Augmentation of pulmonary host defense against Pseudomonas by Fc gamma RIIA cDNA transfer to the respiratory epithelium

Fc gamma receptors on the surface of phagocytic cells bind the Pc region of IgG and mediate binding, phagocytosis, and destruction of particulate anti gens opsonized by the antigen-specific IgG molecule. The present study eval uates the feasibility of converting lung epithelial cells into phagocytic c ells using adenovirus (Ad) vector-mediated gene transfer of Fc gamma RIIA c DNA to induce expression of the human Fc gamma RIIA receptor. Binding and p hagocytosis of opsonized sheep red blood cells (SRBCs) by the A549 human lu ng epithelial cell line after Ad-mediated Fc gamma RIIA gene transfer was d emonstrated using light and fluorescence microscopy and phagocytic assays w ith Cr-51-labeled SRBCs. When A549 cells were infected with an Ad vector ex pressing a Fc gamma RIIA mutant in which 2 of 3 cytoplasmic tyrosines have been replaced with phenylalanine, only binding, but not phagocytosis, of op sonized SRBCs was observed. In vivo expression of Fc gamma RIIA in the lung after intratracheal administration of the AdFc gamma RIIA enhanced clearan ce of opsonized Pseudomonas aeruginosa from the lung in normal rats and in mice deficient in Fc gamma receptor expression. Similar results were observ ed with a chimeric Fc gamma RIIA construct containing the extracellular dom ain of Fc gamma RIIIA. Together, these data demonstrate that Ad-mediated Fc gamma RIIA receptor cDNA expression can mediate the binding and phagocytos is of opsonized particulate antigens by normally nonphagocytic cells, sugge sting that gene-transfer strategies might be used to utilize nonphagocytic cells to clear bacteria or other opsonized particulate antigens from the re spiratory tract.