To establish whether pDCs activate or mature following inoculation with RRV, the frequency of pDCs expressing markers for activation (CD86) or maturation (CD83) was determined by flow cytometry. pDC activation (Figure 2A and 2C) and maturation ( Figure 2B and 2D) occurred at similar levels 12h after stimulation with either live or inactivated rotavirus (p$0.125; Wilcoxon signed rank test), and were significantly increased compared to mock-stimulated cells (p#0.03; Wilcoxon signed rank test). Stimulation with CpG ODN 2395 resulted in activation of a significantly greater percentage of the pDC population than that observed in pDCs exposed to RRV (p = 0.03; Wilcoxon signed rank test). The percent of pDCs matured by CpG ODN 2395 stimulus was also increased, but not significantly compared to those exposed to RRV (p = 0.094; Wilcoxon signed rank test). Viral replication did not inhibit maturation or activation, as pDCs positive for NSP2 expressed CD86 and CD83 at a significantly higher frequency (p#0.008; Wilcoxon signed rank test) than bystander pDCs ( Figure 2E -H). Expression of both molecules was significantly increased in both populations compared to pDCs receiving mock stimulus. Together, these data demonstrate that pDCs retain the ability to activate and mature after viral exposure, likely due to secondary effects, as the presence of replicative rotavirus is dispensable for induction of these phenotypes.