Corona virus general questions mega thread

[StringJunky]

Found this interesting experiment on viral spreading. This video shouldn't be seen as how much virus is spread but what people touch.

 

[CONvenience]

I'm not going through 20 pages to find out if these questions have already been asked:

-After receiving a mRNA and/or Adenovirus vector vaccine, what happens to the cells which produce the spike protein on their surface?  Does the immune system just destroy the cell?

-Which cells have the greatest affinity for the vaccine and/or producing spike protein?  Only the cells physically closest to the injection site?  Life cycles and cell renewal rates vary from cell type to cell type.

-If the cells with spike protein on their surface happen not to be destroyed by the immune system (for example:  someone who is taking an immunosuppressant) , will the spike protein disturb normal cell function and/or communication between cells?  For example, will the spike protein interfere with a substrate (neurotransmitter, enzyme, drug, etc.) recognizing a receptor?

-What happens if spike protein grows from a cancer cell?

 

[studiot]

2 hours ago, CONvenience said:

I'm not going through 20 pages to find out if these questions have already been asked:

Well that's your loss (or inconvenience) then since that is the reason those pages are preserved for posterity on this site.

If you can't be bothered to put in some effort, then why do you expect others to do so for you ?

[CharonY]

9 hours ago, CONvenience said:

I'm not going through 20 pages to find out if these questions have already been asked:

-After receiving a mRNA and/or Adenovirus vector vaccine, what happens to the cells which produce the spike protein on their surface?  Does the immune system just destroy the cell?

-Which cells have the greatest affinity for the vaccine and/or producing spike protein?  Only the cells physically closest to the injection site?  Life cycles and cell renewal rates vary from cell type to cell type.

-If the cells with spike protein on their surface happen not to be destroyed by the immune system (for example:  someone who is taking an immunosuppressant) , will the spike protein disturb normal cell function and/or communication between cells?  For example, will the spike protein interfere with a substrate (neurotransmitter, enzyme, drug, etc.) recognizing a receptor?

-What happens if spike protein grows from a cancer cell?

 

Primary targets are dendritic cells, which present antigens to T and B cells. While they can be killed on occasion, they typically have set lifespan which in part is coordinated via apoptosis.

It should also be noted that mRNA are short-lived, even if they are presented to non-target cells their effects are limited. Only specific cells present antigens on their surface, in most other cases if you introduce RNA they might produce a protein, but it is often also degraded rather quickly by the proteasome.

[CONvenience]

 

1 hour ago, CharonY said:

even if they are presented to non-target cells their effects are limited. Only specific cells present antigens on their surface, in most other cases if you introduce RNA they might produce a protein, but it is often also degraded rather quickly by the proteasome.

This part answered my main questions.  Thank you for your response.

Edited March 5, 2021 by CONvenience

[CharonY]

They generally are partially targeted as they are formulated to be preferentially taken up by phagocytotic cells. I am not really sure about tropism data of the current vaccines. I assume you are thinking of the risk of presentation of other cell types via MHC-I among non-professional antigen presenting cells?

One of the original fears of mRNA vaccines is that they may have broader tropism resulting in widespread MHC-I presentation leading to severe inflammation. So far, no widespread tissue damage has not been reported, which indicate that the effects are likely more localized and targeted

Presentation of antigens is a bit tricky, but fundamentally bits and pieces of proteins can be presented by many cell types via the MHC system. In non-professional antigen presenting cell the main mechanism would be via MHC-I, which allows presentation of peptides (i.e. bits and pieces of proteins) originating from the cytosol. So if such a cell would produce the protein and it gets presented, it could interact with CD8+ T cells likely resulting in target destruction. Attenuated vaccines often result in presentation of both MHC-I and II pathways, for example.

With regard to protein turn-over, it is a bit difficult to tell. Synthesized the proteins are broken down and typically only fragments end up being presented (turnover rate of intact proteins in general covers a huge range depending on protein and cell type from hours to months in extreme cases). Those parts can remain around for a while but not necessarily in the same cell, as they may be released or broken down and taken up by other cells (the phagocytic pathway being the main mechanism of MHC-II presentation). It cannot be regenerated as once the mRNA is broken down, no new protein is going to be produced. However I think I have seen data suggesting that it may be around for a while, but cannot recall the paper (most I can think of focus on the duration of the T cell induction, which is related).