Some people have a version of a gene which could restrain Sars-CoV-2, the coronavirus that causes Covid-19, a study has indicated.
The findings offer an explanation as to why some people have better natural defences against serious infection, scientists say.
Research suggests anti-viral responses are better in people who have a more protective, “prenylated” version of the OAS1 gene, while others have a version that fails to detect the virus.
But if new variants learn to evade the protection offered by the prenylated gene, they could become “substantially more pathogenic and transmissible in unvaccinated populations”, experts say.
The study, A Prenylated dsRNA Sensor Protects against Severe Covid-19, has been published in the journal Science and is the result of work led by the MRC-University of Glasgow Centre for Virus Research.
Prenylation, the attachment of a single molecule of fat to a protein, allows OAS1 to “seek out” the invading virus and “sound the alarm”, researchers say.
The study indicated that patients in hospital who expressed a prenylated version of the gene were associated with protection from severe Covid-19, suggesting it is a “major component of a protective antiviral response”.
It is likely to have given many people natural protection throughout the pandemic.
Researchers also noted those with the “bad” form of OAS1 experienced significantly more frequent levels of severe disease, with intensive care admission or death about 1.6 times more likely in these patients.
The scientists said that about 55 million years ago, horseshoe bats, the presumed source of Sars-CoV-2, lost this protective gene, so the virus did not have to adapt to evade the defence.
“We know viruses adapt, and even Sars-CoV-2 has likely adapted to replicate in the animal reservoir in which it circulates," said Prof Sam Wilson, of the University of Glasgow’s Centre for Virus Research.
“Cross-species transmission to humans exposed the virus Sars-CoV-2 to a new repertoire of antiviral defences, some of which Sars-CoV-2 may not know how to evade.”
Prof Wilson said the study showed the coronavirus that caused the Sars outbreak in 2003 had learnt to evade prenylated OAS1.
“If Sars-CoV-2 variants learn the same trick, they could be substantially more pathogenic and transmissible in unvaccinated populations,” he said.
“This reinforces the need to continually monitor the emergence of new Sars-CoV-2 variants.”
The study was mainly funded by the Medical Research Council, Wellcome and UK Research and Innovation.