“…The ten available X-ray structures ( Figure 1b 36-38,39 ,40 ] revealed that these antibodies can adopt multiple binding modalities to cope with high amino acid diversity and with the structural constraints posed by the presence of conserved Group-1 and Group-2-specific glycans. Despite the restricted propensity of the stem region to mutate, escape mutants have been isolated also for antistem antibodies [41,42 ], and their existence is also supported by the incomplete breadth of certain anti-stem antibodies, for example, the lack of binding to human H2N2 viruses by CR6261 [30]. Finally, a rare antibody, CR9114, was shown to bind to several influenza A and B viruses tested, although neutralizing activity was limited to influenza A [23].…”