Vaginal Microbiome May Protect Women From Chlamydia

A woman’s vaginal microbiome may play a role in whether she is resistant to or susceptible to Chlamydia trachomatis, according to a new study by investigators at the University of Maryland School of Medicine (UMSOM).

The study, published in the journal mBio, could provide insight for the treatment and prevention of this prevalent sexually transmitted infection (STI).

"Chlamydia is a major growing health issue in the US, and more work is needed to understand why some women are apparently naturally protected while other are not," principal investigator Jacques Ravel, PhD, a professor of microbiology and immunology and associate director and senior scientist at the Institute for Genome Sciences (IGS) at UMSOM, said in a statement. "Our novel research aims to decipher the mechanistic and functional underpinnings of communication between the host and the cervicovaginal microbiome to better understand resistance and susceptibility to this infection."

Funded by the National Institute for Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, the study analyzed the vaginal microbiota of 150 women infected with C trachomatis. The research found that different species of Lactobacillus bacteria have different effects on infection, with L iners not optimally protecting human cells against chlamydia, while products of L crispatus did. Investigators attributed the difference to the lactic acid produced by the bacteria, determining that D-lactic acid results in epigenetic modifications that block C trachomatis. L iners does not produce this isoform.

"What we have done in this study through several years of hard work by dedicated researchers is to provide, for the first time, a huge, new stepping stone on which future translational research to exploit the microbiome in the fight against chlamydial infection and disease, can be based," co-principal investigator Patrik Bavoil, PhD, professor & chair of the Department of Microbial Pathogenesis at the University of Maryland School of Dentistry, said in the statement.

The study follows previous research that established an association between vaginal microbiota and STI risk.

“Taken together, the findings reported here suggest that D− lactic acid producing Lactobacillus spp. modulate vaginal epithelial cell homeostasis by regulating a global transcriptional and functional network that includes epigenetic mechanisms that regulate gene expression, ultimately leading to reduction in cell cycling and protection against C trachomatis infection,” the study noted. “The results highlight the need to understand the mechanistic and functional underpinnings of the host response to the cervicovaginal microbiota. Such understanding is a prerequisite to the development of strategies to modulate these natural protective barriers to STI.”

A study presented at the US Centers for Disease Control and Prevention (CDC’s) 2018 STD Conference found that the prevalence of chlamydia among young women was decreasing but remained high.

Overall, cases of chlamydia have been on the rise worldwide, with the CDC reporting 1.7 million cases in the US in 2017, up 22% from 2013, the UMSOM noted. The disease can cause serious health issues, possibly leading to ectopic pregnancy or infertility, if left untreated.

Although no vaccines to prevent chlamydia currently exist, a novel vaccine candidate showed promise in a recent phase 1 clinical trial.