TRANSACTIVATION OF THE EARLY SV40 PROMOTER BY AVIAN INFECTIOUS LARYNGOTRACHEITIS VIRUS IN AVIAN HEPATOMA-CELLS

An avian hepatoma cell line has been reported to be suitable for the c ultivation of avian laryngotracheitis virus (ILTV) (Scholz et al. (199 3) J. Virol. Methods, 273-286; Guo et al. (1993) Am. J. Vet. Res., in press). To provide information for the establishment of avian expressi on systems and for the construction of avian recombinant viruses, five expression plasmids were constructed to test two avian viral and two mammalian viral promoters for their suitability and strength for gene expression in this cell line. Chicken hepatoma cells were transfected with plasmids carrying the bacterial beta-galactosidase (beta-gal) gen e as a reporter gene. The beta-gal gene of three plasmid constructs ex pressed in both E. coli and avian hepatoma cells, while the beta-gal g ene of two other constructs expressed only in avian hepatoma cells. Th e beta-gal gene expressed independently of any viral infection when un der the control of the early Rous sarcoma virus (RSV) promoter or the immediate-early cytomegalovirus (CMV) promoter. However, expression of beta-gal gene under the control of the SV40 early promoter/enhancer a nd the ILTV TK promoter was greatly potentiated when the transfected c ells were co-infected with ILTV. This finding provides a system for th e enhancement of gene expression in avian cells, especially when ILTV is used as vector.