What Is Virotherapy?
Do you know some viruses can kill cancer, and scientists have known this for over a century. Now, researchers around the world work with these cancer-killing bugs in the hopes that cancer treatment will someday go viral, and this is where the name “Virotherapy” comes in. Then what is virotherapy?
Virotherapy is cancer treatment using a virus to find and destroy cancer cells without harming healthy cells. Types of virotherapy include oncolytic virotherapy, viral immunotherapy and viral vectors, which is also called viral gene therapy.
How the different types of virotherapy work:
Oncolytic virotherapy uses viruses to infect and destroy cancer cells without affecting normal cells. Viral immunotherapy uses a virus to deliver an immune-stimulating substance called an antigen to the immune system.
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Viral vectors are laboratory-modified viruses designed to alter cancer cell genes to treat the disease.
Early History of Virotherapy Discovery
Scientists began experimenting with this type of immunotherapy as early as the late 1800s, but over the next 100 years, the field fell in and out of fashion.
In the early 1900s, a surgeon named William Coley became famous for his attempts to fight cancer by exposing patients to extractions drawn from infected tissue. Coley became hooked on the concept after meeting a man whose malignant tumor withered in the face of a severe bacterial infection, according to a review in BMJ Postgraduate Medical Journal.
Coley began infecting his patients with a bacterial savior — the erysipelas virus — and later developed a vaccine from two modified bacteria.
“Coley’s toxins,” as the vaccine was called, became a popular treatment for many cancer types and worked by inducing fever, chills and inflammation in the patient. Numerous case studies supported the idea that infectious disease could send cancer into remission, or eliminate it completely, according to a review in the journal Molecular Therapy. But with the rise of radiotherapy, chemotherapy and other immunosuppressive treatments, emerging virotherapies like Coley’s toxins lost popularity.
Fortunately, Coley’s early work was not completely forgotten. It laid the foundation for the development of today’s immunotherapy and virotherapy cancer treatments.
In 1980s “Molecular virology came into play, and people discovered that certain viruses would replicate better in cancer cells than [in] their normal counterparts.” And when cells become cancerous, they gain dangerous features at the expense of beneficial features found in healthy cells. With the help of modern genetic engineering, researchers now strive to build the best oncolytic virus they can and then match the virus with its cancerous archnemesis.
Oncolytic Viruses health effect
In 2005, China’s State Food and Drug Administration — now known as the China Food and Drug Administration — put the first oncolytic virotherapy on the market. H101, commercially known as Oncorine, is a genetically modified virus that preferentially attacks tumor cells and is used to treat head and neck cancers.
Oncolytic viruses also have the potential to morph into “runaway viruses” — viruses that adapt after administration or recombine with human pathogens already present in a patient and begin ferociously infecting healthy tissue. Researchers remain on the lookout for these runaways, but so far, oncolytic viruses appear safe even in immunosuppressed patients and animal models, according to a 2014 review published in the journal Cell Host Microbe.
Also check: Effects Of Head And Neck Cancer
Oncolytic viruses infect cancer cells. Some viruses naturally infect cancer cells, while other viruses can be modified in the lab to target specific cancer cell types.
The viruses make their way into cancer cells and reproduce rapidly. The rapid viral reproduction ruptures the membranes of cancer cells and destroys them.
The destroyed cancer cells release antigens, which are substances more easily recognized as foreign by the body. This stimulates the immune system to attack remaining tumors, too. Oncolytic viruses seem to destroy tumors in two ways: Directly by rupturing cancer cell members and indirectly by stimulating the immune system to better recognize the cancer and attack it.
Viral Immunotherapy health effect
Viral immunotherapy uses a virus to deliver an immune-stimulating substance called an antigen into the body. The antigen helps the immune system recognize and attack cancer cells. A 2014 phase I clinical trial report published in the medical journal Oncoimmunology describes this type of virotherapy. Researchers evaluated the case of a 68-year-old man with asbestos-related malignant pleural mesothelioma (MPM).
When a response is better than expected, the doctors may publish a report detailing these results. In the ONCOS-102 clinical trial, the man survived 18 months from when treatment began and more than 33 months from diagnosis.
The study scientists reported the response as “remarkable,” given the median survival of patients with MPM varies from 4 to 12 months from diagnosis. Phase I studies test the safety, side effects, best dose and timing of a new treatment. The dose may be increased slowly to find the highest dose that does not cause harmful side effects.
Viral Vectors health effect
Viral vectors are created in the lab. Researchers start with a normal virus and alter it to create one that cannot cause disease. Viral vectors can kill the cancer cells directly or make them more sensitive to conventional treatments such as chemotherapy and radiation therapy.
This type of virotherapy is considered a form of gene therapy because the modified viruses alter genes in targeted cells. Targets can include cancer cells or other malfunctioning cells contributing to genetic diseases.
Some viral vectors target malfunctioning mesothelioma genes. One example of this approach uses a virus to disrupt how mesothelioma cells create the proteins that allow uncontrolled cell growth — a hallmark of all cancers.
In conclusion, more and more reports of promising virotherapy candidates have come out in recent years, according to an article published this year in the journal Nature Reviews Clinical Oncology.