RESUMO
Infectious bursal disease virus (IBDV) can cause disease in chickens characterized by immunosuppression and high mortality. Currently, real-time RT-PCR has been used to quantitate virus-specific RNA and to better understand host response to infection. However, normalization of quantitative real-time RT-PCR is needed to a suitable internal control. We thus investigated the expression pattern of six chicken genes, including beta-actin, 28S rRNA, 18S rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), TATA box-binding protein (TBP) and beta-2-microglobulin, in chicken embryo (CE) cell cultures following a 7-day IBDV infection. The CE cells were inoculated with various multiplicity of infection (MOI) of IBDV vaccine strain Bursine-2, the expression of genes was measured by quantitative real-time PCR-based on cDNA synthesized from either normalized (100 ng) or non-normalized (10 microl) total RNA. The results showed that beta-actin, 28S rRNA, 18S rRNA and GAPDH were the most constantly expressed genes, while TBP and beta-2-microglobulin were markedly induced during the infection course. Of these constant expressed genes, 28S rRNA and 18S rRNA are highly expressed; beta-actin intermediately expressed and GAPDH had a lower expression level in CE cell cultures. Also, beta-actin showed no significant variation in both normalized and non-normalized assays and virus dose-independent of inoculation, while other genes did. beta-Actin was further successfully used as an internal control to quantitate Bursine-2 virus-specific RNA load in CE cell cultures. Thus, beta-actin was suggested as a suitable internal control in studying gene expression as well as virus-specific RNA load in CE cell after IBDV infection.
