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The Vaginal Microbiome: Disease, Genetics and the Environment

The vagina is an interactive interface with the environment, and as such is covered by a protective epithelial surface. This surface is colonized by a biofilm consisting of bacteria and other microorganisms, which through a variety of mechanisms serve to protect the host from invasion by pathogens. Alterations in the normal vaginal microflora; i.e., dysbioses, particularly those associated with bacterial vaginosis, the most common disorder of the female reproductive tract, contribute to risk of sexually transmitted infections, infection by HIV, and are associated with increased risk of adverse pregnancy outcomes including but not limited to spontaneous preterm birth. Physiologic alterations in the host (e.g., menopause and pregnancy), which are beginning to be investigated as potential selective conditions for change in the "normal" vaginal flora, and their impact on disease susceptibility and transmission, remain to be more definitively elucidated. The effects of chronically abnormal physiologic states (e.g., diabetes mellitus) on normal vaginal flora have not been well described or studied. Finally, an almost unexplored area of inquiry is the genetic contribution, including race/ethnicity, to the establishment and maintenance of a "normal" vaginal flora, under normal and physiologically altered circumstances. Our research will shed light on how the vaginal microbiome contributes to adverse obstetrical outcomes and sexually transmitted infections in diverse populations. This project addresses the following questions:

First: Do the genes of the host contribute to the composition of the vaginal microbiome? We hypothesize that a woman's genetic composition significantly affects the ability of certain commensal, parasitic and pathogenic microbes to colonize and/or infect the genital tract. Thus, we will compare and quantify the microbial populations inhabiting the vaginas of monozygotic and dizygotic twins from the Mid Atlantic Twin Registry, and, in the process, address the question of whether there is a relationship between the microbiomes of the vagina, mouth and GI tract.

Second: What changes in the vaginal microbiome are associated with common physiological perturbations or non-infectious pathological states of the host?We hypothesize that "altered" physiologic (pregnancy, menopause) and pathologic (chronic disease, hysterectomy) conditions, or environmental "exposures" (exogenous hormones, antibiotics, chronic immunosuppressant, smoking; douching) can predictably alter the vaginal microenvironment. These alterations will lead to changes in microbial populations within the vagina. Changes in the microbial populations may have impacts, positive or more likely negative, on the spontaneous and future well-being of the affected individual. We are characterizing the effects of these "altered" physiologic and pathologic conditions, and environmental exposures, on the composition of the vaginal microbiome. Finally, we are examining the impact of the important physiological changes incurred during pregnancy on the composition of the microbiome of the female reproductive tract.

Third: What changes in the vaginal microbiome are associated with relevant infectious diseases and conditions? We are testing the hypothesis that infectious diseases predictably alter the vaginal microbiome, and that these changes have an impact on the disease susceptibility, process, and outcome. A predilection for bacterial vaginosis, vaginitis, HIV infection, or other sexually transmitted diseases, is likely associated with a women's vaginal microbial composition. Thus, we will characterize samples from women with a variety of these infectious conditions to determine the contribution of their microbiomes to the disease process and susceptibility.

We are addressing these questions using a combination of high throughput 'nextgen' sequencing technologies. Early studies were performed using the Roche 454 FLX and the first generation Illumina Genome Analyzer II instruments and more recently employing Illumina MiSeq and HiSeq 2500 and 4000 platforms, installed in the Genomics Core of the Nucleic Acids Research Facilities at VCU. Thus, segments of the 16S rRNA genes are amplified from the complex samples taken from various target sites in and around the vagina of each study participant. These segments are sequenced and subjected to taxonomic classification protocols to identify and quantify the bacterial taxa present in each sample. Additionally, total DNA isolated from these samples are subjected to shotgun sequence analysis to empirically reconstruct the metabolic potential of these microbiomes. Finally, specific bacterial clones are completely sequenced and analyzed to associate the unavoidable strain and isolate diversity with the clinical phenotypes presented.