The human papillomavirus (HPV) may hide in small pockets on the surface of tonsils in people who aren’t known to carry the virus, according to researchers at the University of Rochester Medical Center (URMC), which could be pivotal for the prevention of oropharyngeal cancers that form on the tonsils and tongue.
Most people are exposed to HPV by the time they reach mid-adulthood. The HPV-16 and HPV-18 strains cause cervical cancer as well as head and neck cancers. While verified tests exist to detect HPV 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 5% of HPV-infected people will develop cancer of the mouth or throat, the researchers report, suggesting that most people’s immune systems can easily hold back HPV infections. So, the researchers asked why the immune system doesn’t protect the 5% who do develop cancer.
The study found HPV encased in biofilms inside pockets on the tonsil surface known as tonsil crypts where HPV-related head and neck cancers often originate. The researchers studied tissue samples from 102 patients who had elective tonsillectomies. Five of those samples had HPV, and four had the high-risk HPV-16 and HPV-18 strains.
In every case, HPV was found in tonsil crypt biofilms. The researchers, then, believe HPV 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 waits for an opportunity to reinstate infection of 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,” said Matthew Miller, MD, an associate professor of otolaryngology and neurosurgery at URMC.
The researchers plan to investigate potential screening tools such as an oral rinse to detect HPV in the mouth and throat. The next step would be to develop topical antimicrobials that would disrupt the biofilm and allow the immune system to clear the virus. Also, the researchers hope that better HPV screening tools will help determine the impact of the HPV vaccine on the rates of these cancers.
The study, “Prevalence of High-Risk Human Papillomavirus in Tonsil Tissue in Healthy Adults and Colocalization in Biofilm of Tonsillar Crypts,” was published by the JAMA Otolaryngology-Head & Neck Surgery.