All viral preparations were titrated by plaque assay on MA104 cells and expressed as plaque forming units per ml, as described [80] . Hemagglutination assays were performed to determine VP4 content of purified genome-containing and empty TLPs, unpurified RRV and 2/4/6/7 VLPs, as described [88] , and used to ensure that equal quantities of TLPs were added to pDC preparations. Additionally, DLPs were prepared by treating purified genome-containing TLPs with 20 nM of EDTA, thus removing the outer capsid from the virion and resulting in equal particle counts between the two preparations.