Background The cervicovaginal microbiome (CVM) plays a significant role in women’s cervical health and disease. Microbial alterations at the species level and characteristic community state types (CST) have been associated with acquisition and persistence of high-risk human papillomavirus (hrHPV) infections that may result in progression of cervical lesions to malignancy. Current sequencing methods, especially most commonly used multiplex 16S rRNA gene sequencing, struggle to fully clarify these changes because they generally fail to provide sufficient taxonomic resolution to adequately perform species-level associative studies. To improve CVM species designation, we designed a novel sequencing tool targeting microbes at the species taxonomic rank and examined its potential for profiling the CVM. Results We introduce an accessible and practical circular probe-based RNA sequencing (CiRNAseq) technology with the potential to profile and quantify the CVM. In vitro and in silico validations demonstrate that CiRNAseq can distinctively detect species in a mock mixed microbial environment, with the output data reflecting its ability to estimate microbes’ abundance. Moreover, compared to 16S rRNA gene sequencing, CiRNAseq provides equivalent results but with improved sequencing sensitivity. Analyses of a cohort of cervical smears from hrHPV-negative women versus hrHPV-positive women with high-grade cervical intraepithelial neoplasia confirmed known differences in CST occurring in the CVM of women with hrHPV-induced lesions. The technique also revealed variations in microbial diversity and abundance in the CVM of hrHPV-positive women when compared to hrHPV-negative women. Conclusions CiRNAseq is a promising tool for studying the interplay between the CVM and hrHPV in cervical carcinogenesis. This technology could provide a better understanding of cervicovaginal CST and microbial species during health and disease, prompting the discovery of biomarkers, additional to hrHPV, that can help detect high-grade cervical lesions.

The cervicovaginal microbiome (CVM) correlates with women’s cervical health, and variations in its composition are associated with high-risk human papillomavirus (hrHPV) infection outcomes. Cervicovaginal microbes have been grouped into five community state types (CSTs) based on microbial community composition and abundance. However, studying the impact of CSTs in health and disease is challenging because the current sequencing technologies have limited confident discrimination between closely related and yet functionally different bacterial species. Circular probe-based RNA sequencing (ciRNAseq) achieves high-resolution microbiome profiling and therefore provides in-depth and unambiguous knowledge about the composition of the CVM. Based on ciRNAseq profiling of a large cohort of cervical smears (n = 541), we here define subgroups of CSTs I, III, and IV based on intra-CST differences with respect to abundances of Lactobacillus acidophilus (CSTs I-A vs. I-B and CSTs III-A vs. III-B), Lactobacillus iners (CSTs I-A vs. I-B and CSTs III-A vs. III-B), and Megasphaera genomosp type 1 (CSTs IV-A vs. IV-B). Our results further support the existence of subgroups of CST IV-C that are dominant for non-Lactobacillus species and have intermediate microbial diversity. We also show that CST V is associated with uninfected conditions, and CST IV-A associates with hrHPV-induced cervical disease. In conclusion, we characterized new subdivisions of cervicovaginal CSTs, which may further advance our understanding of women’s cervical health and hrHPV-related progression to disease.

Cervical cancer is the third leading cause of female cancers globally, resulting in more than 300,000 deaths every year. The majority of all cervical cancers are caused by persistent infections with high-risk human papillomaviruses (hrHPV) that can progress to cancer via a series of premalignant lesions.