ABSTRACT
Glioblastoma is an extremely aggressive and difficult cancer to treat, which may partly be due to its limited ability to induce T-cell responses. However, combining viral vector vaccines with other therapies to generate tumor-specific T cells may provide a meaningful benefit to patients. Here, we investigated whether heterologous prime-boost vaccination with chimpanzee-derived adenoviral vector ChAdOx1 and modified vaccinia Ankara (MVA) vaccines could generate therapeutically effective CD8+ T-cell responses against a model antigen P1A, a mouse homolog of human tumorassociated Melanoma Antigen GenE (MAGE)-type antigens, expressed by a BGL-1 mouse glioblastoma cell line. We demonstrated that heterologous prime-boost vaccination with ChAdOx1/MVA vaccines targeting P1A generated a high magnitude of CD8+ T cells specific for the P1A35-43 epitope presented by the MHC class I molecule H-2Ld . Prophylactic vaccination with ChAdOx1/MVA-P1A significantly prolonged the survival of syngeneic mice subcutaneously challenged with P1A-expressing BGL-1 tumors. Furthermore, different vaccination schedules significantly impact the magnitude of antigen-specific CD8+ T-cell responses and may impact protective efficacy. However, the substantial induction of myeloid-derived suppressor cells (MDSCs) by this tumor model presents a significant challenge in the therapeutic setting. Future work will investigate the efficacy of this vaccination strategy on intracranial P1A-expressing BGL-1 models.