Neutralization assay comparison of mAb escape by unpassaged and passaged virus.

Viral escape was measured by GFP expression 48 h post infection. Note: Wells scored as “+/-”were considered as negative for mAb escape. Data from deep Illumina sequencing of the samples were used to identify mutations that were associated with mAb escape. These mutations were compared to the mutations that occurred during passage in cell lines and under antiserum selection to understand if the mutations originated during passage or appeared to arise de novo during mAb escape (Table 3). Epitope models were used to visualize the placement of the mutations on the RBD and within the receptor binding motif (RBM) (Fig 2).