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Scientists find 2 species of human coronavirus that can evolve to evade immune system

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A new study has found that two species of seasonal human coronavirus related to SARS-CoV-2 can evolve in certain proteins to evade recognition by the immune system.

The findings of the study, published in the journal eLife, suggested that if SARS-CoV-2 evolves in the same way, current vaccines against the virus may become outdated, requiring new ones to be made to match future strains.

The researchers mentioned that the immune system relies on being able to ‘remember’ the antigens that relate to a specific virus in order to provide immunity against it.

Also read: Genome sequencing of coronavirus in sewage can help detect local variants: Study

However, in some viruses, such as seasonal flu, those antigens are likely to change and evolve in a process called antigenic drift, meaning the immune system may no longer respond to reinfection.

“Some coronaviruses are known to reinfect humans but it is not clear to what extent this is due to our immune memory fading or antigenic drift,” says first author Kathryn Kistler, a Ph.D. student at the Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, US.

“We wanted to investigate whether there is any evidence of coronaviruses related to SARS-CoV-2 evolving to evade our immune responses,” she added.

Methodology

For the research, the team looked at the four seasonal human coronaviruses (HCoVs) which are related to SARS-CoV-2 but typically cause milder symptoms, such as the common cold.

Also read: Covid-19 may awaken antibody response from previous infections: Study

HCoVs have been circulating in the human population for 20-60 years, meaning their antigens would likely have faced pressure to evolve against our immune system.

Findings

The researchers found a high rate of evolution in the spike proteins of two of the four viruses, OC43 and 229E. Nearly all of the beneficial mutations appeared in a specific region of the spike proteins called S1, which helps the virus infect human cells.

This suggests that reinfection by these two viruses can occur as a result of antigenic drift as they evolve to escape recognition by the immune system.

The team also estimated that beneficial mutations in the spike proteins of OC43 and 229E appear roughly once every two to three years, about half to one-third of the rate seen in the flu virus strain, H3N2.



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