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Life Sciences => Physiology & Medicine => COVID-19 => Topic started by: nudephil on 19/05/2020 16:08:52

Title: Can you build up coronavirus immunity by repeated, tiny, increasing exposure?
Post by: nudephil on 19/05/2020 16:08:52
Here's a question from Jon:

Suppose that it is true that one can survive ingesting or snorting a single SARS-CoV-2 particle. Suppose that the next day you snort 2. The next day, either 3 or 4 (depending on if you're a linear kind of a guy or an exponential kind of a girl) and so on. Is this a path to creating immunity while not getting the full blown disease?

Any response?
Title: Re: Can you build up coronavirus immunity by repeated, tiny, increasing exposure?
Post by: nudephil on 19/05/2020 16:21:11
Jon also sent the following to preface the question:

I heard that if one gets a small dose of coronavirus particles, your immune system can clear them easily enough. Sounded strange to me. I thought the whole point was that we do not have a mechanism for clearing the coronavirus until after we have had the disease and have recovered.

Here's how I replied to Jon - posting it here so I can be corrected if I'm wrong:

As far as I understand it - and I'm no virologist myself - there's a distinction here between the innate and the adaptive immune system.

The innate immune system makes no distinction between different pathogens, and acts like a front line of defense. A very tiny dose of virus could be gobbled up by the cells in this system before any infection takes hold.

The adaptive immune system responds directly to SARS-CoV-2 with antibodies and cells that specifically target it. Its ability to clear the virus often depends on the size of the dose, ie on the extent of the infection. A small dose of virus that gets past the innate immune system could be relatively easily cleared by these more complex cell types.

On the subject of your question, I believe this type of mithridatism would have the opposite effect to intended. If it worked, you would be training your adaptive immune system to stop reacting to coronavirus particles - therefore putting you at increased risk when you do actually get infected.
Title: Re: Can you build up coronavirus immunity by repeated, tiny, increasing exposure?
Post by: evan_au on 23/05/2020 23:30:02
Quote from: OP
depending on if you're a linear kind of a guy or an exponential kind of a girl
The problem is that poisons tend to be linear types of guys, and pathogens tend to be exponential types of girls.

If you double your next dose of a poison, you roughly double your chance of dying.
- Unless it is a cumulative poison, in which case another dose of the same size will roughly double your chance of dying...

However, it only takes one virus particle to take hold, and multiply to 100, then 10,000, then 1,000,000 and you are in trouble a few hours later (but you don't realize it for about 5 days).

Some vaccines work with an attenuated virus, where they mutate the virus so it doesn't grow well in humans.
- This converts it from an explosive exponential to a more sedate exponential, allowing your body to mount an immune defence before you get sick
See: https://en.wikipedia.org/wiki/Attenuated_vaccine
Title: Re: Can you build up coronavirus immunity by repeated, tiny, increasing exposure?
Post by: set fair on 01/06/2020 13:00:38
I wouldn't be so quick to dismiss the idea. We tend to think of the addaptive immune response as all about antibodies but T cells can adapt to seek out a speccific virus, so it is not inconceivable that a person could become immune without producing antibodies.

https://www.biospectrumasia.com/news/26/15833/singapore-explores-immunotherapy-for-covid-19-treatment.html
Title: Re: Can you build up coronavirus immunity by repeated, tiny, increasing exposure?
Post by: set fair on 21/07/2020 17:02:52
There is such a thing as being 'exposed but uninfected'. This can lead to a degree of protection or result in a more severe infection, when someone becomes infected. https://www.nature.com/articles/s41586-020-2550-z_reference.pdf 

These references from the Nature paper will give more on this
 
24. Rowland-Jones, S. L. et al. HIV-specific cytotoxic T-cell activity in an HIV-exposed but uninfected infant. Lancet341, 860861 (1993).

25. Park, S.-H. et al. Subinfectious hepatitis C virus exposures suppress T cell responses against subsequent acute infection. Nat Med19, 16381642 (2013).

26. Werner, J. M., Abdalla, A., Gara, N., Ghany, M. G. & Rehermann, B. The hepatitis B vaccine protects re-exposed health care workers, but does not provide sterilizing immunity.
Title: Re: Can you build up coronavirus immunity by repeated, tiny, increasing exposure?
Post by: set fair on 21/08/2020 21:17:40
Here's a simple unvoiced video of t-cell immunity.