Design and characterization of WPRE-enhanced DNA vaccine.

(A) The scheme indicates the composition of the DNA vaccine. The tumor-associated antigen mTH is inserted within the restriction sitesHindIII (5′-end) and XhoI (3′-end) at the multiple cloning site of the pcDNA3.1 vector (Invitrogen, Carlsbad, CA) under the control of the cytomegalovirus (CMV) promoter. The WPRE sequence is inserted after the stop codon within the restriction sites XhoI (5′-end) and XbaI (3′-end). (B) Integrity of genes was demonstrated by restriction enzyme digestion (lanes 1 and 2) with undigested controls shown in lanes 3 and 4 and further verified by nucleotide sequencing. The gel depicts a 1497-bp fragment of mTH and a 641-bp fragment of the WPRE sequence.