A virus engineering innovation promises to revolutionize cancer treatment

Taha Azad, professor and researcher at the Université de Sherbrooke Cancer Research Institute (IRCUS) and the Department of Microbiology and Infectiology in the Faculty of Medicine and Health Sciences at the Université de Sherbrooke. Next to him is Mahsa Ahmadi, his doctoral student in microbiology and co-author of the article, who purified many viruses, oversaw the preclinical studies, and contributed to writing the article.
Photo : Mathieu Lanthier - UdeS

An innovative virus engineering strategy has accelerated the development of the most comprehensive library of oncolytic viruses armed to fight treatment-resistant cancers. Published in the prestigious journal Nature Biomedical Engineering, this technological breakthrough was achieved by the team of Taha Azad, a professor and researcher at the Université de Sherbrooke Cancer Research Institute (IRCUS). Proof of its strong potential for innovation in oncology, the tools developed have enabled the validation, in record time, of a new curative strategy for cancers that might recur after being treated with an armed oncolytic virus.

Oncolytic immunotherapy is a burgeoning therapeutic strategy that involves administering oncolytic viruses. These viruses, which can infect and destroy (lyse) cancer cells, are known for their ability to promote a long-lasting antitumour immune response. Over the past 20 years, scientists have focused on genetically optimizing them into powerful "Mobile Pharmacies" that can overcome treatment resistance.

"Mobile Pharmacies"

Oncolytic viruses can be transformed into "Mobile Pharmacies" by inserting new genes into their genome, called transgenes, to directly deliver into the tumour the therapeutic proteins (weapons) needed to destroy cancer cells. These oncolytic viruses can even be armed to simultaneously produce the immunotherapy treatment and the required weapons to correct the immunosuppressive nature of the tumour microenvironment, such as cytokines, to enhance response to the delivered treatment.

Although this is an attractive idea, engineering such viruses has proven to be more difficult than simply "copying and pasting" genes into their genome. The complexity of many viral genomes and the laborious nature of conventional virus engineering methods have hindered the development of therapeutic oncolytic viruses.

Taha Azad, with (from left to right): Zumama Khalid (PhD student), Abril Ixchel Munoz Zuniga (MSc student), Nika Kooshki Zamani (PhD student) and Mahsa Ahmadi (PhD student), co-authors of the article and IRCUS students in the Microbiology Program at the Faculty of Medicine and Health Sciences. They played a crucial role in performing the tumour immune profiling, cell experiments, and statistical analyses and in the writing the article.
Photo : Mathieu Lanthier - UdeS

Antibiotics to the Rescue

The innovative strategy developed by Taha Azad and his team has reduced the time to engineer oncolytic viruses from months to less than a week. It involves, among other things, the use of a system more robust than CRISPR-Cas9 for inserting transgenes, called "Sleeping Beauty", as well as an iterative strategy that exploits the preferential susceptibility of the viruses used to certain antibiotics.

This strategy has proven to be up to 80 times more effective in selecting oncolytic viruses modified by the insertion of large transgenes, a requirement to transform them into "Mobile Pharmacies". Moreover, out of the 20,000 potential sites for transgene insertion, the team demonstrated that only 135 of them do not affect the ability of oncolytic viruses to multiply in cancer cells and should therefore be used to create "Mobile Pharmacies".

An Armed Library to Propel Oncolytic Immunotherapy

With their new strategy, the team was able to create the most comprehensive library of armed oncolytic viruses (40 in total) in record time while simultaneously validating the viruses' therapeutic efficacy.

Transgenes from 20 different cytokines, which were selected for their ability to modulate the antitumour immune response, were inserted into the genome of two different oncolytic viruses: the vaccinia virus and the herpes simplex virus-1. These DNA viruses were selected, among other reasons, for their ability to support the insertion of large transgenes, an essential characteristic of "Mobile Pharmacies".

Using this library of armed oncolytic viruses, Taha Azad's team quickly identified the cytokines that can enhance the in-vivo therapeutic efficacy of oncolytic viruses in two preclinical models of different cancers: melanoma and colon cancer.

Five (5) cytokines armed in the vaccinia virus produced a complete response for colon cancer. However, the cytokine interleukin-12 (IL12) stood out as one of the best therapeutic proteins to arm both types of oncolytic viruses studied, as it induced a complete response for both tested cancers.

Reattacking Differently to Outsmart the Immune System

A major challenge arose when Taha Azad and his team discovered that arming oncolytic viruses with IL12 stimulates a protective mechanism known to be problematic for oncolytic immunotherapy in cases of recurrence. When an oncolytic virus is administered, it triggers the immune system to recognize and eliminate it. Consequently, if the cancer recurs, administering the same oncolytic virus will be doomed to fail.

To overcome this major problem, the team tested a new therapeutic strategy in their preclinical melanoma model. The innovative strategy involves, among other things, administering a second oncolytic virus (the vaccinia virus) armed with the same cytokine (IL12) but immunologically different from the first administered oncolytic virus (the herpes simplex virus-1). Remarkably, Taha Azad's strategy led to a complete response in all animals: the treatment eliminated all traces of cancer in 100% of the treated animals.

Taha Azad with the remainder of his student team, co-authors of the article, Zahra Ameli (MSc student) and Gabriel St-Laurent (PhD student), who helped purify and characterize the new cytokine-armed viruses.
Photo : Mathieu Lanthier - UdeS

A new generation of students trained by an expert in synthetic biology

The start of Taha Azad's tenure at the IRCUS after his recruitment by the Department of Microbiology and Infectiology in the Faculty of Medicine and Health Sciences at the Université de Sherbrooke has propelled cancer research into the field of synthetic biology at the Institute. An expert in this emerging field, Taha Azad uses his extensive knowledge of synthetic biology to simplify and accelerate the engineering of innovative oncolytic viruses. Since his arrival in June 2022, he took on the major challenge of recruiting six master's and doctoral students for his brand-new laboratory.

In addition to receiving cutting-edge training in synthetic biology, these students have benefited from Taha Azad's research excellence which enabled them to contribute to a major publication in a prestigious scientific journal.

About Taha Azad
- Research Professor, Department of Microbiology and Infectiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke.
- Research Professor, Université de Sherbrooke Cancer Research Institute (IRCUS)
- Researcher, Centre de recherche du CHUS (CRCHUS)