Abstract B41: Analysis of immune responses and tumor protection in C57/Bl6 mice immunized with altered CD8 survivin peptide ligands.

Abstract

Abstract Survivin is an intracellular tumor-associated antigen (TAA) that is broadly expressed in a large variety of tumors as well as tumor-associated endothelial cells, but mostly absent in differentiated tissues. The objective of the present work is to analyze the immune response and tumor protection generated in mice following vaccination with the wild-type (WT) survivin-derived peptide SURV20-28 (ATFKNWPFL) and with the two altered peptide ligand (APL) variants SURV20-28-3P (ATPKNWPFL) and SURV20-28-GP (AGPKNWPFL) that were substituted at non-anchor positions and which both displayed higher binding affinity to H-2-Db. C57/Bl6 mice were inoculated subcutaneously with 100 µg of each peptide in combination with the adjuvants CpG and imiquimod. After four doses, blood samples were taken and intracellular cytokine staining (ICS) analysis was performed to detect IFN-γ and TNF-α producing CD8+ T cells following stimulation with the wild-type peptide SURV20-28. Peptide-specific CD8+ T cells were also analyzed by MHC-tetramer staining. Mice were thereafter challenged with a lethal dose of the syngeneic B16 melanoma cells and tumor growth was evaluated twice weekly for a period of 80 days. ICS data showed that, after stimulation with the WT peptide, only low background levels of IFN-γ were detected in mice vaccinated with the WT peptide, the APL SURV-3P or in the control group (treated only with adjuvants), while approximately 1% of all CD8+ T cells specifically produced IFN-γ in mice immunized with SURV20-28-GP. Furthermore, the highest TNF-α responses were also observed in the mice groups treated with the APL SURV20-28-GP. Analysis with H-2Db/SURV20-28 tetramers confirmed that mice immunized with SURV20-28-GP responded with a significantly higher frequency of specific CD8+ T cells. After tumor challenge, mice were sacrificed upon becoming moribund or when the mean tumor diameter reached 10 mm, as permitted by the approved ethical protocol. In this case, 40% of mice vaccinated with either SURV20-28-3P or SURV20-28-GP remained tumor-free during the entire period of the experiment, while all the animals immunized with the wild type SURV20-28 peptide succumbed to tumor development by day 30, at a similar rate than the control group treated only with the two adjuvants. In conclusion, these results suggest that the use of altered survivin peptides, modified at non-anchor positions, can contribute to increased antitumor responses and protect from tumor challenge in a mouse melanoma tumor model. Citation Format: Yago Pico de Coaña, Adil Doganay Duru, Alvaro Lladser, Adnane Achour, Rolf Kiessling. Analysis of immune responses and tumor protection in C57/Bl6 mice immunized with altered CD8 survivin peptide ligands. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B41.