People with higher levels of T cells from coronaviruses that cause the common colds have less likely to be infected with SARS-CoV-2, according to a new study published in the scientific journal ‘Nature Communications’ and led by researchers at Imperial College London (United Kingdom).
While previous studies have shown that T cells induced by other coronaviruses can recognize SARS-CoV-2, this research examines for the first time how the presence of these T cells at the time of exposure to SARS-CoV-2 influences someone get infected.
The researchers also state that their findings provide a blueprint for a universal second-generation vaccine that could prevent infection by current and future variants of SARS-CoV-2, including omicron. “Exposure to the SARS-CoV-2 virus does not always lead to infection, and we wanted to understand why. We found that high levels of pre-existing T cells, created by the body when infected with other human coronaviruses such as the common cold, can protect against infection with the COVID-19 virus. Although this is an important discovery, it is only one form of protection, and I would like to stress that the best way to protect yourself against COVID-19 is to be fully vaccinated, including the booster dose,” said Dr Rhia Kundu, first author of the study, from the National Heart and Lung Institute at Imperial College London.
The study began in September 2020, when most people in the UK had not been infected or vaccinated against SARS-CoV-2. It included 52 people who lived with someone with a SARS-CoV-2 infection confirmed by PCR and therefore had been exposed to the virus. The participants underwent PCR tests at the beginning and 4 and 7 days later, to determine if they had developed an infection.
Blood samples were taken from the 52 participants between 1 and 6 days after they were exposed to the virus. This allowed the researchers to analyze the levels of preexisting T cells induced by previous common cold coronavirus infections that also cross-recognize SARS-CoV-2 proteins.
The researchers found that there were significantly higher levels of these cross-reactive T cells in the 26 people who were not infected, compared to the 26 who were. These T cells targeted the internal proteins of the SARS-CoV-2 virus, rather than the spike protein on the surface of the virus, to protect themselves from infection.
The Current vaccines do not induce an immune response to these internal proteins. Together with existing effective spike protein vaccines, the researchers say, these internal proteins offer a new vaccine target that could provide long-lasting protection, as T-cell responses persist longer than responses. of antibodies, which decrease a few months after 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 inside the virus. , rather than the spike protein on its surface.The spike protein is under intense immune pressure from vaccine-induced antibodies, driving the evolution of vaccine escape mutants. The internal proteins targeted by the protective T cells that we have identified mutate much less. Consequently, they are highly conserved between the different variants of SARS-CoV-2, including omicron. Therefore, new vaccines that include these internal proteins conserved cells would induce broadly protective T cell responses that should protect against current and future variants of SARS-CoV-2,” says Professor Aji. t Lalvani, lead author of the study.