Cytokine T-cell responses in BAL following ISU-1 or 135 infections. (A) IFN-γ-secreting spot forming cells (SFC) were enumerated by ELISPOT following ex vivo stimulation with ISU-1, 135, or spike peptide pools. The frequency of IFN-γ and TNF secreting CD4 (B) and IFN-γ secreting CD8 (C) T cells were determined using intracellular staining following stimulation with ISU-1, 135, or peptide pools covering the spike protein. Each point represents a single animal. The line on each bar represents mean with SEM. Each point represents a single animal, and midline represents the mean. Two-way ANOVA and Bonferroni multiple test were performed. Asterisks represent significant changes (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001). (D) Spearman rank correlation between respiratory pathology and T-cell responses from both ISU-1- and 135-infected samples at 11 DPI. Asterisks represent significant changes (*P < 0.05, **P < 0.01). Asterisks represent significant changes (*P < 0.05, **P < 0.01 pathology from both ISU-1- and 135-infected).