Porphyromonas gingivalis infection in pregnant mice is associated with placental dissemination, an increase in the placental Th1/Th2 cytokine ratio, and fetal growth restriction

Prenatal programing: at the intersection of maternal stress and immune activation

Exposure to prenatal insults such as maternal stress and pathogenic infections has been associated with an increased risk for neurodevelopmental disorders. The mechanisms by which these programing events occur likely involve complex interactions between the maternal hormonal milieu, the placenta, and the developing fetus, in addition to compounding factors such as fetal sex and gestational stage of development. Despite the diverse biological processes involved, examination of common pathways in maternal stress and immune activation offers intriguing possibilities for elucidation of mechanistic insight. Further, the endocrine and sex-specific placenta is a tissue poised to be a key mediator in fetal programing, located at the intersection of the maternal and embryonic environments. In this review, we will discuss the potential shared mechanisms of maternal stress and immune pathway activation, with a particular focus on the important contribution and role of the placenta.

Identification of signaling pathways mediating cell cycle arrest and apoptosis induced by Porphyromonas gingivalis in human trophoblasts

Epidemiological and interventional studies of humans have revealed a close association between periodontal diseases and preterm delivery of low-birth-weight infants. Porphyromonas gingivalis, a periodontal pathogen, can translocate to gestational tissues following oral-hematogenous spread. We previously reported that P. gingivalis invades extravillous trophoblast cells (HTR-8) derived from the human placenta and inhibits proliferation through induction of arrest in the G(1) phase of the cell cycle. The purpose of the present study was to identify signaling pathways mediating cellular impairment caused by P. gingivalis. Following P. gingivalis infection, the expression of Fas was induced and p53 accumulated, responses consistent with response to DNA damage. Ataxia telangiectasia- and Rad3-related kinase (ATR), an essential regulator of DNA damage checkpoints, was shown to be activated together with its downstream signaling molecule Chk2, while the p53 degradation-related protein MDM2 was not induced. The inhibition of ATR prevented both G(1) arrest and apoptosis caused by P. gingivalis in HTR-8 cells. In addition, small interfering RNA (siRNA) knockdown of p53 abrogated both G(1) arrest and apoptosis. The regulation of apoptosis was associated with Ets1 activation. HTR-8 cells infected with P. gingivalis exhibited activation of Ets1, and knockdown of Ets1 with siRNA diminished both G(1) arrest and apoptosis. These results suggest that P. gingivalis activates cellular DNA damage signaling pathways that lead to G(1) arrest and apoptosis in trophoblasts.

Causes of adverse pregnancy outcomes and the role of maternal periodontal status - a review of the literature

Preterm (PT) and Low birth weight (LBW) are considered to be the most relevant biological determinants of newborn infants survival, both in developed and in developing countries. Numerous risk factors for PT and LBW have been defined in the literature. Infections of the genitourinary tract infections along with various biological and genetic factors are considered to be the most common etiological factors for PT/LBW deliveries. However, evidence suggests that sub-clinical infection sites that are also distant from the genitor-urinary tract may be an important cause for PT/LBW deliveries. Maternal periodontal status has also been reported by many authors as a possible risk factor for PT and LBW, though not all of the actual data support such hypothesis. The aim of this paper is to review the evidence from various published literature on the association between the maternal periodontal status and adverse pregnancy outcomes. Although this review found a consistent association between periodontitis and PT/LBW, this finding should be treated with great caution until the sources of heterogeneity can be explained.

Intrauterine growth restriction: cytokine profiles of trophoblast antigen-stimulated maternal lymphocytes

Intrauterine growth restriction (IUGR) is an important perinatal syndrome that poses several serious short- and long-term effects. We studied cytokine production by maternal peripheral blood lymphocytes stimulated by trophoblast antigens. 36 women with a diagnosis of IUGR and 22 healthy women with normal fetal growth were inducted. Peripheral blood mononuclear cells were stimulated with trophoblast antigens and levels of the proinflammatory cytokines IL-6, IL-8, IL-12, IL-23, IFNγ, and TNFα and the anti-inflammatory cytokines IL-4, IL-10, and IL-13 were measured in culture supernatants by ELISA. IL-8 was produced at higher levels by blood cells of the IUGR group than normal pregnant women, while IL-13 was produced at lower levels. IL-8, IFNγ, and TNFα were higher in IUGR with placental insufficiency than in normal pregnancy. IL-12 levels were higher and IL-10 levels were lower in IUGR with placental insufficiency than in IUGR without placental insufficiency. We suggest that a stronger pro-inflammatory bias exists in IUGR as compared to normal pregnancy and in IUGR with placental insufficiency when compared to IUGR without placental insufficiency. Several ratios of proinflammatory to anti-inflammatory cytokines also support the existence of an inflammatory bias in IUGR.

Periodontal disease in pregnancy: review of the evidence and prevention strategies

This article reviews the current research on periodontal disease and treatment and its potential impact on maternal and newborn outcomes and provides recommendations for care management and prevention. These guidelines will be helpful for nurse professionals who are in a unique position to counsel pregnant women to improve the oral health of expectant mothers.

Oral health and adverse pregnancy outcomes - what's next?

Studies on the link between periodontal disease and adverse pregnancy outcome have gone through several phases. The epidemiological studies predominantly support a positive association between these wide-affecting diseases. During the intervention phase, a few small-scale, single-center studies reported improvement of birth outcome following periodontal treatment, whereas the large-scale multi-center studies did not demonstrate efficacy. Many questions arise with regard to patient population, disease type, and therapy. In addressing these questions, it is crucial that one understands the mechanism underlying the link between these diseases. Two non-mutually exclusive hypotheses exist. In the first, periodontal disease is believed to affect the maternal and fetal immune responses systemically, leading to premature labor. Alternatively, evidence is accumulating that oral bacteria may translocate directly into the pregnant uterus, causing localized inflammation and adverse pregnancy outcome in the presence or absence of clinical periodontitis. The oral-uterine transmission is not limited to the well-recognized periodontal pathogens, but instead may also involve the commensal species. Future studies should investigate these mechanisms, to understand the host susceptibility to oral-uterine transmission. Only when a thorough understanding of the mechanism is achieved can meaningful intervention studies be designed utilizing effective therapies, targeting appropriate populations, and measuring relevant outcomes.

Human trophoblast responses to Porphyromonas gingivalis infection

Porphyromonas gingivalis is a periodontal pathogen that is also associated with preterm low-birthweight delivery. We investigated the transcriptional responses of human extravillous trophoblasts (HTR-8) to infection with P. gingivalis. Over 2000 genes were differentially regulated in HTR-8 cells by P. gingivalis. In ontology analyses of regulated genes, overpopulated biological pathways included mitogen-activated protein (MAP) kinase signaling and cytokine production. Immunoblots confirmed overexpression of the MAP kinase pathway components MEK3, p38 and Max. Furthermore, P. gingivalis infection induced phosphorylation and activation of MEK3 and p38. Increased production of interleukin (IL)-1beta and IL-8 by HTR-8 cells was demonstrated phenotypically by enzyme-linked immunosorbent assay of HTR-8 cell lysates and culture supernatants. Hence, infection of trophoblasts by P. gingivalis can impact signal transduction pathways and modulate cytokine expression, outcomes that could disrupt the maintenance of pregnancy.

Role of arginine deiminase of Streptococcus cristatus in Porphyromonas gingivalis colonization

The ability to attach to a variety of oral surfaces is an important characteristic of Porphyromonas gingivalis. Previous studies have demonstrated that expression and production of FimA, a major subunit protein of the long fimbriae, is required for P. gingivalis colonization. Here we report that a surface protein, arginine deiminase (ArcA) of Streptococcus cristatus, represses FimA production and inhibits biofilm formation of P. gingivalis. This inhibitory function of ArcA is also observed in the formation of heterotypic P. gingivalis-Streptococcus gordonii biofilms. P. gingivalis is released from streptococcal substrates in the presence of ArcA, likely due to an inhibition of FimA production. This work suggests that ArcA may have the potential to be a specific antibiofilm agent to fight P. gingivalis infections.

Altered gene expression in murine placentas in an infection-induced intrauterine growth restriction model: a microarray analysis

The biological mechanisms leading to incomplete intrauterine growth are not completely elucidated and few studies have investigated infection-mediated growth restriction. In this investigation we report the alterations induced by maternal infectious challenge in placental gene expression patterns using a murine model. Pregnant dams were challenged at day E7.5 with the oral human pathogen Campylobacter rectus to elicit fetal growth restriction. At embryonic day E16.5 placentas were collected to compare placental gene expression patterns from normal fetuses of unchallenged dams and growth restricted fetuses from infected dams. Differential gene expression patterns were determined using Agilent Oligo array (G4121A) with a false discovery rate of P<0.05 and pathway analyses were performed. Seventy-four genes were differentially expressed during infection-mediated growth restriction with 9 genes significantly up-regulated, indicating that the effects of maternal infection on gene expression were predominantly suppressive. Pathway analyses indicated that 46 of the 65 genes that were significantly down-regulated were associated with placental/fetal development, and 26 of those were imprinted genes. Among the 9 genes that were up-regulated, 4 are involved in oxygen supply to the fetus and the development of the vascular system. Microarray analysis demonstrated that in the pregnant mouse model, maternal infection that induced growth restriction was associated with down-regulated placental expression of critical growth and developmental related genes, including many imprinted genes. These findings may have significant implications for our understanding of the mechanisms underlying infection-associated human fetal growth restriction and the role of differential placental expression of imprinted genes in fetal growth.

Modulation of allergic airway inflammation by the oral pathogen Porphyromonas gingivalis

Accumulating evidence suggests that bacteria associated with periodontal disease may exert systemic immunomodulatory effects. Although the improvement in oral hygiene practices in recent decades correlates with the increased incidence of asthma in developed nations, it is not known whether diseases of the respiratory system might be influenced by the presence of oral pathogens. The present study sought to determine whether subcutaneous infection with the anaerobic oral pathogen Porphyromonas gingivalis exerts a regulatory effect on allergic airway inflammation. BALB/c mice sensitized and subsequently challenged with ovalbumin exhibited airway hyperresponsiveness to methacholine aerosol and increased airway inflammatory cell influx and Th2 cytokine (interleukin-4 [IL-4], IL-5, and IL-13) content relative to those in nonallergic controls. Airway inflammatory cell and cytokine contents were significantly reduced by establishment of a subcutaneous infection with P. gingivalis prior to allergen sensitization, whereas serum levels of ovalbumin-specific IgE and airway responsiveness were not altered. Conversely, subcutaneous infection initiated after allergen sensitization did not alter inflammatory end points but did reduce airway responsiveness in spite of increased serum IgE levels. These data provide the first direct evidence of a regulatory effect of an oral pathogen on allergic airway inflammation and responsiveness. Furthermore, a temporal importance of the establishment of infection relative to allergen sensitization is demonstrated for allergic outcomes.

The Key Events Dose-Response Framework: its potential for application to foodborne pathogenic microorganisms

The Key Events Dose-Response Framework (KEDRF) is an analytical approach that facilitates the use of currently available data to gain insight regarding dose-response relationships. The use of the KEDRF also helps identify critical knowledge gaps that once filled, will reduce reliance on assumptions. The present study considers how the KEDRF might be applied to pathogenic microorganisms, using fetal listeriosis resulting from maternal ingestion of food contaminated with L. monocytogenes as an initial example. Major biological events along the pathway between food ingestion and the endpoint of concern are systematically considered with regard to dose (i.e., number of organisms), pathogen factors (e.g., virulence), and protective host mechanisms (e.g., immune response or other homeostatic mechanisms). It is concluded that the KEDRF provides a useful structure for systematically evaluating the complex array of host and pathogen factors that influence the dose-response relationship. In particular, the KEDRF supports efforts to specify and quantify the sources of variability, a prerequisite to strengthening the scientific basis for food safety decision making.

Antibody responses to Porphyromonas gingivalis outer membrane protein in the first trimester

BACKGROUND

Porphyromonas gingivalis (Pg) is one of the most harmful periodontal pathogens and it has been reported that Pg is associated with preterm birth (PTB), intrauterine growth retardation (IUGR) and pregnancy-induced hypertension (PIH), discovered by animal experiments and clinical research. The relationship between adverse pregnancy outcomes and maternal antibody response to Pg is controversial. On the other hand, the serum C-reactive protein (CRP) has been recognised as a reliable serum marker of periodontal disease.

AIMS

To determine the significance of antibody responses to Pg affecting pregnancy outcomes in the first trimester.

METHODS

A case-control study was carried out on women with PTB (n = 58), IUGR (n = 91), PIH (n = 32) and without any complications (control, n = 98). The serum level of the CRP and IgG1 against 40-kDa outer membrane protein of Pg (anti-40-kDa OMP Pg-IgG1) in the first trimester was measured.

RESULTS

The IUGR group, and PTB patients whose placentas were diagnosed as chorioamnionitis or whose vaginal flora included Lactobacilli, showed a lower level of anti-40-kDa OMP Pg-IgG1 than the control group. There was no difference in the serum CRP level between each case group and control group.

CONCLUSIONS

These results suggest that a lack of humoral immunity against Pg in early pregnancy is associated with IUGR and some PTB.

Porphyromonas gingivalis invades human trophoblasts and inhibits proliferation by inducing G1 arrest and apoptosis

Porphyromonas gingivalis is an oral pathogen that is also associated with serious systemic conditions such as preterm delivery. Here we investigated the interaction between P. gingivalis and a cell line of extravillous trophoblasts (HTR-8) derived from the human placenta. P. gingivalis internalized within HTR-8 cells and inhibited proliferation through induction of arrest in the G1 phase of the cell cycle. G1 arrest was associated with decreased expression of cyclin D and of CDKs 2, 4 and 6. In addition, levels of CDK inhibitors p15, p16, p18 and p21 were increased following P. gingivalis infection. The amount of Rb was diminished by P. gingivalis, and transient overexpression of Rb, with concomitant upregulation of phospho-Rb, relieved P. gingivalis-induced G1 arrest. HTR-8 cells halted in the G1 phase became apoptotic, and apoptosis was accompanied by an increase in the ratio of Bax/Bcl-2 and increased activity of caspases 3, 7 and 9. HTR-8 cells infected with P. gingivalis also exhibited a sustained activation of ERK1/2, and knock-down of ERK1/2 activity with siRNA abrogated both G1 arrest and apoptosis. Thus, P. gingivalis can invade placental trophoblasts and induce G1 arrest and apoptosis through pathways involving ERK1/2 and its downstream effectors, properties that provide a mechanistic basis for pathogenicity in complications of pregnancy.

Increased TLR4 expression in murine placentas after oral infection with periodontal pathogens

Maternal periodontitis has emerged as a putative risk factor for preterm births in humans. The periodontitis-associated dental biofilm is thought to serve as an important source of oral bacteria and related virulence factors that hematogenously disseminate and affect the fetoplacental unit; however the underlying biological mechanisms are yet to be fully elucidated. This study hypothesized that an oral infection with the human periodontal pathogens Campylobacter rectus and Porphyromonas gingivalis is able to induce fetal growth restriction, placental inflammation and enhance Toll-like receptors type 4 (TLR4) expression in a murine pregnancy model. Female Balb/C mice (n = 40) were orally infected with C. rectus and/or P. gingivalis over a 16-week period and mated once/week. Pregnant mice were sacrificed at embryonic day (E) 16.5 and placentas were collected and analyzed for TLR4 mRNA levels and qualitative protein expression by real-time PCR and immunofluorescence. TLR4 mRNA expression was found to be increased in the C. rectus-infected group (1.98 +/- 0.886-fold difference, P < 0.01, ANOVA) compared to controls. Microscopic analysis of murine placentas showed enhanced immunofluorescence of TLR4 in trophoblasts, mainly in the placental labyrinth layer. Also, combined oral infection with C. rectus and P. gingivalis significantly reduced the overall fecundity compared to controls (16.7% vs. 75%, infected vs. non-infected mice respectively, P = 0.03, Kaplan-Meier). The results supported an enhanced placental TLR4 expression after oral infection with periodontal pathogens. The TLR4 pathway has been implicated in the pathogenesis of preterm births; therefore the abnormal regulation of placental TLR4 may give new insights into how maternal periodontitis and periodontal pathogens might be linked to placental inflammation and preterm birth pathogenesis.

Colonization of maternal and fetal tissues by Porphyromonas gingivalis is strain-dependent in a rodent animal model

OBJECTIVE

The objective of this study was to develop a rodent model of Porphyromonas gingivalis infection during pregnancy.

STUDY DESIGN

Sprague Dawley rats were infected intravenously with 10(5), 10(7), or 10(9) CFU per dam of P gingivalis strain W83, ATCC 33277, or A7436 at gestational day 14 and necropsied at gestational day 18. Maternal organs were cultured to assess the spread of the infection. Six fetal units (placenta, amniotic fluid, membranes, and fetus) per dam were cultured; additional fetal units were examined by histopathology. Polymerase chain reaction was performed on placentas.

RESULTS

Colonization rates were dependent on the strain of P gingivalis used and the infection dose. At an infection dose of 10(9) CFU/dam, P gingivalis W83, ATCC 33277, or A7436 was detected in 33%, 83%, or 100% of placentas, respectively. Epithelial hyperplasia, cellular necrosis, and inflammatory infiltrate were observed in infected placental tissues.

CONCLUSION

This study demonstrated that P gingivalis can invade both maternal and fetal tissues, resulting in chorioamnionitis and placentitis.

Maternal periodontal status and preterm low birth weight delivery: a case-control study

OBJECTIVES

To assess the association between severity and extent of maternal periodontal disease and preterm birth/low birth weight (PLBW) among women in the north of Jordan.

METHODS

A total of 148 woman who gave preterm birth/low birth weight birth and 438 women with uncomplicated full term vaginal delivery were included in this study. Socio-demographic characteristics, antenatal history, medical history, and family medical history were collected through personal interview or abstracted from maternal records. The oral hygiene status, and periodontal and dental parameters were assessed for all women.

RESULTS

The average of probing pocket depth (PPD) and average of clinical attachment level (CAL) were significantly higher among women who gave PLBW babies. The mean gingival recession was not significantly different between the two groups. The percentages of sites with PPD > or = 3 mm and CAL > or = 3 mm were significantly higher among women who gave PLBW babies. Number of decayed teeth, number filled teeth, and number of missing teeth showed no significant association with PLBW delivery.

CONCLUSION

The extent and severity of periodontal diseases appeared to be associated with increased odds of PLBW delivery. Nevertheless, more and larger intervention trials are needed before it can be fully accepted that periodontal infection is a true risk factor for PLBW.

Maternal periodontitis and adverse pregnancy outcomes

OBJECTIVES

Maternal periodontal diseases have been associated with increased risk of preterm birth and restricted fetal growth among relatively low socioeconomic groups. Whether the association can be generalized to middle-class populations remains uncertain. We evaluated periodontitis in relation to preterm birth (<37 weeks' gestation) and small-for-gestational-age (SGA, birth weight below the 10th percentile of birth weight for gestational age) among a group of medically insured women.

METHODS

We conducted a prospective study among participants of Project Viva, a US cohort study of pregnant women and their offspring from 1999 to 2002. Pregnancy outcomes were obtained from medical records. Self-reported periodontitis was assessed during the second trimester of pregnancy, and validated against radiographs. Logistic regression analyses were employed to evaluate the association of periodontitis with pregnancy outcomes adjusted for age, race/ethnicity, smoking status, income, frequency of dental check-ups, prepregnancy body mass index, pregnancy weight gain, gravidity, prior history of preterm birth and history of genitourinary infection.

RESULTS

Of the 1635 women, 72.7% were Caucasian, 65.0% had annual household income >$70 000, 3.8% reported having periodontitis, 6.4% delivered preterm, 5.4% delivered SGA babies, and 11.0% had poor pregnancy outcome (either preterm birth or SGA). The odds ratio (OR) associated with periodontitis was 1.74 (95% CI 0.65-4.66) for preterm delivery and 2.11 (95% CI 0.76-5.86) for SGA individually. When preterm delivery and/or SGA were combined, the OR was 2.26 (95% CI 1.05-4.85) relating periodontitis with poor pregnancy outcome.

CONCLUSION

Within the limitations of the study, the results suggest that periodontitis is an independent risk factor for poor pregnancy outcome among middle-class women.

Detection of Porphyromonas gingivalis in the amniotic fluid in pregnant women with a diagnosis of threatened premature labor

BACKGROUND

Epidemiologic and randomized controlled studies have shown that periodontal diseases may be associated with preterm labor and delivery of infants with low birth weights. The purpose of the present study was to determine the presence of microbial invasion of the amniotic cavity by periodontopathic bacteria in pregnant women with a diagnosis of threatened premature labor.

METHODS

A periodontal examination and collection of amniotic fluid and subgingival plaque samples were performed on women identified as having threatened premature labor (preterm premature rupture of membranes without clinical infection or labor and preterm labor with intact membranes) and a gestational age ranging between 24 and 34 weeks. Samples collected from amniotic fluid and from the four deepest periodontal pockets in each patient were pooled in prereduced transport fluid and cultured. Porphyromonas gingivalis was identified primarily by colony morphology under stereoscopic microscope and rapid biochemical tests. Amniotic fluid or plaque samples were homogenized, DNA was extracted, and polymerase chain reaction (PCR) amplification of 16S rRNA with specific and universal primers was carried out.

RESULTS

Twenty-six women with threatened premature labor were included: eight with preterm premature rupture of membranes and 18 with preterm labor with intact membranes. Eight women presented with gingivitis, 12 with chronic periodontitis, and six without periodontal disease. Microbial invasion of the amniotic cavity as detected by P. gingivalis PCR was 30.8% (eight of 26 patients). In these eight patients, P. gingivalis was present in both the subgingival samples and the respective amniotic fluid sample.

CONCLUSION

The presence of microbial invasion of the amniotic cavity by P. gingivalis could indicate a role for periodontal pathogenic bacteria in pregnant women with a diagnosis of threatened premature labor.

Exploring the relationship between periodontal disease and pregnancy complications

BACKGROUND

Increasing evidence suggests that maternal gingivitis and periodontitis may be a risk factor for preterm birth and other adverse pregnancy outcomes.

TYPES OF STUDIES REVIEWED

To clarify the possible mechanisms behind the association between periodontal disease and preterm delivery, the authors reviewed studies of the effect of infection with periodontal pathogens in animal models on pregnancy outcomes including fetal growth, placental structural abnormalities and neonatal health. After the first report, in 1996, of a potential association between maternal periodontal disease and delivery of a preterm/low-birth-weight infant in humans, many case control and prospective studies were published. This review summarizes these, as well as early studies involving periodontal intervention to reduce risk.

RESULTS

Although there are some conflicting findings and potential problems regarding uncontrolled underlying risk factors, most of the clinical studies indicate a positive correlation between periodontal disease and preterm birth. Recent studies also have shown that there are microbiologic and immunological findings that strongly support the association. The studies indicate that periodontal infection can lead to placental-fetal exposure and, when coupled with a fetal inflammatory response, can lead to preterm delivery. Data from animal studies raise the possibility that maternal periodontal infections also may have adverse long-term effects on the infant's development.

CLINICAL IMPLICATIONS

Education for patients and health care providers regarding the biological plausibility of the association and the potential risks is indicated, but there is insufficient evidence at this time for health care policy recommendations to provide maternal periodontal treatments for the purpose of reducing the risk of adverse pregnancy outcomes.

Evidence of Periopathogenic Microorganisms in Placentas of Women With Preeclampsia

BACKGROUND

Periodontal disease is a chronic inflammatory infectious disease that may act as a focus of infection. Preeclampsia is a pregnancy-specific hypertensive disorder that often leads to maternal morbidity and mortality. Acute atherosis, the placental lesion of preeclampsia, shares many histopathological features with atherosclerosis. Recently, chronic infection was linked to the initiation of atherosclerosis. Oral pathogens have been detected in atherosclerotic plaques, where they may play a role in the development and progression of atherosclerosis. The purpose of the present study was to explore the possibility that periopathogenic bacteria may translocate into the placental tissues of women with preeclampsia.

METHODS

Samples were taken from 16 placentas obtained from cesarean sections of women with preeclampsia and from 14 age-matched healthy pregnant women. Polymerase chain reaction was used to detect Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum ssp., Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and Treponema denticola.

RESULTS

Eight of the 16 (50%) placenta specimens were positive for one or more periopathogenic bacteria in the preeclampsia group, compared to only two of the 14 samples (14.3%) from controls. Bacterial counts were statistically significantly higher in the preeclampsia group for all of the periopathogenic bacteria examined (P <or=0.0055). Although all of the target periopathogenic bacteria were found in the preeclampsia group, only three (P. gingivalis, T. forsythensis, and T. denticola) were found in the control group.

CONCLUSION

The significant presence of periopathogenic microorganisms or their products in human placentas of women with preeclampsia may suggest a possible contribution of periopathogenic bacteria to the pathogenesis of this syndrome.

Transmission of an uncultivated Bergeyella strain from the oral cavity to amniotic fluid in a case of preterm birth

Intrauterine infection is a recognized cause of preterm birth. The infectious organisms are believed to originate primarily from the vaginal tract and secondarily from other parts of the body. It is plausible that microbes in the oral cavity can be transmitted to the pregnant uterus. However, direct evidence supporting such a transmission is lacking. In this study, amniotic fluids of 34 pregnant women were examined by PCR using 16S and 23S rRNA universally conserved primers. Bacterial DNA was amplified from the only patient with clinical intrauterine infection and histologic necrotizing acute and chronic chorioamnionitis. One strain, Bergeyella sp. clone AF14, was detected and was 99.7% identical to a previously reported uncultivated oral Bergeyella strain, clone AK152, at the 16S rRNA level. The same strain was detected in the subgingival plaque of the patient but not in her vaginal tract. The 16S-23S rRNA sequence of clone AF14 matched exactly with the sequences amplified from the patient's subgingival plaque. These observations suggest that the Bergeyella strain identified in the patient's intrauterine infection originated from the oral cavity. This is the first direct evidence of oral-utero microbial transmission. The patient's periodontal health during pregnancy was unclear. She did not have detectable periodontal disease during postpartum examination. Bergeyella spp. had not been previously associated with preterm birth and were detected in subgingival plaque of women without clinical levels of intrauterine infection. Uncultivated species may be overlooked opportunistic pathogens in preterm birth. This study sheds new light on the implication of oral bacteria in preterm birth.

Inhibition of term decidual NK cell cytotoxicity by soluble HLA-G1

OBJECTIVES

Soluble (s)HLA-G1 is produced by trophoblast cells. Aim was to analyze the capacities and mechanisms of sHLA-G1 to regulate interleukin (IL)-2-induced cytotoxicity of natural killer (NK) cells from human deciduas.

METHODS

Natural killer cells were isolated from decidual layers of term placentae, stimulated or not with IL-2 and supplemented with various concentrations of recombinant soluble HLA-G1 (sHLA-G1). For NK cell cytotoxicity assays, K562 cells were used as targets. Expression of signal transducer and activator of transcription 3 (STAT3) and perforin was analyzed by Western blotting. Apoptosis was examined by assessment of poly(ADP-ribose) polymerase cleavage. NK cells were analyzed by flow cytometry for IL-2receptor-alpha (IL-2R alpha; CD25) and transferrin receptor CD71 expression.

RESULTS

Interleukin-2 increases CD71, STAT3, perforin expression and cytotoxic potential of NK cells. Expression of CD71, STAT3 and perforin decreased simultaneously with cytotoxicity and dose-dependently when sHLA-G1 (1.6 micro g/mL-1.6 ng/mL) was added to IL-2 stimulated cultures. sHLA-G1 did not induce apoptosis and CD25 expression was not affected.

CONCLUSION

Interleukin-2R alpha expression is not controlled by sHLA-G1, but its signal transducer STAT3 as well as several downstream effects, such as perforin expression, proliferation and cytotoxicity. The control of STAT3 bioavailability through sHLA-G1 may be a key regulator of the mentioned effects.

Changes of immunoresponse in BALB/c mice neonatally treated with periodontopathic bacterial endotoxin

The aim of this investigation was to analyze the effects of early life exposure to periodontopathic bacterial lipopolysaccharides on immunoresponse. Newborn BALB/c mice were subcutaneously injected with 20 ng lipopolysaccharide of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans or Escherichia coli daily for 2 days, starting within 24 h after birth. The treated mice were given intraperitoneal injections of bovine serum albumin at 180 and 187 days of age. Seventeen hours after each injection, the mice were bled and sera were separated. Their sera were tested in an enzyme-linked immunosorbent assay system. The mean interleukin-4, interleukin-5, interleukin-6 and immunoglobulin E levels in the sera of mice treated neonatally with P. gingivalis lipopolysaccharide were significantly higher than those of the controls. However, in all cases, no significant difference was noted between mice treated neonatally with A. actinomycetemcomitans- or E. coli lipopolysaccharide and control mice. These data suggest that neonatal exposure to P. gingivalis lipopolysaccharide induces changes in immunological responses when the mice reach maturity.

Periodontitis is associated with preeclampsia in pregnant women

BACKGROUND

Recent investigations have demonstrated a positive association between periodontitis and pregnancy complications. The purpose of this study was to determine the effect of periodontitis and the subgingival microbial composition on preeclampsia.

METHODS

A case-control study was carried out in Cali, Colombia that included 130 preeclamptic and 243 non-preeclamptic women between 26 to 36 weeks of pregnancy. Sociodemographic data, obstetric risk factors, periodontal status, and subgingival microbial composition were determined in both groups. Preeclampsia was defined as blood pressure>or=140/90 mm Hg, and >or=2+ proteinuria, confirmed by 0.3 g proteinuria/24 hours of urine specimens. Controls were healthy pregnant women. Odds ratios (ORs) for periodontitis and subgingival microbiota compositions were calculated.

RESULTS

A total of 83 out of 130 preeclamptic women (63.8%) and 89 out of 243 controls (36.6%) had chronic periodontitis (OR: 3.0; 95% confidence interval (CI): 1.91 to 4.87; P<0.001). Clinical attachment loss increased in the case group (4.0+/-0.10 mm) compared to the control group (3.0+/-0.08 mm) (P<0.001). The average newborn birth weight from preeclamptic mothers was 2.453 g, whereas in controls was 2.981 g (P<0.001). Two red complex microorganisms, Porphyromonas gingivalis and Tannerella forsythensis, and the green complex microorganism Eikenella corrodens were more prevalent in the preeclamptic group than in controls (P<0.01).

CONCLUSIONS

Chronic periodontal disease and the presence of P. gingivalis, T. forsythensis, and E. corrodens were significantly associated with preeclampsia in pregnant women. Further research is needed to establish pathogenic mechanisms of active periodontal disease and subgingival periodontopathogens related to preeclampsia development.

Progressive periodontal disease and risk of very preterm delivery

OBJECTIVE

The goal was to estimate whether maternal periodontal disease was predictive of preterm (less than 37 weeks) or very preterm (less than 32 weeks) births.

METHODS

A prospective study of obstetric outcomes, entitled Oral Conditions and Pregnancy (OCAP), was conducted with 1,020 pregnant women who received both an antepartum and postpartum periodontal examination. Predictive models were developed to estimate whether maternal exposure to either periodontal disease at enrollment (less than 26 weeks) and/or periodontal disease progression during pregnancy, as determined by comparing postpartum with antepartum status, were predictive of preterm or very preterm births, adjusting for risk factors including previous preterm delivery, race, smoking, social domain variables, and other infections.

RESULTS

Incidence of preterm birth was 11.2% among periodontally healthy women, compared with 28.6% in women with moderate-severe periodontal disease (adjusted risk ratio [RR] 1.6, 95% confidence interval [CI] 1.1-2.3). Antepartum moderate-severe periodontal disease was associated with an increased incidence of spontaneous preterm births (15.2% versus 24.9%, adjusted RR 2.0, 95% CI 1.2-3.2). Similarly, the unadjusted rate of very preterm delivery was 6.4% among women with periodontal disease progression, significantly higher than the 1.8% rate among women without disease progression (adjusted RR 2.4, 95% CI 1.1-5.2).

CONCLUSION

The OCAP study demonstrates that maternal periodontal disease increases relative risk for preterm or spontaneous preterm births. Furthermore, periodontal disease progression during pregnancy was a predictor of the more severe adverse pregnancy outcome of very preterm birth, independently of traditional obstetric, periodontal, and social domain risk factors.

LEVEL OF EVIDENCE

II-2.

Effects of maternal Campylobacter rectus infection on murine placenta, fetal and neonatal survival, and brain development

BACKGROUND

Maternal periodontal infection has been associated with increased risk of prematurity and low birthweight. Infection and inflammatory pathways that mediate prematurity have also been implicated in neonatal developmental impairments. The objective of this study was to determine whether maternal Campylobacter rectus infection that induces fetal growth restriction in a mouse model also compromises neonatal pup survival, growth, and neurodevelopment.

METHODS

Timed pregnant mice were challenged with C. rectus on gestation day 7.5. One group of animals was sacrificed on embryonic day 16.5 for placental histology and measurement of fetal brain mRNA expression of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma. Another group of animals was allowed to deliver to follow pup survival, growth, and brain structure at day 9.

RESULTS

C. rectus challenge resulted in abnormal placental architecture with inflammation and a 2.8-fold increase in fetal brain expression of IFN-gamma (P = 0.04). Pup birthweight was unaffected by C. rectus exposure, but lethality was 3.9-fold higher after 1 week. Ultrastructurally, the 9-day neonatal brain tissue displayed cellular and myelin alterations consistent with white matter damage.

CONCLUSIONS

Maternal C. rectus infection induces placental inflammation and decidual hyperplasia as well as concomitant increase in fetal brain IFN-gamma. Maternal infection increased pup mortality, and preliminary findings demonstrate ultrastructural changes in the hippocampal region of the neonatal brain, in a manner analogous to the effects of maternal infection on white matter damage seen in humans. Thus, the threat of maternal oral infectious exposure during pregnancy may not be limited to the duration of gestation, but may also potentially affect perinatal neurological growth and development.

An immune response directed to proteinase and adhesin functional epitopes protects against Porphyromonas gingivalis-induced periodontal bone loss

Porphyromonas gingivalis, a pathogen associated with periodontitis, bound to fibrinogen, fibronectin, hemoglobin, and collagen type V with a similar profile to that of its major virulence factor, the cell surface RgpA-Kgp proteinase-adhesin complex. Using peptide-specific, purified Abs in competitive inhibition ELISAs and epitope mapping assays, we have identified potential adhesin binding motifs (ABMs) of the RgpA-Kgp complex responsible for binding to host proteins. The RgpA-Kgp complex and synthetic ABM and proteinase active site peptides conjugated to diphtheria toxoid, when used as vaccines, protected against P. gingivalis-induced periodontal bone loss in the murine periodontitis model. The most efficacious peptide and protein vaccines were found to induce a high-titer IgG1 Ab response. Furthermore, mice protected in the lesion and periodontitis models had a predominant P. gingivalis-specific IL-4 response, whereas mice with disease had a predominant IFN-gamma response. The peptide-specific Abs directed to the ABM2 sequence (EGLATATTFEEDGVA) protected against periodontal bone loss and inhibited binding of the RgpA-Kgp complex to fibrinogen, fibronectin, and collagen type V. Furthermore, the peptide-specific Abs directed to the ABM3 sequence (GTPNPNPNPNPNPNPGT) protected against periodontal bone loss and inhibited binding to hemoglobin. However, the most protective Abs were those directed to the active sites of the RgpA and Kgp proteinases. The results suggest that when the RgpA-Kgp complex, or functional binding motif or active site peptides are used as a vaccine, they induce a Th2 response that blocks function of the RgpA-Kgp complex and protects against periodontal bone loss.

Immunization by Arg-gingipain A DNA vaccine protects mice against an invasive Porphyromonas gingivalis infection through regulation of interferon-gamma production

We previously demonstrated that a Porphyromonas gingivalis rgpA DNA vaccine induced protective immune responses against P. gingivalis infection in mice. In the present study, reduction in lethality against infection by lethal doses of P. gingivalis was observed in the rgpA DNA vaccine-immunized mice. Cytokine levels in the mouse model with nonlethal doses of infection by P. gingivalis were evaluated to analyze the mechanism of protection by immunization with the rgpA DNA vaccine. After nonlethal challenge with invasive P. gingivalis W50, production of interleukin (IL)-2, IL-4, IL-5 and IL-12 was elevated; however, interferon (IFN)-gamma was lower in the serum of the DNA vaccine-immunized mice than in the serum of nonimmunized mice. The regulation of IFN-gamma production elicited by immunization with the rgpA DNA vaccine may play a significant role in protection against P. gingivalis infection in mice.

The effects of intra-amniotic injection of periodontopathic lipopolysaccharides in sheep

OBJECTIVE

Periodontal disease may cause several complications of pregnancy, including fetal death. The purpose of this study was to investigate in sheep the effects of the intra-amniotic injection of lipopolysaccharide from 3 periodontopathic organisms and to compare these effects with those resulting from similar injection of Escherichia coli lipopolysaccharide. The outcomes that were studied included the rates of fetal death and the features of inflammation and lung maturation in survivors.

STUDY DESIGN

At 118 days of pregnancy, ewes that were bearing single fetuses were allocated at random to receive intra-amniotic injections of saline solution (n = 13 fetuses), or lipopolysaccharide from Porphyromonas gingivalis (in doses from 0.1 to 10 mg [n = 22 fetuses]), Actinobacillus actinomycetemcomitans (10 mg [n = 6 fetuses]; 1 mg [n = 6 fetuses]), Fusobacterium nucleatum (10 mg [n = 6 fetuses]) or Escherichia coli (10 mg [n = 14 fetuses]; 1 mg [n = 7 fetuses]). Surviving fetuses were delivered abdominally at 125 days of gestation (term, 150 days).

RESULTS

When compared with Escherichia coli lipopolysaccharide at similar dosages, periodontopathic lipopolysaccharides had high rates of fetal lethality. Only 6 of 22 fetuses that were exposed to intra-amniotic Porphyromonas gingivalis lipopolysaccharide survived doses of 0.1 to 10 mg, and only 3 of 6 fetuses survived 10-mg Actinobacillus actinomycetemcomitans lipopolysaccharide. Escherichia coli lipopolysaccharide did not cause fetal loss when given at doses of 10 mg (n = 14 fetuses) or 1 mg (n = 7 fetuses). Fetuses that survived exposure to these lipopolysaccharides showed features of inflammation in amniotic fluid and cord blood at birth and enhanced lung maturation.

CONCLUSION

Lipopolysaccharides from these 3 periodontopathic organisms have much higher rates of fetal lethality than Escherichia coli lipopolysaccharide but can cause similar intrauterine inflammatory responses and improvements in lung volumes in survivors. Sources of inflammation that are distant from the uterus may underlie a proportion of unexplained stillbirth and other complications of pregnancy.

G(-) anaerobes-reactive CD4+ T-cells trigger RANKL-mediated enhanced alveolar bone loss in diabetic NOD mice

Diabetic patients experience a higher risk for severe periodontitis; however, the underlying mechanism remains unclear. We investigated the contribution of antibacterial T-cell-mediated immunity to enhanced alveolar bone loss during periodontal infection in nonobese diabetic (NOD) mice by oral inoculation with Actinobacillus actinomycetemcomitans, a G(-) anaerobe responsible for juvenile and severe periodontitis. The results show that 1) inoculation with A. actinomycetemcomitans in pre-diabetic NOD mice does not alter the onset, incidence, and severity of diabetes; 2) after A. actinomycetemcomitans inoculation, diabetic NOD mice (blood glucose >200 mg/dl and with severe insulitis) exhibit significantly higher alveolar bone loss compared with pre-diabetic and nondiabetic NOD mice; and 3) A. actinomycetemcomitans-reactive CD4+ T-cells in diabetic mice exhibit significantly higher proliferation and receptor activator of nuclear factor kappaB ligand (RANKL) expression. When diabetic mice are treated with the RANKL antagonist osteoprotegerin (OPG), there is a significant reversal of alveolar bone loss, as well as reduced RANKL expression in A. actinomycetemcomitans-reactive CD4+ T-cells. This study clearly describes the impact of autoimmunity to anaerobic infection in an experimental periodontitis model of type 1 diabetes. Thus, microorganism-reactive CD4+ T-cells and the RANKL-OPG axis provide the molecular basis of the advanced periodontal breakdown in diabetes and, therefore, OPG may hold therapeutic potential for treating bone loss in diabetic subjects at high risk.

Chronic maternal and fetal Porphyromonas gingivalis exposure during pregnancy in rabbits

OBJECTIVE

This study was undertaken to develop a rabbit model of maternal exposure to Porphyromonas gingivalis and determine whether fetal or placental exposure occurs.

STUDY DESIGN

Subcutaneous steel chambers were implanted in 8 New Zealand White female rabbits. On day 7 of pregnancy, 4 rabbits were inoculated through the chamber with 5 x 10 8 CFU/mL live P gingivalis , and 4 rabbits with broth (controls) and sacrificed at term. Polymerase chain reaction was used to detect P gingivalis in maternal and fetal liver and placenta. Fisher exact test was used to compare P gingivalis detection between groups.

RESULTS

Among exposed does, P gingivalis was detected in 33% of the maternal livers, 49% of placentas, and 34% fetal livers compared with none from controls ( P < .001).

CONCLUSION

Chronic maternal exposure to P gingivalis results in systemic dissemination, transplacental passage, and fetal exposure. This model may be useful to study placental and fetal effects of this oral pathogen and to study microbial dissemination across the placenta.

Fusobacterium nucleatum induces premature and term stillbirths in pregnant mice: implication of oral bacteria in preterm birth

Fusobacterium nucleatum is a gram-negative anaerobe ubiquitous to the oral cavity. It is associated with periodontal disease. It is also associated with preterm birth and has been isolated from the amniotic fluid, placenta, and chorioamnionic membranes of women delivering prematurely. Periodontal disease is a newly recognized risk factor for preterm birth. This study examined the possible mechanism underlying the link between these two diseases. F. nucleatum strains isolated from amniotic fluids and placentas along with those isolated from orally related sources invaded both epithelial and endothelial cells. The invasive ability may enable F. nucleatum to colonize and infect the pregnant uterus. Transient bacteremia caused by periodontal infection may facilitate bacterial transmission from the oral cavity to the uterus. To test this hypothesis, we intravenously injected F. nucleatum into pregnant CF-1 mice. The injection resulted in premature delivery, stillbirths, and nonsustained live births. The bacterial infection was restricted inside the uterus, without spreading systemically. F. nucleatum was first detected in the blood vessels in murine placentas. Invasion of the endothelial cells lining the blood vessels was observed. The bacteria then crossed the endothelium, proliferated in surrounding tissues, and finally spread to the amniotic fluid. The pattern of infection paralleled that in humans. This study represents the first evidence that F. nucleatum may be transmitted hematogenously to the placenta and cause adverse pregnancy outcomes. The results strengthen the link between periodontal disease and preterm birth. Our study also indicates that invasion may be an important virulence mechanism for F. nucleatum to infect the placenta.