Immunologic responses to gene transfer into mice via the polymeric immunoglobulin receptor

The respiratory epithelium is the primary target tissue for gene therapy of cystic fibrosis, and several methods of gene transfer permit the introduction of the gene encoding the normal cystic fibrosis transmembrane conductance regulator into cells of the respiratory tract in animals. DNA complexes based on Fab antibodies to secretory component have been used to mediate the delivery and uptake of expression plasmids into the respiratory tract via the polymeric immunoglobulin receptor both in vitro and in vivo. We evaluated the efficacy of gene transfer after several administrations of the DNA complexes, and examined the immunogenicity and toxicity of repetitive administration of anti-secretory component Fab-based complexes. Mice received single or multiple injections of the DNA complexes containing the plasmid pGL2 every 21 days after the initial treatment, and lysates from the lung and liver were assayed for luciferase expression. Luciferase activity was detected in the lungs of mice that received a single injection of the DNA complexes, whereas transgene expression was significantly lower in the mice that received three injections of the DNA complexes (17338 +/- 5469 integrated light units/mg and 3771 +/- 1778 integrated light units/mg, respectively). Serum samples from animals that underwent single or multiple injections were analyzed for a serologic response against the conjugate-DNA complexes by ELISA. No anticomplex antibodies were detected in the mice after a single injection. An escalating antibody response was noted with increasing number of treatments with the conjugate-DNA complexes. This serologic response was directed exclusively against the rabbit-derived, anti-secretory component (anti-SC) Fab antibody, and not against either the plasmid DNA or poly-L-lysine. Single injection of the conjugate-DNA complexes did not result in the consumption of circulating complement. Using direct immunofluorescence, perivascular deposits of immunoglobulin G were found in the liver of animals that received three treatments; no such deposition was detected in the lungs or kidneys. No increase in inflammatory cell infiltrates was observed in tissues after single and repeated injections of the DNA complexes. Thus, we conclude that repeated injections of the anti-SC Fab-based complexes evoked a humoral immune response against the heterologous Fab portion of the complex that was associated with reduced efficiency of gene transfer.