Dataset Information

Bacterial Hyaluronidase Promotes Ascending GBS Infection and Preterm Birth.

ABSTRACT:

Unlabelled

Preterm birth increases the risk of adverse birth outcomes and is the leading cause of neonatal mortality. A significant cause of preterm birth is in utero infection with vaginal microorganisms. These vaginal microorganisms are often recovered from the amniotic fluid of preterm birth cases. A vaginal microorganism frequently associated with preterm birth is group B streptococcus (GBS), or Streptococcus agalactiae However, the molecular mechanisms underlying GBS ascension are poorly understood. Here, we describe the role of the GBS hyaluronidase in ascending infection and preterm birth. We show that clinical GBS strains associated with preterm labor or neonatal infections have increased hyaluronidase activity compared to commensal strains obtained from rectovaginal swabs of healthy women. Using a murine model of ascending infection, we show that hyaluronidase activity was associated with increased ascending GBS infection, preterm birth, and fetal demise. Interestingly, hyaluronidase activity reduced uterine inflammation but did not impact placental or fetal inflammation. Our study shows that hyaluronidase activity enables GBS to subvert uterine immune responses, leading to increased rates of ascending infection and preterm birth. These findings have important implications for the development of therapies to prevent in utero infection and preterm birth.

Importance

GBS are a family of bacteria that frequently colonize the vagina of pregnant women. In some cases, GBS ascend from the vagina into the uterine space, leading to fetal injury and preterm birth. Unfortunately, little is known about the mechanisms underlying ascending GBS infection. In this study, we show that a GBS virulence factor, HylB, shows higher activity in strains isolated from cases of preterm birth than those isolates from rectovaginal swabs of healthy women. We discovered that GBS rely on HylB to avoid immune detection in uterine tissue, but not placental tissue, which leads to increased rates of fetal injury and preterm birth. These studies provide novel insight into the underlying mechanisms of ascending infection.

SUBMITTER: Vornhagen J

PROVIDER: S-EPMC4937215 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Bacterial Hyaluronidase Promotes Ascending GBS Infection and Preterm Birth.

Vornhagen Jay J Quach Phoenicia P Boldenow Erica E Merillat Sean S Whidbey Christopher C Ngo Lisa Y LY Adams Waldorf K M KM Rajagopal Lakshmi L

mBio 20160628 3

<h4>Unlabelled</h4>Preterm birth increases the risk of adverse birth outcomes and is the leading cause of neonatal mortality. A significant cause of preterm birth is in utero infection with vaginal microorganisms. These vaginal microorganisms are often recovered from the amniotic fluid of preterm birth cases. A vaginal microorganism frequently associated with preterm birth is group B streptococcus (GBS), or Streptococcus agalactiae However, the molecular mechanisms underlying GBS ascension are p ...[more]

PMID: 27353757

Similar Datasets

Project description:BackgroundMicrobial invasion of the intraamniotic cavity and intraamniotic inflammation are factors associated with spontaneous preterm birth. Understanding the route and kinetics of infection, sites of colonization, and mechanisms of host inflammatory response is critical to reducing preterm birth risk.ObjectivesThis study developed an animal model of ascending infection and preterm birth with live bacteria (E. coli) in pregnant CD-1 mice with the goal of better understanding the process of microbial invasion of the intraamniotic cavity and intraamniotic inflammation.Study designMultiple experiments were conducted in this study. To determine the dose of E. coli required to induce preterm birth, CD-1 mice were injected vaginally with four different doses of E. coli (103, 106, 1010, or 1011 colony forming units [CFU]) in 40 μL of nutrient broth or broth alone (control) on an embryonic day (E)15. Preterm birth (defined as delivery before E18.5) was monitored using live video. E. coli ascent kinetics were measured by staining the E. coli with lipophilic tracer DiD for visualization through intact tissue with an in vivo imaging system (IVIS) after inoculation. The E. coli were also directly visualized in reproductive tissues by staining the bacteria with carboxyfluorescein succinimidyl ester (CFSE) prior to administration and via immunohistochemistry (IHC) by staining tissues with anti-E. coli antibody. Each pup's amniotic fluid was cultured separately to determine the extent of microbial invasion of the intraamniotic cavity at different time points. Intraamniotic inflammation resulting from E. coli invasion was assessed with IHC for inflammatory markers (TLR-4, P-NF-κB) and neutrophil marker (Ly-6G) for chorioamnionitis at 6- and 24-h post-inoculation.ResultsVaginally administered E. coli resulted in preterm birth in a dose-dependent manner with higher doses causing earlier births. In ex vivo imaging and IHC detected uterine horns proximal to the cervix had increased E. coli compared to the distal uterine horns. E. coli were detected in the uterus, fetal membranes (FM), and placenta in a time-dependent manner with 6 hr having increased intensity of E. coli positive signals in pups near the cervix and in all pups at 24 hr. Similarly, E. coli grew from the cultures of amniotic fluid collected nearest to the cervix, but not from the more distal samples at 6 hr post-inoculation. At 24 hr, all amniotic fluid cultures regardless of distance from the cervix, were positive for E. coli. TLR-4 and P-NF-κB signals were more intense in the tissues where E. coli was present (placenta, FM and uterus), displaying a similar trend toward increased signal in proximal gestational sacs compared to distal at 6 hr. Ly-6G+ cells, used to confirm chorioamnionitis, were increased at 24 hr compared to 6 hr post-inoculation and control.ConclusionWe report the development of mouse model of ascending infection and the associated inflammation of preterm birth. Clinically, these models can help to understand mechanisms of infection associated preterm birth, determine targets for intervention, or identify potential biomarkers that can predict a high-risk pregnancy status early in pregnancy.

Project description:BackgroundFetal inflammatory response mediated by the influx of immune cells and activation of pro-inflammatory transcription factor NF-κB in feto-maternal uterine tissues is the major determinant of infection-associated preterm birth (PTB, live births < 37 weeks of gestation).ObjectiveTo reduce the incidence of PTB by minimizing inflammation, extracellular vesicles (EVs) were electroporetically engineered to contain anti-inflammatory cytokine interleukin (IL)-10 (eIL-10), and their efficacy was tested in an ascending model of infection (vaginal administration of E. coli) induced PTB in mouse models.Study designEVs (size: 30-170 nm) derived from HEK293T cells were electroporated with recombinant IL-10 at 500 volts and 125 Ω, and 6 pulses to generate eIL-10. eIL-10 structural characters (electron microscopy, nanoparticle tracking analysis, ExoView [size and cargo content] and functional properties (co-treatment of macrophage cells with LPS and eIL-10) were assessed. To test efficacy, CD1 mice were vaginally inoculated with E. coli (1010CFU) and subsequently treated with either PBS, eIL-10 (500ng) or Gentamicin (10mg/kg) or a combination of eIL-10+gentamicin. Fetal inflammatory response in maternal and fetal tissues after the infection or treatment were conducted by suspension Cytometer Time of Flight (CyTOF) using a transgenic mouse model that express red fluorescent TdTomato (mT+) in fetal cells.ResultsEngineered EVs were structurally and functionally stable and showed reduced proinflammatory cytokine production from LPS challenged macrophage cells in vitro. Maternal administration of eIL-10 (10 µg/kg body weight) crossed feto-maternal barriers to delay E. coli-induced PTB to deliver live pups at term. Delay in PTB was associated with reduced feto-maternal uterine inflammation (immune cell infiltration and histologic chorioamnionitis, NF-κB activation, and proinflammatory cytokine production).ConclusionseIL-10 administration was safe, stable, specific, delayed PTB by over 72 hrs and delivered live pups. The delivery of drugs using EVs overcomes the limitations of in-utero fetal interventions. Protecting IL-10 in EVs eliminates the need for the amniotic administration of recombinant IL-10 for its efficacy.

Project description:Bacterial infections remain a significant cause of adverse pregnancy outcomes. Ascending infection of group B streptococcus (GBS) or Streptococcus agalactiae from the lower genital tract to the amniotic cavity leads to fetal injury, preterm births, or stillbirths. Factors increasing the invasive potential of bacteria at the maternal-fetal interface are poorly understood. Previous studies have indicated that the GBS hyaluronidase (HylB) can enhance systemic infection by breaking down host hyaluronan into disaccharides that dampen protective TLR2 and TLR4 signaling. Here, we examined the importance of hyaluronan receptors such as TLR2, TLR4, and CD44 in defense against GBS infections during pregnancy. While HylB promoted ascending GBS infection in wild-type (WT) and CD44-deficient mice, surprisingly, mice lacking both TLR2 and TLR4 (TLR2/4) were able to curtail these infections. Interleukin-10 (IL-10) and IL-10-expressing macrophages were significantly increased in the uterine tissues of WT mice during infection with HylB-proficient GBS compared with those of TLR2/4-deficient mice, and this likely promotes immune suppression and GBS dissemination. Consistent with these observations, pregnant IL-10-deficient mice exhibited diminished GBS ascension and dissemination. Similarly, the administration of a blocking antibody against the IL-10 receptor (IL-10R) in WT mice diminished ascending GBS infection. Collectively, these observations indicate that HylB promotes immune suppression in a TLR2/4- and IL-10-dependent manner to enhance the invasive potential of GBS during pregnancy-associated infections. IMPORTANCE Bacteria such as GBS can cause infections during pregnancy leading to preterm births, stillbirths, and neonatal infections. The interaction between host and bacterial factors during infections in the placenta is not fully understood. GBS secretes a hyaluronidase enzyme that is thought to digest host hyaluronan into immunosuppressive disaccharides that dampen TLR2/4 signaling, leading to increased bacterial dissemination and adverse outcomes. In this study, we show that GBS HylB mediates immune suppression and promotes bacterial infection during pregnancy that requires TLR2, TLR4, and IL-10. Understanding the interaction between host and bacterial factors can inform future therapeutic strategies to mitigate GBS infections.

Dataset Information

Bacterial Hyaluronidase Promotes Ascending GBS Infection and Preterm Birth.

Unlabelled

Importance

Publications

Bacterial Hyaluronidase Promotes Ascending GBS Infection and Preterm Birth.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets