Fig. 3. Intranasal immunization of Syrian hamsters with 100 PFU Nsp1-K164A/H165A significantly reduces viral loads in both upper and lower respiratory tract following challenge with Delta and Omicron variants.
a Syrian hamsters were vaccinated with 100 PFU Nsp1-K164A/H165A or infected with 100 PFU WA1/2020 35 days prior to challenge with 104 PFU Delta (n = 6) or BA.1 Omicron (n = 7) isolates on day 0. b–c From 1–5 DPC, infectious virus from nasal wash samples was quantified by focus-forming assays in vaccinated, convalescent, or unvaccinated hamsters (n = 8 for Delta, b; n = 7 for Omicron BA.1, c). Graphs for b and c indicate mean values from a single experiment with standard deviations shown as error bars. ***p = 0.001. d Viral sgRNA levels in lung, trachea, and nasal turbinate samples from 4 DPC (n = 4 each, except WA1/2020-Delta at n = 3) were measured by qRT-PCR. **p = 0.0041, ***p = 0.0008. e Infectious virus titers of lung homogenates at 4 DPC were determined by focus-forming assays. f Viral sgRNA levels in lungs and trachea at 7 DPC with Delta and BA.1 Omicron were measured by qRT-PCR. Infectious and qRT-PCR based titrations of Nsp1-K164A/H165A (n = 3), WA1/2020 (n =n = 3) vaccinated, or unvaccinated (n = 4) biological replicates in one independent challenge experiment each for Delta and Omicron BA.1. ***p = 0.0052. Dot plots represent samples collected from individual animals in a single experiment. Statistical differences were calculated using ordinary one-way analysis of variance (ANOVA) in GraphPad Prism 9.4.0 with Tukey’s multiple comparisons tests. For statistical significance, ****p < 0.0001. Δ delta variant challenge, Ο omicron BA.1 challenge, DPC days post-challenge.