Elisa Brunette

Efficient and sustained gene expression in primary T lymphocytes and primary and cultured tumor cells mediated by adeno-associated virus plasmid DNA complexed to cationic liposomes.

We have used cationic liposomes to facilitate adeno-associated virus (AAV) plasmid transfections of primary and cultured cell types. AAV plasmid DNA complexed with liposomes showed levels of expression several fold higher than those of complexes with standard plasmids. In addition, long-term expression (> 30 days) of the gene, unlike the transient expression demonstrated by typical liposome-mediated transfection with standard plasmids, was observed. Southern analysis of chromosomal DNA further substantiated the hypothesis that the long-term expression was due to the presence of the transgene in the AAV plasmid-transfected group and not in the standard plasmid-transfected group. AAV plasmid-liposome complexes induced levels of transgene expression comparable to those obtained by recombinant AAV transduction. Primary breast, ovarian, and lung tumor cells were transfectable with the AAV plasmid DNA-liposome complexes. Transfected primary and cultured tumor cells were able to express transgene product even after lethal irradiation. High-level gene expression was also observed in freshly isolated CD3+, CD4+, and CD8+ T cells from normal human peripheral blood. Transfection efficiency ranged from 10 to 50% as assessed by intracellular interleukin-2 levels in interleukin-2-transfected cells. The ability to express transgenes in primary tumor and lymphoid cells may be applied toward tumor vaccine studies and protocols which may eventually permit highly specific modulation of the cellular immune response in cancer and AIDS.

Gene Modification of Primary Tumor Cells for Active Immunotherapy of Human Breast and Ovarian Cancer

We have previously shown that cationic liposomes facilitate adeno-associated virus (AAV) plasmid transfections of primary and cultured cell types. To test the clinical feasibility of using genetically modified tumor vaccines for the treatment of breast and ovarian cancers, we have constructed an expression plasmid pMP6IL2 and investigated the use of liposome-mediated gene delivery into primary, uncultured human breast and ovarian tumor cells to produce interleukin 2 (IL-2)-secreting tumor cells. We have demonstrated significant levels of IL-2 expression in tumor cell lines and primary breast and ovarian tumor cells using this AAV-based expression plasmid complexed to cationic liposomes. Transfections with the non-AAV plasmid containing the identical expression cassette as the AAV plasmid induced IL-2 expression in the tumor cell line but failed to produce IL-2 in primary tumor cells. Significant levels of IL-2 were induced with the AAV plasmid regardless of liposome compositions used for transfection. The transfected breast cell line and primary tumor cells were able to express the transgene product for up to 28 days after lethal radiation. The transfection efficiency was comparable for both the tumor cell line and primary tumor cells and ranged from 20 to 50% for both cell types as assessed by intracellular IL-2 staining. Although the primary tumor cell preparations consist of mixed population of cells, at least 40% of the tumor cells expressed the transgene as assessed by immunostaining for IL-2. The ability to efficiently express transgenes in freshly isolated, nondividing tumor cells may potentiate active immunotherapy strategies for gene-based cancer treatment.