Persistent infection with high-risk (HR) human papilloma virus (HPV) is a necessary condition for cervical cancer (CC) development. Recently, several scientific reports indicated the role of vaginal microbiota in the acquisition and persistence of HPV and subsequent development of CC (1). In order to identify metagenomic markers predictive of HR-HPV persistence, we characterized the vaginal microbiota from women screened for HR-HPV comparing microbiota profiles to HR-HPV status (clearance or persistence), after one year follow-up.
Seventy cervico-vaginal HPV –HR positive samples were obtained from a biobank collected within HPV DNA based primary screening program (ISPO, Florence, Italy). The absence of cervical grade lesions was ascertained by colposcopy. Follow-up results after one year from the first sampling were used to further divide the group of HR-HPV+ donors in (i) Clearance: HR-HPV+, including n=27 samples from patients with no evidence of HR- HPV DNA after one year; (ii) Persitence: including n=28 HR-HPV+ samples from patients that maintained the expression of HR-HPV-DNA in the cervico-vaginal environment after one year from the first screening. Pyrosequencing of V3-V5 region of 16S-rDNA gene was performed on bacterial genomic DNA purified from cervicovaginal samples and was used to characterize microbiota and to define community state types (CSTs) in each sample ., Enriched taxa were identified by Linear discriminant analysis effect size (LEfSe). Expression of Gardnerella vaginalis sialidase gene was studied by PCR.
Metataxonomic analysis showed differential microbiota profiles between HPV- and HPV+; an increased biodiversity was revealed in the group of persistence compared to the group of clearance and to the control group. A CST IV subgroup, dominated by selected anaerobic genera (Gardnerella, Prevotella, Megasphoera, Atopobium), frequently associated with bacterial vaginosis (BV), was present in 43% of women in the group of persistence and in only 7% of patients in the group of Clearance. Samples from patients developing persistent HPV infection showed significant enrichment in Atopobium, as well as a high frequency of Gardnerella strains producing sialidase.
The observed differential cervico-vaginal microbiota profiles in women with HPV infection suggest important insight on the role of bacterial vaginal microbiota in HPV infection. We propose the CST IV (BV) subgroup as a risk factor for the persistence of HPV infection and Atopobium as microbial markers of viral persistence.
1. Mitra A, MacIntyre DA, Marchesi JR, Lee YS, Bennett PR, Kyrgiou M. The vaginal microbiota, human papillomavirus infection and cervical intraepithelial neoplasia: what do we know and where are we going next? Microbiome 2016, 4(1):58.