Fig. 1
LAH is a selecting epitope for cross-reactive GC B cells at viral replication site. a X31 HA-binding GC B cells in the lungs were recovered from X31-infected BALB/c mice at day 20 after infection and separated into strain-specific (blue) and cross-reactive (red) cells. Antigen specificity of both populations were evaluated by using mAbs in culture supernatants of single cell cultures. b High-throughput epitope mapping analysis was applied to the cross-reactive GC B cells (X31/Urg HA binders) in the lungs. The data from pooled 36 mice is shown. c Cross-reactive GC B cells were enumerated in the lungs 5 days after the injection of LAH-binding IgG1 (mLAH1), head-binding IgG1 (1E11), and non-binding IgG1 (NSP2). d The number of strain-specific and cross-reactive GC B cells were determined by flow cytometry 5 days after antibody treatment. Each circle represents the result from an individual mouse. The combined data from two independent experiments are shown. e Heterosubtypic reactivity of H3 LAH-binding clones was evaluated by ELISA using rHA as coating antigens. H3; X31, H7; A/Anhui/1/2013, H1; A/Narita/1/2009, H5; NIBRG-14 (originally from A/Vietnam/1194/2004). f Protective function of LAH-binding IgG2a and N297A mutant (100 μg per mouse) was assessed after lethal challenge by X31 (5 × LD50). g Heterosubtypic protection by LAH-binding IgG2a (100 μg per mouse) was assessed after H7N9 challenge (A/Anhui/1/2013, 1 × LD50). The combined data from two independent experiments (n = 10 per group) are shown. Left; body weight loss. Right; survival curve. Values represent mean ± s.d. **P < 0.01. The P-values were determined with a two-tailed Mann–Whitney test d and log-rank test f, g. Source data are provided as a Source Data file
