TRANSFER OF THE HUMAN ALPHA(1)-ANTITRYPSIN GENE INTO PULMONARY MACROPHAGES IN-VIVO

Several viral and nonviral methods have introduced functional genes in to the lungs. An alternative strategy, receptor-mediated gene transfer , exploits the ability of receptors on the surface of cells to bind an d internalize DNA complexes and could potentially be used to deliver g enes to specific cells in the lung. The gene encoding human alpha(1)-a ntitrypsin (A(1)AT) was delivered to macrophages in vitro and in vivo by targeting the mannose receptor with mannose-terminal molecular conj ugates. The human A(1)AT transcript was detected 2 d after transfectio n of macrophages in culture, but transgene expression was transient. H uman A(1)AT protein was secreted into the culture medium, and Western blot hybridization revealed the mature human antiprotease. In addition , Sprague-Dawley rats underwent intravenous injections of increasing d oses of plasmid DNA (0.2 mg, 1.0 mg, and 2.0 mg) complexed to the mole cular conjugate. Four days after transfection, human A(1)AT mRNA was f ound in lungs from six of the 13 rats (46%) that received the higher d oses of plasmid. Transgene expression was limited to cells in perivasc ular and alveolar regions, which conformed to the distribution of pulm onary macrophages. Human A(1)AT was measured in the epithelial lining fluid of rats treated with transfection complexes. Animals that receiv ed 1.0 mg of plasmid had human A(1)AT levels of 7.4 +/- 3.4 pM, which was significantly different from nontransfected and mock-transfected c ontrols. Thus the mannose receptor permitted direct delivery of genes to pulmonary macrophages, though transgene expression was detected in the lung only at low levels.