A recent study has found that a weakened virus could help eliminate cancer in mice. In addition, mice treated with this virus were more resistant to developing tumors later in life.
The study was conducted by researchers from Northwestern University Feinberg School of Medicine in the United States of America, and was published on June 11 in the Journal of Clinical Investigation, and the EurekAlert website wrote about it.
In this study, the researchers used attenuated lymphocytic choriomeningitis virus (LCMV), which is safe even in mice with compromised immunity. This is a very important discovery, as many cancer patients who undergo chemotherapy and other cancer treatments have weak immunity.
Northwestern scientists showed in multiple tumor models — including melanoma and colon cancer — that injecting tumor-bearing mice with this virus resulted in tumor shrinkage and increased survival.
One of the important aspects of this viral treatment is that it shows safety and efficacy even in A body that suffers from weak immunity. She adds that mice that were devoid of killer T cells and B cells (immune cells) were responding to this treatment.
Penaloza-McMaster explained that the lymphocytic choriomeningitis virus generated a high immune response, but it can cause disease, especially in organ transplant patients (they are given medications that suppress the immune system so that the body does not reject the new transplanted organ, so their immunity is weak).
She adds that, however, using molecular biology it is possible to weaken this virus and make it attenuated for use as a safe treatment, while maintaining its ability to generate immunity. The other advantage is that it appears to be able to be used for different types of cancer.
Currently, so-called “oncolytic viruses” are used, which are viruses that target cancer cells and kill them selectively while sparing normal cells, such as the herpes simplex virus, but Penaloza-McMaster said that these treatments are not effective for some tumors. Their use poses safety concerns, especially in immunocompromised patients, which underscores the need for safer alternatives.
How does the virus treat cancer?
Tumors are skilled at evading the immune response by developing strategies to keep the immune system away from the tumor. Injecting the virus into the tumor causes the virus to raise what look like red flags on the tumor to alert the immune system of the presence of an intruder.
The immunosuppressed mice had no T cells, B cells, or macrophages (major immune cells). Despite the absence of these important immune cells, the virus was able to activate alternative immune pathways to fight cancer. One way this was accomplished was through interferons, molecules that signal the presence of an intruder and help mobilize the body’s defense mechanisms.
Preventing cancer in the future
In addition to helping remove tumors, the treatment also helped prevent future cancer in these mice. Healthy mice first treated with lymphocytic choriomeningitis virus therapy were more resistant to developing tumors later in life.
This phenomenon can be explained by a poorly understood biological process known as “trained immunity.” Trained immunity occurs when a previous infection enhances the immune system’s ability to respond to various diseases in the future.
For example, studies have shown that children who received the TB vaccine showed better protection against other microorganisms, not just TB. This is different from the typical vaccine response, such as with the SARS-CoV-2 vaccine, which primarily protects against that specific virus.
“Basically, this treatment may provide broader immune protection, helping the body protect against various diseases beyond the original target,” Penaloza-McMaster said.
The next step in this research is to test the approach in dogs with sarcomas (rare cancers that develop in bones and soft tissues, including fat, muscle, blood vessels, nerves, deep skin tissue and fibrous tissue). If dogs also show improvement, scientists hope to launch a clinical trial using the treatment in humans.