Human papilloma virus (HPV), the culprit behind cervical cancer and some forms of head and neck cancer, may lurk in small pockets on the surface of tonsils in people not known to carry the virus, new research suggests.
The finding could be pivotal for preventing oropharyngeal cancers that form on the tonsils and tongue.
By mid-adulthood, most people have been exposed to HPV. The same strains that cause cervical cancer (mainly HPV 16 and 18) cause head and neck cancers.
While there are verified tests that detect the virus in people before they develop cervical cancer, the same is not true for HPV-related head and neck cancers, which are expected to outnumber cervical cancer cases by 2020.
Only about five percent of infected people will develop cancer of the mouth or throat, suggesting most people’s immune systems can easily hold back infections.
Which begs the question, why doesn’t the immune system protect the five percent who develop cancer?
The answer may lie in biofilms—thin, slimy sheets of bacteria, says Matthew Miller, associate professor of otolaryngology and neurosurgery at the University of Rochester Medical Center.
He and colleagues found HPV encased in biofilms inside pockets on the tonsil surface, called tonsil crypts, which is where HPV-related head and neck cancers often originate.
As reported in the Journal of the American Medical Association, Miller and Katherine Reith, coauthor and an otolaryngology resident, studied tissue samples from 102 patients who had elective tonsillectomies. Five of those samples contained HPV and four contained high risk strains, HPV 16 and 18. In every case, HPV was found in tonsil crypts biofilms.
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The researchers believe the virus is shed from the tonsil during an active infection and gets trapped in the biofilm, where it may be protected from immune attack. In the crypts, the virus likely lays in wait for an opportunity to reinstate infection or invade the tonsil tissue to develop cancer.
“Given the lack of universal HPV immunization and the potential for the virus to evade the immune system even in individuals with detectable HPV in their blood, our findings could have far-reaching implications for identifying people at risk of developing HPV-related head and neck cancers and ultimately preventing them,” Miller says.
The team next plans to investigate potential screening tools, such as an oral rinse, to detect the virus in the mouth and throat—and then develop topical antimicrobials that would disrupt the biofilm and allow the immune system to clear the virus.
While scientists still do not know if HPV vaccines reduce head and neck cancer, Miller recommends all young boys and girls receive a full course of the vaccinations. He hopes that better oral HPV screening tools will help determine the impact of the vaccine on these cancers.
Source: University of Rochester
