Research Article

Archaeosome Adjuvant Overcomes Tolerance to Tumor-Associated Melanoma Antigens Inducing Protective CD8+ T Cell Responses

Figure 4

CD8+ T cell response and tumor protection induced by Ms-Gp100 vaccine. Mice were immunized with 1, 10, or 30 μg Gp100 peptide entrapped in Ms archaeosomes at days 0 and 21. At 5 weeks, representative mice ( per group) were euthanized, the spleen cells were stimulated with IL-2 (0.1 ng/mL) and peptide (25 μg/ml) for 48 h and the frequency of IFN-gamma secreting cells was enumerated by ELISPOT. Mean ± SD ( ) of IFN-gamma secreting cells per 106 spleen cells is indicated. (a) At 5 weeks, in vitro CTL assay was also carried out on spleen cells of representative mice ( per group) immunized with 10 μg Ms-Gp100 (b). Mean Killing ± SD of 2 mice per group at different effector : target ratio is indicated (b). In another group of representative mice vaccinated with 20 μg Ms-Gp100, in vivo CTL response was evaluated on day 7 and day 28. Mean ± SD of mice per group is indicated (c). Finally, response to subcutaneous B16 tumor challenge was evaluated at 6 weeks in groups of naïve ( ), Ms-Gp100 vaccinated ( ), and PBS-Gp100 ( ) vaccinated mice. Survival was monitored based on a maximum tumor size of 300 mm2. Tumor survival data are presented as an aggregate from 3 different experiments conducted, and Gp100 peptide vaccination dose ranged from 25 to 30 μg/injection. Loading was 112 μg peptide/mg archaeosomes and average size 94.3 nm. Survival for Ms-Gp100 group is significantly different ( ) from naïve mice by log-rank test.
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