Figure 4. Vaccine expansion of cross-group protective IAV bnAbs that use minimal SHM.

(A) O1 and O2 were example mAbs expanded after a single immunization with H3ssF or H7ssF, respectively. O1 and O2 sequences contain some of the mutations present in mature 09–1B12, but have far lower SHM, as noted in the amino acid alignments and antibody structure. (B) Neutralization activities of 09–1B12-UCA, O1, O2 and 09–1B12 across: H3N2 (eight diverse viral strains covering >50 years of diversification: A/Aichi/2/1968, A/Bilthoven/1761/1976 A/Beijing/353/1989, A/Johannesburg/33/1994, A/Brisbane/8/1996, A/Fujian/411/2002, A/Perth/16/2009, A/Switzerland/9715293/2013); H7N9 (A/Shanghai/02/2013); H5N1 (A/Vietnam/1203/2004); and H1N1 (A/California/07/2009). Cross-group protecting VH1–18 QxxV bnAbs neutralize group 2 viruses but show more limited neutralizing activity against group 1 IAV^24,46. VRC01 served as an isotype control, 09–1B12 was a positive control for group 2 IAV neutralization and CR6261 was a positive control for group 1 IAV neutralization. N.N. = non-neutralizing (each antibody was run in triplicate, one experiment). (C) Weight loss and survival from lethal H3N2 virus challenge (10⁸ TCID₅₀/ml X-31) following passive transfer of 5 mg/kg O1, O2, 09–1B12 or VRC01 as isotype control [n=20 mice per group, ****P<0.001 (Mantel-Cox test of survivorship), one experiment]. (D) Weight loss and survival from lethal H1N1 challenge [10⁴ TCID₅₀/ml maA/Cal/09^75,76] following passive transfer of 5 mg/kg O1, O2, 09–1B12 or VRC01 as isotype control [n=20 mice per group, ****P<0.0001 (Mantel-Cox test of survivorship), one experiment]. See also Table S4 (in relation to A).