Adenovirus-augmented, receptor-mediated gene delivery and some solutions to the common toxicity problems.

Several years ago it was reported that the entry of adenovirus particles could augment the uptake of polylysine-condensed DNA molecules (Curiel et al. 1991), a phenomenon similar to previously described adenovirus augmentation of both fluid phase markers and receptor-bound molecules (Fernández-Puentes and Carrasco 1980; Fitzgerald et al. 1983). This use of adenovirus to enhance gene delivery has proven to be a fruitful approach. A number of reviews of the general properties of this system have recently been published (Curiel 1993; Cotten and Wagner 1993; Wagner et al. 1994). In this review I will provide a summary of the current methods of generating adenovirus-DNA transfection complexes as well as discussing two of the toxicity problems that we have encountered with this system and describing some solutions to these problems. The first problem encountered was due to virus gene expression and leakiness in the replication defect of the commonly used defective adenovirus strains. This problem was solved by developing a psoralen inactivation method that inactivates the virus DNA and blocks viral gene expression and replication without impairing the entry functions of the virus (Cotten et al. 1994b). The second problem was due to a toxicity generated by cytoplasmic delivery of lipopolysaccharide (LPS, endotoxin) that frequently contaminates bacterial DNA preparations. The LPS problem has been solved by identifying reliable methods of removing LPS from DNA (Cotten et al. 1994a) or by including LPS-binding polymyxin in the transfection medium