Fig. 1.

Ontogeny of the infant-derived bnAb BF520.1. a, c Maximum likelihood phylogenetic relationships of a heavy- and c light-chain antibody gene variable regions. Trees display the inferred naive ancestor (root), BF520.1 from M12 pi (blue), and representative clonal family member next generation sequencing (NGS) reads from M6 pi (black). Units for branch length estimates are nucleotide substitutions per site. b, d Most probable routes of BF520.1 development: Bayesian BF520.1 clonal family phylogenies were sampled from an associated posterior distribution and then summarized to display relative confidences for internal node sequences. Resulting graphics display multiple possible lineages of amino acid transitions and their relative confidences for b heavy- and d light-chain development determined from two NGS technical replicates (left, right). Amino acid substitutions (arrows) connect the inferred naive sequence to the mature BF520.1 sequence via reconstructed ancestral intermediate sequences (nodes). Labeled nodes were chosen as the most probable Bayesian lineage intermediate sequences. The red shading of nodes is proportional to the posterior probability that this ancestral sequence was present in the lineage. For a given node, the blue shading across arrows arising from that node is proportional to the corresponding transition probability. Transient mutations are labeled in gray