To find neutralising antibodies that work against a wide range of variants, the researchers began by immunising mice with a key part of the spike protein known as the receptor-binding domain.
Then, they extracted antibody-producing cells and obtained 43 antibodies from them that recognise the receptor-binding domain.
The researchers screened the 43 antibodies by measuring how well they prevented the original variant of SARS-CoV-2 from infecting cells in a dish.
The researchers selected the two antibodies that were most effective at protecting mice from disease and tested them against a panel of viral variants.
The panel comprised viruses with spike proteins representing all four variants of concern (alpha, beta, gamma and delta), two variants of interest (kappa and iota), and several unnamed variants that are being monitored as potential threats.