Figure 2: Inhibition of PRRSV type 2 (PA8) and type 1 (LV) replication by tilmicosin. Z-mac cells seeded into 96-well plates were treated with various concentrations of tilmicosin ranging between 20 and 80 µg/ml for 24 h, after which time the cells were infected with 100 TCID50 of either PRRSV PA8 (A and B) or LV (C and D) in the presence of the drug. At 18 h pi, culture supernatants were collected for determination of infectious virus yields (TCID50/ml). In parallel, viral RNA was extracted from cells in the same well and subjected to real-time RT-PCR for the N gene of PRRSV PA8 (B) or LV (D). Controls consisted of virusinfected untreated cultures. Virus titers (A and C) and relative fold changes in viral genomic RNA (B and D) are indicated. Data are shown as mean titers with standard errors (A and C) and relative amounts of RNA with standard errors (B and D). One star (*) denotes a statistically significant difference of p<0.05 and two stars (**) denotes a statistically significant in difference of p<0.01.