Some of the viruses that cause our colds belong to coronaviruses, which can cause the immune system to defend and attack, so that the body's immune T cells can easily recognize the new crown virus, and then achieve immune protection against the human body. In addition, previous studies have shown that other coronavirus-induced T cells can recognize SARS-CoV-2.
Recently, in a study at Imperial College London, researchers experimented for the first time how these T cells induced by other coronaviruses affect the likelihood of COVID-19 infection in humans when humans are exposed to SARS-CoV-2.
The findings were published in Nature Communications under the title "Cross-reactive memory T cells associate with protection against SARS-CoV-2 infection in COVID-19 contacts."
Figure 1. Research results (Source: Nature Communications)
Dr. Rhia Kundu, one of the researchers, said that some people do not contract the virus even if they are exposed to SARS-CoV-2, and what the cause is still unknown. This may be because humans have been infected with other types of coronaviruses before, and the cross-reactive T cells they induce can protect this part of the population so that they will not be easily infected with the new coronavirus.
In the study, a total of 52 participants who had been exposed to the virus because they lived with a SARS-CoV-2 infected person were included in the trial, and participants underwent PCR testing before the trial was initiated, 4 days after the trial, and 7 days after the trial to confirm the presence of viral infection. Tested for the virus during the trial, the results showed that 26 people were infected with the new crown virus and 26 people were not yet infected.
Figure 2. Dynamic changes in cross-reactive T cells and RBD-specific antibodies in PCR-positive and negative contacts (Source: Nature Communications)
Within 1-6 days of the participants' exposure to the coronavirus, the researchers took their blood samples and analyzed the levels of pre-stored T cells induced by the participants from infection with other coronaviruses that were shown to recognize the internal proteins of the coronavirus. The researchers found that compared with the 26 people infected with the new crown, the level of cross-reactive T cells in the 26 people who had not yet been infected was significantly higher, and the contacts infected with the new crown were completely absent from such T cells, and such protective T cells mainly targeted the non-stinging protein inside the new crown virus, thereby preventing viral infection.
At present, the new crown vaccine on the market mainly targets the spike protein on the surface of the virus and does not induce an immune response to the protein inside the virus, while these T cells induced by other coronaviruses are targeted by the internal protein of the new crown virus.
Therefore, the researchers note that in addition to our existing spike protein-targeted vaccines, these internal proteins provide a new vaccine target that can provide a more long-lasting immune protection effect for the human body. Because the T cell response lasts longer than the antibody response, the antibody response weakens within a few months of vaccination.
"Spike proteins are subjected to intense immune pressure from vaccine-induced antibodies, driving the evolution of vaccine-escaping mutants. In contrast, we found that protective T cells target internal proteins with much less likely mutations. Therefore, vaccines that target proteins inside the virus are effective against current and future SARS-CoV-2 variants," says Ajit Lalvani, MD, of Imperial College London.
Taken together, this study shows that cross-reactive T cells induced by other coronaviruses can protect the body from coronavirus infection. It is worth mentioning that since cross-reactive T cells target proteins inside the virus rather than spike proteins, this study also provides a new COVID-19 vaccine target, which may greatly enhance the vaccine effect if non-spike antigens can be added to the second-generation vaccine.
Written by | Muzijiu
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Resources:
[1] Kundu R, Narean JS, Wang L, et al. Cross-reactive memory T cells associate with protection against SARS-CoV-2 infection in COVID-19 contacts. Nat Commun. 2022 Jan 10;13(1): 80. doi: 10.1038/s41467-021-27674-x. PMID: 35013199.