MVA, but not VACV WR, induces chemokine production in THP-1 cells and increases chemotaxis of monocytes in a CCR1 dependent manner. A) Total RNA from MVA or VACV WR infected THP-1 cells were isolated 6 hours p.i. and investigated subsequently by multiprobe ribonuclease protection assay using hCK-5 as probe (upper panel) and specific RT-PCR as indicated (lower panel). B) Chemotaxis of THP-1 cells (upper panel) and U-937 cells (lower panel) toward control medium (CM) and culture supernatants from THP-1 cells infected with MVA or VACV WR at 1 MOI for 16 hours. Where indicated, cells were treated with 5 nM of CCR1 antagonist J 113863 or the equivalent amount of solvent (all other samples) before running the assay as described in Figure 3. Data are means ± SD (n = 4). *, P < 0.05. ***, P < 0.001.