The common cold sore virus has been enlisted in the war against cancer and it proved effective in fighting brain tumors in preclinical studies, reported scientists at The University of Texas Health Science Center at Houston (UTHealth) in the journal Nature Communications.

According to published research cited in the report, more than 138,000 people in the US have malignant brain tumors and treatment options are limited. Most people diagnosed with a malignant brain tumor do not survive beyond two years.

“We’ve developed a way to boost the body’s anti-cancer immunity utilizing a modified version of the herpes virus known to cause cold sores,” said Balveen Kaur, PhD, the study’s senior author and professor and vice chair of research in the Vivian L. Smith Department of Neurosurgery at McGovern Medical School at UTHealth.

Brain cancer is difficult to treat because it has ways to disarm the body’s natural defenses. To counteract that, Kaur’s team engineered a virus to express a gene that activates cancer-killing T-cells. This gene is frequently absent or mutated in tumors and its reconstitution enhances anti-cancer immunity.

The researchers tested their modified virus in a mouse model of brain cancer and reported a cure rate of approximately 40%. The virus also imparted a protective immunity against a subsequent tumor challenge.

Therapeutic viruses can destroy cancer without affecting normal tissue. A therapeutic virus has already been approved for use in patients with skin cancer. Arming these viruses with genes has the potential to enhance therapy, Kaur said.

In this case, the investigators engineered the herpes virus to express a gene–PTEN–that triggers the body’s immune response.

The authors reported, “Harnessing viruses as vehicles for gene transfer payloads to boost their anti-tumor efficacy is one way to improve the therapeutic index. Here we sought to boost both the anti-cancer and immune stimulating properties of an oncolytic (engineered herpes) virus through the addition of tumor suppressor gene PTEN.”

Kaur said additional safety testing in animal models will be needed before this therapy can reach patients.