RNA vaccines

Saturday, 28 November 2020 15:56

Comparing polio to COVID-19 is idiotic

We are all capable of moments of idiocy, as doubtless my other half will attest. However, in the home setting, my failings are (usually with good humour) pointed out to me. So, when someone (let’s call them William) wrote on a Facebook post of mine that ‘Comparing polio to covid is idiotic’, I wanted to understand what I had got wrong. 

My original post was about Jonas Salk and the polio vaccine, and the importance of vaccination. For me, it is just as important to get vaccinated against COVID-19 as it is to be vaccinated against polio. William responded to my request for clarification by saying: 

Covid is a coronavirus and they wish use to mass inject the population with no justification using an RNA never used on humans experimental vaccination. Was the polio vaccine an RNA vaccine made using CRISPR/Cas9 gene editing tool directly interfering with our immune systems?  

There’s quite a lot to unpack in that. But I did my best, and here is my response.

Thanks for that William. May I be bold enough to say that you have some misunderstandings here.

Let’s start with where you are correct. COVID-19 is caused by a coronavirus. Polio is caused by an enterovirus. They are from different families of virus. However, they are both what are called RNA viruses.

What is RNA?

Every human cell has a nucleus, which acts as its command centre. These nuclei contain DNA. The DNA in each of my nuclei contains all the instructions to make 'me'. In a nucleus, the DNA copies its instructions multiple times onto other molecules called RNA. The RNA molecules then travel into the rest of the cell, carrying these instructions. The instructions include telling the cell to make certain substances, such as proteins (needed by all cells).

Viruses are much simpler. They consist of a shell made of proteins, with some molecules of either DNA or RNA inside. The fact that viruses use RNA or DNA is what allows them to cause illnesses in humans.

When an RNA virus gets into a cell, the cell thinks that the RNA is from the nucleus and contains instructions from the nucleus. So, it starts making copies of the virus. Viruses that contain DNA often have to work a little harder. They need to get their DNA into the nuclei of cells. Once there, the virus DNA can become a part of the human DNA and start producing instructions on RNA molecules. So, viruses that contain DNA work using a two-step process.

The Immune Army

The cells in your immune system know what sort of proteins your cells should be making. If your immune system spots cells that are producing foreign proteins, it sends in an Immune Army of cells and ‘antibodies’ to destroy anything that has the foreign proteins in them. So, your immune system destroys the virus particles (because they have the protein in them) and any of your own infected cells that are busy building viruses.

The problem is that the Immune Army takes quite a long time to build, and a new army is needed for each disease. So, you often get ill from a disease before you get better again. Luckily, for many diseases parts of the Immune Army stick around in your body. Should the virus get into your cells again, they quickly destroy it and so you don’t get the disease again.

Different types of vaccines

Vaccines are injected into your body to cause an Immune Army to be made. So, yes, I guess in a way it does interfere with your immune system but only in the same way that a real virus interferes with your immune system.

To create the Immune Army, a vaccine can contain ‘inactivated viruses’. To make these vaccines, scientists take the real virus for a disease and treat it with chemicals or heat to stop it being able to infect cells. The ‘inactivated’ version still looks like the real virus and crucially still has the proteins on its coat that your immune system recognises as foreign. Examples include vaccines for polio and rabies.

Other vaccines contain the real virus, which is still able to infect cells but which has been cultivated in a way to make it unable to cause the nasty form of a disease. Examples include the vaccine for bubonic plague.

Other vaccines contain just the protein bits from a virus. These are often made using genetically modified yeast; the yeast churn out millions of copies of one protein from a virus, which is then used to make the vaccine. Examples include vaccines against hepatitis B and HPV.

And there are companies working on these types of vaccine for COVID-19.

However, first off the block are these new RNA vaccines. The vaccines from Pfizer and Moderna contain RNA molecules that have the instructions for one protein from SARS-CoV-2. (There are many SARS-CoV-2 proteins). Once inside your cells, the RNA molecules instruct your cells to produce the virus protein. Your immune system sees this new protein, and assembles its army against it. That’s the Immune Army that will defeat the real virus if it infects you.

Then there is the Oxford vaccine, which uses a slightly different approach. They’ve modified a virus that causes colds. This virus is a DNA virus. With this vaccine, the virus puts DNA into the nuclei of some of your cells, and the DNA then makes the RNA (using the same two-step process as outlined above). The RNA carries the instructions for making one SARS-CoV-2 protein.

Back to William’s points

So, by all means, if this new technology worries you, wait for the more conventional vaccines that will come out next year. But the effect of these new vaccines is the same as the effect of the real virus – they make your own cells produce copies of a virus protein. It’s just that the vaccine doesn’t cause COVID-19. And the point I was making is that we should get vaccinated, I was not making any point about which vaccine to use.

And it has now been used on humans … at least 100 000 of them. That was the point of all the testing.

Oh, and CRISPR/Cas9? William, I have a feeling that your understanding of CRISPR/Cas9 is rather limited. There are no vaccines produced that use this. It is a DNA editing system. If you are interested, the system contains a tracker molecule that can find certain pieces of DNA. This molecule is attached a pair of molecular scissors, which then cut out that piece of DNA when it’s found. It is hoped that we can make treatments for certain cancers caused by viruses using this technique. And the idea has been floated that we can modify the technique to make something to treat people with COVID-19 … the tracker molecule will find the RNA molecules from the virus and the molecular scissors will chop them up into useless bits. There is also a test for COVID-19 being developed using this system. But not a vaccine.

So, there we have an answer to your second point. I’ve not really touched on the idiocy of comparing polio to COVID-19 (only that both diseases are caused by RNA viruses). However, there are plenty of similarities that can be drawn … a future blog post, I think.

Text: Mark Levesley   @marklevesley    levesley.com

 Photo: Staged iron lung ward Food and Drug Administration public domain