Cross-reactive T cells help protect against COVID-19 infection

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London – Cross-reactive memory T cells from previous colds can protect against infection with SARS-CoV-2. Not all people who have had contact with COVID-19 patients develop an infection.

To better understand this phenomenon, researchers from Imperial College London (England) analyzed the immune status and immune responses at the earliest times after SARS-CoV-2 exposure of 52 people (unvaccinated and SARS-CoV-2 naive) who were im Household with someone with PCR-confirmed SARS-CoV-2 infection and therefore exposed to the pandemic virus.

In this study (Nature, 2021; DOI: 10.1038 / s41467-021-27674-x), the test subjects performed PCR tests at the beginning as well as on days 4 and 7 to determine whether they developed an infection. Blood samples taken within 1 to 6 days of exposure to the virus were also analyzed. Among other things, the blood samples were examined for specific T cells induced by previous cold infections with other coronavirus strains (cross-reactive memory T cells).

The researchers found that a total of 50% of the participants did not become infected with SARS-CoV-2 despite exposure. In this cohort, significantly higher levels of cross-reactive memory T cells were found than in comparison to the other half that were infected with SARS-CoV-2.

These specific T cells had previously responded to antigens that targeted internal proteins within a coronavirus, rather than a spike protein on the surface of the virus, to protect against infection. The study authors conclude that the presence of specific memory T cells at the time of SARS-CoV-2 exposure influences whether someone becomes infected. The study authors point out, however, that the study cohort was relatively small and 88% of the participants were of European-indigenous origin.

However, the best measure to protect against COVID-19 is still complete vaccination protection, including the booster dose, emphasized first author of the study Rhia Kundu from the Imperial’s National Heart & Lung Institute in London.

The British researchers believe that SARS-CoV-2 virus internal proteins, alongside existing and effective spike protein-based vaccines, would be suitable as new, universal targets for future vaccines.

Internal proteins as vaccine targets would also protect against infection with current and future SARS-CoV-2 variants, including Omikron. In addition, longer-lasting vaccination protection would be expected, since T-cell reactions last longer than antibody reactions, which subside within a few months after vaccination. © cw / aerzteblatt.de

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