Augmentation of adenovirus 5 vector-mediated gene transduction under physiological pH conditions by a chitosan/NaHCO3 solution.

Chitosan, a cationic polysaccharide, can enhance recombinant adenovirus vector (rAdv)-mediated gene transduction (AMGT) in cells that lack the rAdv receptor, coxsackie-adenovirus receptor (CAR). However, gene transduction using chitosan for such cell types has so far only been successful under non-physiological pH conditions as chitosan is insoluble under physiological pH conditions. Here we report that NaHCO(3) can greatly improve the solubility of chitosan at physiological pH (pH 7.4). We show that this chitosan/NaHCO(3) solution increases AMGT approximately 8-24-fold in several CAR-absent or CAR low-level-expressing cell lines from different species and tissue origins (for example, Chinese hamster ovary, B16, DC2.4 and RD cells). Chitosan/NaHCO(3) also increases AMGT of CAR-positive cell lines 1.6-1.7-fold. The presence of fetal bovine serum during rAdv treatment and impurities in rAdv preparations did not adversely affect transduction efficiency. Moreover, chitosan/NaHCO(3) promotes AMGT efficiency for murine melanoma B16 xenografted tumor cells in C57/BL6 mice. Our new protocol provides a CAR-independent, highly efficient and convenient technique to enhance AMGT both in vitro and in vivo under physiological pH conditions.