Fig. 1: Evaluation of the replication, immunogenicity, and protective efficacy of one or two doses of MPV/S-2P in rhesus macaques.

A Timeline of the evaluation of MPV/S-2P in rhesus macaques. Three groups (n = 4 per group) were immunized by the IN/IT route. Group 1 received a single dose of MPV (empty-vector control, gray), and groups 2 (blue) and 3 (gold) received MPV/S-2P. Twenty-eight days after the first dose, macaques of group 3 received a second dose of MPV/S-2P (boost, 6.3 log₁₀ PFU). Thirty-one to 32 days after a single dose (groups 1 and 2) or day 30 after the second dose (group 3, study day 58), macaques were challenged by the IN/IT route with the vaccine-matched WA1/2020 SARS-CoV-2 strain. Vital signs were documented for the duration of the study (Fig. S1). Macaques were euthanized on day 6 post-challenge. B Replication of MPV and MPV/S-2P in the upper and lower airways was evaluated by immunoplaque assay from nasopharyngeal swabs (NS) and tracheal lavage samples (TL), respectively, collected at the indicated days post immunization (pi) from MPV primed (n = 4), MPV/S-2P primed (n = 8) and boosted (n = 4) macaques. Medians (lines), min and max values (whiskers), 25th to 75th quartiles (boxes), and individual values are shown. The limit of detection was 0.7 log₁₀ PFU/ml and 1 log₁₀ PFU/ml for NS and TL, respectively (dotted line). The number of animals per group of macaques with detectable virus replication is indicated. Two-way ANOVA with Sidak post-test; exact p values are indicated for levels of significance p < 0.05 unless p < 0.0001 (****). Source data are provided in the Source Data file.