LFchimera: a synthetic mimic of the two antimicrobial domains of bovine lactoferrin

Saliva is essential for the maintenance of oral health. When salivary flow is impaired, the risk of various oral diseases such as caries and candidiasis increases drastically. Under healthy conditions, saliva provides effective protection against microbial colonization by the collaborative action of numerous host-defense molecules. This review describes how saliva has been the guideline for the design and characterization of a heterodimeric antimicrobial construct called LFchimera. This construct mimics the helical parts of two antimicrobial domains in the crystal structure of bovine lactoferrin. It shows high antimicrobial activity against a broad spectrum of Gram-positive and Gram-negative bacteria, fungi, and parasites including biowarfare agents such as Bacillus anthracis, Burkholderia pseudomallei, and Yersinia pestis. Further, sublethal concentrations of LFchimera inhibited biofilm formation, the invasiveness of HeLa cells by Yersinia spp., and prevented haemolysis of enteropathogenic Escherichia coli, demonstrating the versatility of these peptides.

[Dissertation 25 years after date 48. The effect of saliva on the -colonisation of oral bacteria]

In the research that formed the basis of the dissertation 'Intervention of saliva in the colonization process of oral bacteria' from 1992, the aggregation or clustering of oral bacteria by saliva was investigated. This prevents bacterial colonisation in the mouth. Major individual differences in aggregation activity of different saliva samples were found to exist, partly determined by the blood group of the saliva donor. As well as being found in red blood cells, AB0 blood group antigens also appear on salivary glycoproteins. This does, however, not hold true for all individuals: this is only the case for so-called secretors. Non-secretors aggregated fewer bacteria than secretors. Later research showed that this was associated with a higher risk of caries. Subsequent research revealed that the complement system, a defence system in blood, was activated by saliva of secretors, but not of non-secretors. This shows that the oral defence systems are influenced by blood group and secretor status, but in a different way than we originally thought.

Bacillus globigii cell size is influenced by variants of the quorum sensing peptide extracellular death factor

Toxin-antitoxin modules are necessary for the mode of action of several antibiotics. One of the most studied toxin-antitoxin modules is the quorum sensing-dependent MazEF system in Escherichia coli. The quorum sensing factor in this system is called the extracellular death factor (EDF), a linear pentapeptide with the sequence NNWNN. In spite of the extensive research on the mazEF system and the involvement of the quorum sensing factor EDF, the effect of EDF itself on bacteria has not yet been studied. In this research, we determined the effect of EDF and variants on cell growth in the Gram-negative bacterium E. coli and the Gram-positive Bacillus globigii. By aligning the zwf gene (from where EDF originates) of different bacterial species, we found 27 new theoretical variants of the peptide. By evaluating growth curves and light microscopy we found that three EDF variants reduced bacterial cell size in B. globigii, but not in E. coli. The D-peptides did not affect cell size, indicating that the effect is stereospecific. Peptides wherein tryptophan was substituted by alanine also did not affect cell size, which indicates that the effect seen is mediated by an intracellular target.

Effect of salivary factors on the susceptibility of hydroxyapatite to early erosion

OBJECTIVE

Salivary pellicle is known to reduce the erosion of enamel and differences in the level of protection exist between individual saliva sources, but which parameters or components are important is not known. The focus of this study was to investigate the relationship between saliva parameters and early erosion of hydroxyapatite (HAp) with an in situ grown saliva film.

METHODS

Twenty-eight volunteers carried two HAp and one porcelain discs in their buccal sulcus for 1.5 h. Next, the discs covered with pellicle and the attached saliva film were exposed extraorally to 50 mM (pH = 3) citric acid for 2 min and unstimulated and stimulated saliva was collected. Calcium loss from HAp after erosive challenge was measured, corrected for calcium loss from pellicle on porcelain discs and averaged. Several salivary parameters were analysed. Pearson's linear correlation and multiple regression analysis were used to study the relation between saliva parameters and HAp erosion.

RESULTS

Significant correlations were found between HAp erosion and the concentration of phosphorus in unstimulated saliva (r = 0.40, p = 0.03) and between HAp erosion and the concentration of sodium (r = -0.40, p = 0.03), chloride (r = -0.47, p = 0.01), phosphorus (r = 0.45, p = 0.01) and flow (r = -0.39, p = 0.04) of stimulated saliva. Multivariate analysis revealed a significant role in the HAp erosion for sodium, urea, total protein, albumin, pH and flow of unstimulated saliva and for sodium, potassium, urea, and phosphorus of stimulated saliva.

CONCLUSIONS

Several salivary parameters are associated with the susceptibility of HAp to erosion.

Application of MLST and pilus gene sequence comparisons to investigate the population structures of Actinomyces naeslundii and Actinomyces oris

Actinomyces naeslundii and Actinomyces oris are members of the oral biofilm. Their identification using 16S rRNA sequencing is problematic and better achieved by comparison of metG partial sequences. A. oris is more abundant and more frequently isolated than A. naeslundii. We used a multi-locus sequence typing approach to investigate the genotypic diversity of these species and assigned A. naeslundii (n = 37) and A. oris (n = 68) isolates to 32 and 68 sequence types (ST), respectively. Neighbor-joining and ClonalFrame dendrograms derived from the concatenated partial sequences of 7 house-keeping genes identified at least 4 significant subclusters within A. oris and 3 within A. naeslundii. The strain collection we had investigated was an under-representation of the total population since at least 3 STs composed of single strains may represent discrete clusters of strains not well represented in the collection. The integrity of these sub-clusters was supported by the sequence analysis of fimP and fimA, genes coding for the type 1 and 2 fimbriae, respectively. An A. naeslundii subcluster was identified with both fimA and fimP genes and these strains were able to bind to MUC7 and statherin while all other A. naeslundii strains possessed only fimA and did not bind to statherin. An A. oris subcluster harboured a fimA gene similar to that of Actinomyces odontolyticus but no detectable fimP failed to bind significantly to either MUC7 or statherin. These data are evidence of extensive genotypic and phenotypic diversity within the species A. oris and A. naeslundii but the status of the subclusters identified here will require genome comparisons before their phylogenic position can be unequivocally established.

Salivary agglutinin/DMBT1SAG expression is up-regulated in the presence of salivary gland tumors

Salivary agglutinin (SAG) is encoded by the gene Deleted in Malignant Brain Tumors 1 (DMBT1) and represents the salivary variant of DMBT1 (DMBT1(SAG)). While SAG is a bona fide anti-caries factor, DMBT1 was proposed as a candidate tumor-suppressor for brain, digestive tract, and lung cancer. Though DMBT1(SAG) is expressed in the salivary glands, its expression in salivary gland tumors is unknown. Here we analyzed DMBT1(SAG) expression in 20 salivary gland tumors and 14 tumor-flanking tissues by immunohistochemistry. DMBT1(SAG) in salivary gland tumors resembles the changes of expression levels known from DMBT1 in tumors in other cancer types. Particularly, DMBT1(SAG) was up-regulated in 10/14 tumor-flanking tissues, and a strong staining of the luminal content in the tumor and/or the tumor-flanking tissue was observed in 14/20 cases. This suggests that, in addition to its role in caries defense, SAG may serve as a potential tumor indicator and/or tumor suppressor in salivary gland tissue.

Immunohistochemical detection of salivary agglutinin/gp-340 in human parotid, submandibular, and labial salivary glands

Salivary agglutinin is a Streptococcus mutans binding protein and a member of the scavenger receptor cysteine-rich superfamily. It is identical to lung gp-340 and brain DMBT1, which possibly play a role in innate immunity and tumor suppression, respectively. The goal of this study was to localize salivary agglutinin in human salivary glands. Two monoclonal antibodies, directed against gp-340, were characterized. mAb 213-1 reacted with sialic acid epitopes and cross-reacted with MUC7. The reaction with mAb 213-6 disappeared after reduction, suggesting that a protein epitope was recognized. In the parotid gland, immunohistochemical labeling with mAb 213-6 was found in the duct cells. In the submandibular gland and labial gland, both serous acini and demilune cells were labeled. In the labial gland, labeling was found at the luminal side of the duct cells. Salivary agglutinin was distinctly localized in salivary glands, but in distinct glandular secretions, no differences in electrophoretic behavior were observed.