Bio-Engineering Vaccinia Viruses for Increased Oncolytic Potential

Abstract

Vaccinia virus has a large and still incompletely understood genome although several strains of this virus are already in clinical development. For the most part, clinical candidates have been attenuated from their wild type vaccine strains through deletion of metabolic genes like the viral thymidine kinase gene.In the present work, we thoroughly examined the genetic elements of vaccinia which could be modulated to tailor the virus as a cancer therapeutic. Using a variety of cancer cell lines and primary tumor explants, we performed a fitness assay that directly compares multiple wild-type Vaccinia strains to identify the genetic elements that together create an optimal “oncolytic engine”. Using a transposon insertion strategy and deep sequencing of viral populations we systematically examined Vaccinia genes that do or do not play a role in the therapeutic activity of the virus. Our studies allowed us to identify a variety of genes in the vaccinia genome that when deleted, augment the oncolytic activity of a newly engineered Vaccinia virus. In the context of this thesis, I define enhanced oncolytic activity as superior therapeutic activity, increased immunogenicity and an improved safety profile, all aspects which we used to compare this novel virus to Vaccinia viruses currently in the clinic.