Fig. 4.

In ovo characteristics of rIBVs. (a) Quantitative RT-qPCR analysis was performed on RNA extracted from the AF of ECEs collected at 12 h intervals after inoculation with IBV H52 BI, rIBV-wt rIBV-wt, rIBV-Δ3a, rIBV-Δ3b, rIBV-Δ5a and rIBV-Δ5b. The data points represent means with standard deviations of five eggs per condition, with all samples being run and analysed in triplicate using a 10-fold dilution series of IBV H52 BI as a reference to determine virus quantity as EID₅₀ ml⁻¹ equivalents. (b) Embryonic death is indicated as a percentage of all remaining animals at each time point. *, significant difference (P<0.05) in comparison with wild-type H52 viruses.