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Vaccination is still the best way to protect someone from COVID-19, but new research suggests that immune system activation of T-cells by common colds may offer some cross-protection.
The study might also provide a blueprint for a second-generation, universal vaccine that could prevent infection from current and future variants, the research team said.
"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 preexisting T-cells, created by the body when infected with other human coronaviruses like the common cold, can protect against COVID-19 infection," said study first author Dr. Rhia Kundu, from Imperial College London's National Heart & Lung Institute, in the United Kingdom.
"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," Kundu added in a college news release. "Instead, the best way to protect yourself against COVID-19 is to be fully vaccinated, including getting your booster dose."
The study began in September 2020, when many people had neither been infected nor vaccinated, and included 52 people in the United Kingdom who lived with someone who had a SARS-CoV-2 infection and had been exposed. The participants took PCR tests after the exposure and again four to seven days later.
Their blood samples were taken within between one and six days of their exposure so that researchers could analyze the levels of pre-existing T-cells they had from previous common cold infections that also cross-recognized proteins of SARS-CoV-2.
The research team found significantly higher levels of these cross-reactive T-cells in the 26 people who did not become infected, compared to the 26 people who did.
To protect against SARS-CoV-2 infection, the T-cells targeted internal proteins within the virus, rather than the spike protein on the surface of the virus that helps it latch on to human cells.
Study limitations include that most of the participants were white Europeans. The findings were published online Jan. 10 in the journal Nature Communications.
Current COVID-19 vaccines don't induce an immune response to those proteins, so this offers a new vaccine target that could provide long-lasting protection, the researchers suggested. T-cell responses persist longer than antibody responses, which wane within a few months of vaccination.
"Our study provides the clearest evidence to date that T-cells induced by common cold coronaviruses play a protective role against SARS-CoV-2 infection. These T-cells provide protection by attacking proteins within the virus, rather than the spike protein on its surface," said senior study author Ajit Lalvani. He is director of the NIHR Respiratory Infections Health Protection Research Unit at Imperial.
"The spike protein is under intense immune pressure from vaccine-induced antibody which drives evolution of vaccine escape mutants. In contrast, the internal proteins targeted by the protective T-cells we identified mutate much less," Lalvani added in the news release. "Consequently, they are highly conserved between the various SARS-CoV-2 variants, including Omicron."
The World Health Organization has more on COVID-19.
SOURCE: Imperial College London, news release, Jan. 10, 2022
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