Complement component 3 (C3) and its activation split-products in saliva associates with periodontitis

Evaluation of circulating IgG antibodies against Porphyromonas gingivalis or its gingipains as serological markers of periodontitis and carriage of the bacterium

BACKGROUND

Increasing evidence indicates that periodontitis contributes to systemic low-grade inflammation. Porphyromonas gingivalis is strongly associated with periodontitis, and antibodies against the bacterium may be used as a serological proxy to account for periodontal status, when studying diseases associated with periodontitis. The aim of the present study is to identify an easily accessible and reliable serological biomarker for determination of periodontal status and oral carriage of the bacterium.

METHODS

Saliva and serum samples were collected from periodontally healthy controls (n = 27), and patients with periodontitis stage II (n = 12) or stages III or IV (n = 44). Serum levels of immunoglobulin G (IgG) antibodies against intact and fragmented P. gingivalis, recombinant gingipains (RgpA and RgpB), and the bacteria Escherichia coli and Capnocytophaga ochracea as controls were quantified with a multiplex bead-based assay. P. gingivalis was identified in saliva using quantitative polymerase chain reaction (qPCR).

RESULTS

Serum IgG antibodies against P. gingivalis whole bacteria were good indicators of periodontitis (area under the curve [AUC]: 0.75, 95% confidence interval [CI]: 0.64-0.85). The same was observed for levels of antibodies against P. gingivalis fragments (AUC: 0.78, 95% CI: 0.68-0.88). Likewise, levels of antibodies against P. gingivalis whole bacteria or P. gingivalis fragments were good indicators of oral carriage of P. gingivalis (AUC: 0.92, 95% CI: 0.86-0.98 and AUC: 0.96, 95% CI: 0.92-1, respectively). Conversely, antibodies against recombinant RgpA and RgpB were not good indicators of periodontitis or oral carriage of the bacterium. None of the antibody levels differed significantly between stage II and stage III or IV periodontitis.

CONCLUSION

Serum IgG antibody levels against heat-inactivated whole P. gingivalis proved to be the preferable biomarker for periodontitis and oral carriage of the bacterium.

Complement components C3b and C4b as potential reliable site-specific diagnostic biomarkers for periodontitis

OBJECTIVE

This study aimed to investigate the correlation between the expression levels of C3b and C4b in human gingival tissue (GT) and gingival crevicular fluid (GCF) and disease severity in human periodontitis and to determine whether C3b and C4b are significant site-specific complementary diagnostic markers for periodontitis.

BACKGROUND

A variety of biomarkers that have potential for informing diagnoses of periodontitis have been proposed. The complement components C3b and C4b were found to be positively correlated with disease severity. The therapeutic effect of targeting C3b and C4b on inflammatory bone loss in experimental periodontitis models has been studied. However, studies on the diagnostic potential of the gingival C3b and C4b expression levels for periodontitis are scarce.

METHODS

The expression levels of C3b and C4b in the GT and GCF were investigated via immunohistochemistry and enzyme-linked immunosorbent assay, respectively. The correlation between the expression levels of C3b and C4b and disease severity with probing depth as well as the clinical attachment level were determined. To evaluate the diagnostic accuracy of the C3b and C4b expression levels at the periodontitis sites, the receiver operating characteristic (ROC) curve, cut-off point, area under the ROC curve, sensitivity, and specificity were analyzed.

RESULTS

The expression levels of C3b and C4b in human GT and GCF were significantly positively correlated with periodontitis severity. The expression levels of combined C3b + C4b in the GT can significantly differentiate the disease status at the tissue level (p < .0001). Similarly, the expression levels of C3b + C4b in GCF can statistically distinguish periodontitis sites from healthy ones (p < .0001).

CONCLUSIONS

Locally deposited C3b and C4b were positively correlated with periodontitis severity and recognized as site-specific diagnostic biomarkers for clinicopathological features in periodontitis. The association between the C3b and C4b network and periodontitis may be further understood and provide a basis for the development of novel screening as well as diagnostic and therapeutic strategies for periodontitis.

Mass Spectrometry-Based Proteomics for Discovering Salivary Biomarkers in Periodontitis: A Systematic Review

Periodontitis is one of the primary causes of tooth loss, and is also related to various systemic diseases. Early detection of this condition is crucial when it comes to preventing further oral damage and the associated health complications. This study offers a systematic review of the literature published up to April 2023, and aims to clearly explain the role of proteomics in identifying salivary biomarkers for periodontitis. Comprehensive searches were conducted on PubMed and Web of Science to shortlist pertinent studies. The inclusion criterion was those that reported on mass spectrometry-driven proteomic analyses of saliva samples from periodontitis cohorts, while those on gingivitis or other oral diseases were excluded. An assessment for risk of bias was carried out using the Newcastle-Ottawa Scale and Quality Assessment of Diagnostic Accuracy Studies or the NIH quality assessment tool, and a meta-analysis was performed for replicable candidate biomarkers, i.e., consistently reported candidate biomarkers (in specific saliva samples, and periodontitis subgroups, reported in ≥2 independent cohorts/reports) were identified. A Gene Ontology enrichment analysis was conducted using the Database for Annotation, Visualization, and Integrated Discovery bioinformatics resources, which consistently expressed candidate biomarkers, to explore the predominant pathway wherein salivary biomarkers consistently manifested. Of the 15 studies included, 13 were case-control studies targeting diagnostic biomarkers for periodontitis participants (periodontally healthy/diseased, n = 342/432), while two focused on biomarkers responsive to periodontal treatment (n = 26 participants). The case-control studies were considered to have a low risk of bias, while the periodontitis treatment studies were deemed fair. Summary estimate and confidence/credible interval, etc. determination for the identified putative salivary biomarkers could not be ascertained due to the low number of studies in each case. The results from the included case-control studies identified nine consistently expressed candidate biomarkers (from nine studies with 230/297 periodontally healthy/diseased participants): (i) those that were upregulated: alpha-amylase, serum albumin, complement C3, neutrophil defensin, profilin-1, and S100-P; and (ii) those that were downregulated: carbonic anhydrase 6, immunoglobulin J chain, and lactoferrin. All putative biomarkers exhibited consistent regulation patterns. The implications of the current putative marker proteins identified were reviewed, with a focus on their potential roles in periodontitis diagnosis and pathogenesis, and as putative therapeutic targets. Although in its early stages, mass spectrometry-based salivary periodontal disease biomarker proteomics detection appeared promising. More mass spectrometry-based proteomics studies, with or without the aid of already available clinical biochemical approaches, are warranted to aid the discovery, identification, and validation of periodontal health/disease indicator molecule(s). Protocol registration number: CRD42023447722; supported by RD-02-202410 and GRF17119917.

B-cell cytokine responses to Porphyromonas gingivalis in patients with periodontitis and healthy controls

BACKGROUND

Cytokine-producing B cells play a well-established role in modifying immune responses in chronic inflammatory diseases. We characterized B-cell cytokine responses against periodontitis-associated bacteria in patients with periodontitis.

METHODS

Blood and saliva samples were collected from patients with periodontitis grade B (N = 31) or grade C (N = 25), and 25 healthy controls (HCs). Mononuclear cells were stimulated with Porphyromonas gingivalis, Fusobacterium nucleatum, Staphylococcus epidermidis, or Cutibacterium acnes, and B-cell production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, interferon (IFN)-γ, IL-10 and transforming growth factor (TGF)-β by B cells was assessed by flow cytometry.

RESULTS

HCs had higher baseline frequencies of B cells producing IFN-γ or TNF-α than grade B patients, but only B cells from grade B patients showed significant differentiation into IFN-γ-, TNF-α-, TGF-β-, or IL-10-producing cells after challenge with P. gingivalis and into IFN-γ-, TGF-β-, or IL-10-producing cells after challenge F. nucleatum. Notably, the baseline frequency of IL-10-producing B cells from grade C patients correlated inversely with clinical attachment loss (AL). The major proportion of the IFN-γ- and TGF-β-producing B cells were CD27+ memory cells, while the IL-10-producing B cells were mainly CD27- CD5- .

CONCLUSIONS

B cells from grade B patients, particularly those harboring P. gingivalis, showed proinflammatory B-cell responses to P. gingivalis. Moreover, the baseline frequency of IL-10-producing B cells in the grade C group correlated inversely with AL, suggesting a diminished immunoregulatory capacity of IL-10-producing B cells in these patients.

C3-targeted host-modulation approaches to oral inflammatory conditions

Periodontitis is an inflammatory disease caused by biofilm accumulation and dysbiosis in subgingival areas surrounding the teeth. If not properly treated, this oral disease may result in tooth loss and consequently poor esthetics, deteriorated masticatory function and compromised quality of life. Epidemiological and clinical intervention studies indicate that periodontitis can potentially aggravate systemic diseases, such as, cardiovascular disease, type 2 diabetes mellitus, rheumatoid arthritis, and Alzheimer disease. Therefore, improvements in the treatment of periodontal disease may benefit not only oral health but also systemic health. The complement system is an ancient host defense system that plays pivotal roles in immunosurveillance and tissue homeostasis. However, complement has unwanted consequences if not controlled appropriately or excessively activated. Complement overactivation has been observed in patients with periodontitis and in animal models of periodontitis and drives periodontal inflammation and tissue destruction. This review places emphasis on a promising periodontal host-modulation therapy targeting the complement system, namely the complement C3-targeting drug, AMY-101. AMY-101 has shown safety and efficacy in reducing gingival inflammation in a recent Phase 2a clinical study. We also discuss the potential of AMY-101 to treat peri-implant inflammatory conditions, where complement also seems to be involved and there is an urgent unmet need for effective treatment.