TARGETING TYPE-II AND CLARA CELLS FOR ADENOVIRUS-MEDIATED GENE-TRANSFER USING THE SURFACTANT PROTEIN-B PROMOTER

We examined the ability of the human surfactant protein B (SP-B) promo ter to confer cell specificity of transgene expression in an adenovira l vector, Using similar replication-deficient adenoviruses (rAd), we c ompared lacZ reporter gene expression driven by the human SP-B promote r (rAd.SPBlacZ) with the ubiquitously expressed Rous sarcoma virus pro moter (rAd.RSVlacZ), rAd.SPBlacZ expressed lacZ in H-441 and A549 lung epithelial cell lines and not in HeLa cells whereas rAd.RSVlacZ expre ssed in all three cell lines. In primary human fetal lung fibroblasts, beta-galactosidase activity from rAd.RSVlacZ transduction increased i n a dose-dependent manner whereas activity from rAd.SPBlacZ remained l ow, In mixed cell cultures prepared from human fetal lung explants tha t contained fibroblasts and type ii cells, X-Gal staining localized rA d.SPBlacZ expression to only type II cells whereas rAd.RSVlacZ express ed in both cell types. In 24-wk gestation human fetal tissue explants infected ex vivo, the RSV promoter directed lacZ expression in lung, t rachea, heart, Liver, and esophagus, whereas with the SP-B promoter la cZ was expressed only in lung, specifically in air space-lining cells. This specificity was maintained in vivo. lacZ expression was undetect able in lung and other tissues after intravenous administration of rAd .SPBlacZ whereas rAd.RSVlacZ expressed primarily in liver. After intra tracheal instillation of rAd.SPBlacZ into mice, X-Gal staining localiz ed expression to type II and Clara cells, In contrast, rAd.RSVlacZ exp ressed in all pulmonary epithelial cell types. Our results indicate th at the SP-B promoter may be useful in targeting type II and Clara cell s for gene therapy of conditions such as inherited deficiency of SP-B.