Publicity to widespread chilly viruses may prepare immune system to battle SARS-CoV-2 – Medical Information Bulletin

One research study cautiously suggests that previous exposure to the common cold virus may play a role in the different immune responses seen in patients infected with the SARS-CoV-2 virus.

Previous research by the same group showed that people who were not exposed to the SARS-CoV-2 virus also carried memory helper T cells, a type of immune cell that responded to the SARS-CoV-2 virus. This puzzling result prompted the research team to investigate whether these T cells were the result of previous exposure to cold coronaviruses. The new study was published in the latest issue of the Science Journal.

The study was conducted with samples taken between March 2015 and March 2018 from participants who were not exposed to the SARS-CoV-2 virus. They then selected the immune cells of these participants that responded to the SARS-CoV-2 virus. Using these cross-reactive immune cells, the scientists identified parts of the SARS-CoV-2 virus that were recognized by the immune cells. They also compared these virus fragments to fragments from four types of cold-causing coronaviruses.

Using a technique to detect activated T cells, the team showed that the reactive T cells that recognize SARS-CoV-2 virus fragments actually cross-react with corresponding fragments of cold virus. This is direct evidence that some groups of people carry memory immune cells that are produced in response to a previous cold virus infection that also reacts with the SARS-CoV-2 virus. Dr. Daniela Weiskopf, co-head of the study, explains: “We have now proven that some people already have T-cell memory against the common cold coronavirus SARS-CoV-2 and precisely recognize molecular structures. "

The presence of the memory immune cells could stimulate the immune system to better recognize and fight the SARS-CoV-2 virus. Dr. Sette, co-leader of the study, explains: “The immunoreactivity can lead to different degrees of protection. A strong T cell response, or a better T cell response, may give you the opportunity to have a much faster and stronger response. “This could explain why some people have milder COVID-19 symptoms compared to others. However, the researchers stress that it is premature and highly speculative to draw any conclusions about pre-existing immune cells against cold viruses and the severity of COVID-19 infection.

This study has shown that the spike protein, which much research has focused on, is not the only part of the SARS-CoV-2 virus that can react with the immune cells. Other parts of the virus also trigger a response from the T cells. It is also highlighted that in addition to the antibody-producing B cells, T cells are also the key to fighting the SARS-CoV-2 virus. However, it cannot yet be concluded that a previous cold infection can protect against SARS-CoV-2.

Written by Bhavana Achary, PhD

References:

Original study: Mateus J., Grifoni A., Tarke A. et al. Selective and cross-reactive SARS-CoV-2 T cell epitopes in non-exposed people (published online before going to press, August 4, 2020). Science. 2020

Press release: https://www.eurekalert.org/pub_releases/2020-08/ljif-etc080320.php

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