Figure 3.

T-cell depletion modulates clinical disease outcomes of BTV-4 MOR2009/07 infection in sheep. (A) Mean ( ± SD) rectal temperatures (°C) above pre-depletion and pre-infection baseline temperatures in each of seven CD4⁺ (purple), CD8⁺ (green), WC1⁺ γδ (blue) T cell- and mock-depleted (red) sheep during infection with BTV-4 MOR2009/07. Raised temperature was defined as 1°C above animal-matched pre-infection baseline, fever by 1.5°C above baseline, and high fever by 2°C above baseline. Un-depleted and uninfected (negative control) sheep (black, n = 5) were included to monitor for contact transmission and general baseline temperature fluctuations. No statistical significance was identified in the means of each T-cell depletion group compared to the mock-depleted group at each time point (p > 0.05), as determined by a non-parametric Kruskal–Wallis test and post-hoc Dunn’s multiple comparisons. (B) Representative gross pathology of experimental bluetongue virus (BTV) infection in T cell- and mock-depleted sheep, characterised by (i, ii) severe facial oedema, (iii) nasal discharge, (iv) reddening of the eyes, (v) mucosal membranes, (vi) coronary band and (vii) tongue, and (viii) lameness and depression. (C) Survival curve of CD4⁺ (purple), CD8⁺ (green), WC1⁺ γδ (blue), and mock (red) T cell-depleted sheep over the duration of BTV-4 MOR2009/07 infection. (D) Mean cumulative daily clinical scores, as a proportion of the number of sheep alive, in CD4⁺, CD8⁺, or WC1⁺ γδ T cell- or mock-depleted sheep during infection with BTV-4 MOR2009/07. (E) Severity index of clinical disease in T cell/mock-depleted and control sheep during infection with BTV-4 MOR2009/07. Total daily clinical scores for all sheep within the CD4⁺ (purple), CD8⁺ (green), WC1⁺ γδ (blue), or mock (red) T-cell depletion groups were divided by the number of sheep alive per day. Negative (transmission) control sheep (n = 5) were uninfected and did not show gross clinical symptoms of BTV throughout the infection timeline.