DNA Vaccines, ZyCoV-D

[Melbourne]

ZyCoV-D is a newish vaccine out of India. It’s a “DNA vaccine”. I’m not sure of the details.

Have they just made some quantity of DNA, and they inject it in your arm?

I thought normal vaccines make you immune to surface starches or surface proteins or surface somethings. Is there overlap between “DNA for COVID spike” and “COVID spike” such that immunity for “spike DNA” is the same as immunity for “surface spike”, or, how do “DNA vaccines” work?

[mikecurtis]

Explained: How Zydus Cadila’s ZyCov-D vaccine for Covid-19 works, and how it...

ZyCov-D is a “plasmid DNA” vaccine — or a vaccine that uses a genetically engineered, non-replicating version of a type of DNA molecule known as a ‘plasmid’.

The plasmids in this case are coded with the instructions to make the spike protein of SARS-CoV-2, the coronavirus that causes Covid-19. Vaccination gives the code to cells in the recipient’s body, so they can begin making the spiky outer layer of the virus. The immune system is expected to recognize this as a threat and develop antibodies in response.

[Melbourne]

How does vaccination ‘give the code to cells in the recipients body’?

I understood that messenger RNA was a message that contained the code that should be built. What is plasmid DNA, and what does it do when it’s injected into your body?

[mikecurtis]

Seems to me , to be very similar to the mRNA vaccine. Just with a different vector.

A plasmid is a type of DNA that is found only in bacterial cells. They are distinct from the chromosomal DNA. When people mention ‘DNA’ they normally refer to the chromosomal DNA — the old, familiar double-helix ladder. The plasmid DNA, unlike the chromosomal DNA, does not carry hereditary information, but its genes give it advantages such as pesticide- and antibiotic-resistance.
. . .

A plasmid DNA vaccine works like this: A piece of DNA encoding the antigen (part of the disease-causing pathogen that induces an immunity response from our bodies) is inserted into a bacterial plasmid. The DNA plasmids carrying the antigen are injected into the muscle. Once the DNA gets inside our cells, they start producing antigens, which triggers an immune response.

Plasmid DNA vaccine

DNA vaccine

[Chronos]

It’s just one more additional step. With a traditional vaccine, you put some foreign proteins in a person’s body. With an RNA vaccine, you put some RNA in a person’s body, and the body uses that RNA to make the proteins. With a DNA vaccine, you put some DNA in a person’s body, and the body uses that DNA to make RNA, then uses that RNA to make proteins.

Why these extra steps are desirable, I’m not entirely sure, though.

[FinsToTheLeft]

@Chronos

With a traditional vaccine, you put some foreign proteins in a person’s body.

With a traditional vaccine, you need need a vector. You don’t simply produce a protein and inject it. The Influenza virus is traditionally made by injecting chicken eggs with the virus, letting it replicate, and then killing the virus without denaturing the proteins. This takes a lot of time, which is the difficulty in matching Influenza strains with the vaccine. We make a bet ahead of time and can’t get a redo if the actual strains vary. mRNA vaccines use a much smaller piece of protein and can be manufactured much faster than using an egg culture.

[FlikTheBlue]

@Chronos

Why these extra steps are desirable, I’m not entirely sure, though.

I haven’t researched this particular vaccine. In general, however, DNA is more stable than RNA. My guess is that the DNA is easier to stabilize than the mRNA used by Pfizer and Moderna, and likely has less stringent storage requirements.