Inhibition of adenovirus replication by the E1A antisense transcript initiated from hsp70 and VA-1 promoters

The E1A region of the adenoviral genome, important for initiation of virus infection and activation of other viral genes, was chosen as a target for engineering antisense RNA (asRNA) to inhibit adenovirus 5 (Ad5) replication in COS-1 cell culture in vitro. The hsp70 promoter, taken from the appropriate heat-shock-protein gene of Drosophila melanogaster, and the VA-1 RNA promoter, derived from the Ad5 gene coding for low-molecular-mass VA-1 RNA and recognized by RNA polymerase III were used as regulatory elements of transcription. The two types of recombinant constructs contained E1A fragments of 710 bp (hsp70 constructs) or 380 or 740 bp (VA-1 RNA constructs) in reverse orientation relative to the promoter position, as well as a transcription termination signal, the SV40 ori, and the gene controlling Geneticin (antibiotic G418) resistance (G418R). After selection of transfected COS-1 cells in the presence of G418, a number of stable G418R cell lines were raised which expressed engineered asRNAs. Plating of Ad5 suspensions of known titre on monolayers of transfected COS-1 cells clearly showed strong inhibition of adenovirus replication by asRNAs: 75% with the hsp70 promoter and 90% with the VA-1 RNA promoter.