Abstract
Malignant peripheral nerve sheath tumor (MPNST) is a rare, aggressive soft-tissue sarcoma with a poor prognosis and is insensitive to immune checkpoint blockade (ICB) therapy. Loss-of-function of the histone modifying polycomb repressive complex 2 (PRC2) components, EED or SUZ12, is one of the main mechanisms of malignant transformation. In a murine model of MPNST, PRC2-loss tumors have an "immune desert" phenotype and intratumoral (IT) delivery immunogenic modified vaccinia virus Ankara (MVA) sensitized the PRC2-loss tumors to ICB. Here we show that IT MQ833, a second-generation recombinant modified vaccinia virus Ankara virus, results in neutrophil recruitment and activation and neutrophil-dependent tumor killing in the MPNST model. MQ833 was engineered by deleting three viral immune evasion genes, E5R, E3L, and WR199, and expressing three transgenes, including the two membrane-bound Flt3L and OX40L, and IL-12 with an extracellular matrix anchoring signal. Furthermore, we explored strategies to enhance anti-tumor effects of MQ833 by co-administration of granulocyte colony-stimulating factor (G-CSF).