Introduction
Researchers have been interested in utilizing viruses to treat cancer for over a century, and in recent years, a growing number of patients have started to show results from this approach.
Certain viruses often infect and destroy tumor cells. This group of viruses, referred to as oncolytic viruses, consists of both naturally occurring viruses and viruses that have been altered in a lab to multiply effectively in cancer cells without harming healthy cells.
Clinical trials are evaluating several viruses as possible cancer therapies. Still, the Food and Drug Administration (FDA) has only licensed one oncolytic virus (a genetically engineered herpes virus used to treat melanoma). It has long been believed that oncolytic viruses may destroy cancer cells directly. However, a growing quantity of evidence indicates that certain oncolytic viruses could function, at least partially, by inducing an immune reaction within the body to combat the cancer. Once a tumor cell is infected, the virus multiplies until the cell explodes. Tumor antigens, for example, are released by dying cancer cells and enable the immune system to identify the malignancy.
According to research, oncolytic viruses warn the immune system that something is incorrect. This may trigger an immune reaction directed either at tumor cells in the immediate vicinity (local response) or at tumor cells in distant body regions (systemic response). Because of this, some scientists view oncolytic viruses as a type of immunotherapy or medical intervention that employs the body's immune system to fight cancer. Nonetheless, a lot of specialists in this field agree that further research is necessary to understand how various oncolytic viruses combat cancer.
What Is Oncolytic Viral Therapy?
Viruses are microscopic particles that infiltrate or infect human cells. Once inside, they take advantage of the genetic machinery to replicate, spreading to neighboring uninfected cells. Certain viruses, such as the human papillomavirus (HPV) in cervical cancer and head and neck cancer and the hepatitis B virus (HBV) in liver cancer, have been linked to the development of certain malignancies. (In the case of hepatitis and HPV, cancer vaccines, a different kind of immunotherapy, have demonstrated the capacity to fight off infection and shield against the development of these malignancies linked to HBV and HPV.
Viruses have lately been employed to target and destroy pre-existing cancers. These viruses, some but not all of which have undergone modification, are referred to as oncolytic viruses and provide a promising therapeutic option for cancer for several reasons:
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Cancer cells are more prone to infection because they frequently have compromised antiviral defenses.
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These naturally occurring viruses can be modified to have beneficial traits, such as a reduced capacity to infect healthy cells, target tumors with therapeutic payloads, and release immune-stimulating compounds once they have infected tumor cells.
These oncolytic viruses can infect cancer cells and induce them to "burst," releasing cancer antigens while also destroying the cancer cells. The immune systems that these antigens trigger may then search for and destroy any residual tumor cells in the area and maybe elsewhere in the body.
In 2015, the Food and Drug Administration (FDA) in the United States authorized Talimogene laherparepvec (T-VEC), the first oncolytic viral immunotherapy, for the treatment of melanoma. A herpes virus that has been modified to reduce its probability of infecting healthy cells and increase the production of the immune-stimulating Granulocyte-macrophage colony-stimulating factor (GM-CSF) protein by infected cancer cells is used in this treatment.
What Is the First FDA-Approved Oncolytic Virus Therapy?
Talimogene laherparepvec, or T-VEC, is a melanoma therapy that was the first oncolytic virus to be approved by the FDA. The therapy, which is injected into tumors, is designed to generate a protein that lowers the risk of herpes and increases the body's generation of immune cells.
According to Howard Kaufman of the Rutgers Cancer Institute in New Jersey, some patients undergoing the therapy have seen a shrinkage of tumors that were not injectable, indicating that T-VEC may elicit a systemic immune response.
Dr. Kaufman, who co-led the clinical trial that resulted in T-VEC's approval, stated that the oncolytic virus destroys tumor cells and releases danger signals that aid in inducing an immune response.
How Does Oncolytic Virus Therapy Interact With the Immune System?
Viruses employ different biological strategies to destroy tumors depending on the tissue or cell they are targeting, the virus itself, and the targeted biochemical pathways. While some viruses function by controlling the immune system locally or systemically, certain viruses primarily attack tumor cells. There is certainly a significant immunological component to the response, especially in cases of direct oncolytic therapy. T-VEC is usually well tolerated by patients in clinical studies, whether it is administered alone or in conjunction with other therapies.
What Are the Side Effects of Oncolytic Viral Therapy?
The type of oncolytic virus and the particular tumors it targets can have side effects, which can also be affected by the patient's general health, location and type of cancer, and other factors. Oncolytic viruses can infect healthy cells and increase immune system activity, occasionally leading to the immune system attacking healthy cells. As a result, using these carries a risk of infection. Patients need to understand the possible risks and side effects associated with certain oncolytic viruses by consulting with their doctors and the rest of their medical team. Among the often reported adverse effects of the oncolytic virus that is now approved include chills, exhaustion, flu-like symptoms, injection site pain, nausea, and fever.
What Do Oncolytic Virus Clinical Trial Platforms Include?
Clinical trials are evaluating the following oncolytic viral platforms:
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Adenoviruses are a prevalent family of viruses that can produce a variety of moderate side effects, such as exhaustion, sore throats, and cold-like symptoms.
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The herpes simplex virus is a type of virus that can lead to oral sores.
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The Maraba virus is a virus that is only present in insects.
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Measles is caused by a highly infectious virus that affects the respiratory system.
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Newcastle disease virus is mostly prevalent in birds; this virus can give people symptoms similar to the flu and mild conjunctivitis.
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Picornaviruses are a family of viruses that may infect mammals and birds and cause a variety of illnesses; one member of this family that is undergoing clinical testing is the coxsackie virus.
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Reoviruses are a family of viruses that may infect a variety of animal species' respiratory and digestive systems.
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The vaccine virus is a virus that was used to help prevent and eradicate smallpox; it seldom infects people and is linked to a rash that covers the body.
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Vesicular stomatitis virus is a member of the Maraba virus family that can give people flu-like symptoms.
Conclusion
Oncolytic viral therapy is a promising new therapeutic modality for cancer. Oncolytic viruses provide a novel treatment approach by selectively destroying cancer cells and inducing an immune response. Positive outcomes from clinical trials have proved the treatment's safety and effectiveness in treating different kinds of cancer. Even while obstacles like immune recognition and delivery techniques still exist, these are being addressed by continuing research and developments in genetic engineering. With further development and incorporation into established cancer treatment procedures, oncolytic viral therapy has the potential to greatly enhance patient outcomes and transform the present scenario of cancer care.
