From Structure to Sequence: Identification of polyclonal antibody families using cryoEM

One of the rate-limiting steps in analyzing immune responses to vaccines or infections is the isolation and characterization of monoclonal antibodies. Here, we present a hybrid structural and bioinformatic approach to directly assign the heavy and light chains, identify complementarity-determining regions and discover sequences from cryoEM density maps of serum-derived polyclonal antibodies bound to an antigen. When combined with next generation sequencing of immune repertoires we were able to specifically identify clonal family members, synthesize the monoclonal antibodies and confirm that they interact with the antigen in a manner equivalent to the corresponding polyclonal antibodies. This structure-based approach for identification of monoclonal antibodies from polyclonal sera opens new avenues for analysis of immune responses and iterative vaccine design. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/439712v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@31a3f5org.highwire.dtl.DTLVardef@103459eorg.highwire.dtl.DTLVardef@1cfc416org.highwire.dtl.DTLVardef@15295cc_HPS_FORMAT_FIGEXP M_FIG C_FIG One Sentence SummaryCryoEM and next generation sequencing were used to identify monoclonal antibodies elicited by HIV Env vaccine candidates.