Construction of recombinant replication-deficient adenoviral vector expressing human BPI. (A) Human BPI cDNA (1.5 kb) was amplified from RNA of human blood CD34⁺ leukocytes by RT-PCR and visualized in 1% agarose gel by electrophoresis (lane 1, DNA size marker; lane 2, BPI cDNA product by RT-PCR). (B) Recombinant shuttle plasmid with BPI cDNA inserted into the E1 region of adenoviral genome (pDC104BPI) was cotransfected with viral rescue plasmid pBHG10loxCreL into 293 cells. Recombinant AdhBPI virus was rescued by homologous recombination between 2 loxP sites present in pDC104BPI and pBHG10loxCreL, which was catalyzed by Cre recombinase encoded by Cre cDNA in pBHG10loxCreL.