Open Access

Joshua D. Bernstock, Nunzio Vicario, Li Rong, Pablo A. Valdes, Bryan D. Choi, Jason A. Chen, Daniel DiToro, Diana S. Osorio, Kara Kachurak, Florian Geßler, James M. Johnston, T. Prescott Atkinson, Richard J. Whitley, Asim K. Bag, G. Yancey Gillespie, James M. Markert, Dragan Maric, Gregory K. Friedman

• Immunotherapy with oncolytic herpes simplex virus-1 therapy offers an innovative, targeted, less-toxic approach for treating brain tumors. However, a major obstacle in maximizing oncolytic virotherapy is a lack of comprehensive understanding of the underlying mechanisms that unfold in CNS tumors/associated microenvironments after infusion of virus. We demonstrate that our multiplex biomarker screening platform comprehensively informs changes in both topographical location and functional states of resident/infiltrating immune cells that play a role in neuropathology after treatment with HSV G207 in a pediatric Phase 1 patient. Using this approach, we identified robust infiltration of CD8+ T cells suggesting activation of the immune response following virotherapy; however there was a corresponding upregulation of checkpoint proteins PD-1, PD-L1, CTLA-4, and IDO revealing a potential role for checkpoint inhibitors. Such work may ultimately lead to an understanding of the governing pathobiology of tumors, thereby fostering development of novel therapeutics tailored to produce optimal responses.