It has been known for a while that long-term infection with HPV, especially with high-risk strains, may increase a woman's chance of developing cervical cancer, the second most common female-specific cancer after breast cancer worldwide. In addition to HPV infection, there are other factors that confer risk to the disease. The imbalance of bacteria in the vagina is one such risk factor, according to a study titled "Linking cervicovaginal immune signatures, HPV and microbiota composition in cervical carcinogenesis in non-Hispanic and Hispanic women," appearing online in the journal Scientific Reports.
The study, carried out by a 7-member team consisting of researchers from the University of Arizona, Maricopa Integrated Health Systems, Dignity Health St. Joseph's Hospital and Medical Center, and College of Medicine-Phoenix, reveals that "unique immune and microbial signatures in the local microenvironment associated with cervical carcinogenesis.”
HPV infection is extremely common in individuals who are sexually active. The good news is that the body's immune system is often effective at eliminating the viruses. In most cases, HPV infections occur without any symptoms, go away within a short time (such as 1-2 months), and do not trigger cancer. However, in some cases, they persist for years and eventually cause cervical cancer. Almost all cervical cancers are associated with HPV infection. It's unknown why some persons get rid of the viruses whereas others fail to do so.
In the new study, the team set out to determine the relationships between HPV, vaginal pH, vaginal microbiota composition, level of genital immune mediators and severity of cervical neoplasm. Their study enrolled 100 premenopausal women, who were divided into five groups on the basis of HPV infection status and the severity of cervical abnormalities. The five groups were called HPV-negative controls, HPV-positive controls, low-grade dysplasia, high-grade dysplasia, and invasive cervical carcinoma.
The researchers identified differences in vaginal microbiota composition between participants who did not have cervical abnormalities with participants who had cervical abnormalities. Specifically, the dominance of the bacteria Lactobacillus, which are related to vaginal health, decreased with the severity of cervical neoplasm, and the potentially pathogenic bacteria Sneathia was enriched in all precancerous groups. Furthermore, the team discovered a number of pro-inflammatory cytokines, including IL-36γ
, that were significantly elevated in cervical carcinoma.
These results suggest that alterations in vaginal microbiota composition might contribute to the development of cervical cancer. The study provides insights into the connection between vaginal microbiota composition and cervical cancer. But it still remains unclear if Sneathia bacteria actively promote HPV infection/cancer formation. So more investigation into this relationship is required.