Patients who have recovered from COVID-19 infection may benefit from strong T cell immunity – and even victims of the common cold may enjoy some immunity, according to a significant new study.
The findings, from research in Singapore, offer hope that humans may have an alternative source of immunity to antibodies.
The researchers compared patients who have recovered from COVID-19 with those recovered from SARS 17 years ago.
Researchers found that patients who had recovered from SARS retained virus specific memory T cells and also enjoyed some protection against the new virus.
Those who had recovered from COVID-19 were all found to have specific T cells.
The same T cells were found in about half of uninfected healthy individuals. The researchers say this could be because of exposure other coronaviruses, such as the common cold.
The research, reported in Nature, was undertaken at the National University of Singapore and the Duke-NUS Medical School. It involved 36 people who had recovered from COVID-19 viral infection, 23 people who had previously suffered from SARS and 37 people with no history of either disease.
Researcher Professor Jenny Low said: "While there have been many studies about SARS-CoV-2, there is still a lot we don’t understand about the virus yet. What we do know is that T cells play an important role in the immune response against viral infections and should be assessed for their role in combating SARS-CoV-2, which has affected many people worldwide.
"Hopefully, our discovery will bring us a step closer to creating an effective vaccine."
Fellow researcher Professor Antonio Bertoletti said: "Our team also tested uninfected healthy individuals and found SARS-CoV-2-specific T cells in more than 50% of them. This could be due to cross-reactive immunity obtained from exposure to other coronaviruses, such as those causing the common cold, or presently unknown animal coronaviruses. It is important to understand if this could explain why some individuals are able to better control the infection."
* T cells may also be the key to a universal flu vaccine, Cardiff University researchers reported in the journal Cell Reports.
They have found protein markers that rarely change across different strains of flu – showing how helper T cells were activated by these proteins.
Researcher Professor Andrew Godkin said: “These are really intriguing results. We have shown that conserved regions of the internal proteins of flu viruses are seen by the immune system. Furthermore, we have shown these sequences are highly conserved across tens of thousands of virus sequences.
“This raises the intriguing question as to why we are not better protected from emerging new strains of flu and related viruses that share these sequences and should trigger memory responses in our immune system.
“We are concentrating our efforts in understanding this question, in the hope this will lead to superior vaccine designs in the future.”
* An analysis in The Lancet Public Health warns that speed is the critical factor in contact tracing. Delays of three days in finding contacts will not stop onward transmission of the virus, according to Professor Mirjam Kretzschmar, from the University of Utrecht, the Netherlands.
The researchers say that mobile apps can speed up contact tracing, even if only 20% of people use them.
Professor Kretzschmar said: "This will help policy makers understand where best to prioritise resources to maximise the chances of success. For example, we found that mobile apps can speed up the process of tracking down people who are potentially infected, but if testing is delayed by three days or more even these technologies can’t stop transmission of the virus."
Nature 15 July 2020
https://www.nature.com/articles/s41586-020-2550-z
Lancet Public Health 16 July 2020
http://www.thelancet.com/journals/lanpub/article/PIIS2468-2667(20)30157-2/fulltext
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