Effects of PRRSV genotype 1 and 2 isolates on IFN-α responses of enriched pDC. (A) PRRSV impact on CpG-induced IFN-α production by pDC. Enriched pDC were stimulated with CpG in presence of the indicated PRRSV isolates added at an MOI of 0.1 TCID50/cell. (B) Induction of IFN-α by prototype 1 LV and LVP23 (MOI of 1 TCID50/cell) in CD172a-enriched pDC (C) Comparative analysis of pDC IFN-α responses induced by various PRRSV strains (MOI of 1 TCID50/cell). (D-E) PBMC (D) and CD14-CD4+ monocyte-depleted enriched pDC (E) stimulated with the prototype of genotype 1 LV, LVP23 and CpG-ODN as control. IFN-α was determined by ELISA in supernatants harvested after 20 h. Boxplots in A, B and C indicate the median (middle line), 25th and 75th percentiles (boxes), maximum and minimum (whiskers) and the mean values (dotted line) calculated from at least three independent experiments with cells from different animals each performed in culture triplicates. Bars in (D) and (E) indicate culture triplicates ± 1 standard deviation. One of two representative experiments is shown. For (A) and (C), significance between isolates are indicated by different letters based on an ANOVA on Ranks and Dunn's Method pairwise multiple comparison (P < 0.05). In (A) not statistically significant suppression compared to mock-treated cells was determined by Mann–Whitney Rank Sum test (P < 0.02) and noted N.S. = not significant.