Activation of T-bet, FOXP3, and EOMES in Target Organs From Piglets Infected With the Virulent PRRSV-1 Lena Strain

Abstract

Transcription factors (TFs) modulate genes involved in cell-type-specific proliferative and migratory properties, metabolic features, and effector functions. Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogen agents in the porcine industry; however, TFs have been poorly studied during the course of this disease. Therefore, we aimed to evaluate the expressions of the TFs T-bet, GATA3, FOXP3, and Eomesodermin (EOMES) in target organs (the lung, tracheobronchial lymph node, and thymus) and those of different effector cytokines (IFNG, TNFA, and IL10) and the Fas ligand (FASL) during the early phase of infection with PRRSV-1 strains of different virulence. Target organs from mock-, virulent Lena-, and low virulent 3249-infected animals humanely euthanized at 1, 3, 6, 8, and 13 days post-infection (dpi) were collected to analyze the PRRSV viral load, histopathological lesions, and relative quantification through reverse transcription quantitative PCR (RT-qPCR) of the TFs and cytokines. Animals belonging to both infected groups, but mainly those infected with the virulent Lena strain, showed upregulation of the TFs T-bet, EOMES, and FOXP3, together with an increase of the cytokine IFN-γ in target organs at the end of the study (approximately 2 weeks post-infection). These results are suggestive of a stronger polarization to Th1 cells and regulatory T cells (Tregs), but also CD4+ cytotoxic T lymphocytes (CTLs), effector CD8+ T cells, and γδT cells in virulent PRRSV-1-infected animals; however, their biological functionality should be the object of further studies.

PRRSV-1 induced lung lesion is associated with an imbalance between costimulatory and coinhibitory immune checkpoints

“…In particular, virulent Lena strain induced a more severe and earlier onset of lung lesion from 6 dpi onwards as consequence of severe interstitial pneumonia, characterized by thickening of the alveolar septa ( Figures 1B , D ), together with extensive foci of suppurative bronchopneumonia composed of neutrophils, cell debris and mucus filling the bronchial, bronchiolar and alveolar lumen ( Figure 1E ). By contrast, no relevant differences between experimental groups were found in the gross and microscopic examination for tracheobronchial lymph node upon PRRSV-1 infection ( Figures 1F , H ), nevertheless, an increase in the number of tingible body macrophages and/or severe lymphoid depletion were observed in particular 3249- and Lena-infected animals ( Figure 1G ; Ruedas-Torres et al, 2021a ).…”

“…Gross and histological findings for lung and tracheobronchial lymph node have been previously reported ( Rodríguez-Gómez et al, 2019 ; Ruedas-Torres et al, 2021a ). Macroscopic score of lungs is represented in Figure 1A (see Rodríguez-Gómez et al, 2019 for more details).…”

“…The sum of all frequencies was an estimation of the percentage of the affected lung in a scale from 0 to 100 ( Rodríguez-Gómez et al, 2019 ). Microscopic evaluation of lung and tracheobronchial lymph node lesion was conducted as previously described ( Rodríguez-Gómez et al, 2019 ; Ruedas-Torres et al, 2021a ). Hematoxylin and eosin-stained sections from cranial, middle and caudal lobes from the right lung and tracheobronchial lymph node were blindly examined and scored by two different pathologists.…”

“…Correlation between the expression of the different immune checkpoints in lung and tracheobronchial lymph node from both groups were assessed by Spearman test, considering relevant those of ρ > 0.55 and p ≤ 0.05. Additionally, correlations between the expression of immune checkpoints and the transcription factor FOXP3, and the macroscopic and microscopic score in lung and tracheobronchial lymph node from the same animals from a parallel study ( Ruedas-Torres et al, 2021a ) were performed. Figures and data analyses were performed with GraphPad Prism 7.0 software (GraphPad Prism software 7.0, Inc., San Diego, CA, USA).…”

Role of transcription factors in porcine reproductive and respiratory syndrome virus infection: A review

“…Another study showed that after infection with the Lena PRRSV strain, the expression of T-bet, Foxp3, and EOMES increased significantly, and at the same time, the expression level of IFN-γ also increased significantly. Importantly, the three significantly overexpressed transcription factors are closely related to the polarization of immune cells (Th1 cells, T cells, CD4+ cytotoxic T lymphocytes, and effector CD8+ T cells) (Ruedas-Torres et al, 2021 ).…”