Characterization of salivary immunoglobulin A responses in children heavily exposed to the oral bacterium Streptococcus mutans: influence of specific antigen recognition in infection

Dietary Immunoglobulin Y by Targeting Both GbpB and GtfB Enhances the Anticaries Effect in Rats

OBJECTIVE

The purpose of this work was to develop an anti-CAT-SYI immunoglobulin Y (IgY) antibody that targeted both GtfB (glucosyltransferase B) and GbpB (glucan-binding protein B) and test its anticaries properties in rats.

METHODS

A new CAT-SYI fusion gene was created utilising functional DNA fragments from the GtfB and GbpB genes. The recombinant antigens, comprising the fused CAT-SYI antigen, GtfB, and GbpB, were expressed and purified using a prokaryotic expression and purification system. The purified recombinant antigens were utilised to immunise laying hens against particular IgY production. The biological activities of these particular IgY antibodies were then assessed both in vitro and in vivo, including their capacity to suppress biofilm formation and tooth caries.

RESULTS

Results indicated that these produced IgY antibodies demonstrated a high antibody titer (>0.1 μg/mL) and could precisely recognise and bind to their respective antigens. Furthermore, it was discovered that these specific IgY antibodies successfully bind to Streptococcus mutans and significantly reduce biofilm development. After 8 weeks of ingesting antigen-specific IgY meals, comprising anti-GtfB IgY and anti-GbpB IgY, the severity of dental caries was dramatically reduced in S mutans-infected Sprague-Dawley rats (P < .01). Anti-CAT-SYI IgY therapy significantly reduced tooth cavities by 89.0% in vivo (P < .05) compared to other treatment groups.

CONCLUSIONS

The anti-CAT-SYI IgY, a multitarget antibody that targets both GtfB and GbpB, displayed excellent inhibitory effects against S mutans, making it a promising targeted method with improved anticaries efficacy and significant application opportunities.

Saliva proteomic profile of early childhood caries and caries-free children

OBJECTIVE

Saliva plays an important antimicrobial role and it is related to the pathogenesis of early childhood caries (ECC). The aim of this study was to compare the proteomic profile of unstimulated saliva of children aged 3-5 years who had ECC and caries-free (CF) children.

MATERIALS AND METHODS

After the saliva collection from 20 children (ECC: n = 10; CF: n = 10), the samples were processed for proteomic analysis on a mass spectrometer.

RESULTS

1638 proteins were identified, of which 355 were present in both groups. A total of 579 proteins were exclusively identified in the CF group and included Leucine-rich alpha-2-glycoprotein, Protein S100-A5, Protein S100-A8 and Mucin-2. Moreover, 704 proteins were exclusively identified in the ECC group, including Enamelin. The differential expression analysis revealed that 112 proteins were up-regulated in the CF group. Among these proteins, we highlighted Hemoglobin subunit gamma-1 (343-fold increase), gamma-2 (336-fold increase) and alpha (40-fold increase).

CONCLUSIONS

The proteomic profile of the saliva varied substantially between the groups. Hemoglobin subunit gamma-1, gamma-2 and alpha may play a protective role in children with ECC. These proteins should be evaluated in future studies, because they may be possible good candidates to be included in anti-caries dental products.

Persistence of salivary antibody responses after COVID-19 vaccination is associated with oral microbiome variation in both healthy and people living with HIV

Coevolution of microbiome and immunity at mucosal sites is essential for our health. Whether the oral microbiome, the second largest community after the gut, contributes to the immunogenicity of COVID-19 vaccines is not known. We investigated the baseline oral microbiome in individuals in the COVAXID clinical trial receiving the BNT162b2 mRNA vaccine. Participants (n=115) included healthy controls (HC; n=57) and people living with HIV (PLHIV; n=58) who met the study selection criteria. Vaccine-induced Spike antibodies in saliva and serum from 0 to 6 months were assessed and comparative analyses were performed against the individual salivary 16S ASV microbiome diversity. High- versus low vaccine responders were assessed on general, immunological, and oral microbiome features. Our analyses identified oral microbiome features enriched in high- vs. low-responders among healthy and PLHIV participants. In low-responders, an enrichment of Gram-negative, anaerobic species with proteolytic activity were found including Campylobacter, Butyrivibrio, Selenomonas, Lachnoanaerobaculum, Leptotrichia, Megasphaera, Prevotella and Stomatobaculum. In high-responders, enriched species were mainly Gram-positive and saccharolytic facultative anaerobes: Abiotrophia, Corynebacterium, Gemella, Granulicatella, Rothia, and Haemophilus. Combining identified microbial features in a classifier using the area under the receiver operating characteristic curve (ROC AUC) yielded scores of 0.879 (healthy controls) to 0.82 (PLHIV), supporting the oral microbiome contribution in the long-term vaccination outcome. The present study is the first to suggest that the oral microbiome has an impact on the durability of mucosal immunity after Covid-19 vaccination. Microbiome-targeted interventions to enhance long-term duration of mucosal vaccine immunity may be exploited.

Presence of Streptococcus mutans and interleukin-6 and -10 in amniotic fluid

AIM

To evaluate the presence of Streptococcus mutans (SM), main pathogen of dental caries, interleukin-6 and -10 in samples of amniotic fluid (AF) and clinical and oral data of the healthy pregnancy, to investigate the SM exposition in intrauterine life and to elucidate the presence of antibodies to SM in newborns' saliva (SA) with undetectable levels of this microorganism described in the previous study.

METHODS

The study involved the participation of 26 women with term deliveries and without gestational complications. General health data were collected through a questionnaire applied to the participants. The volunteers were examined orally, the caries experience (decayed, missing, and filled teeth (DMFT) scores) was calculated and unstimulated SA was collected. The acquisition of AF was performed during cesarean sections and stocked on ice. The analysis of the presence of SM-DNA was performed by real-time PCR assays with specific primers. Levels of IL-6 and IL-10 were performed by ELISA with specific kits for these interleukins in the AF samples.

RESULTS

69.2% of the AF samples had detectable SM, and 65% of the women had the bacteria in the AF and SA at the same time. There was a positive association between the presence of SM in AF and a report of not going to the dentist frequently (p<.05). There was no statistically significant difference between the frequency of AF with or without detection of MS and active caries (p>.05). However, the DMFT scores of women with positive AF for SM were higher than that of women without detectable MS (p<.05). IL-6 levels were higher than IL-10 in AF (p<.05). There were no significant differences in the levels of interleukins between samples with detectable SM or in AF and even with clinical data analysis (p>.05).

CONCLUSIONS

The AF samples have SM in quantifiable levels, probably associated with the greatest caries experience, and seen by the highest DMFT index. Interleukin levels were not related to the presence of MS. The presence of SM in AF may explain the mucosal immune stimulation of newborn children by the previous detection of salivary antibodies against SM.

HIV-Associated Interactions Between Oral Microbiota and Mucosal Immune Cells: Knowledge Gaps and Future Directions

Even with sustained use of antiretroviral therapy (ART), HIV-infected individuals have an increased risk of systemic comorbid conditions and oral pathologies, including opportunistic infections, oral mucosal inflammation, and gingival and periodontal diseases. The immune-mediated mechanisms that drive this increased risk, in the context of sustained viral suppression, are unclear. HIV infection, even when controlled, alters microbial communities contributing to a chronic low-grade inflammatory state that underlies these non-HIV co-morbidities. The higher prevalence of dental caries, and mucosal and periodontal inflammation reported in HIV-infected individuals on ART is often associated with differentially abundant oral microbial communities, possibly leading to a heightened susceptibility to inflammation. This mini-review highlights current gaps in knowledge regarding the microbe-mediated oral mucosal immunity with HIV infection while discussing opportunities for future research investigations and implementation of novel approaches to elucidate these gaps. Interventions targeting both inflammation and microbial diversity are needed to mitigate oral inflammation-related comorbidities, particularly in HIV-infected individuals. More broadly, additional research is needed to bolster general models of microbiome-mediated chronic immune activation and aid the development of precise microbiota-targeted interventions to reverse or mitigate adverse outcomes.

Understanding the Basis of METH Mouth Using a Rodent Model of Methamphetamine Injection, Sugar Consumption, and Streptococcus mutans Infection

“METH mouth” is characterized by severe tooth decay and gum disease, which often causes teeth to break or fall out. METH users are also prone to colonization by cariogenic bacteria such as Streptococcus mutans.

“METH mouth” is a common consequence of chronic methamphetamine (METH) use, resulting in tooth decay and painful oral tissue inflammation that can progress to complete tooth loss. METH reduces the amount of saliva in the mouth, promoting bacterial growth, tooth decay, and oral tissue damage. This oral condition is worsened by METH users’ compulsive behavior, including high rates of consumption of sugary drinks, recurrent tooth grinding, and a lack of frequent oral hygiene. Streptococcus mutans is a Gram-positive bacterium found in the oral cavity and associated with caries in humans. Hence, we developed a murine model of METH administration, sugar intake, and S. mutans infection to mimic METH mouth in humans and to investigate the impact of this drug on tooth colonization. We demonstrated that the combination of METH and sucrose stimulates S. mutans tooth adhesion, growth, and biofilm formation in vivo. METH and sucrose increased the expression of S. mutans glycosyltransferases and lactic acid production. Moreover, METH contributes to the low environmental pH and S. mutans sucrose metabolism, providing a plausible mechanism for bacterium-mediated tooth decay. Daily oral rinse treatment with chlorhexidine significantly reduces tooth colonization in METH- and sucrose-treated mice. Furthermore, human saliva inhibits S. mutans colonization and biofilm formation after exposure to either sucrose or the combination of METH and sucrose. These findings suggest that METH might increase the risk of microbial dental disease in users, information that may help in the development of effective public health strategies to deal with this scourge in our society.

Immunoglobulins, Mucosal Immunity and Vaccination in Teleost Fish

Due to direct contact with aquatic environment, mucosal surfaces of teleost fish are continuously exposed to a vast number of pathogens and also inhabited by high densities of commensal microbiota. The B cells and immunoglobulins within the teleost mucosa-associated lymphoid tissues (MALTs) play key roles in local mucosal adaptive immune responses. So far, three Ig isotypes (i.e., IgM, IgD, and IgT/Z) have been identified from the genomic sequences of different teleost fish species. Moreover, teleost Igs have been reported to elicit mammalian-like mucosal immune response in six MALTs: gut-associated lymphoid tissue (GALT), skin-associated lymphoid tissue (SALT), gill-associated lymphoid tissue (GIALT), nasal-associated lymphoid tissue (NALT), and the recently discovered buccal and pharyngeal MALTs. Critically, analogous to mammalian IgA, teleost IgT represents the most ancient Ab class specialized in mucosal immunity and plays indispensable roles in the clearance of mucosal pathogens and the maintenance of microbiota homeostasis. Given these, this review summarizes the current findings on teleost Igs, MALTs, and their immune responses to pathogenic infection, vaccination and commensal microbiota, with the purpose of facilitating future evaluation and rational design of fish vaccines.

Salivary IgA as a Useful Biomarker for Dental Caries in Down's Syndrome Patients: A Systematic Review and Meta-analysis

The objective of this systematic review and meta-analysis is to critically analyze and summarize studies reporting association of salivary immunoglobulin A (IgA) levels as a biomarker for dental caries in Down syndrome (DS) patients. Using the keywords salivary [All Fields] AND IgA [All Fields] AND ("down syndrome" [MeSH Terms] OR ("down"[All Fields] AND "syndrome" [All Fields]) OR "down syndrome" [All Fields]), an electronic search was conducted via PubMed and Scopus databases by two authors, H. H. and Z. K. independently. Retrieved studies were screened against the predefined exclusion and inclusion criteria. To estimate the risk of bias, quality assessment of included studies was carried using the Newcastle-Ottawa quality assessment scale for observational studies. Primary search resulted in 10 articles from PubMed and 13 articles from Scopus. Ten studies fulfilled the defined selection criteria and evaluated the salivary IgA (sIgA) level in DS patients with dental caries. Five articles were further analyzed in a quantitative synthesis presented in the meta-analysis. Due to a modified lifestyle and compromised oral hygiene in DS patients, understandably, it is still postulated in the literature that the presence of sIgA can have a protective effect on the occurrence of dental caries as compared with healthy counterparts. As indicated by the present meta-analysis, no conclusions can be drawn as to definitively label sIgA as a biomarker for dental caries. Further, well-designed longitudinal clinical studies and translational research are therefore required before the benchmarking of sIgA as a useful biomarker for dental caries in DS patients with preferable molecular insights.

Precision Reengineering of the Oral Microbiome for Caries Management

Technological advancements have revolutionized our understanding of the complexity and importance of the human microbiome. This progress has also emphasized the need for precision therapeutics, as it has underscored the dilemmas, such as dysbiosis and increasing antibiotic resistance, associated with current, broad-spectrum treatment modalities. Dental caries remains the most common chronic disease worldwide, accompanied by a tremendous financial and social burden, despite widespread and efficacious fluoride and hygienic regimens. Over the past several decades, various precision approaches to combat dental caries, including vaccines, probiotics, and antimicrobial compounds, have been pursued. Despite the distinct overall conceptual strengths of each approach, for various reasons, there are currently no approved precision antibiotic therapeutics to prevent dental caries. Specifically targeted antimicrobial peptides (STAMPs) are synthetic molecules that combine the antibiotic moiety of a traditional antimicrobial peptide with a targeting domain to provide specificity against a particular organism. Conjoining the killing domain from the antimicrobial, novispirin G10, and a targeting domain derived from the Streptococcus mutans pheromone, CSP, the STAMP C16G2 was designed to provide targeted killing of S. mutans, widely considered the keystone species in dental caries pathogenesis. C16G2 was able to selectively eliminate S. mutans from complex ecosystems while leaving closely related, yet health-associated, oral species unharmed. This remodeling of the dental plaque community is expected to have significant advantages compared to conventional broad-spectrum mouthwashes, as the intact, surviving community is apt to prevent reinfection by pathogens. Following successful phase I clinical trials that evaluated the safety and basic microbiology of C16G2 treatments, the phase II trials of several C16G2 formulations are currently in progress. C16G2 represents an exciting advance in precision therapeutics, and the STAMP platform provides vast opportunities for both the development of additional therapeutics and the overall study of microbial ecology.

PcsB Expression Diversity Influences on Streptococcus mitis Phenotypes Associated With Host Persistence and Virulence

S. mitis is an abundant member of the commensal microbiota of the oral cavity and pharynx, which has the potential to promote systemic infections. By analyzing a collection of S. mitis strains isolated from the oral cavity at commensal states or from systemic infections (blood strains), we established that S. mitis ubiquitously express the surface immunodominant protein, PcsB (also called GbpB), required for binding to sucrose-derived exopolysaccharides (EPS). Immuno dot blot assays with anti-PcsB antibodies and RT-qPCR transcription analyses revealed strain-specific profiles of PcsB production associated with diversity in pcsB transcriptional activities. Additionally, blood strains showed significantly higher levels of PcsB expression compared to commensal isolates. Because Streptococcus mutans co-colonizes S. mitis dental biofilms, and secretes glucosyltransferases (GtfB/C/D) for the synthesis of highly insoluble EPS from sucrose, profiles of S. mitis binding to EPS, biofilm formation and evasion of the complement system were assessed in sucrose-containing BHI medium supplemented or not with filter-sterilized S. mutans culture supernatants. These analyses showed significant S. mitis binding to EPS and biofilm formation in the presence of S. mutans supernatants supplemented with sucrose, compared to BHI or BHI-sucrose medium. In addition, these phenotypes were abolished if strains were grown in culture supernatants of a gtfBCD-defective S. mutans mutant. Importantly, GtfB/C/D-associated phenotypes were enhanced in high PcsB-expressing strains, compared to low PcsB producers. Increased PcsB expression was further correlated with increased resistance to deposition of C3b/iC3b of the complement system after exposure to human serum, when strains were previously grown in the presence of S. mutans supernatants. Finally, analyses of PcsB polymorphisms and bioinformatic prediction of epitopes with significant binding to MHC class II alleles revealed that blood isolates harbor PcsB polymorphisms in its functionally conserved CHAP-domain, suggesting antigenic variation. These findings reveal important roles of PcsB in S. mitis-host interactions under commensal and pathogenic states, highlighting the need for studies to elucidate mechanisms regulating PcsB expression in this species.

Convergent Evolution of Mucosal Immune Responses at the Buccal Cavity of Teleost Fish

The buccal mucosa (BM) is a critical first line of defense in terrestrial animals. To gain further insights into the evolutionary origins and primordial roles of BM in teleosts here we show that rainbow trout, a teleost fish, contains a diffuse mucosal associated lymphoid tissue (MALT) within its buccal cavity. Upon parasite infection, a fish immunoglobulin specialized in mucosal immunity (sIgT) was induced to a high degree, and parasite-specific sIgT responses were mainly detected in the buccal mucus. Moreover, we show that the trout buccal microbiota is prevalently coated with sIgT. Overall our findings revealed that the MALT is present in the BM of a non-tetrapod species. As fish IgT and mucus-producing cells are evolutionarily unrelated to mammalian IgA and salivary glands, respectively, our findings indicate that mucosal immune responses in the BM of teleost fish and tetrapods evolved through a process of convergent evolution.

Exploiting the Oral Microbiome to Prevent Tooth Decay: Has Evolution Already Provided the Best Tools?

To compete in the relatively exposed oral cavity, resident microbes must avoid being replaced by newcomers. This selective constraint, coupled with pressure on the host to cultivate a beneficial microbiome, has rendered a commensal oral microbiota that displays colonization resistance, protecting the human host from invasive species, including pathogens. Rapid increases in carbohydrate consumption have disrupted the evolved homeostasis between the oral microbiota and dental health, reflected by the high prevalence of dental caries. Development of novel modalities to prevent caries has been the subject of a breadth of research. This mini review provides highlights of these endeavors and discusses the rationale and pitfalls behind the major avenues of approach. Despite efficacy, fluoride and other broad-spectrum interventions are unlikely to further reduce the incidence of dental caries. The most promising methodologies in development are those that exploit the exclusive nature of the healthy oral microbiome. Probiotics derived from the dental plaque of healthy individuals sharply antagonize cariogenic species, such as Streptococcus mutans. Meanwhile, targeted antimicrobials allow for the killing of specific pathogens, allowing reestablishment of a healthy microbiome, presumably with its protective effects. The oral microbiota manufactures a massive array of small molecules, some of which are correlated with health and are likely to antagonize pathogens. The prohibitive cost associated with sufficiently rigorous clinical trials, and the status of dental caries as a non-life-threatening condition will likely continue to impede the advancement of new therapeutics to market. Nevertheless, there is room for optimism, as it appears evolution may have already provided the best tools.

Role of Streptococcus mutans surface proteins for biofilm formation

Streptococcus mutans has been implicated as a primary causative agent of dental caries in humans. An important virulence property of the bacterium is its ability to form biofilm known as dental plaque on tooth surfaces. In addition, this organism also produces glucosyltransferases, multiple glucan-binding proteins, protein antigen c, and collagen-binding protein, surface proteins that coordinate to produce dental plaque, thus inducing dental caries. Bacteria utilize quorum-sensing systems to modulate environmental stress responses. A major mechanism of response to signals is represented by the so called two-component signal transduction system, which enables bacteria to regulate their gene expression and coordinate activities in response to environmental stress. As for S. mutans, a signal peptide-mediated quorum-sensing system encoded by comCDE has been found to be a regulatory system that responds to cell density and certain environmental stresses by excreting a peptide signal molecule termed CSP (competence-stimulating peptide). One of its principal virulence factors is production of bacteriocins (peptide antibiotics) referred to as mutacins. Two-component signal transduction systems are commonly utilized by bacteria to regulate bacteriocin gene expression and are also related to biofilm formation by S. mutans.

Salivary secretory IgA concentration and dental caries in children with Down syndrome

PURPOSE

To evaluate the relationship between salivary secretory immunoglobulin A (sIgA) concentration and dental caries in children with Down syndrome (DS) and compare it with findings in non-DS children.

METHODS

The sample comprised 61 DS children and 52 non-DS children, aged 6 to 14 years. Caries experience, plaque index (PI), and gingival bleeding index (GBI) were recorded. Saliva samples were collected from all children. Total salivary sIgA concentrations were determined using an enzymatic assay method.

RESULTS

Caries experience in primary and permanent dentitions were similar in DS and non-DS children. However, PI and GBI values were significantly lower in DS compared to non-DS children. DS children had higher salivary sIgA concentrations compared to non-DS children. No difference in sIgA concentration was observed between children with and without caries experience in either group.

CONCLUSIONS

DS children have higher salivary sIgA concentrations than non-DS children. However, this finding did not correlate with caries experience in the study population.

The Application of Magnetic Bead Selection to Investigate Interactions between the Oral Microbiota and Salivary Immunoglobulins

The effect of humoral immunity on the composition of the oral microbiota is less intensively investigated than hygiene and diet, in part due to a lack of simple and robust systems for investigating interactions between salivary immunoglobulins and oral bacteria. Here we report the application of an ex situ method to investigate the specificity of salivary immunoglobulins for salivary bacteria. Saliva collected from six volunteers was separated into immunoglobulin and microbial fractions, and the microbial fractions were then directly exposed to salivary immunoglobulins of "self" and "non-self" origin. Antibody-selected bacteria were separated from their congeners using a magnetic bead system, selective for IgA or IgG isotypes. The positively selected fractions were then characterized using gel-based eubacterial-specific DNA profiling. The eubacterial profiles of positively selected fractions diverged significantly from profiles of whole salivary consortia based on volunteer (P≤ 0.001%) and immunoglobulin origin (P≤ 0.001%), but not immunoglobulin isotype (P = 0.2). DNA profiles of separated microbial fractions were significantly (p≤ 0.05) less diverse than whole salivary consortia and included oral and environmental bacteria. Consortia selected using self immunoglobulins were generally less diverse than those selected with immunoglobulins of non-self origin. Magnetic bead separation facilitated the testing of interactions between salivary antibodies and oral bacteria, showing that these interactions are specific and may reflect differences in recognition by self and non-self immunoglobulins. Further development of this system could improve understanding of the relationship between the oral microbiota and the host immune system and of mechanisms underlying the compositional stability of the oral microbiota.

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.

Advances in the microbial etiology and pathogenesis of early childhood caries

Early childhood caries (ECC) is one of the most prevalent infectious diseases affecting children worldwide. ECC is an aggressive form of dental caries, which, left untreated, can result in rapid and extensive cavitation in teeth (rampant caries) that is painful and costly to treat. Furthermore, it affects mostly children from impoverished backgrounds, and so constitutes a major challenge in public health. The disease is a prime example of the consequences arising from complex, dynamic interactions between microorganisms, host, and diet, leading to the establishment of highly pathogenic (cariogenic) biofilms. To date, there are no effective methods to identify those at risk of developing ECC or to control the disease in affected children. Recent advances in deep-sequencing technologies, novel imaging methods, and (meta)proteomics-metabolomics approaches provide an unparalleled potential to reveal new insights to illuminate our current understanding about the etiology and pathogenesis of the disease. In this concise review, we provide a broader perspective about the etiology and pathogenesis of ECC based on previous and current knowledge on biofilm matrix, microbial diversity, and host-microbe interactions, which could have direct implications for developing new approaches for improved risk assessment and prevention of this devastating and costly childhood health condition.

Comparison of immunological and microbiological characteristics in children and the elderly with or without dental caries

The purpose of this study was to determine the relationships among early childhood caries (ECC), root caries (RC), the quantity of Streptococcus mutans in saliva, and the concentrations of total and specific secretory IgA (sIgA). Saliva samples were collected from 70 children, 3-4 yr of age, with and without ECC, and from 43 adults, ≥60 yr of age, with and without RC. The decayed, missing, and filled teeth (dmft) and decayed, missing, and filled surfaces (dmfs) scores of each child, and the root decayed and filled teeth (RDFT) and root decayed and filled surfaces (RDFS) scores of each elderly subject, were determined. The S. mutans levels, total sIgA, and specific sIgA against two virulence antigens of S. mutans in saliva were analysed using quantitative real-time PCR (qPCR) and ELISAs. The quantity of S. mutans was significantly higher in caries-positive subjects within the two populations than in the caries-free subjects; and a positive correlation was found between the quantity of S. mutans and the dmft, dmfs, RDFT, and RDFS scores. In addition, the salivary total sIgA was significantly higher in children with severe early childhood caries (SECC) and in the elderly subjects with RC. Moreover, although the S. mutans level was significantly higher, the concentrations of specific sIgA against S. mutans antigens were significantly lower in samples from elderly subjects than in samples from children. These results support the concept that S. mutans is positively associated with ECC and RC. Furthermore, the levels of S. mutans-specific antibodies in saliva are too low to prevent infection with cariogenic bacteria and to inhibit development of ECC and RC.

The oral microbiome and the immunobiology of periodontal disease and caries

The composition of the oral microbiome differs from one intraoral site to another, reflecting in part the host response and immune capacity at each site. By focusing on two major oral infections, periodontal disease and caries, new principles of disease emerge. Periodontal disease affects the soft tissues and bone that support the teeth. Caries is a unique infection of the dental hard tissues. The initiation of both diseases is marked by an increase in the complexity of the microbiome. In periodontitis, pathobionts and keystone pathogens such as Porphyromonas gingivalis appear in greater proportion than in health. As a keystone pathogen, P. gingivalis impairs host immune responses and appears necessary but not sufficient to cause periodontitis. Historically, dental caries had been causally linked to Streptococcus mutans. Contemporary microbiome studies now indicate that singular pathogens are not obvious in either caries or periodontitis. Both diseases appear to result from a perturbation among relatively minor constituents in local microbial communities resulting in dysbiosis. Emergent consortia of the minor members of the respective microbiomes act synergistically to stress the ability of the host to respond and protect. In periodontal disease, host protection first occurs at the level of innate gingival epithelial immunity. Secretory IgA antibody and other salivary antimicrobial systems also act against periodontopathic and cariogenic consortia. When the gingival immune response is impaired, periodontal tissue pathology results when matrix metalloproteinases are released from neutrophils and T cells mediate alveolar bone loss. In caries, several species are acidogenic and aciduric and appear to work synergistically to promote demineralization of the enamel and dentin. Whereas technically possible, particularly for caries, vaccines are unlikely to be commercialized in the near future because of the low morbidity of caries and periodontitis.

Collagenases in an ether extract of bacterial metabolites used as an immunostimulator induces TNF-α and IFN-γ

Non-specific immunostimulation by bacterial extracts and their components are widely accepted for the prevention and treatment of several infectious diseases. An ether extract of the metabolites of ß-streptococcus, Staphylcoccus albus, Staphylcoccus aureus, Escherichia coli, Haemophilus influenza, Moraxella caterhalis, Salmonella typhi (standard O & H), Salmonella paratyphi (A & B) and Diptheroid bacilli along with bile lipids is used as a licensed drug for immunostimulation. While characterizing the drug, we observed gelatinolytic/collagenolytic activity in the ether extract by zymography. This activity was contributed by each bacterial species as observed by collagen zymography of individual extract. Immuno-blot also confirmed the presence of collagenases in the pooled extract whose activity was estimated to be 0.081 U/ml ± 0.005 by DQ-gelatin assay. The enzyme was purified by immuno-affinity chromatography. Homogeneity of the preparation was demonstrated by SDS-PAGE and SE-HPLC. Degradation of collagen by purified collagenases was visualized by atomic force microscopy and transmission electron microscopy wherein, fragmentation of collagen leading to loss of network structure occurred under physiological conditions. Results indicated that purified collagenases can trigger the release of pro-inflammatory cytokines TNF-α and IFN-γ in-vitro and in-vivo without inducing detectable stress and toxicity on both models. The findings suggest that bacterial collagenases remain stable and biological functional in an organic solvent validating its potential for industrial and medical applications as the enzymes are key regulators of inflammatory and immune responses.

Salivary antibody response to streptococci in preterm and fullterm children: a prospective study

OBJECTIVES

Secretory immunoglobulins present in mucosa surfaces represent the first line of defense of the adaptive immune system against infectious challenges. Preterm (PT) neonates' humoral immunity is diminished compared to full-term (FT) newborns. The identification of important antigens (Ags) of virulence of oral species may help in the investigation of the mechanisms of antigenic stimulation and the development of the mucosal immune response. In the present study, we measured saliva levels of immunoglobulins A (IgA) and M (IgM) and characterized the specificity of IgA against Ags of several streptococcal species found early in life.

METHODS

This was a prospective observational study. Salivary IgA (sIgA) antibody responses to bacterial species that are prototypes of pioneer (Streptococcus mitis, S. sanguinis, S. gordonii) and pathogenic (Streptococcus mutans) microorganisms of the oral cavity were studied in FT and PT children in two visits: at birth (T0) and at 3 months of age (T3). Salivas from 123 infants (72 FT and 51 PT) were collected during the first 10h after birth (T0) and again at 3 months of age (T3). Salivary levels of IgA and IgM antibodies were analysed by enzyme-linked immunosorbent assay (ELISA). A subgroup of 26 FT and 24 PT children were compared with respect to patterns of antibody specificities against different streptococci Ags using Western blot assays.

RESULTS

No significant differences (P>0.05) in salivary levels of IgA and IgM between FT and PT babies were found at birth. At T3, mean sIgA values were similar between groups and sIgM levels were significantly higher in PT than FT (P<0.05). Western blot assays identified positive IgA response to streptococci in the majority of children, especially in the FT group. There were some differences between groups in relation to the frequency of children with positive response to Ags and intensity of IgA response. In general, oral streptococci Ags were more frequently detected and bands were more intense in FT than in PT, especially in T3. Prospective analysis of patterns of sIgA against Ags of different streptococcal species revealed an increase in complexity of the sIgA antibody response from the first day of birth (T0) to T3 in PT and FT.

CONCLUSION

The patterns of sIgA response to streptococci Ags appear to be influenced by the gestational age, which might reflect the level of immunological maturity of the mucosal immune system.

Levels and complexity of IgA antibody against oral bacteria in samples of human colostrum

Streptococcus mutans (SM) have three main virulence antigens: glucan binding protein B (gbpB), glucosyltransferase (Gtf) and antigens I/II (Ag I/II) envolved in the capacity of those bacteria to adhere and accumulate in the dental biofilm. Also, the glycosyltransferases 153 kDa of Streptococcus gordonii (SGO) and 170kDa of Streptococcus sanguinis (SSA) were important antigens associated with the accumulation of those bacterias. Streptococcus mitis (SMI) present IgA1 protease of 202 kDa. We investigated the specificity and levels IgA against those antigens of virulence in samples of human colostrum. This study involved 77 samples of colostrum that were analyzed for levels of immunoglobulian A, M and G by Elisa. The specificity of IgA against extracts of SM and initials colonizators (SSA, SMI, SGO) were analyzed by the Western blot. The mean concentration of IgA was 2850.2 (±2567.2) mg/100 mL followed by IgM and IgG (respectively 321.8±90.3 and 88.3±51.5), statistically different (p<0.05). Results showed that the majority of samples had detectable levels of IgA antibodies to extracts of bacteria antigens and theirs virulence antigens. To SM, the GbpB was significantly lower detected than others antigens of SM (p<0.05). High complexities of response to Ags were identified in the samples. There were no significant differences in the mean number of IgA-reactive Ags between the antigens (p>0.4). So, the breast milk from first hours after birth presented significant levels of IgA specific against important virulence of antigens those oral streptococci, which can disrupt the installation and accumulation process of these microorganisms in the oral cavity.

An innovative approach to treating dental decay in children. A new anti-caries agent

The aim of this work is to evaluate the antimicrobial and cytotoxic activity of a formulation containing silver nanoparticles and chitosan, provisionally called nano silver fluoride (NSF), against Streptococcus mutans in comparison to chlorhexidine and silver diamine fluoride (SDF). The product was characterised by transmission electron microscopy and UV-Vis absorption spectroscopy. The minimum inhibition concentration (MIC) was evaluated by the spectrophotometric microdilution method and turbidity. The minimum bactericide concentration (MBC) was evaluated in brain heart infusion plates, and cytotoxicity was evaluated by haemolytic activity. The MIC and MBC for NSF were, respectively, 33.54 ± 14.52 and 50.32 µg/mL; for SDF were 33.33 ± 14.43 and 50.0 µg/mL, respectively; and for CHX were 3.3 ± 0.5 and 6 µg/mL, respectively. An ANOVA for MIC gave P = 0.032, and for MBC P = 0.035. The cytotoxic effect of NSF compared to SDF demonstrated a statistically significant difference in the MIC value (t test P < 0.05). The NSF formulation may be effective against S. mutans with much lower doses, may have lower toxicity than SDF, and may not stain teeth.

Effect of high-fructose corn syrup on the acidogenicity, adherence and biofilm formation of Streptococcus mutans

BACKGROUND

Although high-fructose corn syrup (HFCS) as a kind of sugar has been widely used in manufactured foods recently, there is little information available regarding its cariogenicity. The aim of this study was to evaluate the cariogenic potential of HFCS.

METHODS

Streptococcus mutans UA159 was inoculated into HFCS media and cultivated. The pH of each culture was measured to assess acidogenicity. Spectrophotometric turbidity was measured to determine the percentage of adherence. Confocal laser scanning microscopy and SYTO-9 staining were employed to observe biofilm formation. Sucrose media was used as a positive control.

RESULTS

The ΔpH in HFCS media was significantly larger than that in sucrose media and the pH in HFCS media decreased faster (p < 0.05). The percentage of adherence of S. mutans in HFCS media was significantly lower than that in sucrose media (p < 0.05). The biofilm formed in sucrose media was significantly thicker than that in HFCS media (p < 0.05).

CONCLUSIONS

The results of this study suggest that the cariogenicity of S. mutans in the presence of HFCS may differ compared to its cariogenicity in the presence of sucrose. Further in vivo studies need to be undertaken to resolve this uncertainty.

Total IgA and IgA reactivity to antigen I/II epitopes in HLA-DRB1*04 positive subjects

Bacterial adherence to the acquired dental pellicle, important in dental caries (caries), is mediated by receptor-adhesins such as salivary agglutinin binding to Streptococcus mutans antigen I/II (I/II). Ten selected I/II epitopes were chosen to determine their reactivity to human salivary IgA. Previous studies suggested that a specific HLA biomarker group (HLA-DRB1*04) may have differential influence of immune responses to I/II. However, it was not known whether secretory IgA (SIgA) responses to the selected epitopes from HLA-DRB1*04 positive subjects were different compared to controls, or across other caries-related factors such as total IgA (TIgA). Thirty-two total subjects were matched according to HLA type, gender, ethnicity and age. HLA genotyping, oral bacterial, immunoglobulin and antibody analyses were performed. A large observed difference emerged with regard to the natural immune reservoir of TIgA in HLA-DRB1*04 positive subjects, specifically, a 27.6% reduction compared to controls. In contrast to all other epitopes studied, HLA-DRB1*04 positive subjects also exhibited reduced reactivity to I/II epitope 834-853. HLA-DRB1*04 positive subjects exhibited lower specific SIgA activity/TIgA to 834-853 and also a lower specific reactivity to 834-853/whole cell S. mutans UA159. Furthermore, HLA-DRB1*04 positive subjects exhibited lower responses to I/II in its entirety. The large observed difference in TIgA and the 834-853 reactivity pattern across multiple measures suggest potentially important connections pertaining to the link between HLA-DRB1*04 and caries.

Secretory immunity with special reference to the oral cavity

The two principal antibody classes present in saliva are secretory IgA (SIgA) and IgG; the former is produced as dimeric IgA by local plasma cells (PCs) in the stroma of salivary glands and is transported through secretory epithelia by the polymeric Ig receptor (pIgR), also named membrane secretory component (SC). Most IgG in saliva is derived from the blood circulation by passive leakage mainly via gingival crevicular epithelium, although some may be locally produced in the gingiva or salivary glands. Gut-associated lymphoid tissue (GALT) and nasopharynx-associated lymphoid tissue (NALT) do not contribute equally to the pool of memory/effector B cells differentiating to mucosal PCs throughout the body. Thus, enteric immunostimulation may not be the best way to activate the production of salivary IgA antibodies although the level of specific SIgA in saliva may still reflect an intestinal immune response after enteric immunization. It remains unknown whether the IgA response in submandibular/sublingual glands is better related to B-cell induction in GALT than the parotid response. Such disparity is suggested by the levels of IgA in submandibular secretions of AIDS patients, paralleling their highly upregulated intestinal IgA system, while the parotid IgA level is decreased. Parotid SIgA could more consistently be linked to immune induction in palatine tonsils/adenoids (human NALT) and cervical lymph nodes, as supported by the homing molecule profile observed after immune induction at these sites. Several other variables influence the levels of antibodies in salivary secretions. These include difficulties with reproducibility and standardization of immunoassays, the impact of flow rate, acute or chronic stress, protein loss during sample handling, and uncontrolled admixture of serum-derived IgG and monomeric IgA. Despite these problems, saliva is an easily accessible biological fluid with interesting scientific and clinical potentials.

Five questions about Streptococcus mutans: theoretical study of its transmission and colonisation

PURPOSE

This theoretical study aimed to identify the decisive (and controllable) factors involved in Streptococcus mutans (Sm) infection through addressing questions about (i) the time and prevalence pattern (including the raison d'etre of the discrete period for the infection or WI) of initial Sm colonisation and (ii) the infant's selection of bacterial types and their diversity, which are not yet definitely answered by empirical works.

METHOD

A model of Sm infection (within-host type) was developed. For questions (i): using the basic model, stochastic simulation was performed to reproduce longitudinal observations of the initial colonisation time. A symmetrical or right-skewed gamma distribution was assumed for the maximum colonisable area (K(max)) and transmission rate (mx). Additionally, 3 or 4 developmental modes of colonisable area [K(t)] were assigned based on the K(max) value. For (ii): by extending the basic model to the two-bacterial type model, intraspecific competition analysis focusing on the differences in mx (received by the infancy) and colonisation ability (θD) was performed.

RESULTS

The basic model simulation showed that mx and K(t) played a pivotal role in determining the individual time of initial colonisation and their variations among infants in forming its prevalence patterns (with or without WI). The competition model simulation showed that higher mx could be more advantageous in competitive colonisation than higher θD under repeated invasions. Accordingly, it played a decisive role in infant's selection of initially, persistently and transiently colonising bacterial types, and thus in their diversity.

CONCLUSIONS

(i) The mx is the primary and controllable (risk) factor that extensively affects various aspects of the Sm infection process. (ii) Also, the growing carrying capacity, i.e., K(t) is another important factor when considering how to effectively delay the onset of the colonisation. (iii) Thus, currently, the most feasible and effective control measure for the infection should be microbiological interventions in the primary host with concurrent oral hygiene and dietary control in the exposed child.

Salivary IgA antibody responses to Streptococcus mitis and Streptococcus mutans in preterm and fullterm newborn children

OBJECTIVES

The intensities and specificities of salivary IgA antibody responses to antigens of Streptococcus mutans, the main pathogen of dental caries, may influence colonization by these organisms during the first 1.5 year of life. Thus, the ontogeny of salivary IgA responses to oral colonizers continues to warrant investigation, especially with regard to the influence of birth conditions, e.g. prematurity, on the ability of children to efficiently respond to oral microorganisms. In this study, we characterised the salivary antibody responses to two bacterial species which are prototypes of pioneer and pathogenic microorganisms of the oral cavity (Streptococcus mitis and Streptococcus mutans, respectively) in fullterm (FT) and preterm (PT) newborn children.

METHODS

Salivas from 123 infants (70 FT and 53 PT) were collected during the first 10h after birth and levels of IgA and IgM antibodies and the presence of S. mutans and S. mitis were analysed respectively by ELISA and by chequerboard DNA-DNA hybridization. Two subgroups of 24 FT and 24 PT children were compared with respect to patterns of antibody specificities against S. mutans and S. mitis antigens, using Western blot assays. Cross-adsorption of 10 infant's saliva was tested to S. mitis, S. mutans and Enterococcus faecalis antigens.

RESULTS

Salivary levels of IgA at birth were 2.5-fold higher in FT than in PT children (Mann-Whitney; P<0.05). Salivary IgA antibodies reactive with several antigens of S. mitis and S. mutans were detected at birth in children with undetectable levels of those bacteria. Adsorption of infant saliva with cells of S. mutans produced a reduction of antibodies recognizing S. mitis antigens in half of the neonates. The diversity and intensity of IgA responses were lower in PT compared to FT children, although those differences were not significant.

CONCLUSION

These data provide evidence that children have salivary IgA antibodies shortly after birth, which might influence the establishment of the oral microbiota, and that the levels of salivary antibody might be related to prematurity.

Bactericidal capacity of silver nanoparticles associated with Gantrez S-97 on Streptococcus mutans

Dental caries is a worldwide public health problem. S mutans plays an important role in the etiology of caries. There have been studies that showed the antimicrobial properties of silver nanoparticles are an effective agent to diminish S. mutans. The objective of this study was to evaluate the bactericidal and bacteriostatic effects of silver nanoparticles in addition to the Gantrez S-27 copolymer, on S mutans.

METHOD

We performed an in vitro experimental study using the liquid microdilution method in order to find the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) with the subcultures obtained. The mixture was obtained by preparing 98 microg/mL of silver nanoparticles (10(3)mol) with Gantrez S-27 2%, in distilled water The readings were performed 24 hours after incubation and on 3 consecutive days. The results showed an average MTC of 6.12 microg /mL and MBC of 6.12 microg /mL.

CONCLUSION

The addition of Gantrez 2% to silver nanoparticles does not alter its antimicrobial effect.

Downregulation of GbpB, a component of the VicRK regulon, affects biofilm formation and cell surface characteristics of Streptococcus mutans

The virulence of the dental caries pathogen Streptococcus mutans relies in part on the sucrose-dependent synthesis of and interaction with glucan, a major component of the extracellular matrix of tooth biofilms. However, the mechanisms by which secreted and/or cell-associated glucan-binding proteins (Gbps) produced by S. mutans participate in biofilm growth remain to be elucidated. In this study, we further investigate GbpB, an essential immunodominant protein with similarity to murein hydrolases. A conditional knockdown mutant that expressed gbpB antisense RNA under the control of a tetracycline-inducible promoter was constructed in strain UA159 (UACA2) and used to investigate the effects of GbpB depletion on biofilm formation and cell surface-associated characteristics. Additionally, regulation of gbpB by the two-component system VicRK was investigated, and phenotypic analysis of a vicK mutant (UAvicK) was performed. GbpB was directly regulated by VicR, and several phenotypic changes were comparable between UACA2 and UAvicK, although differences between these strains existed. It was established that GbpB depletion impaired initial phases of sucrose-dependent biofilm formation, while exogenous native GbpB partially restored the biofilm phenotype. Several cellular traits were significantly affected by GbpB depletion, including altered cell shape, decreased autolysis, increased cell hydrophobicity, and sensitivity to antibiotics and osmotic and oxidative stresses. These data provide the first experimental evidence for GbpB participation in sucrose-dependent biofilm formation and in cell surface properties.

Social inequalities in childhood dental caries: the convergent roles of stress, bacteria and disadvantage

The studies reported here examines stress-related psychobiological processes that might account for the high, disproportionate rates of dental caries, the most common chronic disease of childhood, among children growing up in low socioeconomic status (SES) families. In two 2004-2006 studies of kindergarten children from varying socioeconomic backgrounds in the San Francisco Bay Area of California (Ns = 94 and 38), we performed detailed dental examinations to count decayed, missing or filled dental surfaces and microtomography to assess the thickness and density of microanatomic dental compartments in exfoliated, deciduous teeth (i.e., the shed, primary dentition). Cross-sectional, multivariate associations were examined between these measures and SES-related risk factors, including household education, financial stressors, basal and reactive salivary cortisol secretion, and the number of oral cariogenic bacteria. We hypothesized that family stressors and stress-related changes in oral biology might explain, fully or in part, the known socioeconomic disparities in dental health. We found that nearly half of the five-year-old children studied had dental caries. Low SES, higher basal salivary cortisol secretion, and larger numbers of cariogenic bacteria were each significantly and independently associated with caries, and higher salivary cortisol reactivity was associated with thinner, softer enamel surfaces in exfoliated teeth. The highest rates of dental pathology were found among children with the combination of elevated salivary cortisol expression and high counts of cariogenic bacteria. The socioeconomic partitioning of childhood dental caries may thus involve social and psychobiological pathways through which lower SES is associated with higher numbers of cariogenic bacteria and higher levels of stress-associated salivary cortisol. This convergence of psychosocial, infectious and stress-related biological processes appears to be implicated in the production of greater cariogenic bacterial growth and in the conferral of an increased physical vulnerability of the developing dentition.

Correlation of biological properties with glucan-binding protein B expression profile in Streptococcus mutans clinical isolates

OBJECTIVE

Streptococcus mutans is known to be a primary causative agent of dental caries and its surface proteins have been investigated to specify their association with its virulence. Amongst those, 4 glucan-binding proteins (Gbps) are considered to be important factors due to their glucan-binding properties, of which GbpB has been shown to participate in cell-wall construction and cell separation.

DESIGN

We examined clinical isolates of S. mutans collected from the oral cavities of Japanese and Finnish subjects, and focused on the association of their GbpB expression profiles and biological properties related to virulence.

RESULTS

Western blot analysis of GbpB expression by the isolates revealed a variety of patterns. Strains that showed single and multiple bands were used to designate S and M type strains, respectively, whilst those with no GbpB expression were classified as N type. The distribution of GbpB expression patterns was shown to be quite different between the Japanese and Finnish isolates. Furthermore, the chain length and doubling time of the N type in both populations were significantly longer than those of the other types.

CONCLUSION

Our results suggest variations in S. mutans GbpB expression patterns, which may have relationships with the virulence of S. mutans.

Prospective study of potential sources of Streptococcus mutans transmission in nursery school children

Transmission of Streptococcus mutans, a major dental caries pathogen, occurs mainly during the first 2.5 years of age. Children appear to acquire S. mutans mostly from their mothers, but few studies have investigated non-familial sources of S. mutans transmission. This study prospectively analysed initial S. mutans oral colonization in 119 children from nursery schools during a 1.5-year period and tracked the transmission from child to child, day-care caregiver to child and mother to child. Children were examined at baseline, when they were 5-13 months of age, and at 6-month intervals for determination of oral levels of S. mutans and development of caries lesions. Levels of S. mutans were also determined in caregivers and mothers. A total of 1392 S. mutans isolates (obtained from children, caregivers and mothers) were genotyped by arbitrarily primed PCR and chromosomal RFLP. Overall, 40.3 % of children were detectably colonized during the study, and levels of S. mutans were significantly associated with the development of caries lesions. Identical S. mutans genotypes were found in four nursery cohorts. No familial relationship existed in three of these cohorts, indicating horizontal transmission. Despite high oral levels of S. mutans identified in most of the caregivers, none of their genotypes matched those identified in the respective children. Only 50 % of children with high levels of S. mutans carried genotypes identified in their mothers. The results support previous evidence indicating that non-familial sources of S. mutans transmission exist, and indicate that this bacterium may be transmitted horizontally between children during the initial phases of S. mutans colonization in nursery environments.

Evaluation of genotypic diversity of Streptococcus mutans using distinct arbitrary primers

Streptococcus mutans has been considered one of the main etiological agents of dental caries and the genotypic diversity rather than its salivary counts may be considered as a virulence factor of this bacterium. For genotyping with polymerase chain reaction (PCR) with arbitrary primers, several primers have been used in order to improve complexity and specificity of amplicon patterns. Thus, the aim of this study was to evaluate the degree of agreement of genotypic identification among AP-PCR reactions performed with 5 distinct arbitrary primers of S. mutans isolated from saliva. Stimulated saliva was collected from 11 adult volunteers for isolation of S. mutans, and a total of 88 isolates were genotyped with arbitrary primers OPA 02, 03, 05, 13 and 18. Fourteen distinct genotypes were identified in the saliva samples. Most volunteers (9 out of 11) presented only one genotype. The results of the present study suggest that primers OPA 02, 03, 05 and 13 were suitable for genotypic identification of S. mutans isolates of saliva from adult volunteers.

Mutans streptococcal infection induces salivary antibody to virulence proteins and associated functional domains

The interplay between mucosal immune responses to natural exposure to mutans streptococci and the incorporation and accumulation of these cariogenic microorganisms in oral biofilms is unclear. An initial approach to explore this question would be to assess the native secretory immunity emerging as a consequence of Streptococcus mutans infection. To this end, we analyzed salivary immunoglobulin A (IgA) antibody to mutans streptococcal glucosyltransferase (Gtf) and glucan binding protein B (GbpB) and to domains associated with enzyme function and major histocompatibility complex (MHC) class II binding in two experiments. Salivas were collected from approximately 45-day-old Sprague-Dawley rats, which were then infected with S. mutans SJ32. Infection was verified and allowed to continue for 2 to 2.5 months. Salivas were again collected following the infection period. Pre- and postinfection salivas were then analyzed for IgA antibody activity using peptide- or protein-coated microsphere Luminex technology. S. mutans infection induced significant levels of salivary IgA antibody to Gtf (P < 0.002) and GbpB (P < 0.001) in both experiments, although the levels were usually far lower than the levels achieved when mucosal immunization is used. Significantly (P < 0.035 to P < 0.001) elevated levels of postinfection salivary IgA antibody to 6/10 Gtf peptides associated with either enzyme function or MHC binding were detected. The postinfection levels of antibody to two GbpB peptides in the N-terminal region of the six GbpB peptides assayed were also elevated (P < 0.031 and P < 0.001). Interestingly, the patterns of the rodent response to GbpB peptides were similar to the patterns seen in salivas from young children during their initial exposure to S. mutans. Thus, the presence of a detectable postinfection salivary IgA response to mutans streptococcal virulence-associated components, coupled with the correspondence between rat and human mucosal immune responsiveness to naturally presented Gtf and GbpB epitopes, suggests that the rat may be a useful model for defining mucosal responses that could be expected in humans. Under controlled infection conditions, such a model could prove to be helpful for unraveling relationships between the host response and oral biofilm development.

Biological functions of glucan-binding protein B of Streptococcus mutans

INTRODUCTION

Streptococcus mutans has been implicated as a major causative agent of dental caries in humans. Bacterial components associated with the adhesion phase of S. mutans include glucosyltransferases, protein antigen C and proteins that bind glucan. At least four glucan-binding proteins (Gbp) have been identified; GbpA, GbpB, GbpC and GbpD.

METHODS

In our previous study, the contributions of GbpA and GbpC to the virulence of S. mutans were investigated; however, the biological function of GbpB and its role in the virulence of S. mutans remain to be elucidated. Using a GbpB-deficient mutant strain (BD1), we demonstrated in the present study that GbpB has a role in the biology of S. mutans.

RESULTS

The growth rate of BD1 was lower than that of other strains, while it was also shown to be less susceptible to phagocytosis and to form longer chains than the parental strain MT8148. In addition, electron microscope observations of the cell surfaces of BD1 showed that the cell-wall layers were obscure.

CONCLUSION

These results suggest that GbpB may have an important role in cell-wall construction and be involved in cell separation and cell maintenance.

Do salivary antibodies reliably reflect both mucosal and systemic immunity?

Two major antibody classes operate in saliva: secretory IgA (SIgA) and IgG. The former is synthesized as dimeric IgA by plasma cells (PCs) in salivary glands and is exported by the polymeric Ig receptor (pIgR). Most IgG in saliva is derived from serum (mainly via gingival crevices), although some is locally produced. Gut-associated lymphoid tissue (GALT) and nasopharynx-associated lymphoid tissue (NALT) do not contribute equally to mucosal PCs throughout the body. Thus, enteric immunostimulation is an inadequate mode of stimulating salivary IgA antibodies, which are poorly associated with the intestinal SIgA response, for instance after enteric cholera vaccination. Nevertheless, the IgA response in submandibular/sublingual glands is better related to B cell induction in GALT than the parotid response. Such disparity is suggested by the elevated levels of IgA in submandibular secretions of AIDS patients, paralleling their highly upregulated intestinal IgA system. Moreover, in patients with active celiac disease, IgA antibodies to disease-precipitating gliadin are reliably represented in whole saliva but not in parotid secretion. Parotid SIgA may be more consistently linked to immune induction in palatine tonsils and adenoids (human NALT), as supported by the homing molecule profile of NALT-derived B cell blasts. Also several other variables influence the levels of antibodies in oral secretions. These include difficulties with reproducibility and standardization of immunoassays, the impact of flow rate, acute or chronic stress, protein loss during sample handling, and uncontrolled admixture of serum-derived IgG and monomeric IgA. Despite such problems, saliva remains an interesting biological fluid with great scientific and clinical potentials.

Age-specific salivary immunoglobulin A response to Streptococcus mutans GbpB

In a follow-up study of children infected with Streptococcus mutans at an early age (children previously shown to respond poorly to S. mutans GbpB), there was a delay in their immune response, rather than a complete inability to respond to this antigen. Epitopes in the N-terminal third of GbpB were identified as targets for naturally induced immunoglobulin A antibody in children at an early age.