The limited success that cancer vaccine therapies have in eliminating tumors in patients may be due to their formulation. These findings in a mouse model of melanoma, published this week in Nature Medicine, could have implications for vaccine therapy development in general.

Willem Overwijk and colleagues show that peptide antigens formulated in a water in oil emulsion to induce melanoma-specific immune responses sequester T cells at the site of injection in mice-instead of inducing their recruitment to the tumor site-leading to T cell dysfunction and eventually apoptosis. A peptide and adjuvant formulation that did not persist at the injection site for long periods of time showed superior ability to induce a functional antitumor T cell response. The results suggest that whereas some vaccine adjuvants impair the efficacy of vaccines, formulations that are more rapidly degraded may improve clinical results by preventing retention of T cells at the injection site and redirecting T cells to sites of disease.