Figure 5. Immunization with Tyrp1ee, exo-Tyrp1ee, and Tyrp1ee/ng protects mice from tumor challenge through a mechanism dependent on CD8⁺ T cells.

C57BL/6 mice (15 per group) were immunized once weekly for 4 weeks with different Tyrp1 constructs. Five days after the last vaccination, mice were challenged intradermally with 10⁵ B16 melanoma cells. CD8⁺, CD4⁺, and NK cells were depleted by weekly intraperitoneal injection of 500 μg anti-CD8 (53.6-72), anti-CD4 (GK1.5), or anti-NK (PK-136) administered 3 days before starting immunization. Depleting antibodies were subsequently administrated every week for the duration of the experiment. Rat monoclonal IgG was administered as a control. Kaplan-Meier analyses are shown. (A) Immunization with Tyrp1ee DNA protected ~45% of mice challenged with B16 melanoma (P < 0.01) compared with mice vaccinated with the control (empty vector). Tumor protection was completely abrogated in mice depleted of CD8⁺ T cells, but neither CD4 nor NK cell depletion significantly affected tumor protection induced by immunization with Tyrp1ee. (B) Immunization with exo-Tyrp1ee DNA protected ~80% of mice (P < 0.05) compared with empty vector and was completely abrogated in mice depleted of CD8⁺ T cells. No significant decreases in tumor protection were observed in mice vaccinated with exo-Tyrp1ee and depleted of CD4 and NK cells. (C) Immunization with Tyrp1ee/ng conferred increased tumor protection (~70%) (P < 0.05 compared with empty vector or Tyrp1), which was completely dependent of CD8⁺ T cells.