Fig. 1.

Protection of yolk antibody (IgY) against SARS-CoV-2 challenge in mice. a Flow chart of experimental design for preparing the SARS-CoV-2 specific yolk antibodies. Solid vertical lines indicate weeks of immunization, and egg symbols indicate sampling time points. b, c The humoral response dynamics of immunized laying hens were monitored. SARS-CoV-2 specific binding antibodies were assessed by ELISA. Neutralization activity with live SARS-CoV-2 (WT) was assessed as EC₅₀ by observing the cytopathic effect (CPE). Dotted lines indicate the detection limit. See also supplementary Fig. S1a. d Neutralization of the Wuhan-Hu-1 (WT), Beta, Delta, and Omicron variants of concern (VOCs) by the second boost IgY antibodies were measured by a recombinant lentiviral-based pseudovirus neutralization assay. Sera from three volunteers who had received two doses of inactivated vaccines (Sinopharm) were collected and assayed simultaneously. See also supplementary Fig. S1b, c. e Flow chart of the experimental design for protective testing of the developed IgY antibody. Mice were intranasally (IN) transduced with 8 × 10⁹ virus particle (VP) of Ad5-hACE2 followed by nasal delivery of antibody or PBS-placebo. They were then challenged with SARS-CoV-2 and euthanized at 3 days post-infection for viral load titration and pathological evaluation. Solid lines indicate the timeline of antibodies delivery IN (black), challenge (red), and sacrifice (green). f, g Viral loads in lung and trachea tissues were measured by qRT-PCR. h Lung virus titers were detected by TCID₅₀ assay in Vero E6 cells. i H&E staining of the representative lung tissue sections. Scale bars are 50 μm. See also supplementary Fig. S2. j Immunofluorescence staining detection of the SARS-CoV-2 S protein. Scale bars are 50 μm. Data were shown as mean ± SEM. An unpaired t-test was performed to test statistical significance between the group receiving the IgY antibody and the placebo group (**P < 0.01; ****P < 0.0001)