Pulmonary cytokine responses associated with PEI-DNA aerosol gene therapy

Pulmonary gene therapy with nonviral vectors delivered by instillation or intravenously has typically been associated with co-induction of cytokine responses attributed to the CpG motifs in the bacterial plasmid. Alternative delivery systems are being developed to circumvent the cytokine responses to the plasmid. Aerosol delivery of polyethylenimine--DNA (PEI-DNA) complexes leads to localized, high levels of transgene expression in the lungs. In this study, we show that PEI-DNA aerosol delivery is also associated with induction of tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta) in the lung and bronchoalveolar lavage fluid (BALF). However, there is no increase in the serum levels of these cytokines. The levels of these cytokines peak at 5--8 h after aerosol exposure for lung tissue, and at 24 h for BALF. However, the levels detected are much lower than those observed when PEI-DNA complexes, guanidinium--cholesterol: dioleoylphosphatidyl--ethanolamine liposome--DNA (BGTC:DOPE--DNA) complexes or 1,2-dioleoyl-sn-glycero-3-trimethylammonium--propane--cholesterol:DNA (DOTAP-Chol:DNA) complexes were delivered intravenously. Also, the lung cytokine levels were higher when BGTC:DOPE--DNA complexes were delivered by aerosol to the mice. Although the mechanism remains to be elucidated, the data suggest that aerosol exposure to PEI--DNA complexes can achieve high levels of transgene expression in the lungs without inducing high levels of cytokine responses.