Descendants of the outbreak may have inherited some DNA that affects their response to COVID-19
An ancient coronavirus, or a closely related pathogen, triggered an epidemic among ancestors of present-day East Asians roughly 25,000 years ago, a new study indicates.The discovery opens the way to exploring how genes linked to ancient viral epidemics may contribute to modern disease outbreaks, such as the COVID-19 pandemic. Genes with ancient viral histories might also provide clues to researchers searching for better antiviral drugs, although that remains to be demonstrated.
The team first focused on 420 proteins known to interact with coronaviruses, including 332 that interact with SARS-CoV-2, the virus that causes COVID-19. These interactions could range from boosting immune responses to making it easier for a virus to hijack a cell.
Substantially increased production of all 420 proteins, a sign of past exposures to coronavirus-like epidemics, appeared only in East Asians. Enard’s group traced the viral responses of 42 of those proteins back to roughly 25,000 years ago.
An analysis of the genes known to orchestrate production of those proteins determined that specific variants became more common around 25,000 years ago before leveling off in frequency by around 5,000 years ago. That pattern is consistent with an initially vigorous genetic response to a virus that waned over time, either as East Asians adapted to the virus or as the virus lost its ability to cause disease, Enard said. Twenty-one of the 42 gene variants act either to enhance or deter the effects of a wide array of viruses, not just coronaviruses, suggesting that an unknown virus that happened to exploit similar proteins as coronaviruses could have instigated the ancient epidemic, Enard said.
These findings “show that East Asians have been exposed to coronavirus-like epidemics for a long time and are more [genetically] adapted to epidemics of these viruses,” says evolutionary geneticist Lluis Quintana-Murci of the Pasteur Institute in Paris, who was not involved in the new study.
