Interleukin 15 as selectable marker for gene transfer in lymphocytes

An isolated transgenic mammalian cytotoxic T lymphocyte (CTL) or natural killer (NK) cell expressing IL-15 as a selectable marker for gene transfer and co-expressing at least one protein of interest,

• said cell comprising a lentiviral vector encoding IL-15 and the at least one protein of interest,
• wherein the protein of interest is a protein other than IL-15, and wherein the protein of interest is a protein of therapeutic interest,
• wherein the expression of the IL-15 as a selectable marker results in survival or growth of the mammalian CTL or NK cell in the absence of exogenously added IL-15 and/or IL-2,
• wherein the IL-15 has the amino acid sequence of SEQ ID NO. 1 or an amino acid sequence that has at least 95% sequence identity to SEQ ID NO. 1,
• or the IL-15 is encoded by the nucleotide sequence of SEQ ID NO. 2 or a nucleotide sequence with at least 95% sequence identity to SEQ ID NO. 2,
• and wherein the expression of the IL-15 does not result in the secretion of IL-15 into the culture supernatant in amounts sufficient to support survival and growth of cells that are not transformed or transduced with the IL-15 and/or are not expressing the IL-15 themselves.