Relative gene expression at mRNA level, of innate cytokines mRNA in IBDV-infected bursa. At PIDs 3, 5 and 7, bursal mononuclear cells were isolated from cIBDV- or vIBDV-infected and virus-free control chickens and examined for (A) IFN-α and (B) IFN-β gene expression by qRT-PCR. Results are shown as transcription of the target gene relative to housekeeping gene 28S. The data are expressed as fold change expression in infected chickens over virus-free control. The values represent the mean ± SEM of 4 pools of 3 bursa each at designated PID. #Statistically significant differences between control and vIBDV- or cIBDV-infected groups (p < 0.05). *Statistically significant differences between vIBDV- and cIBDV-infected groups (p < 0.05).