We determined the efficacy of in vitro expanded P14 TCR transgenic CD8 T cells to mediate tumor cell elimination and to protect against viral infection in mice. Contrary to previous studies, an adoptive transfer model without lymphodepletion, vaccination or cytokine treatment was used. Antigen-activated P14 T cells cultured in IL-2-containing medium for 7 days (P14 IL-2 ) exhibited potent effector cell functions in vitro but did not confer protection against melanoma growth or viral infection. In contrast, P14 T cells cultured in IL-15 (P14 ) were highly effective in vivo although they displayed only moderate effector functions in vitro. Therapeutic efficacy correlated with the survival of the transferred T cells in the recipients: P14 IL-2 cells disappeared rapidly whereas P14 IL-15 cells persisted for prolonged time. Decreasing the IL-2 concentration in the culture media improved in vivo survival and efficacy but also lowered the cell yield of the cultures. Finally, we could extend the findings with monoclonal P14 T cells to polyclonal CD8 T cells. Thus, in vitro expansion of antigen-specific CD8 T cells in IL-15 allowed the generation of substantial numbers of T cells without inducing terminally differentiated effector cells that turned out to be unfavorable in the transfer model examined here.Key words: Cytotoxic T cells . Rodent . Tumor immunity . Viral IntroductionAdoptive transfer of antigen-specific CD8 T cells into hosts represents a promising approach to treat tumors and viral infections [1][2][3][4]. To generate sufficient numbers of T cells for this therapy, T cells have to be stimulated and expanded in vitro. In most protocols used today, IL-2 is added to the culture medium to ensure T-cell proliferation, differentiation and survival. Besides IL-2, IL-15 also supports CD8 T-cell growth [5]; however, the phenotype and the functional activity of IL-2-versus IL-15-cultured CD8 T cells differ considerably. Manjunath et al. [6] were the first to show that CD8 T cells from P14 TCR-tg mice specific for gp33 epitope of lymphocytic choriomeningitis virus (LCMV) acquired an effector memory phenotype with high cytolytic activity when cultured in the presence of IL-2 whereas addition of IL-15 led to a central memory phenotype with low effector cell functions. Further analysis in the same TCR transgenic system revealed that these two cytokines were equivalent mitogens for antigen-stimulated CD8 T cells but that IL-2 was more potent in inducing amino acid uptake and protein synthesis [7].For adoptive T-cell therapy, it is important to generate CD8 T cells in vitro, which are efficient in inducing tumor regression or virus clearance in vivo. The degree of specific target cell lysis and the amount of antigen-triggered IFN-g production are frequently used to predict the efficacy of CD8 T cells in vivo. However, several recent studies in the pmel-1 TCR-tg model specific for the self/tumor antigen gp100 of B16 melanoma cells indicated that antigen-stimulated CD8 T cells with a less differentiated phenotype were sup...

The CC chemokine receptor 7 (CCR7) and its two ligands, CCL21 and CCL19, play an important role in migration of immune cells to lymphoid tissue. To analyze the function of CCR7 in T cell immunity to infectious agents in vivo, transgenic (tg) mice expressing CCL21 in an ubiquitous fashion were generated. These mice contained high amounts of CCL21 in the serum ( approximately 0.3 microg/ml that resulted in CCR7 down-regulation and in a strongly impaired migration of T cells toward CCL21 in vitro. Lymph nodes in CCL21-tg mice were reduced in size but with intact microanatomy and normal distribution of T and B cells. CCL21-tg mice showed a significantly decreased CD8 T cell response to lymphocytic choriomeningitis virus after footpad infection, whereas the response after systemic infection was not altered. Likewise, the CD4 T cell response to footpad infection with Leishmania major was considerably lowered and CCL21-tg mice failed to clear parasites from infected skin. Taken together, these data demonstrate the importance of CCR7 in mediating T cell immunity to viral and parasitic pathogens after local infection.

The transfer of T cell receptor (TCR) genes by viral vectors represents a promising technique to generate antigen-specific T cells for adoptive immunotherapy. TCR-transduced T cells specific for infectious pathogens have been described, but their protective function in vivo has not yet been examined. Here, we demonstrate that CD8 T cells transduced with the P14 TCR specific for the gp33 epitope of lymphocytic choriomeningitis virus exhibit protective activities in both viral and bacterial infection models in mice.