Introduction/Background Emerging evidence suggests associations between the vaginal microbiota (VMB) composition, HPV infection, and cervical intra-epithelial neoplasia (CIN), however, causal inference remains uncertain. The use of longitudinal cohorts can enable temporal assessment of the relationship between VMB and the natural history of CIN. We aimed to assess whether VMB composition associates with rates of progression, persistence or clearance in a cohort of young women with histologically confirmed untreated CIN2 lesions.

Methodology 16S rRNA was extracted and sequenced from serial collected liquid based cytology samples of young women with histologically-proven CIN2 that was managed conservatively in Northern California, USA over a 24-month period.

Results Of the 87 women in the cohort, 48.3% had regressed by 12 months (42/87), 72.4% (63/87) by 24 months. High-diversity, Lactobacillus spp. depleted, VMB composition at time of CIN2 diagnosis was associated with higher rates of disease persistence at 12 months, compared to those with Lactobacillus spp. dominance at baseline. Relative abundances of taxa including Megasphaera spp. (p=0.0004), Prevotella timonensis (p=0.015) and Gardnerella vaginalis (p=0.036) were higher in women with persistent disease at 12 months compared to those who regressed. A similar trend was seen by 24-month follow-up, but was not statistically significant. The rate of CIN2 regression was slower in women with Lactobacillus spp. depletion at baseline.

Conclusion Depletion of Lactobacillus spp. and presence of specific anaerobic taxa are associated with CIN2 persistence and slower regression. Further research on the impact of VMB on the natural history of CIN may help identify VMB compositions and specific taxa associated with increased risk of progression and thus offer rational targets for the development of new prevention and treatment strategies.

Disclosure Nothing to disclose.