Innovative Strategies for Enhancing Oncolytic Virus Therapy: From Delivery to Selective Translational Regulation

Abstract

Oncolytic viruses (OVs) are emerging as a promising therapeutic approach with the ability to achieve direct tumour cell death and the induction of antitumour immunity. Nevertheless, their clinical application is hampered by several obstacles, including inefficient delivery to solid tumours and the complex antiviral environment within infected cells that restricts protein production. This thesis focuses on these issues by investigating both the physical delivery of OVs and the translational mechanisms that govern gene expression during viral infection. First, we showed that needle-free injection (NFI) is a feasible and efficient technique for intratumoural injection of OVs, which enhances the distribution of viruses in tumours more efficiently than needle injection, without the loss of infectivity or therapeutic action. These results underscore the need to maximize delivery systems to promote viral propagation in solid tumours. Second, we examined how the antiviral state impacts transgene expression from OVs. Using an oncolytic herpes simplex virus-1 (HSV-1) platform, we showed that standard transgene mRNAs are inefficiently translated during infection. By incorporating a viral 5′ leader sequence into the transgene cassette, we significantly enhanced protein production and improved antitumour efficacy in vivo, demonstrating that adaptation to the host translational environment is critical for maximizing therapeutic output. Finally, using RNA sequencing and ribosome profiling, we characterized the translational landscape of glioblastoma cells during infection with the oncolytic Maraba virus MG1. Despite global suppression of protein synthesis, a subset of host mRNAs exhibited increased translational efficiency independent of transcript abundance, revealing a marked uncoupling between transcription and translation. We identified a purine-rich cis-regulatory element within the 5′ untranslated regions of some of the transcripts that promotes selective translation under antiviral stress conditions. Functional studies demonstrate that this R-motif enhances translation and regulates expression of genes such as GLDC, which acts as a host restriction factor limiting viral spread. Collectively, this work establishes translation as a critical regulatory layer shaping the outcome of oncolytic virotherapy. By integrating delivery optimization with mechanistic insights into translational control, this thesis provides a framework for improving OV design through both enhanced tumour targeting and sustained protein expression in the antiviral environment. These findings have broad implications for the development of more effective oncolytic viruses and other gene-based therapeutic platforms.