Relatives of SARS-CoV-2 Evolve Against Immune Responses

A recent study published in the journal eLife has demonstrated that 2 distinct species of seasonal human coronavirus that are related to the SARS-CoV-2 virus are able to evolve in some proteins in order to escape being recognized by the immune system. This may suggest that the coronavirus disease 2019 (COVID-19) may evolve in a similar way, which can cause vaccines to become outdated and new ones to be developed.

"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," Kathryn Kistler, first author on the study and a PhD student at the Vaccine and Infectious Disease Division of the Fred Hutchinson Cancer Research Center said. "We wanted to investigate whether there is any evidence of coronaviruses related to SARS-CoV-2 evolving to evade our immune responses."

The team used various computational methods in order to compare the genetic sequences of different strains of 4 seasonal human coronaviruses that are related to SARS-CoV-2 but are not typically as serious with only mild symptoms, like the common cold. Because these viruses have been in circulation for between 20 and 60 years, their antigens were likely to have faced pressure to evolve against the immune system.

Investigators were especially interested in changes that may have occurred in viral proteins which can contain antigens like spike proteins.

Findings from the study showed that in 2 of the spike proteins (OC43 and 229E), there was a very high rate of evolution. The majority of the mutations that the virus benefited from were found in a specific region called S1, which aids in the virus infecting cells. These results suggest that the 2 viruses are able to reinfect an individual as a result of antigenic drift.

"Due to the high complexity and diversity of HCoVs, it is not entirely clear if this means that other coronaviruses, such as SARS-CoV-2, will evolve in the same way," Trevor Bedford, Associate Member at the Vaccine and Infectious Disease Division of the Fred Hutchinson Cancer Research Center and senior author on the study said. "The current vaccines against COVID-19, while highly effective, may need to be reformulated to match new strains, making it vital to continually monitor the evolution of the virus' antigens."