Commensal, ‘low-risk’ strains of human papillomavirus (HPV) often found in human skin appear to exert an indirect, protective effect against the development of squamous cell carcinoma (SCC).
This is the conclusion of a paper by researchers from Massachusetts General Hospital in Boston, which was published in Nature (Oct. 30, 2019).
In a press release from the hospital, it is noted that patients with immune systems that are suppressed due to disease or medical therapy are at greatly increased risk for varieties of cancer that have been linked to viral infections, particularly squamous cell carcinoma (SCC) of the skin.
Senior author Dr. Shawn Demehri, an investigator in the hospital’s Center for Cancer Immunology, said in the release that while multiple studies have tried to show a link between HPV infections and SCC, none have been able to show that HPVs actually drive the development of these common skin cancers.
In their study, Dr. Demehri and his colleagues worked with experimental models and tissue samples from human skin cancer, and found that the presence of commensal papillomaviruses–low-risk forms of HPV that dwell on the skin of a large majority of people–appeared to have an indirect protective rather than harmful effects against SCC.
“This is the first evidence that commensal viruses could have beneficial health effects both in experimental models and also in humans, and it turns out that this beneficial effect has to do with cancer protection,” said Dr. Demehri. “The role of these commensal viruses, in this case papillomaviruses, is to induce immunity that then is protecting patients from skin cancers.”
Loss of immunity, rather than the cancer-causing effects of HPVs, are the primary driver of the more than 100-fold increase in skin cancer risk among individuals with suppressed immune systems, the researchers say. They note that their findings suggest a novel method for preventing skin cancer using a vaccine based on T cells, the essential immune-system cells that identify other cells as abnormal or foreign and mark them for destruction.
“T cell-based vaccines against commensal HPVs may provide an innovative approach to boost this antiviral immunity in the skin and help prevent warts and skin cancers in high-risk populations,” the researchers wrote.
They note that augmenting natural immunity against HPV immunity may further improve the effectiveness of immunotherapy against SCC using immune checkpoint inhibitors.