design: Using the Gentra Puregene Core kit A (Qiagen), DNA was extracted from 2.6e6 cells sorted for cell-surface SARS-CoV-2 S1-Fc binding (AF647 high). Individual integrated gRNA sequences were amplified by PCR (primers: sgRNA_outer_F: AGGCTTGGATTTCTATAACTTCGTATAGCATACATTATAC; sgRNA_outer_R: ACATGCATGGCGGTAATACGGTTATC). Illumina adaptors were added in an additional round of PCR (P5-sgRNA_inner_F: AATGATACGGCGACCACCGAGATCTACACTCTCTTGTGGAAAGGACGAAACACCG; P7-index-sgRNA_inner_R: CAAGCAGAAGACGGCATACGAGATnnnnnnnGTGACTGGAGTTCAGACGTGTGCTCTTCCGATCCGACTCGGTGCCACTTTTTC. Sequencing was carried out using the Illumina MiniSeq platform (Illumina sequencing primer (5'-3'): AGACTATAAGTATCCCTTGGAGAACCACCTTGTTGG .