Genetic immunization using naked plasmid DNA (pDNA) has gained considerable interest since demonstration of humoral and cellular immune response (1,2). The potential advantages of DNA vaccines over conventional vaccines include: (1) high stability of pDNA, (2) low manufacturing costs, (3) lack of infection risk associated with attenuated viral vaccines, (4) capacity to target multiple antigens on one plasmid, and (5) ability to elicit both humoral and cellular immune responses. Furthermore, DNA immunization has been effective in eliciting an immune response with various administration routes such as intramuscular (IM), intradermal (ID), intraperitoneal, intravenous, oral, intranasal (IN), ocular, and transdermal/topical administrtation (3). Until recently, i.m. injection was the primary route of administration for DNA vaccines. However, this method may be traumatic, especially in infants and painful and requires trained staff. Hence, much attention has been focused on pDNA vaccines, especially for topical DNA vaccination. In addition to common advantages of DNA vaccines (4,5), topical DNA vaccines can elicit mucosal immune response in vivo. Furthermore, topical DNA vaccines have the advantages of simplicity, accessibility, painlessness, and economy. But the immune responses elicited are relatively low and weak.