Artificial antigen-presenting cells plus IL-15 and IL-21 efficiently induce melanoma-specific cytotoxic CD8+ CD28+ T lymphocyte responses

ObjectiveTo develop a novel artificial antigen-presenting system for efficiently inducing melanoma-specific CD8⁺ CD28⁺ cytotoxic T lymphocyte (CTL) responses.MethodsCell-sized Dynabeads® M-450 Epoxy beads coated with H-2K^b: Ig-TRP2_180-188and anti-CD28 antibody were used as artificial antigen-presenting cells (aAPCs) to induce melanoma-specific CD8⁺CD28⁺ CTL responses with the help of IL-21 and IL-15. Dimer staining, proliferation, ELISPOT, and cytotoxicity experiments were conducted to evaluate the frequency and activity of induced CTLs.ResultsDimer staining demonstrated that the new artificial antigen-presenting system efficiently induced melanoma TRP2-specific CD8⁺CD28⁺CTLs. Proliferation and ELISPOT assays indicated that the induced CTLs rapidly proliferate and produce increased IFN- γ under the stimulation of H-2K^b: Ig-TRP2-aAPCs, IL-15, and IL-21. In addition, cytotoxicity experiments showed that induced CTLs have specific killing activity of target cells.ConclusionsThe new artificial antigen-presenting system including aAPCs plus IL-21 and IL-15 can induce a large number of antigen-specific CD8⁺ CD28⁺ CTLs against the melanoma. Our study provides evidence for a novel adoptive immunotherapy against tumors.