A) Stability of the pBAC-BoHV-4-U plasmid in E. coli DH10B. DH10B containing the pBAC-BoHV-4-U were passaged for 21 consecutive days, BAC DNA from the culture was prepared on the indicated days (3, 6, 9, 12,15, 18 and 21), HindIII digested and analyzed on ethidium bromide stained agarose gel. B) BEK or C) BEK expressing cre cells (BEK/cre) at 3 and 5 days post electroporation with pBAC-BoHV-4-U, where BAC-BoHV-4-U virus is reconstituted causing CPE and spreading through the cellular monolayer as shown by both phase contrast and fluorescence images (in B). Whereas, due to the expression of cre and the BAC cassette containing GFP is removed from the BAC-BoHV-4-U reconstituted, CPE is appreciable in phase contrast images but not in fluorescence (in C). D) Replication kinetics of BoHV-4-A-U reconstituted virus in BEK/cre cells (the BAC cassette has been removed by cre), compared with those of the parental BAC-BoHV-4-U (virus reconstituted on un-expressing cre BEK cells) still containing the BAC cassette and the BoHV-4-U isolate. The data presented are the means ± standard errors of triplicate measurements, P > 0,05 for all time points as measured by Student's t test.