De novo identification of VRC01 class HIV-1–neutralizing antibodies by next-generation sequencing of B-cell transcripts

Significance An extraordinary influx of sequencing information is revolutionizing biological inquiry. While sequences of entire antibody repertoires are straightforward to obtain, understanding antibody function on the basis of sequence alone has remained elusive. Can bioinformatics identify function-specific antibodies within the ocean of B cell transcripts representing unrelated specificities? We undertook the challenge of identifying antibodies of the VRC01 class. These antibodies individually neutralize up to 90% of HIV-1; although they share less than 50% sequence identity they do have characteristic sequence motifs and evolutionary relatedness. Our bioinformatics methods identified heavy and light chains from a new donor that could form functional antibodies and neutralize HIV-1 effectively. Identification of HIV-1 neutralizing antibodies of the VRC01 class can thus occur solely on the basis of bioinformatics analysis of a sequenced antibody repertoire. Next-generation sequencing of antibody transcripts provides a wealth of data, but the ability to identify function-specific antibodies solely on the basis of sequence has remained elusive. We previously characterized the VRC01 class of antibodies, which target the CD4-binding site on gp120, appear in multiple donors, and broadly neutralize HIV-1. Antibodies of this class have developmental commonalities, but typically share only ∼50% amino acid sequence identity among different donors. Here we apply next-generation sequencing to identify VRC01 class antibodies in a new donor, C38, directly from B cell transcript sequences. We first tested a lineage rank approach, but this was unsuccessful, likely because VRC01 class antibody sequences were not highly prevalent in this donor. We next identified VRC01 class heavy chains through a phylogenetic analysis that included thousands of sequences from C38 and a few known VRC01 class sequences from other donors. This “cross-donor analysis” yielded heavy chains with little sequence homology to previously identified VRC01 class heavy chains. Nonetheless, when reconstituted with the light chain from VRC01, half of the heavy chain chimeric antibodies showed substantial neutralization potency and breadth. We then identified VRC01 class light chains through a five-amino-acid sequence motif necessary for VRC01 light chain recognition. From over a million light chain sequences, we identified 13 candidate VRC01 class members. Pairing of these light chains with the phylogenetically identified C38 heavy chains yielded functional antibodies that effectively neutralized HIV-1. Bioinformatics analysis can thus directly identify functional HIV-1–neutralizing antibodies of the VRC01 class from a sequenced antibody repertoire.