BSR-T7 (70), 293T (CelluloNet BioBank BB-0033-00072; SFR BioSciences, Lyon, France), 293-3-46 (71), Vero-hSLAM (72), Vero (si2), and Vero-hSLAM (si1) (2) cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) (Life Technologies) supplemented with 10% heat-inactivated fetal bovine serum (FBS) (30 min at 56°C), 1% l-glutamine, and gentamicin (10 μg/ml) at 37°C and with 5% CO2. Medium of 293-3-46 helper cells was supplemented with G418 (1.2 mg/ml). To rescue recombinant viruses, the helper cell line 293-3-46, stably expressing T7 polymerase, MeV N, and P, was transfected using the ProFection Kit with two plasmids coding for the MeV genome and MeV-L protein (pEMC-La) (71). Three days after transfection, the cells were overlaid on Vero-si2 cells. Upon appearance, isolated syncytia were picked and individually propagated on Vero-si2 cells. Virus stock was produced after a second passage at an MOI of 0.03 in the Vero-si2 cell line. This stock was checked to rule out mycoplasma contamination; had its N, P1, P2, M, and L genes sequenced; and was titrated on the relevant host cell before use.