Zika Virus Oncolytic and Tumor Vaccine Adjuvant Immunotherapy Treatment of Murine Glioblastoma GL261

Abstract

Glioblastomas (GBMs) are highly aggressive brain tumors with a five-year survival rate of <5% upon diagnosis [1]. Current treatments have become routine, with little improvement in survival the last ten years which has opened the door for experimentation with oncolytic and immunotherapies. The Zika virus (ZIKV) is a relatively asymptomatic Flavivirus which infects and kills fetal neural stem cells (fNSCs) [45], neural progenitor cells (NPCs) [46], and induced pluripotent stem cell (iPSC) derived neurospheres [47] through apoptosis and autophagy. Current literature implicates Tyro3, Axl, TIM-1, and DC-SIGN as putative ZIKV entry receptors [51]. Here, an in vitro characterization of murine GBM cell line GL261 was carried out examining the presence of these putative receptors as well as their susceptibility to viral infection. The presence of Tyro3 and Axl RNA was confirmed by qRT-PCR and RNA-Seq although their role in ZIKV infection is still undetermined. GL261 cells were found to potentially become infected by ZIKV as shown by viral RNA presence in cells although a Plaque Forming Assay (PFA) was mostly negative indicating viral replication and cell death may not be occurring. After implanting GL261 tumors into mice and treating different groups with varying concentrations of ZIKV, it was found that ZIKV did not improve survival, potentially confirming the results found through the PFA. Treatment of tumor implanted mice with an irradiated tumor vaccine previously infected with ZIKV, GM-CSF, and ZIKV directly into the tumor site did dramatically improve overall survival. The working hypothesis of increased survival is that of a powerful immune response as shown by these effects disappearing after using SCID mice with no immune system. Confirmation is currently ongoing through additional experimentation.