Vaginal pH value can affect the susceptibility to human papillomavirus infection

Cervical cancer is the fourth most common cancer among women, with persistent high-risk human papillomavirus (HPV) infection being responsible for its progression. In healthy, pre-menopausal women, the vaginal pH value is maintained at 3.8-4.5, but various factors can affect it. Previous studies have suggested the relationship between vaginal pH value and HPV infection. In this study, we aimed to explore the relationship between vaginal pH and susceptibility of HPV infection.

In our study, we retrospectively collected medical information from women who underwent leukorrhea examination at our hospital. We excluded women with infectious diseases or cancer, those who were pregnant or within 6 months post-delivery, and those without HPV test results within 6 months. The association between percentage of HPV infection and vaginal pH value was analyzed. Furthermore, we prepared HPV pseudovirus (PsVs) by co-transfecting structure plasmids and report plasmids in 293FT cells. In vitro, we changed the pH value of cell culture medium to investigate its influence on HPV PsVs infection. In vivo, we changed mouse's vaginal pH value to investigate its influence on HPV PsVs infection.

Our retrospective study included 3115 women aged 20-78, including 2531 women with HPV negative and 584 women with HPV positive. The percentages of both HPV infection and high-risk HPV infection were higher in women with a vaginal pH value ≥5.0 compared to those with a pH value < 5.0. In vitro, HPV PsVs infection rate was higher in cell culture medium of higher pH value, dominantly due to the influence of pH value on the stage of HPV PsVs adhering to cell surface. Neither of the cell surface HPV receptors Syndecan-1 nor integrin α6 was found to be changed obviously in different pH values. In vivo, more HPV PsVs were adhered to the mouse's vaginal epithelial cells with the increase of the vaginal pH value.

Our study suggests a possible association between vaginal pH value and HPV infection. The pH value can influence the susceptibility of HPV PsVs infection by affecting the adhering of HPV PsVs to cells in vivo and in vitro. Additionally, the cell surface HPV receptors Syndecan-1 and Integrin α6 do not seem to be affected by pH value, and the specific mechanism needs to be further explored.