CD4 and influenza: The two bNAbs lineages whose evolution has been traced (one a lineage of non-CD4 mimicking, CD4-binding site antibodies [13] and the other a V1, V2 glycan-binding antibody [11]) have relatively long CDRH3 regions (20 and 35 amino acids, respectively) and degrees of somatic hypermutation (i.e. 14% and 17% of VH amino acids, respectively) that are greater than nearly all IgG antibodies specific for influenza and other pathogens (average 7–8%) but less than those of many HIV bNAbs, which commonly exceed 30% [7,15,16].