Fig. 6. AR-CoV/IAV elicits protection against coinfection with IAV and the SARS-CoV-2 Delta variant in mice.

a Schematic diagram of experimental design. Groups of AR-CoV/IAV- or placebo-immunized mice were intranasally challenged with 2 × 10⁵ PFU of IAV (A/California/07/2009) 73 days after the initial immunization, followed by infection with 1.2 × 10⁴ PFU of SARS-CoV-2 Delta variant 2 days later. Mice were sacrificed 4 days post-IAV infection for viral detection and histopathological analysis. b Weight changes of infected mice (n = 5) were recorded for 4 days post-infection and are shown as the mean ± SEM. c, d Viral RNA copies of IAV (c) and SARS-CoV-2 (d) in the lung tissues of infected mice (AR-CoV/IAV, n = 4; placebo, n = 5) were determined by qRT–PCR and are shown as the mean ± SEM. e Histopathologic analysis of lung sections from coinfected mice. Scale bar, 100 μm. Data are shown as the mean ± SEM. Statistical differences were analyzed by using two-way ANOVA with multiple comparison tests or two-tailed unpaired t tests. *P < 0.05, ****P < 0.0001.