Dr. John Campbell in the UK produced a video a few
days ago showing that people who had recovered from the original SARS virus in
2003 have memory T-cells (and probably memory B-cells) which cross react with
SARS-CoV2.
Similarly, in some parts of the world, people who live
around certain animals are exposed to beta-coronaviruses. Their T[cells can recognized SARS-CoV2.
Exposure to the four “common cold” coronaviruses does
not produce this cross-reactivity.
It appears that no one who recovered from SARS in 2003
and is alive today has gotten COVID19.
Campbell believes that, despite a few scattered
reports of reinfections, most people who have recovered from a SARS-CoV2 infection
will have memory T-cells and B cells that will protect them even after antibodies
disappear.
He also believes that asymptomatic persons who recover
and show low antibody counts recovered with the strength of their T-cell response.
However, sometimes SARS-CoV2 can enter some T-cells
(with a 147 receptor, I think) but it does not reproduce inside them (as HIV
does).
This information could be important in developing therapeutics
and other vaccine strategies. It could mean that most people (at least if they
can avoid long lasting complications) will have lasting immunity from natural
infection. Already, there are reports of
young adults who repeatedly test negative by swab test despite repeated exposures.
Campbell says there are other obscure immunoglobulins in the nasal and throat
mucosa which do fight the coronavirus.
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