Figure 3.
Intranasally immunized Delta-RBD protein with or without Omicron-S priming induced broadly anti-SARS-CoV-2 neutralizing antibodies
Sera from immunized K18-hACE2 mice 10 days after the last immunization were tested for neutralizing antibodies (Abs) against pseudotyped SARS-CoV-2 wild-type strain and variants.
(A) Neutralizing Abs against pseudotyped original SARS-CoV-2 wild-type strain.
(B) Neutralizing Abs against pseudotyped SARS-CoV-2 Delta variant.
(C) Neutralizing Abs against pseudotyped SARS-CoV-2 Omicron BA1 subvariant.
(D) Neutralizing Abs against pseudotyped SARS-CoV-2 Omicron BA2 subvariant.
(E) Neutralizing Abs against pseudotyped SARS-CoV-2 Omicron BA5 subvariant.
(F) Neutralizing Abs against pseudotyped SARS-CoV-2 Omicron XBB subvariant.
The pseudovirus neutralization assay was performed in 293T cells expressing SARS-CoV-2 receptor, human ACE2 (hACE2/293T), and 50% neutralizing Ab titer was reported as NT50 against respective pseudovirus infection. The data are shown as mean ± s.e.m. of five mice in each group. Delta-RBD-i.m. or Delta-RBD-i.n. indicates Delta-RBD protein intramuscular or intranasal immunization. Omicron-S-i.m. or Omicron-S-i.n. indicates Omicron-S protein intramuscular or intranasal immunization. S-i.m. + RBD-i.n. indicates i.m. priming with the Omicron-S protein followed by i.n. boosting with the Delta-RBD protein. Controls, PBS with relevant adjuvants injected via i.m., i.m. + i.n., or i.n. route. ∗ (p < 0.05), ∗∗ (p < 0.01), and ∗∗∗ (p < 0.001) designate significant differences among different groups. The experiments were repeated twice, and similar data were acquired.