Impact of vaginal microbiota on HPV infections – Prof Anna-Lise Williamson
Prof Anna-Lise Williamson
- Faculty of Health Sciences, Institute of Infectious Disease and Molecular Medicine, University of Cape Town
- Email: Anna-Lise.Williamson@uct.ac.za
Title of the project
Investigation of the impact of the vaginal microbiota on human papillomavirus infections.
Worldwide cervical cancer is the second most common cancer in women and the leading cause of cancer mortality in South African women. The role of specific HPV types in the pathogenesis of cervical cancer and its precursors, and in other anogenital cancers has been well established. While past studies have linked HPV, HIV and studies on immunity and inflammation, no studies have been done on the impact of the total genital microbiota on HPV or immune responses. The bacterial microbiota of the female genital tract is known to protect the vagina from pathogens, and disruption of the healthy flora results in bacterial vaginosis (BV) which in turn can impact on reproductive health, including the acquisition of sexually transmitted diseases. Studies of the microbiome of the female genital tract have revealed that women without vaginal disease have a relatively restricted range of bacteria, dominated by Lactobacillus species compared with the oral cavity and the colon. The normal vaginal microbiome has evolved not to induce inflammation, probably due to the large quantities of fatty acids produced by the anaerobic bacteria. However, when BV develops, the range of bacterial species in the vagina changes to more complex combinations of largely anaerobic bacteria. It has been postulated that BV impacts negatively on the immune response in the female genital tract as well as making women more susceptible to sexually transmitted diseases. These conditions would make women more susceptible to HPV infection. Oestrogen level also plays a role in the type of microbiota present. There are no reported studies on the complex microbiota and its influence on HPV prevalence or natural history. The project involved sequencing of all the bacteria present in the genital tract. The sequence was then analysed to identify which bacteria are present.
The researchers have successfully characterized the genital bacterial populations (microbiota) of 149 South African women. They have shown that very few of the women have Lactobacillus dominated genital microbiotas. Lactobacilli are considered a “healthy” and protective vaginal microbiota. Most of the women had diverse genital bacterial populations. They were able to identify a few key bacterial types that were in significantly higher abundance in women infected with high risk human papillomavirus than in uninfected women. The precise role that these bacteria may play in infection should be the subject of future studies. The role of the microbiota in persistence of HPV infection, a central aspect in the development of cervical lesions and cancer, should be investigated.