Using trehalose delivered by the intramuscular injection of plasmid DNA as an adjuvant for transgene expression.

Background: Intramuscular injection is a popular and effective approach to administer naked plasmid for transgene expression. The use of an adjuvant can provide a straightforward approach for enhancing transgene expression.

Methods: Expression plasmid was formulated with various concentrations of trehalose for injection into the skeletal muscles of C57BL/6 mice. The effects of trehalose on gene dosage and the duration of transgene expression were assessed. The levels of transgene expression were indicated by levels of luciferase expression of the homogenized whole skeletal muscle or by histological X-gal staining of beta-galactosidase expression. Trehalose was also added to serum to examine the ability of protecting the DNA from degradation.

Results: It was found that an optimal trehalose concentration of 10 mM will achieve a level of transgene expression that is seven-fold higher than in the absence of trehalose. When compared with other disaccharides, only the incorporation of trehalose can effectively enhance transgene expression. Trehalose is able to improve transgene expression by intramuscular injection at a low gene dosage as well as prolong the duration of transgene expression.

Conclusions: Trehalose is an effective adjuvant for intramuscular administration of naked plasmid with respect to both enhanced levels and prolonged duration of transgene expression, most likely due to retarding plasmid degradation.