Porcine reproductive and respiratory syndrome virus induces CD4+CD8+CD25+Foxp3+ regulatory T cells (Tregs)

The aim of this study was to analyze the regulatory T cells (Tregs) induced by the porcine reproductive and respiratory syndrome virus (PRRSV) in pigs. Serum, blood, tonsil, and mediastinal lymph nodes' samples were obtained at different time post-infection (dpi). The frequencies of CD4+CD8−CD25+Foxp3+, CD4+CD8+CD25+Foxp3+, or CD4−CD8+CD25+Foxp3+ phenotypes were determined in PBMC and lymph node cells, and cells producing IL-10 or TGF-β were analyzed. PRRSV increased the number of CD4+CD8+CD25+Foxp3+ cells at 14 dpi, whereas CD4+CD8−CD25+Foxp3+ remained constant until 28 dpi. Positive correlation exists between viremia and induced regulatory cells. CD4+CD8+CD25+Foxp3+-induced Treg cells were consistently observed in lymphoid tissues. Analysis of IL-10- and TGF-β-producing cell demonstrated that in response to PRRSV, CD4+CD8−Foxp3low and CD4+CD8+Foxp3high cells increase moderately the proportion of IL-10+ cells. TGF-β was only observed in the CD4+CD8+Foxp3high population after PRRSV stimulation. In conclusion, PRRSV infection increases the frequency of Tregs with the phenotype CD4+CD8+CD25+Foxp3high and produces TGF-β.