Serotype 5 ΔE1, E3 based replication-deficient adenoviruses were generated as previously described29. Briefly, oligonucleotides targeting rat GK were designed and selected using the Genebank accession number, L38990. Sense shRNA-GK 5′-TCA GAG TGA TGC TGG TCA A-3′ and antisense shRNA-GK 5′-TTG ACC AGC ATC ACT CTG A-3′ sequences shared no homology with other rat coding sequences by BLAST analysis. A ring sequence of nine base pairs (TTC AAG AGA) existed between the sense and antisense strands. Control shRNA oligonucleotides were designed and selected to target β-galactosidase from E. coli: sense5′-CGC GCC AAG GCC AGA CGC GAA TTA TTT CAA GAG AAT AAT TCG CGT CTG GCC TTT TTT TTT TAA T-3′ and antisense 5′-TAA AAA AAA AAG GCC AGA CGC GAA TTA TTC TCT TGA AAT AAT TCG CGT CTG GCC TTG G-3′. The expression cassette was then cloned into the adenoviral shuttle vector. All shRNAs (Invitrogen, Rockville, MD, USA) were synthesized and designed to contain both AscI and PacI restriction enzyme sites (New England Biolabs, Ipswich, MA, USA), which were used to ligate them into the plasmid, pDC311.2-OFF-EGFP downstream of the human H1 promoter, as previously described29. The plasmid was then cotransfected with the Ad genomic plasmid, pBHGlox∆E1,3Cre (Admax system, Microbix Biosystems, Ontario, Canada) into HEK293A cells. Virus particles were released by heat shock, and cell debris was removed by centrifugation for 5 min at 5000× g. The particles were recovered from the supernatant by filtration through a 0.45-µm filter. The resulting adenoviral expression vectors (Ad-shGK-EGFP and Ad-shβGal-EGFP) were tittered by EGFP expression using the Adeno-XTM Rapid Titer Kit Protocol (Clontech, Mountain View, CA, USA).