Interferon induction, production and sensitivity. (A) Left panel, interferon beta mRNA as quantified by real-time RT-PCR in 293-lp cells infected with rSCV or r7bΔTMD at an MOI of 5. Medium from mock-infected cells or cells infected at the same MOI with NDV served as controls. One PCR unit (y-axis) represents ten times the minimum concentration of interferon beta RNA detectable by the assay. (A) Right panel, interferon alpha secreted in supernatant of the same cells, as measured by EIA. The IFN standard exemplifies the sensitivity and linear range of the assay. (B) Viral RNA concentrations measured by real-time RT-PCR after two days of infection in cells pre-treated with increasing concentrations of interferon beta (x-axis). The left panel shows the results of triplicate experiments on Vero cells, the right panel shows results of duplicate experiments on CaCo-2 cells. For each graph the zero value indicates the Log RNA concentration achieved without interferon, to which the rest of the data were normalized. Viruses and cells used in each experiment are stated in the panels.