Immunology of Diseases of the Oral Cavity

The Effects of Khat Chewing among Djiboutians: Dental Chemical Studies, Gingival Histopathological Analyses and Bioinformatics Approaches

This study examined the effects of khat chewing on oral gingival conditions by adopting a targeted process which combined physicochemical analyses of the teeth, histopathological examinations of the gums, and bioinformatics modeling. The physicochemical evaluation of teeth in khat consumers compared to non-consumers was carried out using specific analytical techniques; hence, the results of this initial investigation revealed significant erosion of the tooth enamel due to khat chewing, as well as an alteration of the essential chemical composition of the teeth. Additionally, the histopathological analyses complemented preliminary studies by showing severe inflammation of the gums and oral mucosa in khat users. The understanding of these studies was enriched by bioinformatics analysis, where modeling was carried out via computational methods. This analytical phase examined molecular docking mechanisms, including the interaction between cathinone, the main alkaloid of khat, and the protein receptors involved in the protection of gingival tissues against infections. In summary, this multidisciplinary research provided an in-depth view of the oral health issues related to khat chewing, combining experimental studies with bioinformatics perspectives.

Ex vivo study of molecular changes of stained teeth following hydrogen peroxide and peroxymonosulfate treatments

White teeth can give confidence and tend to be associated with a healthier lifestyle in modern society. Therefore, tooth-bleaching strategies have been developed, including the use of hydrogen peroxide. Recently, peroxymonosulfate has been introduced as an alternative bleaching method to hydrogen peroxide. Although both chemicals are oxidizing agents, their effects on the molecular composition of the stained teeth are yet unknown. In this study, the molecular profiles of teeth bleached with hydrogen peroxide and peroxymonosulfate were compared using Liquid Chromatography-Tandem Mass Spectrometry. Statistical analyses were used to assess the samples. In addition, reference spectral libraries and in silico tools were used to perform metabolite annotation. Overall, principal component analysis showed a strong separation between control and hydrogen peroxide and peroxymonosulfate samples (p < 0.001). The analysis of molecular changes revealed amino acids and dipeptides in stained teeth samples after hydrogen peroxide and peroxymonosulfate treatments. Noteworthy, the two bleaching methods led to distinct molecular profiles. For example, diterpenoids were more prevalent after peroxymonosulfate treatment, while a greater abundance of alkaloids was detected after hydrogen peroxide treatment. Whereas non-bleached samples (controls) showed mainly lipids. Therefore, this study shows how two different tooth-whitening peroxides could affect the molecular profiles of human teeth.

Oral findings in patients with cartilage-hair hypoplasia - cross-sectional observational study

BACKGROUND AND OBJECTIVES

Cartilage-hair hypoplasia (CHH) is a rare chondrodysplasia with associated primary immunodeficiency. The aim of this cross-sectional study was to examine oral health indicators in individuals with CHH.

METHODS

In total, 23 individuals with CHH, aged between 4.5 and 70 years, and 46 controls aged between 5 and 76 years were clinically examined for periodontal disease, presence of oral mucosal lesions, tooth decay, masticatory system function, and malocclusions. A chairside lateral flow immunoassay test of active-matrix metalloproteinase was obtained from all the adult participants with a permanent dentition. Laboratory signs of immunodeficiency were recorded for individuals with CHH.

RESULTS

Individuals with CHH and controls had similar prevalence of gingival bleeding on probing (median 6% vs. 4%). Oral fluid active-matrix metalloproteinase concentration was greater than 20 ng/ml in 45% of study subjects in both groups. However, deep periodontal pockets, 4 mm or deeper, were more common in individuals with CHH as compared to the controls (U = 282.5, p = 0.002). Similarly mucosal lesions were significantly more common in individuals with CHH (30% vs. 9%, OR = 0.223, 95%CI 0.057-0.867). The median sum of the number of decayed, missing due to caries, and filled teeth was nine for the individuals with CHH and four for controls. In the CHH cohort, 70% displayed an ideal sagittal occlusal relationship. Malocclusion and temporomandibular joint dysfunction prevalence were similar in both study groups.

CONCLUSIONS

Individuals with CHH have more frequently deep periodontal pockets and oral mucosal lesions than general population controls. Routine intraoral examination by a dentist at regular intervals should be recommended to all individuals with CHH.

Detection of Toxoplasma gondii-specific antibodies in pigs using an oral fluid-based commercial ELISA: Advantages and limitations

Toxoplasma gondii is a major food-borne parasite and undercooked meat of infected pigs represents an important source of infection for humans. Since infections in pigs are mostly subclinical, adequate diagnostic tests for use at the farm level are pursued. Oral fluid (OF) was shown to be a promising matrix for direct and indirect detection of infections with various pathogens in pigs. The objective of this study was to assess whether T. gondii infections in pigs could be diagnosed using an indirect ELISA kit adapted for OF samples (OF-ELISA). Routine serology and OF-immunoblot (IB) were used as standards for the comparison. For this, serial OF samples from sows (n = 8) and fatteners (n = 3) experimentally inoculated with T. gondii oocysts, individual field samples from potentially exposed sows (n = 9) and pooled OF samples from potentially exposed group-housed fatteners (n = 195 pig groups, including 2,248 animals) were analysed for antibodies against T. gondii by ELISA. For individual animals, OF-ELISA exhibited a relative diagnostic specificity of 97.3% and a relative diagnostic sensitivity of 78.8%. In experimentally infected animals, positive OF-ELISA results were observed from 1.5 weeks post inoculation (pi) until the end of the experimental setup (8 to 30 weeks pi); however, values below the estimated cut-off were occasionally observed in some animals despite constant seropositivity. In potentially exposed individual animals, OF- and serum-ELISA results showed 100% agreement. In group-housed fatteners, antibodies against T. gondii could be reliably detected by OF-ELISA in groups in which at least 25% of the animals were seropositive. This OF-ELISA, based on a commercially available serum-ELISA, may represent an interesting non-invasive screening tool for detecting pig groups with a high exposure to T. gondii at the farm level. The OF-ELISA may need further adjustments to consistently detect individual infected pigs, probably due to variations in OF antibody concentration over time.

Impaired salivary SIgA antibodies elicit oral dysbiosis and subsequent induction of alveolar bone loss

OBJECTIVE

Secreted IgA (SIgA) plays a central role in preventing bacterial and viral infections on mucosal surfaces by neutralizing toxins and viruses and inhibiting bacterial attachment to epithelial cells. However, the role of salivary SIgA antibodies (Abs) in regulating oral flora is still unknown. This study aimed to evaluate the association among oral bacteria, their metabolites and periodontitis in IgA-deficient (IgA KO) and wild-type (WT) control mice.

METHODS

Microcomputed tomography (micro-CT) analysis was used to assess alveolar bone resorption as a development of periodontitis. The bacterial profiles of saliva were determined using the next-generation sequencing assays. Furthermore, the metabolites in saliva were measured and compared using CE-TOFMS.

RESULTS

Salivary microbiota of IgA KO mice revealed a remarkably decreased frequency of Streptococcus, and increased percentages of Aggregatibacer, Actinobacillus, and Prevotella at the genus level when compared with those of WT. Compared to WT control mice of the same age, the level of alveolar bone loss was significantly increased in IgA KO mice, and infiltration of osteoclasts was found on the surface of the alveolar bone. The metabolome profile indicated that the metabolites of IgA KO mice had greater variability in carbon metabolic, urea cycle, and lipid pathways than WT mice.

CONCLUSION

These results suggest that salivary SIgA plays an important role in regulating and maintaining normal oral microflora to prevent the development of periodontal disease.

Complement activation links inflammation to dental tissue regeneration

OBJECTIVES

Complement is an efficient plasma immune surveillance system. It initiates inflammation by inducing vascular modifications and attracting immune cells expressing Complement receptors. Investigating Complement receptors in non-immune cells pointed out Complement implication in the regeneration of tissue such as liver, skin, or bone. This review will shed the light on Complement implication in the initial steps of dental tissue regeneration.

MATERIALS AND METHODS

Review of literature was conducted on Complement local expression and implication in oral tissue regeneration in vivo and in vitro.

RESULTS

Recent data reported expression of Complement receptors and soluble proteins in dental tissues. Cultured pulp fibroblasts secrete all Complement components. Complement C3b and MAC have been shown to control bacteria growth in the dental pulp while C3a and C5a are involved in the initial steps of pulp regeneration. Indeed, C3a induces pulp stem cell/fibroblast proliferation, and fibroblast recruitment, while C5a induces neurite growth, guides stem cell recruitment, and odontoblastic differentiation. Similarly, cultured periodontal ligament cells produce C5a which induces bone marrow mesenchymal stem cell recruitment.

CONCLUSIONS

Overall, this review highlights that local Complement synthesis in dental tissues plays a major role, not only in eliminating bacteria but also in the initial steps of dental tissue regeneration, thus providing a link between dental tissue inflammation and regeneration.

CLINICAL RELEVANCE

Complement provides an explanation for understanding why inflammation preceeds regeneration. This may also provide a biological rational for understanding the reported success conservative management of mature permanent teeth with carious pulp exposure.

Nasal double DNA adjuvant induces salivary FimA-specific secretory IgA antibodies in young and aging mice and blocks Porphyromonas gingivalis binding to a salivary protein

BACKGROUND

We previously showed that nasal administration of a combination of dendritic cell (DC) targeted DNA plasmid expressing Flt3 ligand and CpG oligodeoxynucleotides 1826 as a mucosal adjuvant (double adjuvant, DA) provoked protective immunity in the upper respiratory tract of young adult and aging mice. Here, we investigated whether the nasal DA system induces secretory (S)IgA antibodies (Abs) toward recombinant fimbrillin (rFimA) of Porphyromonas gingivalis (P. gingivalis) in the saliva of young adult and aging mice. Further, we examined the functional applicability of rFimA-specific salivary SIgA Abs.

METHODS

BALB/c mice (8- or 48-week-old) were nasally immunized with rFimA plus DA three times at weekly intervals. Control mice were nasally administered rFimA alone. Saliva samples were collected 1 week after the final immunization, and were subjected to rFimA-specific ELISA. To examine the functional applicability of rFimA-specific SIgA Abs, IgA-enriched saliva samples were subjected to an inhibition assay in order to assess the numbers of P. gingivalis cells bound to the salivary protein statherin.

RESULTS

The 8- and 48-week-old mice administered nasal rFimA plus DA showed significantly increased levels of rFimA-specific SIgA Abs in saliva and elevated numbers of CD11c+ DCs in sublingual glands (SLGs), periglandular lymph nodes (PGLNs) and submandibular glands (SMGs) as well as nasopharyngeal-associated lymphoid tissues (NALT) compared to mice administered rFimA alone. Further, rFimA-specific SIgA Abs-containing saliva, in which IgG Abs of 8- and 48-week-old mice administered nasal rFimA plus DA were removed, significantly inhibited binding of P. gingivalis to the salivary protein.

CONCLUSIONS

These findings show that this DA system could be an effective nasal vaccine strategy for the enhancement of P. gingivalis-specific protective immunity in the oral cavity of adolescents and older individuals.