allow the message to be “read,” translated into proteins, and then quickly destroyed – within minutes for proteins that require tight control, or up to a few hours for others.
When the instructions are no longer present, protein production halts until the protein factories receive a new message.
Utilizing mRNA for Vaccination
All of the properties of mRNA piqued the interest of vaccine developers. A vaccine’s goal is to get your immune system to react to a harmless version or part of a germ so that when you encounter the real thing, you’ll be ready to fight it off. Researchers discovered a way to introduce and protect an mRNA message containing the code for a portion of the spike protein on the surface of the SARS-CoV-2 virus.
The vaccine contains only enough mRNA to produce enough spike protein for a person’s immune system to produce antibodies that will protect them if they are later exposed to the virus. The mRNA in the vaccine is quickly destroyed by the cell, just like any other mRNA. The mRNA cannot enter the cell nucleus and has no effect on a person’s DNA.
Despite the fact that these are new vaccines, the underlying technology was developed many years ago and has been improved incrementally over time. As a result, the vaccines have undergone extensive safety testing. The success of these mRNA vaccines against COVID-19 in terms of safety and efficacy suggests a promising future for new vaccine therapies that can be rapidly tailored to new, emerging threats. Early-stage clinical trials with mRNA vaccines for influenza, Zika, rabies, and cytomegalovirus have already been conducted. Certainly, innovative scientists are already working on therapies for other diseases or disorders that could benefit from a strategy similar to that used for COVID-19 vaccines.