Identifying functional anti-Staphylococcus aureus antibodies by sequencing antibody repertoires of patient plasmablasts

•Deep sequencing of plasmablast antibody repertoires in S. aureus infection•Single-cell barcoding enables recovery of natively paired heavy and light immunoglobulin chains.•Identification of clonal families of antibodies with shared rearrangements•Antibodies from clonal populations are enriched for S. aureus binding.•Patient-derived S. aureus-specific antibodies differentially enhance phagocytosis.

Infection by Staphylococcus aureus is on the rise, and there is a need for a better understanding of host immune responses that combat S. aureus. Here we use DNA barcoding to enable deep sequencing of the paired heavy- and light-chain immunoglobulin genes expressed by individual plasmablasts derived from S. aureus-infected humans. Bioinformatic analysis of the antibody repertoires revealed clonal families of heavy-chain sequences and enabled rational selection of antibodies for recombinant expression. Of the ten recombinant antibodies produced, seven bound to S. aureus, of which four promoted opsonophagocytosis of S. aureus. Five of the antibodies bound to known S. aureus cell-surface antigens, including fibronectin-binding protein A. Fibronectin-binding protein A-specific antibodies were isolated from two independent S. aureus-infected patients and mediated neutrophil killing of S. aureus in in vitro assays. Thus, our DNA barcoding approach enabled efficient identification of antibodies involved in protective host antibody responses against S. aureus.