ADENOVIRAL-MEDIATED GENE-TRANSFER OF HUMAN SURFACTANT PROTEIN-B TO RESPIRATORY EPITHELIAL-CELLS

Human surfactant protein B (SP-B) is a 79-amino acid, phospholipid-associated polypeptide expressed by respiratory epithelial cells of the lung. SP-B is essential for lung function, enhancing the spreading and stability of surfactant phospholipids that serve to reduce surface tension at the alveolar air-liquid interface. Congenital absence of SP-B results in neonatal respiratory failure and death. In the present work, we constructed a replication-deficient adenoviral vector, Av1SP-B1, in which the human SP-B cDNA is expressed under control of the Rous sarcoma virus (RSV) promoter in an E1-E3-deleted adenovirus type 5 (Ad5)-based vector system. Av1SP-B1 was produced in 293 kidney cells, directing the synthesis of the SP-B protein and SP-B peptides. Av1SP-B1 directed the synthesis of SP-B mRNA, precursor and active 8-9 kD polypeptide in immortalized mouse lung epithelial cells (MLE-12 cells), demonstrating complete processing to the human SP-B protein by these cells. Synthesis of human SP-B mRNA was detected as early as 12 h after infection and was maximal 48 h after infection in vitro. Northern blot analysis demonstrated that human SP-B mRNA was expressed in the lungs of cotton rats infected with AV1SP-B1 but not in those of uninfected animals or in animals infected with a reporter adenoviral vector, Av1LacZ4. In situ hybridization demonstrated the abundance and localization of the transferred human SP-B mRNA. Av1SP-B1 directed the expression of SP-B peptide and oligomeric forms in cotton rats treated intratracheally with the vector, demonstrating that vector-derived precursor SP-B is processed after in vivo adenoviral vector-mediated gene transfer. Av1SP-B1 may be useful for in vivo gene therapy of SP-B deficiency.