title: Adjuvant IL-15 does not enhance the efficacy of tumor cell lysate-pulsed dendritic cell vaccines for active immunotherapy of T cell lymphoma.
abstract: There has been a recent interest in using IL-15 to enhance antitumor activity in several models because of its ability to stimulate CD8+ T cell expansion, inhibit apoptosis and promote memory T cell survival and maintenance. Previously, we reported that C6VL tumor lysate-pulsed dendritic cell vaccines significantly enhanced the survival of tumor-bearing mice by stimulating a potent tumor-specific CD8+ T cell response. In this study, we determined whether IL-15 used as immunologic adjuvant would augment vaccine-primed CD8+ T cell immunity against C6VL and further improve the survival of tumor-bearing mice. We report that IL-15 given after C6VL lysate-pulsed dendritic cell vaccines stimulated local and systemic expansion of NK, NKT and CD8+ CD44hi T cells. IL-15 did not, however, augment innate or cellular responses against the tumor. T cells from mice infused with IL-15 following vaccination did not secrete increased levels of tumor-specific TNF-alpha or IFN-gamma or have enhanced C6VL-specific CTL activity compared to T cells from recipients of the vaccine alone. Lastly, IL-15 did not enhance the survival of tumor-bearing vaccinated mice. Thus, while activated- and memory-phenotype CD8+ T cells were dramatically expanded by IL-15 infusion, vaccine-primed CD8+ T cell specific for C6VL were not significantly expanded. This is the first account of using IL-15 as an adjuvant in a therapeutic model of active immunotherapy where there was not a preexisting pool of tumor-specific CD8+ T cells. Our results contrast the recent studies where IL-15 was successfully used to augment tumor-reactivity of adoptively transferred transgenic CD8+ T cells. This suggests that the adjuvant potential of IL-15 may be greatest in settings where it can augment the number and activity of preexisting tumor-specific CD8+ T cells.
authors: Graduate Program in Immunology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
authors: Erin
authors: E
authors: Gatza
authors: Craig Y
authors: CY
authors: Okada
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D018414:CD8-Positive T-Lymphocytes; D003713:Dendritic Cells / Q000276:immunology*; D005260:Female; D007156:Immunologic Memory; D007167:Immunotherapy / Q000379:methods; D016233:Immunotherapy, Active; D019409:Interleukin-15 / Q000276:immunology*; D007694:Killer Cells, Natural; D016399:Lymphoma, T-Cell / Q000276:immunology* / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D013534:Survival; D014407:Tumor Cells, Cultured / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; D019409:Interleukin-15