Figure 4.

T-cells are required for survival following CCHFV infection. IFNAR^−/− mice were treated with antibodies to deplete CD4⁺, CD8⁺, or both CD4⁺ and CD8⁺ cells on day −2, +3, +10, and +17 relative to CCHFV challenge. (A) On day 8 PI, depletion efficacy was evaluated in a subset of mice by flow cytometry to enumerate number of CD3⁺, CD3⁺CD4⁺, or CD3⁺CD8⁺ T-cells in the liver. N = 6 per group. p values calculated with two-way ANOVA with Tukey-s multiple comparisons test. (B) Following CCHFV challenge, mice were weighed daily and monitored for survival (C). n = 20–32 mice per group. (B) Error bars indicate standard error of measurement. Statistical test comparing isotype-treated mice with depleted mice was performed using a two-way ANOVA with Dunnett’s multiple comparison test. (C) Indicated statistical comparison between groups performed using Log-rank test with Bonferroni’s correction for multiple comparisons. ** p < 0.01, **** p <0.0001. (D,E) At indicated time-points PI, mice were euthanized and viral RNA in the liver or spleen quantified by qRT-PCR. Dashed line indicates limit of detection. Statistical comparison to isotype-treated mice performed using two-way ANOVA with Sidak’s multiple comparison test. (F,G) At day 8 PI, blood levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were evaluated. Indicated statistical comparisons performed using an ordinary One-way ANOVA with Tukey’s multiple comparison test. ns p > 0.05, * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.