Baculoviruses were propagated in Spodoptera frugiperda 9 (Sf9) insect cells using SF-900 serum-free medium (Invitrogen) at 27 o C. RSV A2 strain was propagated in HEp-2 cells (ATCC, Manassas, VA) in Dulbecco's modified Eagle's medium (Life Technologies, Gaithersburg, MD) supplemented with 3% heat-inactivated fetal calf serum, 2 mM glutamine, 20 mM HEPES, nonessential amino acid, penicillin, and streptomycin and titrated for infectivity by plaque assay as described elsewhere (20) .