FIG 4.

Elimination of infectious IBDV from DF-1P cells. Persistently infected DF-1P cultures were subjected to a prolonged (180-day) treatment with 7DMA, an inhibitor of viral RNA polymerases of RNA viruses. After the treatment, cultures were maintained for 30 days in the absence of the inhibitor to facilitate the recovery of potentially surviving IBDV populations. Thereafter, untreated (P) and 7DMA-treated (P-7DMA) DF-1P cell cultures were used to search for the presence of IBDV RNA and the structural IBDV VP3 polypeptide. Samples from mock [M]- and acutely infected DF-1 (A) cells were used as controls. (A) RNAs extracted from the different cultures were used to perform an RT-qPCR analysis using primers hybridizing at the VP3 coding region (genome segment A). Each determination was carried out in triplicate. Presented data correspond to the means ± standard deviations from three independent experiments. Brackets indicate pairwise data comparisons. **, P < 0.001 as determined by two-way analysis of variance (ANOVA). (B) Cell extracts were subjected to SDS-PAGE followed by Western blotting using antibodies specifically recognizing either the IBDV structural VP3 or the cellular α-tubulin polypeptides.