IMMUNOLOGICAL RESPONSES TO GENE-TRANSFER INTO MICE VIA THE POLYMERIC IMMUNOGLOBULIN RECEPTOR

The respiratory epithelium is the primary target tissue for gene thera py of cystic fibrosis, and several methods of gene transfer permit the introduction of the gene encoding the normal cystic fibrosis transmem brane conductance regulator into cells of the respiratory tract in ani mals. DNA complexes based on Fab antibodies to secretory component hav e been used to mediate the delivery and uptake of expression plasmids into the respiratory tract via the polymeric immunoglobulin receptor b oth in vitro and in vivo. We evaluated the efficacy of gene transfer a fter several administrations of the DNA complexes, and examined the im munogenicity and toxicity of repetitive administration of anti-secreto ry component. Fab-based complexes. Mice received single or multiple in jections of the DNA complexes containing the plasmid pGL2 every 21 day s after the initial treatment, and lysates from the lung and liver wer e assayed for luciferase expression. Luciferase activity was detected in the lungs of mice that received a single injection of the DNA compl exes, whereas transgene expression was significantly lower in the mice that received three injections of the DNA complexes (17 338 +/- 5469 integrated light units/mg and 3771 +/- 1778 integrated light units/mg, respectively). Serum samples from animals that underwent single or mu ltiple injections were anlayzed for a serologic response against the c onjugate-DNA complexes by ELISA. No anticomplex antibodies were detect ed in the mice ater a single injection. An escalating antibody respons e was noted with increasing number of treatments with the conjugate-DN A complexes. This serologic response was directed exclusively against the rabbit-derived, anti-secretory component (anti-SC) Fab antibody, a nd not against either the plasmid DNA poly-L-lysine. Single injection of the conjugate-DNA complexes did not result in the consumption or ci rculating complement. Using direct immunofluorescence, perivascular de posits of immunoglobulin G were found in the liver of animals that rec eived three treatments; no such deposition was detected in the lungs o r kidneys. No increase in inflammatory cell infiltrates was observed i n tissues after single and repeated injections of the DNA complexes. T hus, we conclude that repeated injections of the anti-SC Fab-based com plexes evoked a humoral immune response against the heterologous Fab p ortion of the complex that was associated with reduced efficiency of g ene transfer.