MRNA Vaccine: How It Works & Questions Answered

[brajesh]

TL;DR Summary

What happens to the cell after it produces the spike protein? Does it get killed?

Here is my understanding of how an mRNA vaccine works and some questions where I am not clear:

I understand that an mRNA vaccine is delivered via lipid spheres containing the mRNA,.
The cell brings it inside the cell thinking it's fat?
Then the mRNA is read by the cell machinery to produce the spike protein?
The spike protein is presented outside the cell?
The immune system recognizes an intruder and attacks the cell?
So is the original cell killed in this process?

 

[jim mcnamara]

Your questions are in blue. My answers are black and are simplified.

I understand that an mRNA vaccine is delivered via lipid spheres containing the mRNA,.
They are variously called liposomes, micelles, there are other terms. This is how non-fat soluble nutrients - like vitamin C or copper complexes get out of the gut and into cells. Moving through cell membranes.

The cell brings it inside the cell thinking it's fat?
No. see above.

Then the mRNA is read by the cell machinery to produce the spike protein?
Yes.

The spike protein is presented outside the cell?

It moves out via the Golgi apparatus, yes. Sort of like 'I do not know what to do with this stuff, so let me dump it.'

The immune system recognizes an intruder and attacks the cell?

No. The immune system sees a foreign protein. This triggers an extremely complex response that builds up special immune memory cells as well as antibodies specific for that protein. No cell killing.

So is the original cell killed in this process?
No.

 

[brajesh]

thank you for the nice simple explanation @jim mcnamara :)

 

[Ygggdrasil]

The immune system recognizes an intruder and attacks the cell?

No. The immune system sees a foreign protein. This triggers an extremely complex response that builds up special immune memory cells as well as antibodies specific for that protein. No cell killing.

So is the original cell killed in this process?
No.

Are you sure about this? I was under the impression that cytotoxic T-cells recognize cells presenting foreign antigens and target them for destruction.

 

[jim mcnamara]

CD8 T cells can kill infected cells, especially those with viral infections. That is correct I believe. So what cells are killed during immunogenesis? If the patient achieves "immune response mediated sterility", then all infected cells have been killed as have all virus particles/antigens been eliminated.. This does happen. But it cannot be across the board. Otherwise, for example, mRNA vaccines would be 100% effective (parameter=sterility), 100% of the time. Correct?

Therefore, some fraction of the time, all "infected" cells are killed. And some cells, at a minimum, are almost always killed, I presume.

-- https://www.cdc.gov/vaccines/covid-19/hcp/mrna-vaccine-basics.html --
see: Mechanisms for action - dendritic cells and macrophages in lymph nodes

So, I opted for none, maybe "most" would have been better.

 

[Laroxe]

Yes for the longer term adaptive response there are a number of different cells which sample the antigens and deliver these samples to lymphatic tissue. This stimulates the development of germinal centres which produce lots of B Lymphocytes which produce antibodies, only the lymphocytes that provide a reasonable antibody match are kept and allowed to divide. This process allows for the best matching antibodies to be selected and at every challenge the antibodies are refined even further.
Some of these B lymphocytes become long lived memory cells that allow for the rapid development of antibodies if the virus is encountered again.