4-day time course of Northern blot analysis and multicycle growth. Replicate cultures of Vero cells were infected with rhMPV or rhMPV/ΔM2-2 at MOI of 0.1 PFU/cell. Cells and supernatants were harvested daily. Total RNA was extracted, and 7 replicate aliquots were separated on 1% agarose gel in the presence of 0.44 M formaldehyde gel, transferred to a nylon membrane and hybridized with digoxigenin-labeled single-stranded anti-sense riboprobes to detect mRNA as follows: A) M2 riboprobe; B) SH riboprobe; C) N riboprobe; D) F riboprobe; E) G riboprobe. F) Sense P, M, and F riboprobes were combined to detect genomic RNA. G) RNA in a duplicate gel was visualized with ethidium bromide and photographed under UV light. H) Titers of samples prior to RNA extraction were determined by plaque assay in Vero cells.