Characterization of a fowl adenovirus 9 (FAdV-9) early promoter and its application in generating dual expression FAdV-9s.

The CMV immediate early promoter from the EGFP expression plasmid pEGFP-N1 was replaced with the very left end of the fowl adenovirus 9 (FAdV-9) genome (ntds 73-574) to demonstrate and delineate the promoter function of this sequence. Expression of an EGFP ORF which replaced ORF1 and ORF2 demonstrated that the native promoter can drive down stream foreign gene expression. Replacement of ORF1 and ORF2 with a bicistronic cassette, incorporating a 493 bp IRES from an Ontario strain of avian encephalomyelitis virus (AEV) separating an EGFP ORF and mCherry ORF allowed for expression of both ORFs from a recombinant FAdV. These results provide an additional platform for multivalent vaccines development based on a native FAdV-9 promoter and an avian virus IRES.