Scientists have identified a pattern of mutations in the novel coronavirus which enable it to evade the immune system’s antibodies, findings that shed light on how the virus may possibly escape existing vaccines and therapeutics.

According to the researchers, including those from the University of Pittsburgh in the U.S., the coronavirus undergoes selective deletions in parts of its genetic sequence that encode for the shape of its spike protein.

The spike protein is the part of the coronavirus which enables it to infect host cells, and is also the segment of the virus against which the body produces neutralising antibodies.

The study, published in the journal Science, assessed nearly 1,50,000 gene sequences of the spike protein collected from many parts of the world, and found that in variants possessing the deletion mutations, formerly neutralising antibodies cannot grab hold of the virus.

Based on the analysis, the scientists identified a form of virus “escape” that resulted from a common, strong selective pressure for the coronavirus to undergo such a change.

They found at least nine instances where such variants arose in patients whose COVID-19 infections were persistent.

According to the study, the scientists first came across these neutralisation-resistant mutations in a sample from an immunocompromised patient, who was infected with coronavirus for 74 days before ultimately dying from COVID-19.

The researchers believe this long time of “cat and mouse” play between the immune system and the coronavirus in such patients gives “ample opportunity” to initiate a “co-evolutionary dance”.

They said this competition results in “worrisome mutations” in the viral genome that are resulting in variants of the coronavirus such as the ones first reported in the UK and South Africa.

“Evolution was repeating itself. By looking at this pattern, we could forecast. If it happened a few times, it was likely to happen again,” said Kevin McCarthy, a co-author of the study from the University of Pittsburgh.

While it is yet to be determined how far these mutations erode protection, McCarthy said “At some point, we’re going to have to start reformulating vaccines, or at least entertain that idea.”