Figure 3.
Innate immune cell depletion compromises CCP-mediated immunity against SARS-CoV-2 during prophylaxis in K18-hACE2 mice
(A) Experimental design to test the contribution of macrophages (CD45+Ly6G−Ly6C−CD11b+CD68+) and neutrophils CD45+CD11b+Ly6G+) in K18-hACE2 mice challenged with WA1 SARS-CoV-2-nLuc (1 × 105 FFU, i.n.) and treated prophylactically (i.p.; −1 dpi, 1 mL/20–25 g body weight) with indicated CCPs. αCSF1R or αLy6G mAbs (i.p., 20 mg/kg body weight) were used to deplete macrophages and neutrophils respectively every 48 h starting 2 days before infection. Human and rat isotype mAb-treated cohorts served as controls (Isotype). Animals were followed by BLI every 2 days as indicated.
(B) Representative BLI images of SARS-CoV-2-nLuc-infected mice in ventral (v) and dorsal (d) positions. Scale bars denote radiance (photons/s/cm2/steradian).
(C and D) Temporal quantification of nLuc signal as flux (photons/s) computed non-invasively.
(E) Temporal changes in mouse body weight with initial body weight set to 100%. Cross symbol, death.
(F) Kaplan-Meier survival curves of mice (n = 4 per group) statistically compared by log-rank (Mantel-Cox) test.
(G and H) Fold change in cytokine mRNA expression in brain and lung tissues at the time of death after necropsy. The data were normalized to Gapdh mRNA expression in the same sample and that in uninfected mice after necropsy. Each curve in (C–E) and each data point in (G–H) represents an individual mouse. Data in (C–H) are from two independent experiments and n = 2 mouse per group. Grouped data in (C–E) and (G–H) were analyzed by 2-way ANOVA followed by Tukey’s multiple comparison tests. Statistical significance for group comparisons to isotype control are shown in black, with CCP-3 to CCP-3+αLy6G shown in purple, with CCP5 to CCP-5+αLy6G shown in light red, CCP-6+αCSF1R shown in green, and with CCP-6 αLy6G shown in red. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001; ∗∗∗∗p < 0.0001; mean values ± SD are depicted. See also Figures S2 and S3