Fig. 1: Anti-H5 mAbs bind broadly to HA proteins of virus variants and inhibit virus replication in vitro.

a Binding breadth of anti-H5 mAbs to H5 protein from avian isolates (purple), a cattle isolate (orange), and human isolates (blue), was evaluated by ELISA in duplicates. As positive control, an anti-HA antibody, CR9114³² was used. Data shown is minimal binding concentration (ug/ml), defined as the lowest concentration with a signal greater than 3 standard deviations (SD) above blanks. b MAbs ability to block the virus-host receptor interaction was assessed by hemagglutination inhibition (HI) assay in duplicates. As positive control, serum (1:10) from a mouse infected with A/bald eagle/FL/W22-134-OP/2022 (H5N1-A/PR/8/34 reassortant) was used. Data shows minimal HI concentration (ug/ml), defined as the lowest concentration that shows HI activity. c Efficacy of the anti-H5 mAbs to inhibit viral replication was evaluated using an in vitro neutralization assay against A/bald eagle/FL/W22-134-OP/2022 (H5N1-A/PR/8/34 reassortant), in duplicates, with controls identical to part A. Data shows minimal neutralizing titer (ug/ml), defined as the lowest concentration where neutralization is observed. d MAbs capacity to inhibit neuraminidase (NA) activity of clade 2.3.4.4b virus was tested in duplicates, with an anti-NA antibody, 1G01¹⁷, as positive control. Data shown is the 50% inhibitory concentration (IC₅₀) (ug/ml). Negative control for all the assays was an anti-SARS-CoV-2 spike antibody¹⁸. Source data are provided as a Source Data file.