T cells from common colds caused by coronaviruses can further protect against COVID-19, as researchers demonstrate that higher levels of these T cells mean SARS-CoV-2 infection is less likely.
A study by researchers from Imperial College London (UK), led by Rhia Kundu, set out to investigate the effect of T cells from common coronavirus infections, such as the common cold, on SARS-CoV-2 infection. The group found that when these common cold T cells are present at the time of SARS-CoV-2 exposure, they can protect against COVID-19 infection. The findings demonstrate a potential new vaccine target capable of mimicking this T cell protection to prevent infection against current and future SARS-CoV-2 variants.
Fifty-two people living with someone who had positive COVID-19 PCR test results were enrolled in the study in September 2020. None of the participants were vaccinated, nor had they previously been infected by SARS-CoV-2. The participants did a PCR test on days 1, 4 and 7 of the study to determine whether they had been infected by the exposure to the virus via the infected household member. Blood samples were also taken within 1–6 days of exposure to SARS-CoV-2.
The team analyzed these samples for antibodies specific to the SARS-CoV-2 receptor binding domain, quantifying the antibody levels using a highly sensitive and specific double antigen binding assay. The results demonstrated that there were significantly higher levels of cross-reactive T cells in those that did not become infected with SARS-CoV-2 after exposure, compared to those that did.
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“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,” Kundu explained.
“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.”
Interestingly, the T cells provided protection against COVID-19 infection by targeting internal proteins of the SARS-CoV-2 virus, rather than surface proteins, such as the spike protein, which is targeted by current vaccines.
“The spike protein is under intense immune pressure from vaccine-induced antibody (sic) which drives evolution of vaccine escape mutants. In contrast, the internal proteins targeted by the protective T cells we identified mutate much less. Consequently, they are highly conserved between the various SARS-CoV-2 variants, including omicron. New vaccines that include these conserved, internal proteins would therefore induce broadly protective T cell responses that should protect against current and future SARS-CoV-2 variants,” senior author Ajit Lalvani explained.
Limitations identified by the authors were that there was a small number of participants, and 88% were of white European ethnicity, which ultimately hindered their ability to model demographic factors. Despite this, the team’s findings provide a blueprint for a second-generation universal SARS-CoV-2 vaccine targeting core viral proteins.
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