People Testing Negative For Antibodies May Still Be Immune To COVID-19
Monit KhannaUpdated on Jul 03, 2020, 10:17 IST
Karolinska Institute have discovered (published in Biorxiv) that people who are testing negative for COVID-19 antibodies could still be immune to the novel coronavirusThey found that for every person testing positive for antibodies, two were found to have specific T-cells which identify and destroy infected cellsHowever, according to Marcus Buggert, co-author of the study, this doesn't mean that we're close to COVID-19 herd immunity.
In the fight against COVID-19, researchers are trying hard to create a vaccine that could make us immune to the novel coronavirus, while simultaneously they're constantly on the lookout for antibodies in people that can fight the coronavirus.
And now, researchers at the Karolinska Institute have discovered (published in Biorxiv) that people who are testing negative for COVID-19 antibodies could still be immune to the novel coronavirus.
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The Swedish institute tested 200 people for both antibodies and T-cells. In case you didn't know, T-cells are responsible for identifying and destroying cells infected with COVID-19. The test subjects included blood donors as well as the group of people that first got infected in Sweden after entering the country from infected nations like Italy.
They found that for every person testing positive for antibodies, two were found to have specific T-cells which identify and destroy infected cells.
Soo Aleman one of the researchers in the study explains, "One interesting observation was that it wasn't just individuals with verified COVID-19 who showed T-cell immunity but also many of their exposed asymptomatic family members. Moreover, roughly 30 percent of the blood donors who'd given blood in May 2020 had COVID-19-specific T-cells, a figure that's much higher than previous antibody tests have shown."
However, according to Marcus Buggert, co-author of the study, this doesn't mean that we're close to COVID-19 herd immunity.
He emphasizes that more analysis is necessary to understand whether the COVID-19 destroying-T-cells are able to provide 'sterilising immunity', which basically means, whether they can completely shut down the virus or protect someone from getting sick while also disabling it to not get transmitted.
Whenever people have spoken about immunity from COVID-19, they've spoken about antibodies which are essentially 'Y' shaped proteins that in Buggert's words, are like missiles shooting down a target. They fuse to the virus before it gets a chance to enter our body.
T-cells, on the other hand, attack the already infected cells in our body, destroying them and disabling them from multiplying and spreading further to the existing healthy cells. Moreover, it is a part of our immune system and also possesses a memory, so the moment it recognises a particular virus, it knows that it needs to destroy it.
The team claims that more research is needed to fully understand T-cells. Moreover, T-cells are more complex and harder to detect than antibodies, as they require special labs and only small batches of samples are tested for several days.
Buggert explains, "Larger and more longitudinal studies must now be done on both T cells and antibodies to understand how long-lasting the immunity is and how these different components of COVID-19 immunity are related."