Fig. 6: Protective efficacy of NanoSTING against the pathogenic SARS-CoV-2 Delta (B.1.617.2) VOC and IFN evasive SARS-CoV-2 Alpha VOC (B.1.1.7).

A We treated groups of 12 Syrian Golden hamsters, each with a single dose of 120 µg NanoSTING, and later challenged with ∼3 × 10⁴ CCID₅₀ of SARS-CoV-2 Delta VOC on day 0 by the intranasal route. We euthanized half of the hamsters (n = 6) hamsters on day 2 and determined viral titers of lung and nasal tissues. We rechallenged the remaining 6 hamsters on day 28 and tracked the body weight change until day 35. B Percent body weight change compared to the baseline at the indicated time intervals. C Percent body weight change monitored during the primary infection (day 0–day 6). D, E Viral titers measured by endpoint titration assay in nasal tissues and lungs post-day 2 of infection. The dotted line indicates the limit of detection of the assay (LOD). F Percent body weight change monitored after rechallenge (day 28–day 35). G We tested groups of 9 hamsters, each with two different doses of NanoSTING (30 µg and 120 µg) and 24 h later challenged with the ∼3 × 10⁴ CCID₅₀ of SARS-CoV-2 Alpha VOC (B.1.1.7). On day 2, five animals from each group were euthanized for assessing the viral titers and remaining animals used for the histopathology at day 5. No animals were excluded in this study. H Change in body weight of hamsters. I, J Pathology scores and a representative hematoxylin and eosin (H & E) image of the lung showing histopathological changes in lungs of hamsters treated with NanoSTING (30 µg) and PBS; all images were acquired at 10× and 20×; scale bar, 100 µm. K, L Viral titers were quantified in the lung and nasal tissue by endpoint titration assay on day 2 after the challenge. The dotted line indicates the limit of detection of the assay (LOD). Individual data points represent independent biological replicates taken from discrete samples; vertical bars show mean values with error bars representing SEM. Each dot represents an individual hamster. For (D, E, I, K, L), analysis was performed using a two-tailed Mann–Whitney U-test. For (C, H), data was compared via a mixed-effects model for repeated measures analysis. Lines depict group mean body weight change from day 0; error bars represent SEM. Asterisks indicate significance compared to the placebo-treated animals at each time point. Mann–Whitney U-test ****p < 0.0001; ***p < 0.001; **p < 0.01; *p < 0.05; ns not significant. For (B), the p-values are as follows: Day 4: p = 6e−3, Day 5: p = 1e−3, and Day 6: p = 5e−5. For (H), the exact p-values comparing the 30 µg NanoSTING group to the Placebo group are Day 3: p = 5e−3, Day 4: p = 6e−7, and Day 5: p = 10e−9. Additionally, for the 120 µg NanoSTING and Placebo-treated group, the p-values are Day 4: p = 2e−5 and Day 5: p = 3.5e−9. Data presented as combined results from two independent experiments [A−F Challenge study with SARS-CoV-2 Delta VOC, G−L challenge study with SARS-CoV-2 Alpha VOC)], each involving one independent animal experiment. Gender was tested as a variable, and an equal number of male and female hamsters were included in the study. See also Supplementary Figs. 11 and 12. Figure 6A, G—Created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license (https://creativecommons.org/licenses/by-nc-nd/4.0/deed.en). Number of animals used in the study: n = 12/group (for A−F), n = 9/group (for G–L). Source data are provided as a Source Data file.