Cationic liposome-mediated enhanced generation of human HLA-restricted RSV-specific CD8+ CTL

Generation of human CD8+ cytotoxic T-lymphocyte (CTL) activity against respiratory syncytial virus (RSV) using peripheral blood leukocytes (PBL) in vitro is inefficient. Lipofectamine, a polycationic liposome, previously shown to enhance the transfection efficiency of DNA in cells, was evaluated for enhancing RSV CTL activity. Stimulator cells were prepared by infecting human PBL with RSV with or without Lipofectamine for 3 hr and then transferred to responder cells. After 8 days of incubation, CTL lysis of autologous target cells infected with RSV (also treated with Lipofectamine) was determined in a 4-hr 51chromium release assay. Lipofectamine treatment significantly enhanced HLA-restricted RSV-specific CD8+ CTL activity (up to sevenfold, P < 0.05–0.001). Lipofectamine treatment also enhanced cell surface RSV antigen expression and increased the frequencies of HLA-A,B,C+/RSV+ and HLA-DR+/RSV+ leukocytes as demonstrated by flow cytometry. These results demonstrate the usefulness of cationic liposomes in augmenting cell surface antigen expression and increasing the efficiency of generation of human RSV-specific CD8+ CTL activity.