London- People with higher levels of T-cells from common cold coronaviruses are less likely to become infected with SARS-CoV-2, according to new research. The study, by Imperial College London researchers, provides the first evidence of a protective role for these T-cells.
While previous studies have shown that T-cells induced by other coronaviruses can recognise SARS-CoV-2, the new study, published in Nature Communications, examines for the first time how the presence of these T-cells at the time of SARS-CoV-2 exposure influences whether someone becomes infected.
The researchers also stated their findings provide a blueprint for a second-generation, universal vaccine that could prevent infection from current and future SARS-CoV-2 variants, including Omicron.
"Being exposed to the SARS-CoV-2 virus doesn't always result in infection, and we've been keen to understand why. We found that high levels of pre-existing T cells, created by the body when infected with other human coronaviruses like the common cold, can protect against Covid-19 infection," said Dr Rhia Kundu, from Imperial's National Heart and Lung Institute.
"While this is an important discovery, it is only one form of protection, and I would stress that no one should rely on this alone. Instead, the best way to protect yourself against Covid-19 is to be fully vaccinated, including getting your booster dose," she added.
The study included 52 people who lived with someone with PCR-confirmed SARS-CoV-2 infection and who had therefore been exposed to the virus. The participants did PCR tests at the outset and 4 and 7 days later, to determine if they developed an infection.
Blood samples from the 52 participants were taken within 1-6 days of them being exposed to the virus. This enabled the researchers to analyse the levels of pre-existing T-cells induced by previous common cold coronavirus infections that also cross-recognise proteins of the SARS-CoV-2 virus.
The researchers found that there were significantly higher levels of these cross-reactive T-cells in the 26 people who did not become infected, compared to the 26 people who did become infected. These T-cells targeted internal proteins within the SARS-CoV-2 virus, rather than the spike protein on the surface of the virus, to protect against infection.
Current vaccines do not induce an immune response to these internal proteins. The researchers said that - alongside our existing effective spike protein-targeting vaccines - these internal proteins offer a new vaccine target that could provide long-lasting protection because T-cell responses persist longer than antibody responses which wane within a few months of vaccination.
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