09-1B12-UCA B cells were transferred (or not transferred) to recipient mice that were 2 sequentially immunized with H3ssF (day 0 prime + day 42 boost) and then lethally challenged (day 56) with subtype-matched H3N2 influenza virus (108TCID50/mL X-31) or group-unmatched H1N1 influenza virus (104TCID50/mL mouse-adapted A/California/2009 [maA/Cal/09]42,43). The genetic distance of these influenza virus subtypes is also shown by the accompanying phylogenetic tree of HA IAV diversity (group 2, purple; group 1, blue). Weight loss and survival were monitored over 21 days. For subtype-matched H3N2 challenge:p< 0.0001 between 09-1B12-UCA cells + H3ssF vs. Sigma adjuvant;p< 0.001 between H3ssF alone vs. Sigma adjuvant (n= 10 mice per group, Mantel-Cox test of survivorship, one experiment). For group-unmatched H1N1:p< 0.025 between 09-1B12-UCA cells + H3ssF vs. H3ssF alone;p< 0.001 between 09-1B12-UCA cells + H3ssF vs. Sigma adjuvant alone, where then= 2 surviving from H3ssF only group (absence of 09-1B12-UCA cells) was not statistically significant (p> 0.05) (n= 10 mice per group, Mantel-Cox test of survivorship, one experiment). See alsoFigures S2andS3(in relation to A–D) andS4(in relation to E).
