A study has found that some people are able to clear the Covid-19 virus quickly due to strong immune response from existing T-cells, which could lead to a new generation of vaccine development.
In a study published in Nature, researchers found that individuals with potential exposure to Covid-19 do not necessarily develop PCR or antibody positivity, suggesting some may clear sub-clinical infection before seroconversion.
T-cells can contribute to the rapid clearance of SARS-CoV-2 and other coronavirus infections. The researchers hypothesised that pre-existing memory T-cell responses, with cross-protective potential against SARS-CoV-2, would expand in vivo to support rapid viral control, aborting infection.
Leo Swadling, an immunologist at University College London and lead author of the paper, told The Guardian: “Everyone has anecdotal evidence of people being exposed but not succumbing to infection. What we didn’t know is whether these individuals really did manage to completely avoid the virus or whether they naturally cleared the virus before it was detectable by routine tests.”
Researchers measured SARS-CoV-2-reactive T-cells of healthcare workers at the beginning of the pandemic. Despite being exposed to the virus, some of them did not test positive. It was noted that some of them had also developed significant T-cell responses after exposure but produced negative PCR tests and did not possess antibodies. It appears that these individuals were experiencing ‘abortive infection’ where the virus was entering the body but being cleared by T-cells very quickly.
Speaking to the Guardian, Alexander Edwards, associate professor in biomedical technology at the University of Reading, said: “This study identifies [a new] intermediate outcome – enough virus exposure to activate part of your immune system but not enough to experience symptoms, detect significant levels of virus or mount an antibody response.”
He added: “Insights from this study could be critical in design of a different type of vaccine…A vaccine that primes T-cell immunity against different viral protein targets that are shared between many different coronaviruses would complement our spike vaccines that induce neutralising antibodies. Because these are components within the virus, antibodies are less effective – instead, T-cells come into play.”
The study’s authors include: Mariana Diniz, Nathalie Schmidt, Oliver Amin, Aneesh Chandran, Emily Shaw, Mahdad Noursadeghi and Antonio Bertoletti. It can be accessed here.