COVID virus has adapted to evade antiviral proteins called interferons that are important front-line defence of the innate immune system, according to a study.

While the adaptive arm of the immune system responds definitively to infection by generating antibodies and T cells, the innate arm forms an earlier, first line of defence by recognising conserved molecular patterns in pathogens.

"SARS-CoV-2 just recently crossed the species barrier into humans and continues to adapt to its new host," said Eric Poeschla, Professor of Medicine, at the University of Colorado School of Medicine.

"Much attention has deservedly focused on the virus's serial evasions of neutralising antibodies. The virus seems to be adapting to evade innate responses as well," he added, in the paper published in Proceedings of the National Academy of Sciences.

Interferons are central molecules in the innate immune system that trigger a cascade of antiviral responses in cells within minutes of infection. As such, the interferon pathway could significantly reduce the levels of virus initially produced by an infected individual.

"They are clinically viable therapeutic agents that have been studied for viruses like HIV-1 for years," said Mario Santiago, Associate Professor of Medicine at the varsity.

The team looked at up to 17 different human interferons and found that some interferons, such as IFNalpha8, more strongly inhibited SARS-CoV-2. Importantly, later variants of the virus have developed significant resistance to their antiviral effects.

For example, substantially more interferon would be needed to inhibit the omicron variant than the strains isolated during the earliest days of the pandemic, Santiago explained.