Augmentation of pulmonary host defense against Pseudomonas by FcγRIIA cDNA transfer to the respiratory epithelium

Abstract

Fcg receptors on the surface of phagocytic cells bind the Fc region of IgG and mediate binding, phagocytosis, and destruction of particulate antigens opsonized by the antigen-specific IgG molecule. The present study evaluates the feasibility of converting lung epithelial cells into phagocytic cells using adenovirus (Ad) vector–mediated gene transfer of FcgRIIA cDNA to induce expression of the human FcgRIIA receptor. Binding and phagocytosis of opsonized sheep red blood cells (SRBCs) by the A549 human lung epithelial cell line after Ad-mediated FcgRIIA gene transfer was demonstrated using light and fluorescence microscopy and phagocytic assays with 51Cr-labeled SRBCs. When A549 cells were infected with an Ad vector expressing a FcgRIIA mutant in which 2 of 3 cytoplasmic tyrosines have been replaced with phenylalanine, only binding, but not phagocytosis, of opsonized SRBCs was observed. In vivo expression of FcgRIIA in the lung after intratracheal administration of the AdFcgRIIA enhanced clearance of opsonized Pseudomonas aeruginosa from the lung in normal rats and in mice deficient in Fcg receptor expression. Similar results were observed with a chimeric FcgRIIA construct containing the extracellular domain of FcgRIIIA. Together, these data demonstrate that Ad-mediated FcgRIIA receptor cDNA expression can mediate the binding and phagocytosis of opsonized particulate antigens by normally nonphagocytic cells, suggesting that gene-transfer strategies might be used to utilize nonphagocytic cells to clear bacteria or other opsonized particulate antigens from the respiratory tract.