The Importance of the Macrophage in Oncolytic Adenovirus Therapy

For many patients standard chemo- and/or radio-therapy treatments for cancer are not curative and are associated with significant side-effects. Using viruses to treat cancer is an example of the newer biological therapies being developed. Viruses can be modified to multiply in cancer cells at much higher rates than in healthy cells, producing a wave of infection that spreads through solid tumour deposits and destroys them (a process called oncolysis). To date there have been around 30 clinical trials using oncolytic adenoviruses in patients with cancer. While the side effects even with large doses of virus are fairly mild, the success rates have been variable. One of the limitations to viral therapy is the patient‘s immune system that quickly recognises the virus as foreign and starts to remove it from the tumour before it has had a chance to cause significant tumour-cell death. The project that I propose to undertake is to investigate the interactions between the host immune system and the oncolytic adenovirus. The ultimate aim is to develop a way of modifying the patient‘s immune response to minimise its detrimental effect on the virus thus enhancing the virus anti-tumour potency.

Background: Oncolytic adenoviral therapy exploits the inherent ability of replicating viruses to destroy their host cell as part of the lytic life cycle, which is targeted to tumour cells by complementary mutations and/or selective transcription. One of the limitations to viral therapy is the host immune system that acts to clear the virus quickly, recognising it as foreign. The purpose of this project is to investigate the role of the innate immune system, in particular the macrophage, in oncolytic adenoviral therapy.
Aims: Determine the effect of the macrophage on viral replication; identify the molecular factors that enable macrophages to clear adenoviruses from the body;
identify the molecular ways by which the virus E3B gene deletion increases macrophage infiltration; and, develop a new strategy to modulate macrophage activity and enhance anti-tumour potency of oncolytic adenovirus in vivo.
Methodology: A cell-killing assay will be used to determine the infectability of macrophage by adenovirus. Serial dilution replication assays will measure the ability of an adenovirus to replicate within a macrophage. Western blotting will be used to measure expression of early and late viral proteins within the macrophage. Macrophage function studies will determine the roles of phagocytosis and NO production. A chemotaxis assay will be used to analyse the effect of cytokines/chemokines, secreted by macrophages, on other macrophages. Macrophage cytokine and chemokine gene expression profiles will be assessed using micro-fluidic array cards. The gene expression data will be used to design an in vivo study. The aim of this is to attenuate macrophage function by selectively blocking cytokine or chemokine function to improve oncolytic virus persistence within a tumour, and hence, anti-tumour potency.
Scientific/Medical Opportunity: The scientific opportunities of this project include the ability to dissect in detail the host immune response to adenoviral therapy. The medical opportunities include the potential to improve the anti-tumour potency of oncolytic adenovirus therapy. The project is also likely to provide greater insight into the interaction between the immune system and the tumour environment.