Salivary concentration of the antimicrobial peptide LL-37 in children

Dental caries in children and vitamin D deficiency: a narrative review

Dental caries represents one of the most prevalent health problems in childhood. Numerous studies have assessed that vitamin D deficiency is highly related to dental caries in primary and permanent teeth in children. The aim of this study is to elaborate a narrative review about proposed mechanisms by which vitamin D deficiency interacts with dental caries process in children. Vitamin D deficiency during pregnancy may cause intrauterine enamel defects, and through childhood is accompanied by insufficient activity of antibacterial peptides, decreased saliva secretion, and a low level of calcium in saliva.  Conclusion: In conclusion, vitamin D deficiency would increase the risk of caries in the primary and/or permanent dentition. Relationship between vitamin D deficiency and dental caries is evident enough for vitamin D deficiency to be considered as a risk factor for dental caries in children. Optimal levels of vitamin D throughout pregnancy and childhood may be considered an additional preventive measure for dental caries in the primary and permanent dentition.

Potential role of salivary vitamin D antimicrobial peptide LL-37 and interleukins in severity of dental caries: an exvivo study

INTRODUCTION

Vitamin D performs various functions as a hormone by promoting calcium absorption but plays a major role in innate immunity,cell differentiation, cell maturation through its genomic effects via vitamin D receptor. The immune response also plays a major role in tooth surface and supporting structure destruction and playing a major factor in high caries formation. The inflammatory cytokines are released has proinflammatory cytokines and stimulate cells in disease process. Therefore, in the present study we have evaluated the association of salivary vitamin D, LL-37, interleukins 6 and 17A in various levels of severity of dental caries.

METHOD

Ethical approval was obtained (NU/CEC/2020/0339), 377 individuals reporting to department of conservative dentistry and endodontics, AB Shetty memorial institute of dental sciences were included based on inclusion criteria. The individuals were further divided into caries free(N = 105) and caries active(N = 272) based on their caries prevalence. The salivary were collected and evaluated for vitamin D, LL-37,IL-17A and IL-6.Results were statistically analysed with SPSS vs 22 (IBM Corp, USA). Normally distributed data were expressed as mean ± SD. Skewed data were expressed as median and interquartile range. To compare (mean) outcome measures between the two groups unpaired independent t-test was applied and for values in median IQR, Mann Whitney U test was used. All statistical analysis for P value were two-sided and significance was set to P ≤ 0.05.

RESULTS

The study showed that, the salivary vitamin D statistically decreased with increasing severity of caries which showed that vitamin D plays an important role in prevention of caries. Antimicrobial peptide LL-37 was higher in caries free group but was not statistically significant, salivary IL-6 level was higher in caries active group but intergroup comparison did not show significant difference. Salivary IL-17A did not show statistically significant between caries active and caries free group.

CONCLUSION

The salivary levels of vitamin D may play a vital role in prevalence of dental caries and its severity which can be a underlying cause in presence of other etiological factors.

Comparison of oral cavity protein abundance among caries-free and caries-affected individuals-a systematic review and meta-analysis

Objective

Some salivary proteins seem to be differently abundant among caries-free (CF) and caries-affected (CA) individuals, but previous results are contradictory precluding that definitive conclusion be drawn. A pooled analysis of the available evidence may provide more robust data on identifying oral cavity protein patterns among CF and CA individuals. This systematic review and meta-analysis (PROSPERO CRD42021269079) aimed to compare the oral cavity protein abundance among caries-free and caries-affected individuals.

Methods

This study was conducted following PRISMA guidelines. PubMed, Embase, and Web of Science databases were systematically assessed (up to February 2023) to retrieve clinical studies written in English, German, or in Latin-based languages that compared the oral cavity protein abundance among CF and CA individuals. Data extraction and methodological quality assessment (NIH guidelines) were independently performed by two investigators. Qualitative synthesis was performed from all included studies and meta-analysis was performed using a random-effects model with inverse variance for studies that reported the concentration of proteins or enzymatic activity. Standardized mean difference (SMD) with respective 95% confidence interval (CI) were calculated for each outcome.

Results

A total of 90 studies (two cohort and 88 cross-sectional designs) of more than 6,000 participants were selected for data extraction, being the quality of evidence graded as "fair" for most of them. The oral cavity of CF individuals presented lower total protein concentration [SMD = 0.37 (95% CI: 0.07-0.68; 18 studies)], lower total antioxidant capacity [SMD = 1.29 (95% CI: 0.74-1.85); 17 studies], and lower carbonic anhydrase activity [SMD = 0.83 (95% CI: 0.58-1.09); three studies], whereas CA individuals presented lower carbonic anhydrase concentration [SMD = -0.66 (95% CI: -1.00 to -0.32); three studies], urease [SMD = -0.95 (IC 95%: -1.72 to -0.17); four studies], and arginine deiminase system [SMD = -2.07 (95% CI: -3.53 to -0.62); three studies] activities. Antimicrobial peptides, secretory immunoglobulin-A concentrations and alpha-amylase activity were similar among individuals.

Conclusion

Differences on oral cavity protein abundance were observed among CF and CA individuals. These data indicate some protein patterns for the oral health and dental caries conditions. Even when statistically significant, some of the results were not very consistent. Cohort studies need to be conducted to validate these results.

Antimicrobial Peptides and Interleukins in Cleft Soft Palate

Cleft palate is one of the most common and well-studied congenital anomalies; however, the role of protective tissue factors in its pathophysiology is still debated. The aim of our study was to evaluate interleukin and antimicrobial peptide appearance and distribution in cleft palate. Eight soft palate samples were obtained during veloplasty procedures. Immunohistochemical staining was applied to detect HBD-2-, HBD-3-, HBD-4-, LL-37-, IL-10-, and CD-163-positive cells via light microscopy. For statistical evaluation, the Mann-Whitney U test and Spearman's rank correlation coefficient were used. A significant difference between study groups was observed for HBD-2 and IL-10 in epithelial and connective tissue as well as HBD-4 in connective tissue. The number of HBD-3-positive cells was moderate in the patients, and few were observed in the controls. The number of LL-37-positive cells varied from a moderate amount to a numerous amount in both study groups, whilst CD-163 marked a moderate number of positive cells in patients, and a few-to-moderate amount was observed in the controls. Numerous correlations between studied factors were revealed in cleft tissues. The increase in antimicrobial peptides HBD-2 and HBD-4 and anti-inflammatory cytokine IL-10 suggested a wide compensatory elevation of the local immune system against cleft-raised tissue changes. The correlations between the studied factors (HBD-2, HBD-3, HBD-4, LL-37, and IL-10) proved the synergistic involvement of common local defense factors in postnatal cleft palate morphopathogenesis.

Antibiofilm properties of cathelicidin LL-37: an in-depth review

Notwithstanding ceaseless endeavors toward developing effective antibiofilm chemotherapeutics, biofilm-associated infections continue to be one of the most perplexing challenges confronting medicine today. Endogenous host defense peptides, such as the human cathelicidin LL-37, are being propounded as promising options for treating such infectious diseases. Over the past decennium, LL-37 has duly received tremendous research attention by virtue of its broad-spectrum antimicrobial activity and immunomodulatory properties. No attempt has hitherto been made, as far as we are aware, to comprehensively review the antibiofilm effects of LL-37. Accordingly, the intent in this paper is to provide a fairly all-embracing review of the literature available on the subject. Accumulating evidence suggests that LL-37 is able to prevent biofilm establishment by different bacterial pathogens such as Acinetobacter baumannii, Aggregatibacter actinomycetemcomitans, Bacteroides fragilis, Burkholderia thailandensis, Cutibacterium acnes, Escherichia coli, Francisella tularensis, Helicobacter pylori, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pyogenes. Inhibition of bacterial adhesion, downregulation of biofilm-associated genes, suppression of quorum-sensing pathways, degradation of biofilm matrix, and eradication of biofilm-residing cells are the major mechanisms responsible for antibiofilm properties of LL-37. In terms of its efficacy and safety in vivo, there are still many questions to be answered. Undoubtedly, LL-37 can open up new windows of opportunity to prevent and treat obstinate biofilm-mediated infections.

Co-relation of salivary calcium and vitamin D with dental caries - an ex-vivo study

Introduction and Aim: Calcium and vitamin D3 play a pivotal role in many biological functions like hard tissue mineralization and tooth formation. Both are dietary elements with a known concentration in the saliva, therefore directly affecting the rate and progression of dental caries. The aim of the study was to compare the salivary vitamin D and calcium levels in caries active and caries free adult patients.   Materials and Methods: Tarson’s saliva collection tubes were used to collect 5 ml of saliva samples from 110 patients. The supernatant obtained from the centrifuged saliva was stored at -4°C. Analysis of calcium levels was done using the Arsenazo method. Commercially available vitamin D Elisa kit (Epitope diagnostics) was used for the analysis of vitamin D levels.   Results: The mean salivary vitamin D levels were higher in the caries free group (66.57mg/dl) when compared to the caries active group (56.43mg/dl). The mean salivary calcium level was elevated in the caries free group (27.09mg/dl) when compared to the caries active group (6.84 mg/dl).   Conclusion: The filtrates in saliva play a major role in the occurrence of dental caries through a demineralization and remineralization cycle. Vitamin D in saliva causes a decrease in bacterial aggregation and biofilm formation through the protective role of peptides, causing decreased demineralization of the tooth surface and increased level of free calcium ions in the saliva.

The Levels of the Human-β-Defensin-2 and LL-37 in the Sputum of Children with Cystic Fibrosis: A Case–control Study and Literature Review

BACKGROUND: Cystic fibrosis (CF) is a genetic disorder with an autosomal-recessive type of inheritance. Based on their host-defending and pro-inflammatory functions, antimicrobial peptides (AMPs) likely have one of the central roles in the pathogenesis of lung disease in CF. AIM: The purpose of the study was to measure the concentration of AMPs in the sputum of children with CF and evaluate any correlation with a bacterial profile of the lungs. METHODS: Lung colonization was evaluated using a culture-dependent method, sputum was utilized. A sandwich-ELISA was used to measure hBD-2 and hCAP-18/LL-37 in the sputum. RESULTS: There were 27 children enrolled in the study group, median age of inclusion was 11.4 (8.5; 14.8) years old. The control group consisted of 14 children, 11.6 (8.6; 12.6) years old. The concentration of AMPs was not correlating with participants` age (rs = −0.286, p = 0.148 – defensin hDB-2; rs = −0.084, p = 0.676 – cathelicidin hCAP-18/LL-37). The concentration of hBD-2 was from 64.01 to 813.61 pg/mL. The concentration of hCAP-18/LL-37 was from 3.24 to 35.98 ng/mL. There were significant differences in the content of AMPs on respiratory samples between study and control group (U = 976.5, p = 0.001 – for hBD-2; U = 1080.5, p < 0.001). The correlation between current infection Pseudomonas aeruginosa and concentration of hBD-2 (rs = 0.167; p = 0.406) was not found. However, the presence of P. aeruginosa correlated with density of neutrophilic infiltration (rs = 0.622; p = 0.001). The concentration of hBD-2 showed direct medium correlation with total cells count (rs = 0.881, p < 0.001). Correlation between current infection P. aeruginosa and concentration of hCAP-18/LL-37 (rs = 0.788; p < 0.001) was observed. With increases in total cell count and relative neutrophils count, the concentration of hCAP-18/LL-37 was increased and the power of the association was medium (rs = 0.453; p = 0,018; rs = 0,592; p = 0,001). The correlation between concentrations of hBD-2 and hCAP-18/LL-37 (rs = 0.316, p > 0.1) was not found. CONCLUSIONS: Measured AMPs correlated with cellular inflammatory markers and, probably, their overexpression is dedicated to stimulating a cellular component of innate immune response; there was no correlation between bacterial colonization of lungs and levels of hBD-2, so our findings sustain that P. aeruginosa is a leading but non-single contributor to persistent local inflammation in polymicrobial lungs.

Regulation of LL-37 in Bone and Periodontium Regeneration

The goal of regenerative therapy is to restore the structure and function of the lost tissues in the fields of medicine and dentistry. However, there are some challenges in regeneration therapy such as the delivery of oxygen and nutrition, and the risk of infection in conditions such as periodontitis, osteomyelitis, etc. Leucine leucine-37 (LL-37) is a 37-residue, amphipathic, and helical peptide found only in humans and is expressed throughout the body. It has been shown to induce neovascularization and vascular endothelial growth factor (VEGF) expression. LL-37 also stimulates the migration and differentiation of mesenchymal stem cells (MSCs). Recent studies have shown that LL-37 plays an important role in the innate defense system through the elimination of pathogenic microbes and the modulation of the host immune response. LL-37 also manifests other functions such as promoting wound healing, angiogenesis, cell differentiation, and modulating apoptosis. This review summarizes the current studies on the structure, expression, and function of LL-37 and highlights the contributions of LL-37 to oral cavity, periodontium, and bone regeneration.

Cathelicidin LL-37 in Health and Diseases of the Oral Cavity

The mechanisms for maintaining oral cavity homeostasis are subject to the constant influence of many environmental factors, including various chemicals and microorganisms. Most of them act directly on the oral mucosa, which is the mechanical and immune barrier of the oral cavity, and such interaction might lead to the development of various oral pathologies and systemic diseases. Two important players in maintaining oral health or developing oral pathology are the oral microbiota and various immune molecules that are involved in controlling its quantitative and qualitative composition. The LL-37 peptide is an important molecule that upon release from human cathelicidin (hCAP-18) can directly perform antimicrobial action after insertion into surface structures of microorganisms and immunomodulatory function as an agonist of different cell membrane receptors. Oral LL-37 expression is an important factor in oral homeostasis that maintains the physiological microbiota but is also involved in the development of oral dysbiosis, infectious diseases (including viral, bacterial, and fungal infections), autoimmune diseases, and oral carcinomas. This peptide has also been proposed as a marker of inflammation severity and treatment outcome.

Role of salivary physicochemical and peptide levels in dental caries among children: An original research

Introduction:

Dental caries is a common oral disease that still needs to be thoroughly evaluated for understanding the pathophysiology. Hence, in our study, we evaluate the physicochemical and the peptide properties of the saliva and their role in dental caries among children.

Materials and Methods:

We conducted an observational in vitro study among 100 subjects of age 5–15 years. Decayed, missing, and filled surface (DMFT)/dmft was used to calculate the caries activity. The unstimulated saliva was evaluated for the peptides “LL-37, human neutrophil peptide (HNP) 1-3, and human beta-defensin-3” by ELIZA and for the “pH, buffer, and flow rate” of the saliva. The data thus obtained were analyzed to correlate caries and the salivary physiochemical and peptides using the “linear regression analysis.” P < 0.05 was deliberated as significant.

Results:

Although no statistically significant variation was seen between low and high caries risk groups and the salivary parameters in our study, we observed a negative correlation of the salivary peptides and caries. For the salivary peptide “HNP1-3,” there was a statistically significant variation.

Conclusion:

The salivary peptides may be carioprotective. However, further research has to be done to establish the mechanism of the action of these substances against caries.

Associations of early childhood caries with salivary beta defensin-3 and childhood anemia: a case-control study

Background

Human beta defensin-3 (HβD-3) is an antimicrobial peptide present in saliva that protects tooth surfaces from microbial attack. These peptides are part of innate immunity so levels may be affected by different systemic diseases like anemia. Therefore, anemia may predispose an affected child to an increased risk of dental caries. The objectives of this study were to determine the association of early childhood caries (ECC) with HβD-3 levels and observe the association of HβD-3 levels with childhood anemia.

Methods

A total of 80 children admitted in a pediatric medical ward, age 48–71 months, of either sex were included in the study. The included children were categorized as cases (children with ECC n = 40) and controls (children without ECC n = 40). Children were further segregated into the anemic and non-anemic sub-groups based on the hospital record of hemoglobin level. The salivary concentration of HβD-3 was measured by Enzyme-Linked Immuno-sorbent assay (ELISA). IBM SPSS version 20 software was used for statistical analysis. Two sample t-test and one-way ANOVA were used to compare mean values while spearman was used for correlations at p < 0.05.

Results

The mean Salivary HβD-3 level in cases (8.87 ± 4.30) was significantly higher (p = 0.042) as compared to controls (7.23 ± 2.57). Salivary HβD-3 level in patients with caries and without anemia was highest (10.80 ± 4.50) whereas salivary HβD-3 level in the presence of caries and anemia was lowest (6.94 ± 3.13) amongst all groups. This difference was statistically significant (p = 0.001). Salivary HβD-3 level was found to be moderately correlated with cases (p = 0.002). An inverse correlation was found between salivary HβD-3 level and anemia (r = -0.479, p = 0.002).

Conclusion

Anemia may affect the innate immunity of children, and may result in a decreased level of salivary HβD3, thus increasing vulnerability to decay.

Evaluation of possible biomarkers for caries risk in children 6 to 12 years of age

Background: Electrolytes, proteins, and other salivary molecules play an important role in tooth integrity and can serve as biomarkers associated with caries. Objective: To determine the concentration of potential biomarkers in children without caries (CF) and children with caries (CA). Methods: Unstimulated saliva was collected, and the biomarkers quantified in duplicate, using commercial Enzyme Linked Immunosorbent Assay (ELISA) kits to determine IgA, fibronectin, cathelicidin LL-37, and statherin levels, as well as colorimetric tests to detect formate and phosphate. Results: Significantly higher concentrations of statherin was detected in the CF group (Median: 94,734.6; IQR: 92,934.6-95,113.7) compared to the CA2 group (90,875.0; IQR: 83,580.2-94,633.4) (p = 0.03). Slightly higher median IgA (48,250.0; IQR: 31,461.9-67,418.8) and LL-37 levels (56.1; IQR 43.6-116.2) and a lower concentration of formate were detected in the CF group (0.02; IQR 0.0034-0.15) compared to the group with caries (IgA: 37,776.42; IQR: 33,383.9-44,128.5; LL-37: 46.3; IQR: 40.1011-67.7; formate: 0.10; IQR: 0.01-0.18), but these differences were not statistically significant. Conclusion: The fact that these compounds have been identified as good markers for caries among European adults highlights the difficulty of identifying universal biomarkers that are applicable to all ages or to different populations.

Cathelicidin levels in nasal secretions are associated with the severity of acute bronchiolitis

OBJECTIVE

To investigate the association of serum vitamin D and nasal secretion antimicrobial peptides (AMPs) levels with the severity of acute bronchiolitis.

STUDY DESIGN

We conducted a prospective single pediatric tertiary care center cohort study of inpatients aged 0-18 months with a first episode of acute bronchiolitis from November 1st 2014 to April 30th 2017. Disease severity was determined by the length of hospitalization and supplemental hospital data. Qualitative measurements included serum 25(OH)D and nasal secretion LL-37 and β-defensin-2 levels. Correlations were examined with the Mann-Whitney and Kruskal-Wallis criteria for qualitative and the correlation coefficient Spearman's rho for quantitative factors. Multiple linear and logarithmic regression were performed to adjust for confounding factors.

RESULTS

The study population consisted of 153 infants and toddlers with median age 3.1 months (interquartile range:1.6-4.9). No association was found between serum 25(OH)D and AMPs nasal secretions levels. Serum 25(OH)D and nasal secretion β-defensin-2 levels were not associated with the severity of bronchiolitis. In contrast, LL-37 levels were inversely associated with the length of hospitalization (rho = -0.340, p = .001), the need for medication use (p = .001), as well as the duration of oxygen supplementation (rho = -0.339, p = .001), and intravenous fluid administration (rho = -0.323, p = .001). This association remained significant after adjustment for potential confounders.

CONCLUSION

A significant association between LL-37 nasal secretions levels with the severity of acute bronchiolitis was found in hospitalized infants and toddlers. The role of LL-37 in the pathogenesis of bronchiolitis merits further investigation.

Immunomodulatory Expression of Cathelicidins Peptides in Pulp Inflammation and Regeneration: An Update

The role of inflammatory mediators in dental pulp is unique. The local environment of pulp responds to any changes in the physiology that are highly fundamental, like odontoblast cell differentiation and other secretory activity. The aim of this review is to assess the role of cathelicidins based on their capacity to heal wounds, their immunomodulatory potential, and their ability to stimulate cytokine production and stimulate immune-inflammatory response in pulp and periapex. Accessible electronic databases were searched to find studies reporting the role of cathelicidins in pulpal inflammation and regeneration published between September 2010 and September 2020. The search was performed using the following databases: Medline, Scopus, Web of Science, SciELO and PubMed. The electronic search was performed using the combination of keywords "cathelicidins" and "dental pulp inflammation". On the basis of previous studies, it can be inferred that LL-37 plays an important role in odontoblastic cell differentiation and stimulation of antimicrobial peptides. Furthermore, based on these outcomes, it can be concluded that LL-37 plays an important role in reparative dentin formation and provides signaling for defense by activating the innate immune system.

Association of salivary physicochemical characteristics and peptide levels with dental caries in children

AIM

The purpose of this investigation was to evaluate the association of physicochemical properties and antimicrobial peptide levels of saliva with caries activity in children.

MATERIALS AND METHODS

The required volume of unstimulated saliva was collected from 41 children aged 3-12 years with no systemic diseases. Caries activity was calculated using DMFS and dmfs records for each participating child. Collected saliva samples were then examined for their flow rate, pH, and buffering capacity. The concentration of three peptides was assessed including LL-37, human neutrophil peptide (HNP) 1-3, and human beta-defensin (HBD)-3 through an enzyme-linked immunosorbent assay. The correlation between caries activity score (CAS) and salivary variables was looked using the linear regression and Spearman's correlation method. The comparison of CAS means between high- and low-value groups of salivary items was performed using independent sample t-test while the association of CAS and salivary parameters in categorical scale was tested by Chi-square test.

RESULTS

No statistically significant differences were found between the CAS means at low and high categories of each salivary physicochemical parameter and those of antimicrobial peptides. There was a negative correlation between HNP1-3 and CAS and also between HBD-3 and CAS, but these results were not statistically meaningful. High HNP1-3 concentration was noted in 67% of the low caries rate group and 29% of the high caries rate group, with a statistically significant difference between the low and high caries rate groups (P = 0.019).

CONCLUSION

Salivary inherent factors are not dominant determinants in caries activity. The current results may suggest that α-defensins (HNP1-3) have a protective role against dental caries.

Antimicrobial peptides for the prevention and treatment of dental caries: A concise review

The objective of this study was to perform a comprehensive review of the use of antimicrobial peptides for the prevention and treatment of dental caries. The study included publications in the English language that addressed the use of antimicrobial peptides in the prevention and treatment of caries. These publications were also searchable on PubMed, Web of Science, Embase, Scopus, the Collection of Anti-Microbial Peptides and the Antimicrobial Peptide Database. A total of 3,436 publications were identified, and 67 publications were included. Eight publications reported seven natural human antimicrobial peptides as bactericidal to Streptococcus mutans. Fifty-nine publications reported 43 synthetic antimicrobial peptides developed to mimic natural antimicrobial peptides, fusing peptides with functional sequences and implementing new designs. The 43 synthetic antimicrobial peptides were effective against Streptococcus mutans, and nine peptides specifically targeted Streptococcus mutans. Ten antimicrobial peptides had an affinity for hydroxyapatite to prevent bacterial adhesion. Six antimicrobial peptides were also antifungal. Four antimicrobial peptides promoted remineralisation or prevented the demineralisation of teeth by binding calcium to hydroxyapatite. In conclusion, this study identified 67 works in the literature that reported seven natural and 43 synthetic antimicrobial peptides for the prevention and treatment of caries. Most of the antimicrobial peptides were bactericidal, and some prevented bacterial adhesion. A few antimicrobial peptides displayed remineralising properties with hydroxyapatite.

Activity of five antimicrobial peptides against periodontal as well as non-periodontal pathogenic strains

Background: Due to the increasing emergence of multi-resistant bacteria the search for alternative antimicrobial substances is of high interest. Promising agents are antimicrobial peptides which are host defense molecules of the innate immune system in a wide range of different species. Objectives: The aim of this study was to assess the activity of nisin, melittin, lactoferrin, parasin-1 and LL-37 against 35 oral bacteria and Candida albicans employing the gold standard method for anaerobic susceptibility testing. Methods: The activity of the peptides was determined by an agar dilution method under anaerobic and aerobic conditions. The test media contained final peptide concentrations between 0.125 µg/ml and 8 µg/ml (melittin, lactoferrin, parasin-1, LL-37) and between 0.125 µg/ml and 128 µg/ml (nisin). Results: Nisin completely inhibited the growth of Megasphaera sp., Bifidobacterium longum, Parvimonas micra, Actinomyces israelii, Actinomyces naeslundii, Actinomyces odontolyticus, Prevotella intermedia, Streptococcus anginosus, Streptococcus constellatus and Staphylococcus aureus. Melittin and lactoferrin reduced the growth of Megasphaera sp., P. micra, B. longum (melittin) and Selenomonas flueggei (lactoferrin). Parasin-1 and LL-37 showed no activity. Conclusion: AMPs, especially nisin and to a smaller degree lactoferrin, might be promising alternatives to antibiotics because of their antimicrobial activity, high resistance to environmental conditions and partially low costs.

Design, Engineering and Discovery of Novel α-Helical and β-Boomerang Antimicrobial Peptides against Drug Resistant Bacteria

In an era where the pipeline of new antibiotic development is drying up, the continuous rise of multi-drug resistant (MDR) and extensively drug resistant (XDR) bacteria are genuine threats to human health. Although antimicrobial peptides (AMPs) may serve as promising leads against drug resistant bacteria, only a few AMPs are in advanced clinical trials. The limitations of AMPs, namely their low in vivo activity, toxicity, and poor bioavailability, need to be addressed. Here, we review engineering of frog derived short α-helical AMPs (aurein, temporins) and lipopolysaccharide (LPS) binding designed β-boomerang AMPs for further development. The discovery of novel cell selective AMPs from the human proprotein convertase furin is also discussed.

Can Salivary Biomarkers Be Used as Predictors of Dental Caries in Young Adolescents?

Background

Identifying caries predictors in the subpopulation at risk is one of the preconditions for developing effective caries prevention measures. The present exploratory study aimed to examine the significance of socio-demographic characteristics, dietary-hygiene habits, salivary pH, and salivary antimicrobial HNP-1, hBD-2, and LL-37 peptides as potential caries risk predictors in children ages 11–13 years.

Material/Methods

This prospective 1-year study enrolled 213 children ages 11–13 years. The subjects underwent a dental examination and their mothers were interviewed. Unstimulated saliva was collected from the subjects to determine its pH value, as well as the salivary levels of HNP-1, hBD-2, and LL-37 peptides in 85 of the subjects. After 12 months, the 1-year caries incidence rate was recorded. Logistic regression analysis was used to estimate the ability of selected variables to predict caries risk.

Results

The univariable logistic regression analysis determined that the most significant independent caries risk predictors were: sex (female) (OR=2.132, p=0.007), mothers’ education (OR=1.986, p=0.020), salivary pH (OR=0.270, p=0.043), oral hygiene index (OR=1.886, p=0.015), and daily tooth brushing frequency (OR=0.565, p=0.042). The multivariable model showed that sex and oral hygiene-related variables were the most important caries predictors.

Conclusions

Salivary HNP-1, hBD-2, and LL-37 peptides were not found to have a significant predictive value. Therefore, socio-demographic and oral hygiene variables remain important caries predictors in early adolescents, suggesting the importance of the mechanical control of biofilm as the key measure for preventing caries. However, there is still a need for effective caries risk biomarkers, and additional research is needed in this area of caries risk prediction.

Vitamin D Deficiency and Oral Health: A Comprehensive Review

Vitamin D (VD) levels have been gaining growing attention in Oral Health. During growth and adulthood, VD deficiency (VDD) is associated with a wide variety of oral health disorders, and impaired VD synthesis may expedite some of these conditions. In children, severe VDD can induce defective tooth mineralization, resulting in dentin and enamel defects. As a consequence, these defects may increase the risk of the onset and progression of dental caries. Further, VDD has been associated with higher prevalence of periodontitis and gingival inflammation, and several recent preclinical and clinical studies have unveiled potential pathways through which Vitamin D may interact with the periodontium. VDD correction through supplementation may contribute to a successful treatment of periodontitis; however, alveolar bone regeneration procedures performed in baseline VDD patients seem more prone to failure. Vitamin D may also be linked with some oral pathology entities such as certain oral cancers and events of osteonecrosis of the jaw. This review aims to provide comprehensive evidence of how VD levels should be considered to promote good oral health, and to summarize how VDD may hamper oral development and its role in certain oral conditions.

Salivary LL-37 and periodontal health in children exposed to passive smoking

BACKGROUND

Antimicrobial peptides play an important role in the local defence of oral cavity. Cigarette smoke has detrimental effects on immune defence mechanisms. The effect of passive smoking on salivary LL-37, as an antimicrobial peptide, in children has not yet been reported.

AIM

The aims of this study were to evaluate salivary LL-37 levels in PS-exposed and PS-unexposed children and to investigate the association between salivary LL-37 levels and periodontal clinical parameters.

DESIGN

Unstimulated salivary samples were collected from 180 children (90 PS-exposed [38 girls and 52 boys; mean age: 9.36 ± 1.60 years] and 90 PS-unexposed [43 girls and 47 boys; mean age: 9.02 ± 1.71 years]) in this study. Periodontal clinical parameters, including plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment level (CAL), were recorded in all children. Salivary cotinine and LL-37 levels were measured by enzyme-linked immunosorbent assay.

RESULTS

PI and GI values in PS-exposed children were significantly higher than those in PS-unexposed children. The mean salivary cotinine concentration was significantly higher in PS-exposed children than in control subjects. The mean salivary LL-37 concentration of PS-exposed children was significantly lower (100.71 ± 72.14 pg/mL) than that of PS-unexposed children (151.84 ± 107.89 pg/mL).

CONCLUSION

Passive smoking could suppress salivary LL-37 concentrations in children.

Reassessing the Host Defense Peptide Landscape

Current research has demonstrated that small cationic amphipathic peptides have strong potential not only as antimicrobials, but also as antibiofilm agents, immune modulators, and anti-inflammatories. Although traditionally termed antimicrobial peptides (AMPs) these additional roles have prompted a shift in terminology to use the broader term host defense peptides (HDPs) to capture the multi-functional nature of these molecules. In this review, we critically examined the role of AMPs and HDPs in infectious diseases and inflammation. It is generally accepted that HDPs are multi-faceted mediators of a wide range of biological processes, with individual activities dependent on their polypeptide sequence. In this context, we explore the concept of chemical space as it applies to HDPs and hypothesize that the various functions and activities of this class of molecule exist on independent but overlapping activity landscapes. Finally, we outline several emerging functions and roles of HDPs and highlight how an improved understanding of these processes can potentially be leveraged to more fully realize the therapeutic promise of HDPs.

Human salivary proteins and their peptidomimetics: Values of function, early diagnosis, and therapeutic potential in combating dental caries

Saliva contains a large number of proteins that play various crucial roles to maintain the oral health and tooth integrity. This oral fluid is proposed to be one of the most important host factors, serving as a special medium for monitoring aspects of microorganisms, diet and host susceptibility involved in the caries process. Extensive salivary proteomic and peptidomic studies have resulted in considerable advances in the field of biomarkers discovery for dental caries. These salivary biomarkers may be exploited for the prediction, diagnosis, prognosis and treatment of dental caries, many of which could also provide the potential templates for bioactive peptides used for the biomimetic management of dental caries, rather than repairing caries lesions with artificial materials. A comprehensive understanding of the biological function of salivary proteins as well as their derived biomimetic peptides with promising potential against dental caries has been long awaited. This review overviewed a collection of current literature and addressed the majority of different functions of salivary proteins and peptides with their potential as functional biomarkers for caries risk assessment and clinical prospects for the anti-caries application.

Salivary proteins and peptides in the aetiology of caries in children: Systematic literature review

BACKGROUND

To assess the relationship of chosen salivary proteins and peptides levels with the occurrence of caries in children.

METHODS

PubMed, MEDLINE and EMBASE databases from 2000 to 2018 were researched for original observational studies published in English. The risk of bias and quality of the included papers were assessed regarding the guidelines by Fowkes and Fulton.

RESULTS

Twenty-two studies were included in the review, from which the issue of glycoproteins (including immunoglobulins), AMPs and salivary enzymes was discussed. The research involved primary dentition (13 papers), as well as mixed (7) and permanent dentition (5). Caries assessment included visual inspection, dmft/s and DMFT/S indexed; quantity of Streptococcus mutans and Lactobacillus spp. bacteria; and caries risk assessment.

DISCUSSION

The results of studies regarding the connection between salivary peptides and proteins and caries development in children are promising; however, further investigations should be undertaken. The majority of studies included are case-control and cross-sectional; however, it is necessary to conduct more cohort studies with adequate follow-up prior to considering this as markers for caries risk assessment.

Age-related changes in immune function (immune senescence) in caries and periodontal diseases: a systematic review

AIM

To systematically review the evidence regarding immune senescence in the pathogenesis of periodontitis and dental caries.

METHODS

A systematic search of electronic databases utilizing medical subject headings (MeSH terms) supplemented by screening of review articles and other relevant texts was undertaken.

RESULTS

Seventy-three articles were included (43 for periodontitis, 30 for caries). Study results were found to be generally heterogeneous. Regarding periodontitis, human studies suggest evidence for altered neutrophil function and increased production of pro-inflammatory mediators (e.g. interleukin-1β, interleukin-6 and prostaglandin E₂ ) in older compared to younger subjects, and animal experiments suggest increased expression of genes that contribute to a pro-inflammatory state in older compared to younger animals. Regarding dental caries, research relating to changes in immune functioning and the impact of ageing is in its infancy. A small number of studies have reported components of innate and adaptive immunity that affect the composition of saliva and dental biofilms with possible impacts on caries progression.

CONCLUSION

There is evidence that immune functioning related to periodontitis and (less investigated) dental caries alters with increasing age. In both conditions, age-associated mechanistic changes in immune functioning are complex and incompletely understood and it is not clear how these relate to disease susceptibility.

Signaling by a Conserved Quorum Sensing Pathway Contributes to Growth Ex Vivo and Oropharyngeal Colonization of Human Pathogen Group A Streptococcus

Bacterial virulence factor production is a highly coordinated process. The temporal pattern of bacterial gene expression varies in different host anatomic sites to overcome niche-specific challenges. The human pathogen group A streptococcus (GAS) produces a potent secreted protease, SpeB, that is crucial for pathogenesis. Recently, we discovered that a quorum sensing pathway comprised of a leaderless short peptide, SpeB-inducing peptide (SIP), and a cytosolic global regulator, RopB, controls speB expression in concert with bacterial population density. The SIP signaling pathway is active in vivo and contributes significantly to GAS invasive infections. In the current study, we investigated the role of the SIP signaling pathway in GAS-host interactions during oropharyngeal colonization. The SIP signaling pathway is functional during growth ex vivo in human saliva. SIP-mediated speB expression plays a crucial role in GAS colonization of the mouse oropharynx. GAS employs a distinct pattern of SpeB production during growth ex vivo in saliva that includes a transient burst of speB expression during early stages of growth coupled with sustained levels of secreted SpeB protein. SpeB production aids GAS survival by degrading LL37, an abundant human antimicrobial peptide. We found that SIP signaling occurs during growth in human blood ex vivo. Moreover, the SIP signaling pathway is critical for GAS survival in blood. SIP-dependent speB regulation is functional in strains of diverse emm types, indicating that SIP signaling is a conserved virulence regulatory mechanism. Our discoveries have implications for future translational studies.

Sensitivity of caries pathogens to antimicrobial peptides related to caries risk

OBJECTIVES

Antimicrobial peptides (AMPs) represent important facets of the immune system controlling infectious diseases. However, pathogens show varying susceptibilities to AMPs. This study investigates the susceptibilities of strains of Streptococcus mutans (SM), Actinomyces naeslundii (AN), and Lactobacillus spp. (LB) towards AMPs and if there are correlations between the appearance of such high-risk strains and clinical caries status.

MATERIAL AND METHODS

Plaque samples were collected from patients along with clinical examinations. Bacterial strains were identified via selective media, matrix-assisted laser desorption/ionization analysis-time of flight (MALDI-TOF), and arbitrary-primed-PCR (AP-PCR). Each strain was tested for susceptibility to LL-37, HBD-2, HNP-1, and HNP-3 or phosphate-buffered saline as negative control in a biofilm model on hydroxylapatite discs. Survival rates and resulting risk classification for each strain were determined. Correlations were calculated between the number of high-risk strains (all/S. mutans) appearing in patients and their clinical caries status.

RESULTS

Forty-seven patients were included with mean DMFT values of 11.4 ± 8.7. A total of 8 different SM, 30 LB, and 47 AN strains were detected. One-way ANOVA indicated that type/concentration of AMPs had major influence on reductions of Lactobacilli and Actinomyces. Seventeen strains of AN, 2 of SM, and 6 of LB had low susceptibilities to AMPs. The number of such strains in patients showed significant positive correlations to the DMFT values (all p = 0.001; r = 0.452; S. mutans p < 0.0001, r = 0.558).

CONCLUSION

The occurrence of low susceptible strains to AMPs seems to correlate with the individual caries status.

CLINICAL RELEVANCE

The results may lead to new ways to identify individuals with increased caries risk.

Combined analysis of the salivary microbiome and host defence peptides predicts dental disease

Understanding the triad of host response, microbiome and disease status is potentially informative for disease prediction, prevention, early intervention and treatment. Using longitudinal assessment of saliva and disease status, we demonstrated that partial least squares modelling of microbial, immunological and clinical measures, grouped children according to future dental disease status. Saliva was collected and dental health assessed in 33 children aged 4 years, and again 1-year later. The composition of the salivary microbiome was assessed and host defence peptides in saliva were quantified. Principal component analysis of the salivary microbiome indicated that children clustered by age and not disease status. Similarly, changes in salivary host defence peptides occurred with age and not in response to, or preceding dental caries. Partial least squares modelling of microbial, immunological and clinical baseline measures clustered children according to future dental disease status. These data demonstrate that isolated evaluation of the salivary microbiome or host response failed to predict dental disease. In contrast, combined assessment of both host response together with the microbiome revealed clusters of health and disease. This type of approach is potentially relevant to myriad diseases that are modified by host–microbiome interactions.

Salivary Protein Roles in Oral Health and as Predictors of Caries Risk

This work describes the current state of research on the potential relationship between protein content in human saliva and dental caries, which remains among the most common oral diseases and causes irreversible damage in the oral cavity. An understanding the whole saliva proteome in the oral cavity could serve as a prerequisite to obtaining insight into the etiology of tooth decay at early stages. To date, however, there is no comprehensive evidence showing that salivary proteins could serve as potential indicators for the early diagnosis of the risk factors causing dental caries. Therefore, proteomics indicates the promising direction of future investigations of such factors, including diagnosis and thus prevention in dental therapy.

Significance and Diagnostic Role of Antimicrobial Cathelicidins (LL-37) Peptides in Oral Health

Cathelicidins are a group of oral antimicrobial peptides that play multiple vital roles in the human body, such as their antimicrobial (broad spectrum) role against oral microbes, wound healing, and angiogenesis, with recent evidences about their role in cancer regulation. Cathelicidins are present in humans and other mammals as well. By complex interactions with the microenvironment, it results in pro-inflammatory effects. Many in vitro and in vivo experiments have been conducted to ultimately conclude that these unique peptides play an essential role in innate immunity. Peptides are released in the precursor form (defensins), which after cleavage results in cathelicidins formation. Living in the era where the major focus is on non-invasive and nanotechnology, this ultimately leads to further advancements in the field of salivaomics. Based on current spotlight innovations, we have highlighted the biochemistry, mode of action, and the importance of cathelicidins in the oral cavity.

Salivary proteins and microbiota as biomarkers for early childhood caries risk assessment

Early childhood caries (ECC) is a term used to describe dental caries in children aged 6 years or younger. Oral streptococci, such as Streptococcus mutans and Streptococcus sorbrinus, are considered to be the main etiological agents of tooth decay in children. Other bacteria, such as Prevotella spp. and Lactobacillus spp., and fungus, that is, Candida albicans, are related to the development and progression of ECC. Biomolecules in saliva, mainly proteins, affect the survival of oral microorganisms by multiple innate defensive mechanisms, thus modulating the oral microflora. Therefore, the protein composition of saliva can be a sensitive indicator for dental health. Resistance or susceptibility to caries may be significantly correlated with alterations in salivary protein components. Some oral microorganisms and saliva proteins may serve as useful biomarkers in predicting the risk and prognosis of caries. Current research has generated abundant information that contributes to a better understanding of the roles of microorganisms and salivary proteins in ECC occurrence and prevention. This review summarizes the microorganisms that cause caries and tooth-protective salivary proteins with their potential as functional biomarkers for ECC risk assessment. The identification of biomarkers for children at high risk of ECC is not only critical for early diagnosis but also important for preventing and treating the disease.

The innate host response in caries and periodontitis

INTRODUCTION

Innate immunity rapidly defends the host against infectious insults. These reactions are of limited specificity and exhaust without providing long-term protection. Functional fluids and effector molecules contribute to the defence against infectious agents, drive the immune response, and direct the cellular players.

AIM

To review the literature and present a summary of current knowledge about the function of tissues, cellular players and soluble mediators of innate immunity relevant to caries and periodontitis.

METHODS

Historical and recent literature was critically reviewed based on publications in peer-reviewed scientific journals.

RESULTS

The innate immune response is vital to resistance against caries and periodontitis and rapidly attempts to protect against infectious agents in the dental hard and soft tissues. Soluble mediators include specialized proteins and lipids. They function to signal to immune and inflammatory cells, provide antimicrobial resistance, and also induce mechanisms for potential repair of damaged tissues.

CONCLUSIONS

Far less investigated than adaptive immunity, innate immune responses are an emerging scientific and therapeutic frontier. Soluble mediators of the innate response provide a network of signals to organize the near immediate molecular and cellular response to infection, including direct and immediate antimicrobial activity. Further studies in human disease and animal models are generally needed.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Influence of saliva on the oral microbiota

Saliva plays a major role in determining the composition and activity of the oral microbiota, via a variety of mechanisms. Molecules, mainly from saliva, form a conditioning film on oral surfaces, thus providing receptors for bacterial attachment. The attached cells use saliva components, such as glycoproteins, as their main source of nutrients for growth. Oral bacteria work sequentially and in a concerted manner to catabolize these structurally complex molecules. Saliva also buffers the pH in the biofilm to around neutrality, creating an environment which is conducive to the growth of many oral bacteria that provide important benefits to the host. Components of the adaptive and innate host defences are delivered by saliva, and these often function synergistically, and at sublethal concentrations, so a complex relationship develops between the host and the resident microbiota. Dysbiosis can occur rapidly if the flow of saliva is perturbed.

Evidence of sexual dimorphism in placental vitamin D metabolism: Testosterone inhibits calcitriol-dependent cathelicidin expression

Male fetus and neonates show increased immune vulnerability compared to females, which results in a higher risk of perinatal infections. These differences could partially be due to sex steroids differential modulation of vitamin D metabolism; since calcitriol, the most active vitamin D metabolite, regulates immune responses and transcriptionally induces the antimicrobial peptide cathelicidin in the human placenta. Calcitriol availability depends on CYP27B1 and CYP24A1 expression, the cytochromes involved in its synthesis and degradation, respectively. However, the effects of testosterone upon these enzymes and the final biological outcome upon the calcitriol-dependent immune-target cathelicidin in the placenta have not been studied. In this study we show that testosterone significantly inhibited CYP27B1 while stimulated CYP24A1 gene expression in cultured trophoblasts. These effects were accompanied by CREB activation through cAMP-independent and androgen receptor-dependent mechanisms. Male placental cotyledons showed reduced basal CYP27B1 and cathelicidin gene expression compared to females (P<0.05). Testosterone concentration was higher in the cord blood of male neonates (P=0.007), whereas cathelicidin levels were lesser compared to females (P=0.002). Altogether our results suggest that male placentas produce less cathelicidin due to decreased calcitriol bioavailability. We propose that the observed sex-dependent differences in placental vitamin D metabolism contribute in fetal responses to infections and could partially explain why the increased male fetuses immune vulnerability. Moreover, gestational hyperandrogenemia could adversely affect placental vitamin D metabolism independently of fetal sex.

Antimicrobial peptides in saliva of children with severe early childhood caries

OBJECTIVE

Controversies exist regarding the relationship between the concentrations of antimicrobial peptides (AMPs) and presence of dental caries in children. Thus, the aim of this study was to examine levels of AMPs in saliva of caries-free (CF), early childhood caries (ECC) and severe early childhood caries (S-ECC) children to determine if the levels of these salivary peptides individually or in combinations were related to caries severity and mutans streptococci levels.

DESIGN

36 to 60 month-old children were selected to participate in this study. Children were grouped into CF group (n=29), ECC group (n=25) and S-ECC group (n=29). Saliva was collected from children for microbiological analysis by culture. Salivary concentrations of cathelicidin LL-37, human β-defensin 2 (hBD-2), human β-defensin 3 (hBD-3) and histatin-5 (HTN-5) were determined by ELISA.

RESULTS

Salivary concentrations of AMPs did not differ among CF, ECC and S-ECC groups. Data showed positive correlations between mutans streptococci levels and salivary hBD-2 or HTN-5. Positive correlations were found between hBD-2, hBD-3, LL-37 and HTN-5. Combinations among AMPs, mainly LL-37, were positively associated with caries levels.

CONCLUSIONS

Salivary concentrations of AMPs individually were not associated with the severity of early childhood caries. The stimulus of caries appears to trigger a biological response, however, with a combination of these peptides.

Circulating Cathelicidin Concentrations in a Cohort of Healthy Children: Influence of Age, Body Composition, Gender and Vitamin D Status

Cathelicidin is an antimicrobial peptide whose circulating levels are related to vitamin D status in adults. This study sought to determine if circulating cathelicidin concentrations in healthy children are related to the age of the child, body composition and vitamin D status at birth and at the time of the study visit. Blood samples were obtained during yearly visits from 133 children, ages 2–7, whose mothers had participated in a pregnancy vitamin D supplementation RCT. Radioimmunoassay and ELISA were performed to analyze 25(OH)D and cathelicidin, respectively. Statistical analyses compared cathelicidin concentrations with concentrations of 25(OH)D at various time points (maternal levels throughout pregnancy, at birth, and child’s current level); and with race/ethnicity, age, gender, BMI, percent fat, and frequency of infections using Student’s t-test, χ², Wilcoxon ranked-sum analysis, and multivariate regression. The cohort’s median cathelicidin concentration was 28.1 ng/mL (range: 5.6–3368.6) and did not correlate with 25(OH)D, but was positively correlated with advancing age (ρ = 0.236 & p = 0.005, respectively). Forty patients evaluated at two visits showed an increase of 24.0 ng/mL in cathelicidin from the first visit to the next (p<0.0001). Increased age and male gender were correlated with increased cathelicidin when controlling for race/ethnicity, percent fat, and child’s current 25(OH)D concentration (p = 0.028 & p = 0.047, respectively). This study demonstrated that as children age, the concentration of cathelicidin increases. Furthermore, male gender was significantly associated with increased cathelicidin concentrations. The lack of association between vitamin D status and cathelicidin in this study may be due to the narrow range in observed 25(OH)D values and warrants additional studies for further observation.

Relationship between the IgA antibody response against Streptococcus mutans GbpB and severity of dental caries in childhood

OBJECTIVE

Explore the associations between the severity of dental caries in childhood, mutans streptococci (MS) levels and IgA antibody response against Streptococcus mutans GbpB. Moreover, other caries-related etiological factors were also investigated.

DESIGN

36-60 month-old children were grouped into Caries-Free (CF, n=19), Early Childhood Caries (ECC, n=17) and Severe Early Childhood Caries (S-ECC, n=21). Data from socio-economic-cultural status, oral hygiene habits and dietary patterns were obtained from a questionnaire and a food-frequency diary filled out by parents. Saliva was collected from children for microbiological analysis and detection of salivary IgA antibody reactive with S. mutans GbpB in western blot.

RESULTS

S-ECC children had reduced family income compared to those with ECC and CF. There was difference between CF and caries groups (ECC and S-ECC) in MS counts. Positive correlations between salivary IgA antibody response against GbpB and MS counts were found when the entire population was evaluated. When children with high MS counts were compared, S-ECC group showed significantly lower IgA antibody levels to GbpB compared to CF group. This finding was not observed for the ECC group.

CONCLUSIONS

This study suggests that children with S-ECC have reduced salivary IgA immune responses to S. mutans GbpB, potentially compromising their ability to modify MS infection and its cariogenic potential. Furthermore, a reduced family income and high levels of MS were also associated with S-ECC.

Oral innate immunity in HIV infection in HAART era

Oral innate immunity, an important component in host defense and immune surveillance in the oral cavity, plays a crucial role in the regulation of oral health. As part of the innate immune system, epithelial cells lining oral mucosal surfaces not only provide a physical barrier but also produce different antimicrobial peptides, including human β-defensins (hBDs), secretory leukocyte protease inhibitor (SLPI), and various cytokines. These innate immune mediators help in maintaining oral homeostasis. When they are impaired either by local or systemic causes, various oral infections and malignancies may be developed. Human immunodeficiency virus (HIV) infection and other co-infections appear to have both direct and indirect effects on systemic and local innate immunity leading to the development of oral opportunistic infections and malignancies. Highly active antiretroviral therapy (HAART), the standard treatment of HIV infection, contributed to a global reduction of HIV-associated oral lesions. However, prolonged use of HAART may lead to adverse effects on the oral innate immunity resulting in the relapse of oral lesions. This review article focused on the roles of oral innate immunity in HIV infection in HAART era. The following five key questions were addressed: (i) What are the roles of oral innate immunity in health and disease?, (ii) What are the effects of HIV infection on oral innate immunity?, (iii) What are the roles of oral innate immunity against other co-infections?, (iv) What are the effects of HAART on oral innate immunity?, and (v) Is oral innate immunity enhanced by HAART?

Antimicrobial peptides: an alternative for innovative medicines?

Antimicrobial peptides are small molecules with activity against bacteria, yeasts, fungi, viruses, bacteria, and even tumor cells that make these molecules attractive as therapeutic agents. Due to the alarming increase of antimicrobial resistance, interest in alternative antimicrobial agents has led to the exploitation of antimicrobial peptides, both synthetic and from natural sources. Thus, many peptide-based drugs are currently commercially available for the treatment of numerous ailments, such as hepatitis C, myeloma, skin infections, and diabetes. Initial barriers are being increasingly overcome with the development of cost-effective, more stable peptides. Herein, we review the available strategies for their synthesis, bioinformatics tools for the rational design of antimicrobial peptides with enhanced therapeutic indices, hurdles and shortcomings limiting the large-scale production of AMPs, as well as the challenges that the pharmaceutical industry faces on their use as therapeutic agents.

Salivary concentration of the antimicrobial peptide LL-37 in patients with oral lichen planus

Background

The antimicrobial peptide LL-37 is a significant molecule of innate immunity and recent studies indicate that it plays an important role in maintaining oral health. Yet limited knowledge exists on its role in oral diseases and oral lichen planus (OLP) in particular.

Objective

The study aimed to examine: 1) the salivary concentration of LL-37 in patients with OLP and healthy subjects, 2) the relation between the type (reticular or erosive) and size of OLP lesions and LL-37 concentration, and 3) the effect of the therapeutic modalities on LL-37 levels.

Design

The salivary peptide concentration in samples from 20 patients and 30 healthy subjects at the same age range was determined by ELISA.

Results

Despite the wide variation in peptide concentration found in both groups, the healthy subjects exhibited significantly lower levels than patients. Patients with the erosive form had significantly higher peptide concentrations than patients with the reticular form. Systemic treatment with corticosteroids resulted in a significant decrease of the salivary peptide concentration, while other treatment modalities, such as administration of vitamins A and E or local application of corticosteroids had no effect. Improved clinical appearance of the lesions was followed by a decrease in the salivary LL-37 level.

Conclusions

Salivary concentration of LL-37 correlates to the manifestation of mucosa lesions in OLP patients, the highest levels being observed in the most severe cases. This increase in peptide levels may protect against lesion infection and promote a quick wound healing.

Salivary antimicrobial proteins associate with age-related changes in streptococcal composition in dental plaque

Secretion of antimicrobial proteins (AMPs) and salivary antibodies can modify biofilm formation at host body surfaces. In adolescents, associations have been reported between dental caries and salivary AMPs. AMPs demonstrate direct antimicrobial effects at high concentrations, and at lower more physiological concentrations they mediate changes in host cell defenses, which may alter the local environment and indirectly shape local biofilm formation. The expression of salivary AMPs in preschool children, at an age when the oral bacteria are known to change, has not been investigated. We sought to investigate salivary AMP expression in the context of previously well-documented changes in the oral cavities of this age group including salivary immunoglobulin A (IgA), oral bacteria and dental caries. Dental plaque and saliva were collected from 57 children aged 12-24 months at baseline, of whom 23 children were followed-up at 3 years of age. At each time, saliva was assessed for LL37, human neutrophil peptides 1-3, calprotectin, lactoferrin, salivary IgA, total plaque bacteria and Streptococcus mutans. Over time, concentrations of AMPs, S. mutans and bacteria-specific salivary IgA increased. Caries experience was also recorded when children were 3 years old. Concentrations of AMPs were highest in the saliva of 3-year-old children with the greatest burden of S. mutans. These data suggest that salivary AMPs are variable over time and between individuals, and are linked with bacterial colonization. At follow up, the majority of children remained caries free. Larger longitudinal studies are required to confirm whether salivary AMP levels are predictive of caries and whether their modulation offers therapeutic benefit.

Mechanisms and fitness costs of resistance to antimicrobial peptides LL-37, CNY100HL and wheat germ histones

Antimicrobial peptides (AMPs) represent a potential new class of antimicrobial drugs with potent and broad-spectrum activities. However, knowledge about the mechanisms and rates of resistance development to AMPs and the resulting effects on fitness and cross-resistance is limited. We isolated antimicrobial peptide (AMP) resistant Salmonella typhimurium LT2 mutants by serially passaging several independent bacterial lineages in progressively increasing concentrations of LL-37, CNY100HL and Wheat Germ Histones. Significant AMP resistance developed in 15/18 independent bacterial lineages. Resistance mutations were identified by whole genome sequencing in two-component signal transduction systems (pmrB and phoP) as well as in the LPS core biosynthesis pathway (waaY, also designated rfaY). In most cases, resistance was associated with a reduced fitness, observed as a decreased growth rate, which was dependent on growth conditions and mutation type. Importantly, mutations in waaY decreased bacterial susceptibility to all tested AMPs and the mutant outcompeted the wild type parental strain at AMP concentrations below the MIC for the wild type. Our data suggests that resistance to antimicrobial peptides can develop rapidly through mechanisms that confer cross-resistance to several AMPs. Importantly, AMP-resistant mutants can have a competitive advantage over the wild type strain at AMP concentrations similar to those found near human epithelial cells. These results suggest that resistant mutants could both be selected de novo and maintained by exposure to our own natural repertoire of defence molecules.

Peptides as the next generation of anti-infectives

Synthesis and large-scale manufacturing technologies are now available for the commercial production of even the most complex peptide anti-infectives. Married with the potential of this class of molecule as the next generation of effective, resistance-free and safe antimicrobials, and a much better understanding of their biology, pharmacology and pharmacodynamics, the first regulatory approvals and introduction into clinical practice of these promising drug candidates will likely be soon. This is a key juncture in the history/life cycle of peptide anti-infectives and, perhaps, their commercial and therapeutic potential is about to be realized. This review highlights the promise of these agents as the next generation of therapeutics and summarizes the challenges faced in, and lessons learned from, the past.

Salivary concentration of free LL-37 in edentulism, chronic periodontitis and healthy periodontium

OBJECTIVE

The antimicrobial peptide LL-37, a component of innate immunity, has an important role in maintaining oral health. This study aimed to investigate the concentration of free LL-37 in whole saliva of periodontally healthy, edentulous and chronic periodontitis subjects.

DESIGN

Unstimulated whole saliva was sampled from 154 subjects (76 periodontally healthy, 20 edentulous, and 58 subjects with chronic periodontitis). All participants were in good general health. The salivary LL-37 was determined by ELISA.

RESULTS

The median salivary concentrations of free LL-37 were 30.5, 22.5, and 1.8ng/ml for the healthy, the chronic periodontitis and the edentulous group, respectively. The differences in concentration between the edentulous and the others were statistically significant (Mann-Whitney test, p<0.001). In the healthy subjects, women displayed significantly higher peptide concentrations compared to men (Mann-Whitney test, p<0.05). The intra-subject variation in LL-37 concentration was wider for the healthy (range 0.75-285ng/ml) and chronic periodontitis patients (range 1-207ng/ml) than for the edentulous subjects (range 0.15-4.4ng/ml).

CONCLUSIONS

The present findings show that edentulism correlates with a substantial decrease in salivary levels of free LL-37, thus indicating the considerable contribution of the gingival tissues in the secretion of the peptide in the oral environment.

A comprehensive summary of LL-37, the factotum human cathelicidin peptide

Cathelicidins are a group of antimicrobial peptides. Since their discovery, it has become clear that they are an exceptional class of peptides, with some members having pleiotropic effects. Not only do they possess an antibacterial, antifungal and antiviral function, they also show a chemotactic and immunostimulatory/-modulatory effect. Moreover, they are capable of inducing wound healing, angiogenesis and modulating apoptosis. Recent insights even indicate for a role of these peptides in cancer. This review provides a comprehensive summary of the most recent and relevant insights concerning the human cathelicidin LL-37.

Vitamin D and the human antimicrobial peptide LL-37 enhance group a streptococcus resistance to killing by human cells

The CsrRS two-component regulatory system of group A Streptococcus (GAS; Streptococcus pyogenes) responds to subinhibitory concentrations of the human antimicrobial peptide LL-37. LL-37 signaling through CsrRS results in upregulation of genes that direct synthesis of virulence factors, including the hyaluronic acid capsule and streptolysin O (SLO). Here, we demonstrate that a consequence of this response is augmented GAS resistance to killing by human oropharyngeal keratinocytes, neutrophils, and macrophages. LL-37-induced upregulation of SLO and hyaluronic acid capsule significantly reduced internalization of GAS by keratinocytes and phagocytic killing by neutrophils and macrophages. Because vitamin D induces LL-37 production by macrophages, we tested its effect on macrophage killing of GAS. In contrast to the reported enhancement of macrophage function in relation to other pathogens, treatment of macrophages with 1α,25-dihydroxy-vitamin D3 paradoxically reduced the ability of macrophages to control GAS infection. These observations demonstrate that LL-37 signals through CsrRS to induce a virulence phenotype in GAS characterized by heightened resistance to ingestion and killing by both epithelial cells and phagocytes. By inducing LL-37 production in macrophages, vitamin D may contribute to this paradoxical exacerbation of GAS infection. IMPORTANCE It remains poorly understood why group A Streptococcus (GAS) causes asymptomatic colonization or localized throat inflammation in most individuals but rarely progresses to invasive infection. The human antimicrobial peptide LL-37, which is produced as part of the innate immune response to GAS infection, signals through the GAS CsrRS two-component regulatory system to upregulate expression of multiple virulence factors. This study reports that two CsrRS-regulated GAS virulence factors-streptolysin O and the hyaluronic acid capsule-are critical in LL-37-induced resistance of GAS to killing by human throat epithelial cells and by neutrophils and macrophages. Vitamin D, which increases LL-37 production in macrophages, has the paradoxical effect of increasing GAS resistance to macrophage-mediated killing. In this way, the human innate immune response may promote the transition from GAS colonization to invasive infection.