Mucin-Like Domain of Ebola Virus Glycoprotein Enhances Selective Oncolytic Actions against Brain Tumors

Given that the Ebola virus (EBOV) infects a wide array of organs and cells yet displays a relative lack of neurotropism, we asked whether a chimeric vesicular stomatitis virus (VSV) expressing the EBOV glycoprotein (GP) might selectively target brain tumors. The mucin-like domain (MLD) of the EBOV GP may enhance virus immune system evasion. Here, we compared chimeric VSVs in which EBOV GP replaces the VSV glycoprotein, thereby reducing the neurotoxicity associated with wild-type VSV. A chimeric VSV expressing the full-length EBOV GP (VSV-EBOV) containing the MLD was substantially more effective and safer than a parallel construct with an EBOV GP lacking the MLD (VSV-EBOVΔMLD). One-step growth, reverse transcription-quantitative PCR, and Western blotting assessments showed that VSV-EBOVΔMLD produced substantially more progeny faster than VSV-EBOV. Using immunodeficient SCID mice, we focused on targeting human brain tumors with these VSV-EBOVs. Similar to the findings of our previous study in which we used an attenuated VSV-EBOV with no MLD that expressed green fluorescent protein (GFP) (VSV-EBOVΔMLD-GFP), VSV-EBOVΔMLD without GFP targeted glioma but yielded only a modest extension of survival. In contrast, VSV-EBOV containing the MLD showed substantially better targeting and elimination of brain tumors after intravenous delivery and increased the survival of brain tumor-bearing mice. Despite the apparent destruction of most tumor cells by VSV-EBOVΔMLD, the virus remained active within the SCID mouse brain and showed widespread infection of normal brain cells. In contrast, VSV-EBOV eliminated the tumors and showed relatively little infection of normal brain cells. Parallel experiments with direct intracranial virus infection generated similar results. Neither VSV-EBOV nor VSV-EBOVΔMLD showed substantive infection of the brains of normal immunocompetent mice. IMPORTANCE The Ebola virus glycoprotein contains a mucin-like domain which may play a role in immune evasion. Chimeric vesicular stomatitis viruses with the EBOV glycoprotein substituted for the VSV glycoprotein show greater safety and efficacy in targeting brain tumors in immunodeficient mice when the MLD was expressed within the EBOV glycoprotein than when EBOV lacked the mucin-like domain.