Fig. 5: Immune protection of S-Trimer against SARS-CoV-2 challenge in nonhuman primates.

Rhesus macaques (n = 6/group) were immunized with 30 µg S-Trimer adjuvanted with 0.25 mL AS03, 30 µg S-Trimer adjuvanted with 1.5 mg CpG 1018 plus 0.75 mg alum, or PBS vehicle control twice on Day 0 and Day 21 and were challenged on Day 35 with 2.6 × 10⁶ TCID50 (60% intratracheal and 40% intranasal) live SARS-CoV-2 virus. Following SARS-CoV-2 challenge, clinical observation data were collected based on a changes in body weight and b changes in body temperature at 0, 1, 3, 5 (n = 6) and 7 dpi (n = 4). c At necropsy at 5 dpi (n = 2 × 8 samples/group) and 7 dpi (n = 4 × 8 samples/group), lung tissues were collected for measurement of viral loads based on genomic RNA (gRNA). d Throat swab, anal swab, tracheal brush, and nasal swab specimens at 1, 3, 5 (n = 6) and 7 dpi (n = 4) were collected for measurement of viral loads based on gRNA. Body weight and body temperature data are presented as mean values ± SEM. All viral load data are presented as geometric mean values ± SEM. e Histopathological examinations in lungs from inoculated animals was conducted at necropsy. Lung tissues were collected and IHC staining with antibody specific to SARS-CoV-2 Spike protein was conducted. Representative specimens are shown from two independent experiments, scale bar are 200 μm. For Body weight and temperature change statistical analysis, all comparisons were compared to 0 dpi with Two-way ANOVA multiple comparison test. The statistical analysis of viral load in lung tissues with Kruskal–Wallis ANOVA with Dunn’s multiple comparisons test and analysis of viral load in swabs with Two-way ANOVA multiple comparisons test were all compared to the vehicle control group. P values < 0.05 were considered significant. ns represents no significant.