Gram-negative anaerobes elicit a robust keratinocytes immune response with potential insights into HS pathogenesis

Hidradenitis Suppurativa (HS) is a chronic autoinflammatory skin disease with activated keratinocytes, tunnel formation and a complex immune infiltrate in tissue. The HS microbiome is polymicrobial with an abundance of commensal gram-positive facultative (GPs) Staphylococcus species and gram-negative anaerobic (GNA) bacteria like Prevotella, Fusobacterium and Porphyromonas with increasing predominance of GNAs with disease severity. We sought to define the keratinocyte response to bacteria commonly isolated from HS lesions to probe pathogenic relationships between HS and the microbiome. Type strains of Prevotella nigrescens, Prevotella melaninogenica, Prevotella intermedia, Prevotella asaccharolytica, Fusobacterium nucleatum, as well as Staphylococcus aureus and the normal skin commensal Staphylococcus epidermidis were heat-killed and co-incubated with normal human keratinocytes. RNA was collected and analysed using RNAseq and RT-qPCR. The supernatant was collected from cell culture for protein quantification. Transcriptomic profiles between HS clinical samples and stimulated keratinocytes were compared. Co-staining of patient HS frozen sections was used to localize bacteria in lesions. A mouse intradermal injection model was used to investigate early immune recruitment. TLR4 and JAK inhibitors were used to investigate mechanistic avenues of bacterial response inhibition. GNAs, especially F. nucleatum, stimulated vastly higher CXCL8, IL17C, CCL20, IL6, TNF and IL36γ transcription in normal skin keratinocytes than the GPs S. epidermidis and S. aureus. Using RNAseq, we found that F. nucleatum (and Prevotella) strongly induced the IL-17 pathway in keratinocytes and overlapped with transcriptome profiles of HS patient clinical samples. Bacteria were juxtaposed to activated keratinocytes in vivo, and F. nucleatum strongly recruited murine neutrophil and macrophage migration. Both the TLR4 and pan-JAK inhibitors reduced cytokine production. Detailed transcriptomic profiling of healthy skin keratinocytes exposed to GNAs prevalent in HS revealed a potent, extensive inflammatory response vastly stronger than GPs. GNAs stimulated HS-relevant genes, including many genes in the IL-17 response pathway, and were significantly associated with HS tissue transcriptomes. The close association of activated keratinocytes with bacteria in HS lesions and innate infiltration in murine skin cemented GNA pathogenic potential. These novel mechanistic insights could drive future targeted therapies.

Perturbation of the gut microbiome by Prevotella spp. enhances host susceptibility to mucosal inflammation

Diverse microbial signatures within the intestinal microbiota have been associated with intestinal and systemic inflammatory diseases, but whether these candidate microbes actively modulate host phenotypes or passively expand within the altered microbial ecosystem is frequently not known. Here we demonstrate that colonization of mice with a member of the genus Prevotella, which has been previously associated to colitis in mice, exacerbates intestinal inflammation. Our analysis revealed that Prevotella intestinalis alters composition and function of the ecosystem resulting in a reduction of short-chain fatty acids, specifically acetate, and consequently a decrease in intestinal IL-18 levels during steady state. Supplementation of IL-18 to Prevotella-colonized mice was sufficient to reduce intestinal inflammation. Hence, we conclude that intestinal Prevotella colonization results in metabolic changes in the microbiota, which reduce IL-18 production and consequently exacerbate intestinal inflammation, and potential systemic autoimmunity.

Members of Prevotella Genus Distinctively Modulate Innate Immune and Barrier Functions in a Human Three-Dimensional Endometrial Epithelial Cell Model

BACKGROUND

Prevotella species are commonly isolated from the reproductive tract of women with obstetric/gynecologic health complications. However, contributions of this genus to changes in local microenvironment are not well characterized. Our objective was to evaluate species-specific effects of Prevotella on the human endometrial epithelium.

METHODS

Thirteen Prevotella strains, originally isolated from the human oral cavity, amniotic fluid, endometrium, or vagina (including women with bacterial vaginosis), were obtained from BEI and ATCC resources. Bacteria were evaluated in silico and in vitro using human endometrial epithelial cells (EEC) grown as monolayers or a 3-dimensional (3D) model.

RESULTS

Genomic characterization illustrated metabolic and phylogenetic diversity of Prevotella genus. Among tested species, P. disiens exhibited cytotoxicity. Scanning electron microscopy analysis of the 3D EEC model revealed species-specific colonization patterns and alterations of ultracellular structures. Infection with sialidase-producing P. timonensis resulted in elongated microvilli, and increased MUC3 and MUC4 expression. Infections with Prevotella species, including P. bivia, did not result in significant proinflammatory activation of EEC.

CONCLUSIONS

Collectively, findings indicate that Prevotella species are metabolically diverse and overall not cytotoxic or overtly inflammatory in EEC; however, these bacteria can form biofilms, alter barrier properties of the endometrial epithelium, and ultimately impact colonization of secondary colonizers.

Toll like Receptor signalling by Prevotella histicola activates alternative NF-κB signalling in Cystic Fibrosis bronchial epithelial cells compared to P. aeruginosa

Cystic Fibrosis (CF), caused by mutations affecting the CFTR gene, is characterised by viscid secretions in multiple organ systems. CF airways contain thick mucus, creating a gradient of hypoxia, which promotes the establishment of polymicrobial infection. Such inflammation predisposes to further infection, a self-perpetuating cycle in mediated by NF-κB. Anaerobic Gram-negative Prevotella spp. are found in sputum from healthy volunteers and CF patients and in CF lungs correlate with reduced levels of inflammation. Prevotella histicola (P. histicola) can suppress murine lung inflammation, however, no studies have examined the role of P. histicola in modulating infection and inflammation in the CF airways. We investigated innate immune signalling and NF-kB activation in CF epithelial cells CFBE41o- in response to clinical stains of P. histicola and Pseudomonas aeruginosa (P. aeruginosa). Toll-Like Receptor (TLR) expressing HEK-293 cells and siRNA assays for TLRs and IKKα were used to confirm signalling pathways. We show that P. histicola infection activated the alternative NF-kB signalling pathway in CF bronchial epithelial cells inducing HIF-1α protein. TLR5 signalling was responsible for the induction of the alternative NF-kB pathway through phosphorylation of IKKα. The induction of transcription factor HIF-1α was inversely associated with the induction of the alternative NF-kB pathway and knockdown of IKKα partially restored canonical NF-kB activation in response to P. histicola. This study demonstrates that different bacterial species in the respiratory microbiome can contribute differently to inflammation, either by activating inflammatory cascades (P. aeruginosa) or by muting the inflammatory response by modulating similar or related pathways (P. histicola). Further work is required to assess the complex interactions of the lung microbiome in response to mixed bacterial infections and their effects in people with CF.

Increased Th17 activation and gut microbiota diversity are associated with pembrolizumab-triggered tuberculosis

INTRODUCTION

A hypersensitivity response akin to immune reconstitution inflammatory syndrome (IRIS) has been proposed as a mechanism responsible for anti-PD-1 therapy-induced tuberculosis. IRIS is associated with enhanced activation of IL-17A-expressing CD4 + T cells (Th17). Gut microbiota is thought to be linked to pulmonary inflammation through the gut-lung axis.

MATERIALS AND METHODS

We used ImmuCellAI to investigate the T cell population in lung cancer and tuberculosis samples. Then, we applied flow cytometry to monitor the expression levels of the Th17 cell activation marker CD38 in the peripheral blood of a patient experiencing adverse events, including tuberculosis, in response to pembrolizumab. The gut microbiome was examined by 16S rRNA sequencing to examine the alterations caused by pembrolizumab.

RESULTS

The percentage of Th17 cells was increased in both lung cancer and tuberculosis. FACS analysis showed that pembrolizumab induced substantial CD38 expression in Th17 cells. The patient's fecal samples showed that the diversity of the gut microbiota was significantly increased in response to the pembrolizumab cycle. One enriched genus was Prevotella, which has previously been linked to lung inflammation and Th17 immune activation.

DISCUSSION

The observed Th17 activation in our patient was consistent with a role of Th17-mediated IRIS in pembrolizumab-triggered tuberculosis. Pembrolizumab might trigger airway inflammation with a Th17 phenotype through microbiota interactions in the gut-lung axis.

Microbiota-driven interleukin-17-producing cells and eosinophils synergize to accelerate multiple myeloma progression

The gut microbiota has been causally linked to cancer, yet how intestinal microbes influence progression of extramucosal tumors is poorly understood. Here we provide evidence implying that Prevotella heparinolytica promotes the differentiation of Th17 cells colonizing the gut and migrating to the bone marrow (BM) of transgenic Vk*MYC mice, where they favor progression of multiple myeloma (MM). Lack of IL-17 in Vk*MYC mice, or disturbance of their microbiome delayed MM appearance. Similarly, in smoldering MM patients, higher levels of BM IL-17 predicted faster disease progression. IL-17 induced STAT3 phosphorylation in murine plasma cells, and activated eosinophils. Treatment of Vk*MYC mice with antibodies blocking IL-17, IL-17RA, and IL-5 reduced BM accumulation of Th17 cells and eosinophils and delayed disease progression. Thus, in Vk*MYC mice, commensal bacteria appear to unleash a paracrine signaling network between adaptive and innate immunity that accelerates progression to MM, and can be targeted by already available therapies.

Human gut microbiome: hopes, threats and promises

The microbiome has received increasing attention over the last 15 years. Although gut microbes have been explored for several decades, investigations of the role of microorganisms that reside in the human gut has attracted much attention beyond classical infectious diseases. For example, numerous studies have reported changes in the gut microbiota during not only obesity, diabetes, and liver diseases but also cancer and even neurodegenerative diseases. The human gut microbiota is viewed as a potential source of novel therapeutics. Between 2013 and 2017, the number of publications focusing on the gut microbiota was, remarkably, 12 900, which represents four-fifths of the total number of publications over the last 40 years that investigated this topic. This review discusses recent evidence of the impact of the gut microbiota on metabolic disorders and focus on selected key mechanisms. This review also aims to provide a critical analysis of the current knowledge in this field, identify putative key issues or problems and discuss misinterpretations. The abundance of metagenomic data generated on comparing diseased and healthy subjects can lead to the erroneous claim that a bacterium is causally linked with the protection or the onset of a disease. In fact, environmental factors such as dietary habits, drug treatments, intestinal motility and stool frequency and consistency are all factors that influence the composition of the microbiota and should be considered. The cases of the bacteria Prevotella copri and Akkermansia muciniphila will be discussed as key examples.

Gut dendritic cell activation links an altered colonic microbiome to mucosal and systemic T-cell activation in untreated HIV-1 infection

HIV-1-associated disruption of intestinal homeostasis is a major factor contributing to chronic immune activation and inflammation. Dendritic cells (DCs) are crucial in maintaining intestinal homeostasis, but the impact of HIV-1 infection on intestinal DC number and function has not been extensively studied. We compared the frequency and activation/maturation status of colonic myeloid DC (mDC) subsets (CD1c(+) and CD1c(neg)) and plasmacytoid DCs in untreated HIV-1-infected subjects with uninfected controls. Colonic mDCs in HIV-1-infected subjects had increased CD40 but decreased CD83 expression, and CD40 expression on CD1c(+) mDCs positively correlated with mucosal HIV-1 viral load, with mucosal and systemic cytokine production, and with frequencies of activated colon and blood T cells. Percentage of CD83(+)CD1c(+) mDCs negatively correlated with frequencies of interferon-γ-producing colon CD4(+) and CD8(+) T cells. CD40 expression on CD1c(+) mDCs positively associated with abundance of high prevalence mucosal Prevotella copri and Prevotella stercorea but negatively associated with a number of low prevalence mucosal species, including Rumminococcus bromii. CD1c(+) mDC cytokine production was greater in response to in vitro stimulation with Prevotella species relative to R. bromii. These findings suggest that, during HIV infection, colonic mDCs become activated upon exposure to mucosal pathobiont bacteria leading to mucosal and systemic immune activation.

General immune status and oral microbiology in patients with different forms of periodontitis and healthy control subjects

Objective

Immunological processes in the etiopathogenesis of periodontitis, especially the aggressive form, are not well understood. This study examined clinical as well as systemic immunological and local microbiological features in healthy controls and patients with different forms of periodontitis.

Materials and Methods

14 healthy subjects, 15 patients diagnosed with aggressive periodontitis, and 11 patients with chronic periodontitis were recruited. Periodontal examination was performed and peripheral blood was collected from each patient. Lymphocyte populations as well as the release of cytokines by T-helper cells were determined by flow cytometry and enzyme linked immunosorbent spot assay. Subgingival plaque samples were taken from each individual and immediately cultivated for microbiological examination.

Results

When stimulating peripheral blood mononuclear cells (PBMCs) with lipopolysaccharide, a higher IL-1β release was found in patients with moderate chronic periodontitis compared to the other groups (p<0.01). Numbers of B-cells, naïve and transitional B-cells, memory B-cells, and switched memory B-cells were within the reference range for all groups, but patients with chronic periodontitis showed the highest percentage of memory B-cells without class switch (p = 0.01). The subgingival plaque differed quantitatively as well as qualitatively with a higher number of Gram-negative anaerobic species in periodontitis patients. Prevotella denticola was found more often in patients with aggressive periodontitis (p<0.001) but did not show an association to any of the systemic immunological findings. Porphyromonas gingivalis, which was only found in patients with moderate chronic periodontitis, seems to be associated with an activation of the systemic immune response.

Conclusion

Differences between aggressive periodontitis and moderate chronic periodontitis are evident, which raises the question of an inadequate balance between systemic immune response and bacterial infection in aggressive periodontitis.

Helicobacter pylori induced gastric immunopathology is associated with distinct microbiota changes in the large intestines of long-term infected Mongolian gerbils

Background

Gastrointestinal (GI) inflammation in mice and men are frequently accompanied by distinct changes of the GI microbiota composition at sites of inflammation. Helicobacter (H.) pylori infection results in gastric immunopathology accompanied by colonization of stomachs with bacterial species, which are usually restricted to the lower intestine. Potential microbiota shifts distal to the inflammatory process following long-term H. pylori infection, however, have not been studied so far.

Methodology/Principal Findings

For the first time, we investigated microbiota changes along the entire GI tract of Mongolian gerbils after 14 months of infection with H. pylori B8 wildtype (WT) or its isogenic ΔcagY mutant (MUT) strain which is defective in the type IV secretion system and thus unable to modulate specific host pathways. Comprehensive cultural analyses revealed that severe gastric diseases such as atrophic pangastritis and precancerous transformations were accompanied by elevated luminal loads of E. coli and enterococci in the caecum and together with Bacteroides/Prevotella spp. in the colon of H. pylori WT, but not MUT infected gerbils as compared to naïve animals. Strikingly, molecular analyses revealed that Akkermansia, an uncultivable species involved in mucus degradation, was exclusively abundant in large intestines of H. pylori WT, but not MUT infected nor naïve gerbils.

Conclusion/Significance

Taken together, long-term infection of Mongolian gerbils with a H. pylori WT strain displaying an intact type IV secretion system leads to distinct shifts of the microbiota composition in the distal uninflamed, but not proximal inflamed GI tract. Hence, H. pylori induced immunopathogenesis of the stomach, including hypochlorhydria and hypergastrinemia, might trigger large intestinal microbiota changes whereas the exact underlying mechanisms need to be further unraveled.

Bacteria in the vaginal microbiome alter the innate immune response and barrier properties of the human vaginal epithelia in a species-specific manner

BACKGROUND

Bacterial vaginosis increases the susceptibility to sexually transmitted infections and negatively affects women's reproductive health.

METHODS

To investigate host-vaginal microbiota interactions and the impact on immune barrier function, we colonized 3-dimensional (3-D) human vaginal epithelial cells with 2 predominant species of vaginal microbiota (Lactobacillus iners and Lactobacillus crispatus) or 2 prevalent bacteria associated with bacterial vaginosis (Atopobium vaginae and Prevotella bivia).

RESULTS

Colonization of 3-D vaginal epithelial cell aggregates with vaginal microbiota was observed with direct attachment to host cell surface with no cytotoxicity. A. vaginae infection yielded increased expression membrane-associated mucins and evoked a robust proinflammatory, immune response in 3-D vaginal epithelial cells (ie, expression of CCL20, hBD-2, interleukin 1β, interleukin 6, interleukin 8, and tumor necrosis factor α) that can negatively affect barrier function. However, P. bivia and L. crispatus did not significantly upregulate pattern-recognition receptor-signaling, mucin expression, antimicrobial peptides/defensins, or proinflammatory cytokines in 3-D vaginal epithelial cell aggregates. Notably, L. iners induced pattern-recognition receptor-signaling activity, but no change was observed in mucin expression or secretion of interleukin 6 and interleukin 8.

CONCLUSIONS

We identified unique species-specific immune signatures from vaginal epithelial cells elicited by colonization with commensal and bacterial vaginosis-associated bacteria. A. vaginae elicited a signature that is consistent with significant disruption of immune barrier properties, potentially resulting in enhanced susceptibility to sexually transmitted infections during bacterial vaginosis.

Divergent pro-inflammatory profile of human dendritic cells in response to commensal and pathogenic bacteria associated with the airway microbiota

Recent studies using culture-independent methods have characterized the human airway microbiota and report microbial communities distinct from other body sites. Changes in these airway bacterial communities appear to be associated with inflammatory lung disease, yet the pro-inflammatory properties of individual bacterial species are unknown. In this study, we compared the immune stimulatory capacity on human monocyte-derived dendritic cells (DCs) of selected airway commensal and pathogenic bacteria predominantly associated with lungs of asthma or COPD patients (pathogenic Haemophillus spp. and Moraxella spp.), healthy lungs (commensal Prevotella spp.) or both (commensal Veillonella spp. and Actinomyces spp.). All bacteria were found to induce activation of DCs as demonstrated by similar induction of CD83, CD40 and CD86 surface expression. However, asthma and COPD-associated pathogenic bacteria provoked a 3-5 fold higher production of IL-23, IL-12p70 and IL-10 cytokines compared to the commensal bacteria. Based on the differential cytokine production profiles, the studied airway bacteria could be segregated into three groups (Haemophilus spp. and Moraxella spp. vs. Prevotella spp. and Veillonella spp. vs. Actinomyces spp.) reflecting their pro-inflammatory effects on DCs. Co-culture experiments found that Prevotella spp. were able to reduce Haemophillus influenzae-induced IL-12p70 in DCs, whereas no effect was observed on IL-23 and IL-10 production. This study demonstrates intrinsic differences in DC stimulating properties of bacteria associated with the airway microbiota.

Susceptibility of various oral bacteria to antimicrobial peptides and to phagocytosis by neutrophils

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the susceptibility of nonperiodontopathic and periodontopathic bacteria to major defense mechanisms for bacterial clearance in gingival sulcus.

MATERIAL AND METHODS

Twenty strains of 13 oral bacterial species were studied for their susceptibility to phagocytosis by human neutrophils and to the antimicrobial peptides LL-37 and human beta defensin-3. The minimum inhibitory concentrations of LL-37 and human beta defensin-3 were determined by a liquid dilution assay, and susceptibility to phagocytosis was examined by a flow cytometric phagocytosis assay.

RESULTS

The minimum inhibitory concentrations of LL-37 and human beta defensin-3 varied greatly, depending on the strain and species. Although a significant difference between the non- and periodontopathic groups was not observed, the red-complex bacteria were more resistant to LL-37 than the others (p=0.004). The susceptibility of oral bacteria to phagocytosis was quite variable, depending on the species but not on the strains. The periodontopathic bacteria, especially Actinobacillus actinomycetemcomitans and the red-complex triad, were more resistant to phagocytosis than were the nonperiodontopathic bacteria (p=0.0003). In addition, bacteria resistant both to antimicrobial peptides and to phagocytosis were more common in the periodontopathic group.

CONCLUSION

Our results indicate that immune evasion may contribute to the pathogenicity of some periodontopathic bacteria.

Parotid salivary S-IgA antibodies during experimental gingivitis in smokers and non-smokers

Persons who smoke display a less pronounced increase of gingival bleeding in the experimental gingivitis model as compared with non-smokers. The aim of the present study was to investigate whether this could partly be explained by differences in levels of parotid total secretory IgA (S-IgA) or parotid S-IgA reactive with selected oral microorganisms. Parotid saliva samples were obtained from 11 smoking and 14 non-smoking volunteers, at baseline, after 5 and 14 days of full mouth experimental gingivitis. Output levels of total S-IgA and of specific S-IgA reactive with cell extracts from Actinobacillus actinomycetemcomitans, Actinomyces naeslundii, Campylobacter rectus, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Peptostreptococcus micros, Streptococcus gordonii and Streptococcus mutans were determined in the samples by means of ELISA. Smokers and non-smokers were found to have similar output levels (microg/min) of total S-IgA, and the values did not significantly change during the experimental gingivitis trial. Parotid salivary outputs (units/min) of the bacteria-specific S-IgA at baseline and at days 5 and 14, were not different between smokers and non-smokers; no changes were observed during the experimental gingivitis trial. The present observations indicate that total S-IgA and bacteria-specific S-IgA in saliva are not main factors that can explain the less pronounced increase of gingival bleeding in the experimental gingivitis model in smokers as compared with non-smokers.

Maternal periodontitis and prematurity. Part II: Maternal infection and fetal exposure

Clinical data from the first 812 deliveries from a cohort study of pregnant mothers entitled Oral Conditions and Pregnancy (OCAP) demonstrate that both antepartum maternal periodontal disease and incidence/progression of periodontal disease are associated with preterm birth and growth restriction after adjusting for traditional obstetric risk factors. In the current study we present measures of maternal periodontal infection using whole chromosomal DNA probes to identify 15 periodontal organisms within maternal periodontal plaque sampled at delivery. In addition, maternal postpartum IgG antibody and fetal exposure, as indexed by fetal cord blood IgM level to these 15 maternal oral pathogens, was measured by whole bacterial immunoblots. The potential role of maternal infection with specific organisms within 2 bacterial complexes most often associated with periodontitis, conventionally termed "Orange" (Campylobacter rectus, Fusobacterium nucleatum, Peptostreptococcus micros, Prevotella nigrescens, and Prevotella intermedia) and "Red" (Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola) complexes, respectively, to prematurity was investigated by relating the presence of oral infection, maternal IgG, and fetal cord IgM, comparing full-term to preterm (gestational age < 37 weeks). The prevalence of 8 periodontal pathogens was similar among term and preterm mothers at postpartum. There was a 2.9-fold higher prevalence of IgM seropositivity for one or more organisms of the Orange or Red complex among preterm babies, as compared to term babies (19.9% versus 6.9%, respectively, P = 0.0015, chi square). Specifically, the prevalence of positive fetal IgM to C. rectus was significantly higher for preterm as compared to full-term neonates (20.0% versus 6.3%, P = 0.0002, as well as P. intermedia (8.8% versus 1.1%, P = 0.0003). A lack of maternal IgG antibody to organisms of the Red complex was associated with an increased rate of prematurity with an odds ratio (OR) = 2.2; confidence interval (CI) 1.48 to 3.79), consistent with the concept that maternal antibody protects the fetus from exposure and resultant prematurity. The highest rate of prematurity (66.7%) was observed among those mothers without a protective Red complex IgG response coupled with a fetal IgM response to Orange complex microbes (combined OR 10.3; P < 0.0001). These data support the concept that maternal periodontal infection in the absence of a protective maternal antibody response is associated with systemic dissemination of oral organisms that translocate to the fetus resulting in prematurity. The high prevalence of elevated fetal IgM to C. rectus among premature infants raises the possibility that this specific maternal oral pathogen may serve as a primary fetal infectious agent eliciting prematurity.

Characterisation and selection of a Lactobacillus species to re-colonise the vagina of women with recurrent bacterial vaginosis

This paper reports the results of characterising and selecting a strain of Lactobacillus for potential use as a probiotic in regenerating the vaginal flora of women with recurrent episodes of bacterial vaginosis (BV). BV is a condition characterised by a depletion of vaginal lactobacilli accompanied by an overgrowth of a mixed vaginal flora of aerobic, anaerobic and micro-aerophilic species in very large numbers. BV has been associated with various gynaecological and obstetric complications and has an extremely high recurrence rate, due in part to the failure to establish a normal vaginal flora after antimicrobial therapy. A total of 60 vaginal isolates of lactobacilli was assessed for characteristics considered important for vaginal re-colonisation. The characteristics studied were the in-vitro inhibitory activity of the lactobacilli against bacterial species isolated from women with recurrent BV, acid production after growth of the lactobacilli in liquid culture, production of hydrogen peroxide (H2O2) and adhesiveness of the lactobacilli to exfoliated vaginal epithelial cells (VEC). Four strains of lactobacilli, L. acidophilus (61701 and 61880), L. crispatus (55730) and L. delbrueckii subsp. delbrueckii (65407), demonstrated the greatest inhibitory activity against the BV-associated bacterial species. Two of these isolates (55730 and 61880) produced H2O2. All four isolates produced a highly acidic environment after growth in liquid medium (pH <4). Only one of these (strain 61701) was strongly adherent to VEC (>100 bacteria/VEC). A further isolate (L. acidophilus 48101) did not demonstrate maximum inhibitory activity against BV-associated bacteria, but was found to be a strong producer of H2O2 and was also highly adherent to VEC. Isolates 61701 and 48101 could be candidates for use as probiotics for vaginal re-colonisation.

Bovine polymorphonuclear neutrophil-mediated phagocytosis and an immunoglobulin G2 protease produced by Porphyromonas levii

Acute interdigital phlegmon (AIP) is a commonly occurring anaerobic bacterial infection in cattle. This study examined in vitro the interaction of bovine polymorphonuclear granulocytic neutrophils (PMN) from blood with bacterial species involved in AIP. Polymorphonuclear neutrophils were purified from whole bovine blood, exposed to one of the three putative etiologic agents of AIP and comparatively assessed for phagocytosis using light microscopy. Fusobacterium necrophorum and Prevotella intermedia were effectively phagocytosed by PMN, but Porphyromonas levii was phagocytosed significantly less effectively by PMN. The effect of high titre anti-P. levii bovine serum on antibody-mediated phagocytosis by PMN was also evaluated. High titre serum increased the efficiency of phagocytosis of P. levii by bovine PMN. This was independent of heat labile complement factors. Antibodies specific for P. levii were assessed for protease activity capable of cleaving bovine immunoglobulins (IgG, IgG1, IgG2, and IgM). Partially purified supernatant from broth cultures of P. levii were incubated with biotinylated immunoglobulins (Igs). Samples were taken from times 0 to 72 h and examined using SDS-PAGE followed by Western blot analysis. Streptavidin-alkaline phosphatase and NBT-BCIP were used to visualize the Igs for heavy and light chains as well as lower molecular weight fragments of these glycoproteins. Porphyromonas levii produced an immunoglobulin protease which readily cleaved bovine IgG into fragments, but did not act against IgM. Specifically, the enzyme may be a significant virulence factor as it may act to neutralize the antibodies demonstrated necessary for effective PMN-mediated phagocytosis.

Inflammatory cytokine production and specific antibody responses against possible causative bacteria in patients with multilesional periapical periodontitis

We examined the induction of inflammatory cytokines (including interleukin-1, interleukin-6, interleukin-8, and tumor necrosis factor-alpha) by several species of possible causative bacteria in periapical periodontitis. Assays were done on human whole blood cultures from patients with differing numbers of periapical lesions; those having radiographically clear periapical lesions in 10 or more teeth (high lesion group), in one or two teeth (low lesion group), and healthy volunteers having no periapical lesions (no lesion group). Prevotella melaninogenica ATCC 25845 induced interleukin-6 more strongly in subjects from the high lesion group than in the other groups. To ascertain the degree of sensitization by test bacteria, we examined the reactivities of antibodies in serum and saliva from the six subjects to different bacterial species. Porphylomonas gingivalis cells reacted strongly with sera from the high lesion group. Thus, Prevotella melaninogenica and Porphylomonas gingivalis may be involved in multilesional periapical periodontitis by inducing specific cytokines and/or humoral immune responses.

Serum antibodies reacting with subgingival species in refractory periodontitis subjects

The purpose of this investigation was to compare the levels of serum IgG antibody to 85 subgingival species in 32 refractory periodontitis, 56 successfully treated, and 33 periodontally healthy subjects. Refractory subjects showed mean full mouth attachment loss and/or >3 sites showing attachment loss >2.5 mm within 1 year after 2 treatment modalities, scaling and root planing and surgery plus systemically administered tetracycline. Successfully-treated subjects showed mean attachment level gain and no sites with attachment loss >2.5 mm, 1 year post-therapy. Periodontally healthy subjects exhibited no pocket or attachment level >3 mm, and no evidence of progressing attachment loss during 1 year of monitoring. Baseline serum was obtained from each subject and tested against 85 subgingival species, including reference strains and strains isolated from refractory subjects, using checkerboard immunoblotting. Significance of differences in levels of serum antibody among groups were sought using the Kruskal-Wallis test. Refractory subjects constituted a heterogeneous group based on their serum antibody response to subgingival species. Some individuals had antibody reactions to many subgingival species, while other subjects showed fewer or low numbers of responses. On average, refractory subjects exhibited higher numbers and levels of serum antibody reactions to a wide range of subgingival species than successfully treated or periodontally healthy subjects. Differences in serum antibody among clinical groups were more striking at higher threshold levels of antibody (>50 microg/ml and > 100 microg/ml). The data showed that a subject was 10.1 x more likely to be refractory if the subject exhibited antibody reactions with >9 subgingival species at >50 microg/ml (p<0.001, after adjusting for multiple comparisons). Serum antibody to a subset of the test species differed among the clinical groups. Porphyromonas gingivalis, Bacteroidesforsythus, and some strains isolated from refractory subjects (a novel Neisseria sp., Enterococcus faecalis, Prevotella loescheii and Prevotella oulora) elicited high serum antibody in the successfully treated and refractory subjects. High levels of serum antibody to a Microbacterium lacticum-like organism, Streptococcus oralis, Streptococcus constellatus, Actinobacillus actinonmycetemcomitans serotype c and Haemophilus aphrophilus significantly increased the likelihood of a subject being refractory to conventional periodontal therapy.

Reduced serum IgG reactivities with bacteria from dental plaque in HIV-infected persons with periodontitis

Serum samples were obtained from 44 HIV-seropositive (HIV+) and 37 HIV-seronegative (HIV-) persons that were grouped according to periodontal status. Serum IgG and IgA reactivities towards Streptococcus mutans, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis. Prevotella intermedia, Prevotella nigrescens and Fusobacterium nucleatum were measured by means of ELISA. HIV+ persons with chronic marginal periodontitis showed significantly lower IgG reactivities to the periodontal pathogens A. actinomycetemcomitans, P. gingivalis, P. intermedia and F. nucleatum as compared with their HIV- counterparts (p < 0.05). Specific serum IgA reactivities were similar in the two periodontitis groups, except for P. nigrescens where the HIV+ group with chronic marginal periodontitis had lower values than their systemically healthy counterparts (p < 0.05). The results indicate that HIV infection affects the humoral serum immune responses against bacteria in dental plaque; the depressed antibody responses may contribute to the increased susceptibility for periodontal infections in HIV-infected patients.

Conservation of fimbriae and the hemagglutinating adhesin HA-Ag2 among Porphyromonas gingivalis strains and other anaerobic bacteria studied by epitope mapping analysis

Monoclonal antibodies characterized as antifimbria and anti-HA-Ag2 were used in immunoblotting to examine the antigenic distribution of fimbriae and HA-Ag2 among a collection of human and animal Porphyromonas strains and human Prevotella and Bacteroides strains. The results showed that fimbrial and HA-Ag2 antigenic structures are peculiar to the species Porphyromonas gingivalis.

Inhibition of Prevotella and Capnocytophaga immunoglobulin A1 proteases by human serum

Oral Prevotella and Capnocytophaga species, regularly isolated from periodontal pockets and associated with extraoral infections, secret specific immunoglobulin A1 (IgA1) proteases cleaving human IgA1 in the hinge region into intact Fab and Fc fragments. To investigate whether these enzymes are subject to inhibition in vivo in humans, we tested 34 sera from periodontally diseased and healthy individuals in an enzyme-linked immunosorbent assay for the presence and titers of inhibition of seven Prevotella and Capnocytophaga proteases. All or nearly all of the sera inhibited the IgA1 protease activity of Prevotella buccae, Prevotella oris, and Prevotella loescheii. A minor proportion of the sera inhibited Prevotella buccalis, Prevotella denticola, and Prevotella melaninogenica IgA1 proteases, while no sera inhibited Capnocytophaga ochracea IgA1 protease. All inhibition titers were low, ranging from 5 to 55, with titer being defined as the reciprocal of the dilution of serum causing 50% inhibition of one defined unit of protease activity. No correlation between periodontal disease status and the presence, absence, or titer of inhibition was observed. The nature of the low titers of inhibition in all sera of the IgA1 proteases of P. buccae, P. oris, and P. loescheii was further examined. In size exclusion chromatography, inhibitory activity corresponded to the peak volume of IgA. Additional inhibition of the P. oris IgA1 protease was found in fractions containing both IgA and IgG. Purification of the IgG fractions of five sera by passage of the sera on a protein G column resulted in recovery of inhibitory IgG antibodies against all three IgA1 proteases, with the highest titer being for the P. oris enzyme. These finding indicate that inhibitory activity is associated with enzyme-neutralizing antibodies.

Extracts of periodontopathic microorganisms lack functional superantigenic activity for murine T cells

Products of periodontopathic bacteria exert immunomodulatory effects on various lymphoid cell populations, some of which have been implicated in the pathogenesis of periodontitis. It has recently been suggested that some of these bacterial products may possess superantigenic (SAg) activity. SAg bind simultaneously to the V beta chain of T cell receptors and to class II major histocompatibility complex molecules, thereby activating as many as 35% of T cells to proliferate and produce cytokines. In order to examine this question, the proliferation of splenic and thymic T cells from immunologically naive, 3-6-wk-old Balb/c (H-2d), C57BL/6 (H-2b) and C3H/HeJ (H-2k) mice was assessed in response to sonic extracts of periodontopathogens. Laboratory and/or reference strains of a.o. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens were used as stimulants. Staphylococcal enterotoxin B (SEB), a known superantigen, was utilized as a positive control. Unfractionated spleen cells responded to several of the tested preparations of the different bacteria, as well as to SEB, Con A and Escherichia coli LPS. Thymocytes responded to Con A and SEB, but not to LPS or to any sonic extract. Spleen cells depleted of B cells by panning responded to SEB and Con A, but not to LPS and showed a reduced response to sonicates. The residual response of B cell-depleted spleen cells was reduced essentially to background by treatment with anti-Thy 1.2 + C'. Similar results were obtained in the presence of 5% added mitomycin-treated antigen presenting cells, indicating that these cells were not limiting. These results demonstrate that extracts of periodontopathic bacteria do not stimulate murine T cells in a manner consistent with superantigenic activation.

Antibody response to Prevotella spp. in patients with ventilator-associated pneumonia

Although anaerobic bacteria are frequently isolated from the oropharyngeal flora, their potential pathogenic role in ventilator-associated pneumonia (VAP) has been poorly investigated. In order to evaluate the pathogenic role of Prevotella spp. isolated from protected specimen brushes, we investigated the systemic humoral response with the enzyme-linked immunosorbent assay (ELISA) and Western blot (immunoblot) in 13 patients who developed a VAP associated with Prevotella species (group I). The antigen used was a mixture of whole-cell proteins taken from four reference Prevotella strains. We compared the antibody levels observed in these patients with those measured in 30 patients who developed a VAP unrelated to anaerobic bacteria (group II), in 27 patients with dental stumps (group III), and in 30 healthy patients (group IV) who had Prevotella species on dental plaque. The ELISA levels obtained in the four groups showed significant differences between group I and each of the three control groups (P < 0.05). The antibody profiles obtained by Western blot showed an intensity of response roughly superposable over levels obtained by ELISA and a species specificity. These findings suggested that colonization of these patients with Prevotella species may have been associated with an infectious process leading to a systemic humoral response and that these bacteria could play a role in VAP.

Cell envelope and cell wall immunization of Macaca fascicularis: effect on the progression of ligature-induced periodontitis

The nonhuman primate, Macaca fascicularis, was used to study the role of immunization with selected members of the periodontopathic microbiota in the longitudinal progression of ligature-induced periodontitis. Animals were immunized with cell envelope antigens prepared from Porphyromonas gingivalis and Prevotella intermedia, and a mixture prepared from Fusobacterium nucleatum, Campylobacter rectus, and Actinomyces viscosus. Serum immunoglobulin G (IgG), IgM and IgA isotype antibodies increased significantly in all immunization groups and were specific for each of the immunogens. P. gingivalis and P. intermedia immunization resulted in a stabilization of the proportions of these species throughout most of the experiment. The high P. gingivalis antibody titer resulted in low P. gingivalis numbers being recovered. P. gingivalis immunization, while lowering recoverable viable P. gingivalis, resulted in significantly increased levels of Prevotella loescheii, Prevotella buccae, Bacteroides macacae and Prevotella melaninogenica compared with preligation and preimmunization levels. Actinobacillus actinomycetemcomitans, Capnocytophaga spp. and Eikenella spp. remained at preligation levels postimmunization. Campylobacter spp. increased significantly during the course of the experiment in all groups, whereas the levels of Fusobacterium spp. decreased. Plaque indices and bleeding on probing showed significant increases in all groups following ligation, with the placebo group showing the greatest increase. Pocket depth measurements revealed that , whereas the placebo animals showed an approximate 5% increase, the P. gingivalis- and P. intermedia-immunized groups showed nearly a 20% increase in pocket depth. Attachment level measurements showed significantly greater attachment loss in the P. gingivalis- and P. intermedia-immunized groups, and the F. nucleatum + C. rectus + A. viscosus immunization appeared to prevent significant changes in pocket depth/attachment level loss. Radiographic measurement of bone loss by computer-assisted densitometric image analysis revealed that the placebo group lost bone throughout the experiment. P. gingivalis- and P. intermedia-immunized groups showed an exacerbated loss of bone density and the group immunized with F. nucleatum + C. rectus + A. viscosus exhibited significantly lower amounts of bone loss when analyzed by computer-assisted densitometric image analysis, compared with the other immunized groups. Although immunization with P. gingivalis and P. intermedia cell envelope antigens had an effect on their emergence in the complex microbiota of the developing periodontal pocket, this immunization also resulted in greater bone loss than immunization with F. nucleatum + C. rectus + A. viscosus, suggesting that, whereas selective members of the putative periodontopathic microbiota may play a direct role in periodontal tissue destruction, the complexity of the subgingival microbiota dictates that considerable scrutiny is required to select useful immunogens that can elicit functional protection from periodontal tissue destruction induced by oral microorganisms that already colonize or infect the host.

In vivo cleavage of immunoglobulin A1 by immunoglobulin A1 proteases from Prevotella and Capnocytophaga species

Immunoglobulin A1 (IgA1) proteases secreted by oral Prevotella and Capnocytophaga species specifically cleave IgA1 at the same peptide bond in the hinge region, leaving intact monomeric Fab and Fc fragments. Assuming that Prevotella- and Capnocytophaga-induced Fab fragments of IgA1 expose a specific immunogenic neoepitope at the cleavage site, we established an enzyme-linked immunosorbent assay to measure human serum antibodies to this neoepitope as indirect evidence of in vivo activity of Prevotella and Capnocytophaga IgA1 proteases. The assay used a monoclonal antibody with specificity for the neoepitope, and the ability to block binding of the monoclonal antibody to the neoepitope was investigated. Absorption of sera with Prevotella melaninogenica-induced Fab fragments of IgA1 resulted in removal of antibodies blocking binding of the monoclonal antibody, whereas absorption with Fab fragments induced by bacterial IgA1 proteases of other cleavage specificities did not remove blocking antibodies. Consequently, we assume that the antibodies detected had been induced by a neoepitope an the Fab fragment of IgA1 exposed exclusively after cleavage with IgA1 proteases from Prevotella and Capnocytophaga, indicating in vivo activity of these IgA1 proteases. Evidence, though indirect, of in vivo activity of Prevotella and Capnocytophaga IgA1 proteases was present in 42 of 92 sera examined and in a significantly higher proportion of sera from adults with periodontal disease compared with control individuals. No correlation with disease was observed for the juvenile periodontitis groups.

Effect of periodontal treatments on serum IgG antibody titers against periodontopathic bacteria

Serum IgG antibody titers to 7 periodontopathic bacteria in periodontitis patients were measured at the 1st visit and after various periodontal treatments with clinically successful improvement, in order to evaluate what kind of factors are associated with changes of serum antibody titers. 20 patients (10 male and 10 female from 23 to 61 years old) with adult, rapidly progressive periodontitis were enrolled in this study. All patients received initial preparation and most of them also underwent surgical procedure. After the treatments, the mean probing pocket depths decreased from 3.72 mm to 1.56 mm. Serum samples were collected from patients at the initial and final examinations. Serum IgG antibody titers against sonicated antigens of Porphyromonas gingivalis FDC 381, Prevotella intermedia ATCC 25611, Prevotella loescheii ATCC 15930, Fusobacterium nucleatum subspecies nucleatum ATCC 25586, Actinobacillus actinomycetemcomitans FDC Y4, Eikenella corrodens FDC 1073 and Capnocytophaga ochracea # M 12 were determined by enzyme-linked immunosorbent assay. The mean antibody titers to P. gingivalis and P. intermedia decreased significantly after the treatment as compared to their pretreatment levels. The antibody titer to P. gingivalis, especially, decreased in all of the patients examined. A significant relationship was found between the decreased antibody titer to P. gingivalis and the number of teeth which received periodontal surgery, as well as treatment length, and the relationship between the decreased antibody titer to P. intermedia and the number of extracted teeth was also significant. These results suggest that the changes of serum IgG titers against P. gingivalis and P. intermedia are related to the suppression of such pathogens in subgingival plague.

Characterization of immunoglobulin G-degrading proteases of Prevotella intermedia and Prevotella nigrescens

Degradation of immunoglobulins is thought to be an important factor in the causation of periodontal diseases by hindering local host defenses and by providing nutrients to the periodontal microflora. In this study, we characterized the proteolytic activity against human immunoglobulin G (IgG) of 20 strains of Prevotella intermedia and Prevotella nigrescens isolated from periodontal pockets and oral abscesses. IgG degradation was studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. All strains degraded IgG within 48 h after growth in trypticase-yeast extract medium (TY) supplemented with 0.3% IgG. Incorporating IgG in TY broth enhanced bacterial growth. Protease profiles (zymography), which revealed the presence of 1-4 IgG-degrading proteolytic bands in bacterial cell extracts, became more complex after growth in the presence of IgG. A 38-kDa protease capable of degrading IgG nonspecifically was present in almost all strains. The proteolytic activity was mainly located on the surface of the cell envelope. Two strains of P. intermedia and P. nigrescens ATCC 33563 were selected for further studies. Bacterial cell suspensions in phosphate-buffered saline completely degraded human IgG, IgA and IgM within 24 h. This activity depended on reducing conditions and was inhibited at temperatures above 50 degrees C. The pH optimum of immunoglobulin degradation was at pH 7. Strains cultured at 42 degrees C showed a markedly reduced capacity to degrade IgG. Inhibition studies revealed that breakdown of IgG was caused by a cysteine protease(s). The capacity of P. intermedia and P. nigrescens to degrade immunoglobulins may explain their association with polymicrobial oral diseases.

A longitudinal study from prepuberty to puberty of gingivitis. Correlation between the occurrence of Prevotella intermedia and sex hormones

A longitudinal study of 24 subjects progressing normally from prepuberty to puberty was undertaken to evaluate the effects of sex hormone levels on clinical and microbiologic parameters and on serum antibodies. During elementary school, at the beginning of the longitudinal monitoring, 2 groups, 12 subjects with gingivitis and 12 gingivitis-free subjects, were selected and observed through puberty. Bone ages and self-assessment of secondary sex characteristics were used to confirm puberty. A statistically significant increase in the proportions of Prevotella intermedia including Prevotella nigrescens and serum antibody levels against P. intermedia was seen in gingivitis group throughout the longitudinal study. Serum levels of testosterone in boys and estradiol and progesterone in girls was positively correlated with levels of P. intermedia and P. nigrescens. In puberty, a slight but significant increase in GI scores over prepuberty has been shown; however, there was no significant change in PlI from prepuberty to puberty. Our study confirmed that there was a statistically significant increase in gingival inflammation and in the proportion of P. intermedia and P. nigrescens in puberty relative to the baseline value, except in the gingivitis-free male group. Our findings suggest that these increases are correlated with elevation in systemic levels of the sex hormones.

Effect of initial therapy on dynamics of immunogloblin G levels to some periodontopathic bacteria in serum and gingival crevicular fluid

Using enzyme-linked immunosorbent assay, the IgG antibody levels to specific gram-negative periodontopathic bacteria in serum of 21 adult periodontitis patients and the gingival crevicular fluid (GCF) from 42 sites with destructive lesions and 21 healthy sites were evaluated before and after initial preparation. Porphyromonas gingivalis, Bacteroides forsythus, Prevotella intermedia, Prevotella nigrescens, Campylobacter rectus, Treponema denticola and Actinobacillus actinomycetemcomitans in subgingival plaque samples from the patients were examined by indirect immunofluorescence microscopy. Subgingival plaque, GCF, and serum samples were taken at baseline and three weeks after initial preparation. For 14 patients, changes in clinical parameters due to the initial preparation were correlated with reduction of periodontopathogens and to IgG antibody levels in GCF and serum against them. P. gingivalis, T. denticola and C. rectus were found to be predominant in destructive sites. No significant differences were found in GCF IgG antibody levels between destructive and healthy sites. In destructive sites, the prevalence of P. gingivalis and C. rectus was significantly correlated with elevated IgG antibody against these microorganisms in GCF. The initial preparation resulted in significant reduction of serum IgG antibody levels against all microorganisms tested. No decrease in GCF IgG antibody was observed, but levels to P. gingivalis and C. rectus were significantly increased (p<0.05). The assessment of GCF IgG antibodies to specific periodontopathic bacteria may be of considerable value in reflecting the conditions of periodontitis.