New research conducted at the University of Otago, in New Zealand, found that the protein E7, expressed in the high risk human papilloma virus 16 (HPV16), appears to prevent the immune system from fighting the virus.
The study, “Suppression of the CD8 T cell response by human papillomavirus type 16 E7 occurs in Langerhans cell-depleted mice,” published in Scientific Reports, might be of great importance considering that HPV16 is a leading cause of cervical cancer.
Nearly 10 to 20 percent of women with an HPV infection fail to clear the virus from their bodies within two years, which puts them at much higher risk of developing cervical cancer. Usually, virus clearance is associated with an immune response from specific types of T-cells while persistence of viral infection is linked to the absence of an immune system response.
Associate professor Merilyn Hibma, the study’s lead author, acknowledged that the mechanisms involved in HPV16 proteins that silence the immune system are still largely debated, but new knowledge is providing better understanding.
“Our new findings show that E7, in the absence of other HPV16 proteins, is sufficient enough to cause a range of effects on specialized cells normally involved in priming the body’s T-cells to combat viral infection,” Hibma said in a press release.
The E7 protein has been shown to be required for maintaining malignant characteristics during cervical cancer progression. The new research shows that E7 expression depletes the immune cells that recruit and activate T-cell responses against HPV infection, which suggests that targeting E7 may improve the body’s ability to clear HPV infections.
“This knowledge also helps us to understand how cancer cells avoid being detected by the immune system as E7 is also produced by cervical cancer cells. From this we may be able to identify new ways to block cancer suppression of the immune response. This approach is similar to ‘checkpoint inhibitors’ such as Keytruda and Opdivo,” Hibma said.
About 500,000 women worldwide are diagnosed annually with cervical cancer. According to the National Institutes of Health (NIH), nearly all cases of cervical cancer are caused by specific types of HPV. Of more than 100 types of HPV, HPV-16 and HPV-18 cause about 70% of cervical cancers worldwide.