In a study from Duke-NUS Medical School, scientists found long-lasting immune cells that specifically recognize the SARS-CoV-2 virus were found in the noses of people who were infected following vaccination.
These virus-specific T cells, which were not present in those who had only been vaccinated, are expected to confer an additional layer of protection against COVID-19.
Most antiviral immunity studies have been performed with peripheral blood, yet the primary site of SARS-CoV-2 infection is in the nasal cavity.
Immune cells, called T cells, that live in the nasal cavity and recognize virus-infected nose cells can play an important role in rapidly containing and eliminating the infection.
In the study, the team analyzed the T cells in nasal swab samples taken from 16 people who received two doses of the Pfizer-BioNTech mRNA vaccine but had not yet been infected with SARS-CoV-2.
They also analyzed the T cells from nasal samples of another 34 people who had received two or three doses of the same vaccine and were later infected with SARS-CoV-2.
The team examined the T cells to determine the different types and to find out if they could specifically recognize different proteins of SARS-CoV-2.
Interestingly, virus-specific T cells were found almost exclusively in the noses of the group who had received the vaccine and then went on to become infected with the virus.
They were not found in the nasal cavities of the group who had only received the vaccine, even though virus-specific T cells could be found in their blood.
The team also found that the T cells in the vaccinated and then infected group persisted for at least 20 weeks and were able to recognize various SARS-CoV-2 proteins, including the non-spike proteins that are more conserved between the different viral variants
This is important because it means that these T cells would likely be capable of recognizing cells infected with the Omicron variant of SARS-CoV-2 despite its extensive spike protein mutations.
The researchers note that further research is needed to confirm these results due to the small sample size and other limitations of their study.
Furthermore, it will be important to investigate how long these nasal-resident, virus-specific T cells last after 20 weeks to understand their long-term impact on COVID-19 protection.
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The study was conducted by Professor Antonio Bertoletti et al and published in the Journal of Experimental Medicine.
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