Abstract
Common vaccines for infectious diseases have been repurposed as cancer immunotherapies. The intratumoral administration of these repurposed vaccines can induce immune cell infiltration into the treated tumor. Here, we have used an approved trivalent live attenuated measles, mumps, and rubella (MMR) vaccine in our previously developed PeptiENV cancer vaccine platform. The intratumoral administration of this novel MMR-containing PeptiENV cancer vaccine significantly increased both intratumoral as well as systemic tumor-specific T cell responses. In addition, PeptiENV therapy, in combination with immune checkpoint inhibitor therapy, improved tumor growth control and survival as well as increased the number of mice responsive to immune checkpoint inhibitor therapy. Importantly, mice pre-vaccinated with the MMR vaccine responded equally well, if not better, to the PeptiENV therapy, indicating that pre-existing immunity against the MMR vaccine viruses does not compromise the use of this novel cancer vaccine platform.