Intranasal parainfluenza virus-vectored vaccine expressing SARS-CoV-2 spike protein of Delta or Omicron B.1.1.529 induces mucosal and systemic immunity and protects hamsters against homologous and heterologous challenge
Fig 5
Mucosal and serum antibody responses in immunized hamsters upon SARS-CoV-2 challenge.
On day 23 or 24 pc, the six remaining hamsters per subgroup were euthanized, and bronchoalveolar lavage (BAL) and sera were collected (see Fig 1C for timeline of the experiment) for evaluation of the antibody response by ELISA (IgG) or DELFIA (IgA and sIgA) (A-C) or ACE2 binding inhibition assay (D-E). (A) Anti-S IgG (left panel), IgA (middle panel) and sIgA (right panel) antibody titers in BAL (limit of detection: 1 log10, dotted line for IgG and IgA). N = 6 hamsters per subgroup with the exception of n = 5 for B/HPIV3 immunized/WA1/2020 challenged, B/HPIV3/S-6P-immunized/BA.1 challenged, B/HPIV3/S-Delta-6P-immunized/BA.1 challenged, B/HPIV3/S-Omicron-6P-immunized/WA1/2020 challenged and n = 4 for B/HPIV3/S-6P-immunized/Delta challenged. The anti-S sIgA DELFIA titers were determined for hamsters with sufficient volumes of remaining BAL samples, and the animal numbers and fractions of hamsters with detectable levels are indicated on top of the graph. (B-C) Serum anti-S IgG (B) and IgA (C) titers after challenge (left panels) and fold changes (in log10) of post-challenge titers over post-immunization titers (right panels). N = 6 with the exception of n = 5 for B/HPIV3-immunized/WA1/2020 challenged. Purified preparations of S from the Wuhan-Hu-1 strain were used as antigens in the ELISA. Each hamster is represented by a symbol and medians with interquartile ranges are shown. One-way ANOVA with Tukey post-test; exact p values are indicated for levels of significance p < 0.05. (D-E) Binding inhibition of soluble ACE2 protein to SARS-CoV-2 S proteins from 20 different variants by serum antibodies from immunized and challenged hamsters. Data are represented as a heatmap with one heatmap per challenge virus and with the median percent inhibition of ACE2 binding relative to a non-serum control indicated (D) or as radar plots (E). N = 6 with the exception of n = 5 for B/HPIV3-immunized/WA1/2020 challenged.