Endocarditis-associated oral streptococci promote rapid differentiation of monocytes into mature dendritic cells

Serine-Rich Repeat Adhesins Contribute to Streptococcus gordonii-Induced Maturation of Human Dendritic Cells

Dendritic cells (DCs) play a pivotal role in the induction of immunity by recognition, capture, process, and presentation of antigens from infectious microbes. Streptococcus gordonii is able to cause life-threatening systemic diseases such as infective endocarditis. Serine-rich repeat (SRR) glycoproteins of S. gordonii are sialic acid-binding adhesins mediating the bacterial adherence to the host and the development of infective endocarditis. Thus, the SRR adhesins are potentially involved in the bacterial adherence to DCs and the maturation and activation of DCs required for the induction of immunity to S. gordonii. Here, we investigated the phenotypic and functional changes of human monocyte-derived DCs treated with wild-type S. gordonii or the SRR adhesin-deficient mutant. The mutant poorly bound to DCs and only weakly increased the expression of CD83, CD86, MHC class II, and PD-L1 on DCs compared with the wild-type. In addition, the mutant induced lower levels of TNF-α, IL-6, and IL-12 than the wild-type in DCs. When DCs sensitized with the mutant were co-cultured with autologous T cells, they induced weaker proliferation and activation of T cells than DCs stimulated with the wild-type. Blockade of SRR adhesin with 3′-sialyllactose markedly reduced S. gordonii binding and internalization, causing attenuation of the bacterial immunostimulatory potency in DC maturation. Collectively, our results suggest that SRR adhesins of S. gordonii are important for maturation and activation of DCs.

Dental plaque microbial profiles of children from Khartoum, Sudan, with congenital heart defects

Few studies have focused on the bacterial species associated with the deterioration of the dental and gingival health of children with congenital heart defects (CHD). The aims of this study were (1) to examine the dental plaque of children with CHD in order to quantify bacterial load and altered bacterial composition compared with children without CHD; and (2) to investigate the correlation between the level of caries and gingivitis and dental biofilm bacteria among those children. In this cross-sectional study, participants were children (3-12 years) recruited in Khartoum State, Sudan. A total of 80 CHD cases from the Ahmed Gasim Cardiac Centre and 80 healthy controls from randomly selected schools and kindergartens were included. Participants underwent clinical oral examinations for caries (decayed, missing, and filled teeth indices [DMFT] for primary dentition, and DMFT for permanent dentition), and gingivitis (simplified gingival index [GI]). Pooled dental biofilm samples were obtained from four posterior teeth using paper points. Real-time quantitative polymerase chain reaction was used for the detection and quantification of Streptococcus mutans, Streptococcussanguinis, and Lactobacillus acidophilus. Checkerboard DNA-DNA hybridization was used for the detection of 40 additional bacterial species. CHD cases had a significantly higher caries experience (DMFT = 4.1 vs. 2.3, p < 0.05; DMFT = 1.4 vs. 0.7, p < 0.05) and a higher mean number of examined teeth with gingivitis (4.2 vs. 2.0; p < 0.05) compared with controls. S. mutans counts were significantly higher among the CHD cases (p < 0.05). Checkerboard results revealed that 18/40 bacterial species exhibited significantly higher mean counts among CHD cases (p < 0.01). Correlation analyses revealed that among CHD cases, the detection levels of Tannerella forsythia, Campylobacter rectus, Fusobacterium nucleatum subsp. vincentii, F. nucleatum subsp. nucleatum, and F. nucleatum subsp. polymorphum were highly positively correlated with GI. CHD cases harbor more cariogenic and periodontopathogenic bacterial species in their dental plaque, which correlated with higher levels of caries and gingivitis.

Current stress and poor oral health

Background

Psychological stress appears to contribute to poor oral health systemically in combination with other chronic diseases. Few studies directly examine this relationship.

Methods

Data from a cross-sectional study of 2,412 participants between the ages of 25–64 years old living in the City of Toronto between 2009 and 2012 were used to examine the relationship between current stress and two self-rated oral health outcomes (general oral health and oral pain). Dental care utilization and access to dental insurance were examined as effect modifiers.

Results

A positive relationship between current stress and poor oral health was observed for both outcomes (oral pain coefficient 0.32, 95 % CI 0.26–0.38; general oral health coefficient 0.28, 95 % CI 0.19–0.36). Effects on oral pain were stronger for the uninsured, while effects on general oral health were stronger with decreasing socioeconomic position.

Conclusions

Our findings suggest that individuals with greater perceived stress also report poorer oral health, and that this relationship is modified by dental insurance and socioeconomic position. These findings warrant a greater focus on the role of psychological stress in the development of oral disease, including how perceived stress contributes to health inequities in self-reported oral health status. Patients experiencing stressful lives may differentially require closer monitoring and more vigilant maintenance of their oral health, above and beyond that which is needed to achieve a state of health in the oral environment of less stressed individuals. There may be health promoting effects of addressing psychosocial concerns related to dental care - particularly for the poor and uninsured.

Inflammatory Response in Infective Endocarditis

Endocarditis remains a devastating disease with a high mortality despite timely diagnosis and treatment. The mainstays of treatment include appropriate antibiotics and when indicated, removal of the septic focus. This sounds extremely simple and belies the necessity for a sophisticated multidisciplinary approach to its treatment, the success of which depends not just on the right antibiotic at the right dosage via the right portal, but also on a profound understanding of the inflammatory and infective pathophysiology at work. This review aims at assisting both the clinician and the lab-based physician in the task.

Post-infectious group A streptococcal autoimmune syndromes and the heart

There is a pressing need to reduce the high global disease burden of rheumatic heart disease (RHD) and its harbinger, acute rheumatic fever (ARF). ARF is a classical example of an autoimmune syndrome and is of particular immunological interest because it follows a known antecedent infection with group A streptococcus (GAS). However, the poorly understood immunopathology of these post-infectious diseases means that, compared to much progress in other immune-mediated diseases, we still lack useful biomarkers, new therapies or an effective vaccine in ARF and RHD. Here, we summarise recent literature on the complex interaction between GAS and the human host that culminates in ARF and the subsequent development of RHD. We contrast ARF with other post-infectious streptococcal immune syndromes - post-streptococcal glomerulonephritis (PSGN) and the still controversial paediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), in order to highlight the potential significance of variations in the host immune response to GAS. We discuss a model for the pathogenesis of ARF and RHD in terms of current immunological concepts and the potential for application of in depth "omics" technologies to these ancient scourges.

Streptococcus gordonii promotes rapid differentiation of monocytes into dendritic cells through interaction with the sialic acid-binding adhesin

Infective endocarditis is frequently attributed to oral streptococci. Although the pathogenetic mechanisms are not well understood, interaction between streptococci and phagocytes is thought to be important for infective endocarditis. In this study, HL-60 cell-derived monocytes were characterized following interaction with Streptococcus gordonii DL1. Exposure of monocytes to S. gordonii DL1 induced up-regulation of the dendritic cell (DC) markers CD83, CD1a, CD86, and interleukin-12, while monocyte markers PU.1 and MafB, which are typically present at low levels in mature DCs, were down-regulated. Interaction of HL-60-derived monocytes with S. gordonii DL1 was instructive for DC differentiation in the absence of released cytokines. Furthermore, neither the filtered culture medium of S. gordonii nor the hsa mutant, deficient in sialic acid-binding activity, was able to induce the differentiation of HL-60 cells. Taken together, these data suggest that monocytes stimulated with S. gordonii DL1 rapidly undergo monocyte-to-DC differentiation through interaction with the bacterial surface receptor Hsa and that this response may be the initial step in infective endocarditis by oral streptococci.

Expression of Toll-like receptor 2 and 4 in inflamed pulp in severe combined immunodeficiency mice

INTRODUCTION

Toll-like receptors (TLRs) are important receptors mediating innate immune responses because they detect factors released from bacterial cell wall components during inflammatory reactions. However, the role of TLRs in dental pulp, which is bounded by hard tissues, is poorly understood. The purpose of this study was to investigate the relationship between the innate immune system and the defense of pulp tissue by using immunodeficient mice that lack an adaptive immune response

METHODS

Mice with severe combined immunodeficiency (SCID) were used as a model because they lack an adaptive immune response. The expression of TLR-2 and TLR-4 in experimentally inflamed pulps in SCID mice was measured by quantitative real-time polymerase chain reaction and immunohistochemistry. Total RNA was isolated from pulp tissues at 0 to 24 hours after bacterial dentinal infection. Anti-TLR-2, anti-TLR-4 cells, anti-CD64, and antinestin cells were detected with labeled streptavidin-biotin methods.

RESULTS

TLR-2 messenger RNA was detected at 3 hours after bacterial infection and then gradually increased from 9 to 24 hours. Numerous TLR-2- and CD64-positive cells detected on macrophages and dendritic-like cells, and TLR-4- and CD64-positive macrophages were detected in the early stage of pulpitis.

CONCLUSION

These results suggest that the expression of TLR-2 and TLR-4 may be triggered by bacterial infection in irreversible pulpitis without a need for an adaptive immune response. Those signals may relate to pulpal responses to bacterial infection.

Microbiology of odontogenic bacteremia: beyond endocarditis

SUMMARY

The human gingival niche is a unique microbial habitat. In this habitat, biofilm organisms exist in harmony, attached to either enamel or cemental surfaces of the tooth as well as to the crevicular epithelium, subjacent to a rich vascular plexus underneath. Due to this extraordinary anatomical juxtaposition, plaque biofilm bacteria have a ready portal of ingress into the systemic circulation in both health and disease. Yet the frequency, magnitude, and etiology of bacteremias due to oral origin and the consequent end organ infections are not clear and have not recently been evaluated. In this comprehensive review, we address the available literature on triggering events, incidence, and diversity of odontogenic bacteremias. The nature of the infective agents and end organ infections (other than endocarditis) is also described, with an emphasis on the challenge of establishing the link between odontogenic infections and related systemic, focal infections.

Innate Immune Responses of the Dental Pulp to Caries

Various cells and inflammatory mediators are involved in the initial pulpal responses to caries. This review focuses on the cellular, neuronal, and vascular components of pulpal innate responses to caries. Discussion will include dentinal fluid, odontoblasts, neuropeptides, and neurogenic inflammation, which are not classic immune components but actively participate in the inflammatory response as the caries progress pulpally. Summaries of innate immune cells as well as their cytokines and chemokines in healthy and reversible pulpitis tissues are presented.

Rapid tissue factor induction by oral streptococci and monocyte-IL-1beta

The ability of pro-inflammatory cytokines to promote coagulation prompted the hypothesis that pro-inflammatory cytokines induced by oral streptococci might play a role in the pathogenesis of viridans endocarditis. We used supernatant fluids from peripheral blood mononuclear monocyte (PBMC) cultures, stimulated for just 4-6 hrs with representative streptococcal isolates, to study cytokines that promoted endothelial tissue factor (TF) activity. Neutralizing antibodies demonstrated that interleukin-1beta (IL-1beta) was a major early endothelial TF inducer, and that recombinant IL-1beta was comparable with the supernatant fluid in activity. IL-1beta-rich supernatant fluids from oral streptococci-stimulated or lipopolysaccharide-stimulated PBMC cultures up-regulated the expression of endothelial ICAM-1 and E-selectin. These molecules could help trap TF-producing monocytes or dendritic cells bearing streptococci at the site. Thus, the rapid IL-1beta-inducing capacity of oral streptococci could facilitate the early deposition of bacteria in fibrin clots and promote endocarditis.