Bacterial vaginosis and health-associated bacteria modulate the immunometabolic landscape in 3D model of human cervix

Abstract

Bacterial vaginosis (BV) is an enigmatic polymicrobial condition characterized by a depletion of health-associated Lactobacillus and an overgrowth of anaerobes. Importantly, BV is linked to adverse gynecologic and obstetric outcomes: an increased risk of sexually transmitted infections, preterm birth, and cancer. We hypothesized that members of the cervicovaginal microbiota distinctly contribute to immunometabolic changes in the human cervix, leading to these sequelae. Our 3D epithelial cell model that recapitulates the human cervical epithelium was infected with clinical isolates of cervicovaginal bacteria, alone or as a polymicrobial community. We used Lactobacillus crispatus as a representative health-associated commensal and four common BV-associated species: Gardnerella vaginalis, Prevotella bivia, Atopobium vaginae, and Sneathia amnii. The immunometabolic profiles of these microenvironments were analyzed using multiplex immunoassays and untargeted global metabolomics. A. vaginae and S. amnii exhibited the highest proinflammatory potential through induction of cytokines, iNOS, and oxidative stress-associated compounds. G. vaginalis, P. bivia, and S. amnii distinctly altered physicochemical barrier-related proteins and metabolites (mucins, sialic acid, polyamines), whereas L. crispatus produced an antimicrobial compound, phenyllactic acid. Alterations to the immunometabolic landscape correlate with symptoms and hallmarks of BV and connected BV with adverse women’s health outcomes. Overall, this study demonstrated that 3D cervical epithelial cell colonized with cervicovaginal microbiota faithfully reproduce the immunometabolic microenvironment previously observed in clinical studies and can successfully be used as a robust tool to evaluate host responses to commensal and pathogenic bacteria in the female reproductive tract.

Importance of the Immune Microenvironment in the Spontaneous Regression of Cervical Squamous Intraepithelial Lesions (cSIL) and Implications for Immunotherapy

“…Lactobacilli play an important role in the defense to pathogens through their ability to produce lactic acid and maintain a low pH, which is harmful to most pathogens [ 132 ]. In contrast, vaginal dysbiosis is associated with an increase in pH, the induction of local inflammation and release of chemotactic mediators [ 133 ]. Indeed, the increased microbial diversity typical of vaginal dysbiotic states, is associated with the production of pro-inflammatory cytokines and chemokines, as was shown in women with low abundance of lactobacilli, possibly through the activation of the NF-κB signaling pathway [ 134 ].…”

Commensal Urinary Lactobacilli Inhibit Major Uropathogens In Vitro With Heterogeneity at Species and Strain Level

“…For example, recent examination of urinary isolates of L. crispatus found that they use phenyl-lactic acid to inhibit growth of uropathogens E. coli and E. faecalis ( Abdul-Rahim et al., 2021 ). This shows similarity of the L. crispatus urinary strains with relatives from the vagina as well as diverse food sources ( Jacobsen et al., 1999 ; Valerio et al., 2004 ; Hütt et al., 2016 ; Łaniewski and Herbst-Kralovetz, 2021 ). Additionally, mixed urinary bacterial communities from asymptomatic postmenopausal women and those with acute UTI were shown to interact differently, supporting the idea of complex intermicrobial interactions within the urinary microbiome and potential differential effects on UTI progression ( Zandbergen et al., 2021 ).…”

Immunometabolic Analysis of Mobiluncus mulieris and Eggerthella sp. Reveals Novel Insights Into Their Pathogenic Contributions to the Hallmarks of Bacterial Vaginosis

“…with the highest fold change (1150-fold) of all the metabolites measured. Although the role of this metabolite in the cervicovaginal microenvironment is still not clear, we have previously observed its accumulation following infections with other vaginal bacteria ( Łaniewski and Herbst-Kralovetz, 2021 ; Salliss et al., 2021 ). The severity of BV has been associated with increased risk of HIV and other STI acquisition ( Allsworth and Peipert, 2011 ); thus, contribution of Eggerthella spp.…”

“…Organotypic 3-D human cervical epithelial cell models recapitulate many features of parental tissue that are not observed in monolayer cell culture models. Our advanced 3-D cell culture model exhibits physiologically relevant features, such as TLR expression, microvilli, intercellular junctional complexes and secretory material that could influence how BV-associated bacteria can colonize the model in a way similar to in vivo tissues ( Gardner et al., 2020 ; Łaniewski and Herbst-Kralovetz, 2021 ; Salliss et al., 2021 ) These features provide a more accurate representation of the in vivo state which is more amenable to translational research efforts and studying host-microbe interactions; however, each model system has its strengths, weaknesses and utility ( Hjelm et al., 2010 ; Radtke and Herbst-Kralovetz, 2012 ; Radtke et al., 2012 ; Herbst-Kralovetz et al., 2016 ). The close relation of 3-D human cervical epithelial cells to cervical tissue allows us to investigate how these pathogens can cause pathophysiological changes to the cervicovaginal microenvironment and epithelia.…”