An optimized caries model of Streptococcus mutans in rats and its application for evaluating prophylactic vaccines

Dental caries is a prevalent oral disease that mainly results from Streptococcus mutans. Susceptibility to S. mutans decreased rapidly after weaning in a well-known rat model. However, owing to the lack of time to establish protective immunity ahead of challenge, the weaning rat model is suboptimal for assessing prophylactic vaccines against S. mutans infection. In this study, we found that, in adult rats, S. mutans cultured under air-restricted conditions showed dramatically increased colonization efficacy and accelerated development of dental caries compared with those cultured under air-unrestricted conditions. We propose that S. mutans cultured under air-restricted conditions can be used to develop an optimal caries model, especially for the evaluation of prophylactic efficacy against S. mutans. Therefore, we used the anti-caries vaccine, KFD2-rPAc, to reevaluate the protection against the challenge of S. mutans. In immunized rats, rPAc-specific protective antibodies were robustly elicited by KFD2-rPAc before the challenge. In addition to inhibiting the initial and long-term colonization of S. mutans in vivo, KFD2-rPAc immunization showed an 83% inhibitory efficacy against the development of caries, similar to that previously evaluated in a weaning rat model. These results demonstrate that culturing under air-restricted conditions can promote S. mutans infection in adult rats, thereby helping establish a rat infection model to evaluate the prophylactic efficacy of vaccines and anti-caries drugs.

Assessment of bacterial exposure on phagocytic capability and surface marker expression of sputum macrophages and neutrophils in COPD patients

Defective phagocytosis has been shown in chronic obstructive pulmonary disease (COPD) bronchoalveolar lavage and blood monocyte-derived macrophages. Phagocytic capabilities of sputum macrophages and neutrophils in COPD are unknown. We investigated phagocytosis in these cells from COPD patients and controls. Phagocytosis of Streptococcus pneumoniae or fluorescently labelled non-typeable Haemophilus influenzae (NTHi) by sputum macrophages and neutrophils was determined by gentamycin protection assay (COPD; n = 5) or flow cytometry in 14 COPD patients, 8 healthy smokers (HS) and 9 healthy never-smokers (HNS). Sputum macrophages and neutrophils were differentiated by adherence for the gentamycin protection assay or receptor expression (CD206 and CD66b, respectively), by flow cytometry. The effects of NTHi on macrophage expression of CD206 and CD14 and neutrophil expression of CD16 were determined by flow cytometry. There was greater uptake of S. pneumoniae [~10-fold more colony-forming units (CFU)/ml] by sputum neutrophils compared to macrophages in COPD patients. Flow cytometry showed greater NTHi uptake by neutrophils compared to macrophages in COPD (67 versus 38%, respectively) and HS (61 versus 31%, respectively). NTHi uptake by macrophages was lower in HS (31%, p = 0.019) and COPD patients (38%, p = 0.069) compared to HNS (57%). NTHi uptake by neutrophils was similar between groups. NTHi exposure reduced CD206 and CD14 expression on macrophages and CD16 expression on neutrophils. Sputum neutrophils showed more phagocytic activity than macrophages. There was some evidence that bacterial phagocytosis was impaired in HS sputum macrophages, but no impairment of neutrophils was observed in HS or COPD patients. These results highlight the relative contributions of neutrophils and macrophages to bacterial clearance in COPD.

PepO is a target of the two-component systems VicRK and CovR required for systemic virulence of Streptococcus mutans

Streptococcus mutans, a cariogenic species, is often associated with cardiovascular infections. Systemic virulence of specific S. mutans serotypes has been associated with the expression of the collagen- and laminin-binding protein Cnm, which is transcriptionally regulated by VicRK and CovR. In this study, we characterized a VicRK- and CovR-regulated gene, pepO, coding for a conserved endopeptidase. Transcriptional and protein analyses revealed that pepO is highly expressed in S. mutans strains resistant to complement immunity (blood isolates) compared to oral isolates. Gel mobility assay, transcriptional, and Western blot analyses revealed that pepO is repressed by VicR and induced by CovR. Deletion of pepO in the Cnm+ strain OMZ175 (OMZpepO) or in the Cnm- UA159 (UApepO) led to an increased susceptibility to C3b deposition, and to low binding to complement proteins C1q and C4BP. Additionally, pepO mutants showed diminished ex vivo survival in human blood and impaired capacity to kill G. mellonella larvae. Inactivation of cnm in OMZ175 (OMZcnm) resulted in increased resistance to C3b deposition and unaltered blood survival, although both pepO and cnm mutants displayed attenuated virulence in G. mellonella. Unlike OMZcnm, OMZpepO could invade HCAEC endothelial cells. Supporting these phenotypes, recombinant proteins rPepO and rCnmA showed specific profiles of binding to C1q, C4BP, and to other plasma (plasminogen, fibronectin) and extracellular matrix proteins (type I collagen, laminin). Therefore this study identifies a novel VicRK/CovR-target required for immune evasion and host persistence, pepO, expanding the roles of VicRK and CovR in regulating S. mutans virulence.

Temperature regulates the recognition activities of a galectin to pathogen and symbiont in the scleractinian coral Pocillopora damicornis

Lectins serve as essential pattern recognition receptors, and play important roles in the recognition of non-self and mediation of innate immune response in metazoans. Scleractinian corals are vulnerable to pathogen infection and endosymbiosis disruption under heat stress that can finally lead to coral bleaching. In this study, a cDNA sequence encoding one galectin was cloned in scleractinian coral Pocillopora damicornis (PdGLT-1). The deduced PdGLT-1 protein shared highest amino acid sequence similarity (99%) with galectin from Stylophora pistillata (XP_022806650.1), and was composed of one signal peptide, one Collagen domain and one Gal-Lectin domain. PdGLT-1 recombinant protein (rPdGLT-1) was expressed and purified in vitro. Binding activities of rPdGLT-1 to bacteria and symbiont were determined using western blotting method. Results showed that rPdGLT-1 was able to bind to gram-positive bacterium Streptococcus mutans, gram-negative bacteria Vibrio coralliilyticus and Escherichia coli, with the highest activity for V. coralliilyticus, and further agglutinated them. The bound rPdGLT-1 to Symbiodinium (10-10⁴ cells mL^-1) was detectable, and its binding ability was concentration-dependent. Furthermore, dual binding activities were determined under different temperatures (20, 25, 30 and 35 °C), and the optimal temperatures were found to be 25 and 30 °C for V. coralliilyticus and Symbiodinium, respectively. Results suggested that PdGLT-1 could recognize pathogenic bacteria and symbiotic dinoflagellates Symbiodinium. However, their recognition activities were repressed under high temperature (>30 °C). This study provided insights into the underlying mechanism of lectin modulation to heat bleaching through its pathogen and Symbiodinium recognition in the scleractinian coral P. damicornis.

Evaluation of Total Salivary Secretory Immunoglobulin A and Mi/fans-specific SIgA among Children having Dissimilar Caries Status

INTRODUCTION

The occurrence of dental caries has become quite a common phenomenon nowadays. The varying levels of salivary secretory immunoglobulin A (SIgA) usually determine the progression of caries. The present study was aimed to determine the correlation between SIgA and mutans-specific antigen SIgA in children having different caries status. Scanning electron microscopic analysis was also completed to correlate the results.

MATERIALS AND METHODS

This study comprised 60 subjects, who were divided into three groups depending on caries status. In all, saliva was collected to determine the level of SIgA and mutans-specific antigen SIgA using enzyme linked immunosorbent assay (ELISA). The World Health Organization (WHO) criteria and method were used to evaluate dental caries. Bradford reagent was used to evaluate the levels of protein in the antigen. Furthermore, 20 sections of enamel were randomly obtained to estimate the severity of caries development among groups.

RESULTS

Categorical characteristics among all groups were compared by basic statistical analysis and Chi-squared test. Mean age (years) was found to be 9.214 ± 2.28, 9.5 ± 2.51, and 10.2 ± 2.35 in groups I, II, and III respectively. Mutans-specific IgA level (|jg/mL) was 34.63 ± 7.46, 28.24 ± 4.52, and 23.56 ± 1.62 in groups I, II, and III respectively. Total SIgA (jg/mL) was 142.53 ± 22.4, 186.10 ± 24.70, and 214.8 ± 27.56 in groups I, II, and III respectively. Caries index was 6.74 ± 2.16, 2.32 ± 0.86, and 0 ± 0 in groups I, II, and III respectively.

CONCLUSION

Immunoglobulin A is dominantly present in saliva and it plays a significant role in prevention of dental caries. Hence, dental caries is more likely to develop in subjects with low level of salivary IgA (high caries index).

CLINICAL SIGNIFICANCE

A low level of IgA may be associated with a high risk of developing dental caries. This association may possibly be useful in predicting the future caries status. Accordingly, suitable caries-preventive measures can be selected and employed.

Effectiveness of an Antigen-Specific Streptococcus mutans Chairside Test as Compared to a Culture-Based S. mutans Test

Purpose: To compare the effectiveness of an antigen-specific Streptococcus mutans (S. mutans) chairside test to a culture based S. mutans test.Methods: Fifty-three patients receiving dental hygiene care at the University of Missouri-Kansas City, School of Dentistry were enrolled in the study. Stimulated saliva was collected from the patients and utilized for both bacteria tests. The antigen-specific test was compared to the culture-based bacteria test and to a caries risk assessment measuring sensitivity and specificity.Results: The majority of participants were male (53%) with high caries risk (60%). The culture based test results were primarily negative (62%); while the antigen-specific test had more positives (76%). The sensitivity and specificity comparing the antigen-specific test to the culture based test was high (88%, 95% CI = (78%, 97%) and low (25%, 95% CI = (13%, 37%), respectively. The sensitivity and specificity comparing the antigen-specific test to caries risk was high (83%, 95% CI = (72%, 93%) and low (38%, 95% CI = (24%, 51%) respectively.Conclusions: While the sensitivity of the antigen-specific test was high for both the culture-based test and caries risk, the specificity was low for both. These results suggest that the antigen-specific test tends to give a higher proportion of false positive results.

Effect of topical anti-Streptococcus mutans IgY gel on quantity of S. mutans on rats' tooth surface

This study aims to evaluate the effect of anti-Streptococcus mutans IgY gel on quantity of S. mutans on rats' tooth surface. Sprague Dawley rats were exposed intra-orally with S. mutans Xc and were fed a caries-inducing diet 2000. The 24 rats were divided into four groups: group A had their teeth coated with IgY gel; group B received sterilized water as a control; group C had their teeth coated with IgY gel starting on the 29(th) day; and group D had their teeth coated with a gel without IgY. Plaque samples were swabbed from the anterior teeth for S. mutans colony quantification, and saliva was collected to measure immunoreactivity by enzyme-linked immunosorbent assay. The results indicated that the quantity of S. mutans in rats treated with IgY gel showed significant difference compared with the controls. After coating with IgY anti-S. mutans gel, the mean immunoreactivity in rat saliva was higher than that of the no treatment group. In conclusion, topical application with anti-S. mutans IgY gel reduced the quantity of S. mutans on the tooth surface.

Salivary profile in diabetic patients: biochemical and immunological evaluation

BACKGROUND

The aim of this study was to evaluate the biochemical and immunological characteristics of saliva from diabetic patients compared to non-diabetic adults.

METHODS

Eighty-eight diabetic adults and 39 non-diabetic adults (control) were included in the study. Glucose, urea, calcium, total protein and amylase were determined by a colorimetric method. The levels of secretory IgA and the IgA anti-Streptococcus mutans and anti-insulin IgA antibodies were measured by enzyme-linked immunosorbent assay (ELISA). Caries status was evaluated using the DMFT index.

RESULTS

Glucose, urea, calcium, anti-S. mutans IgA, total IgA, and anti-insulin IgA were significantly higher in diabetic patients, whereas total protein and amylase levels were lower in these patients. There was no positive correlation between blood and salivary glucose levels in either group. Diabetic patients had a higher DMFT index.

CONCLUSIONS

The present study showed for the first time that IgA levels in diabetic patients'saliva, shows correlation with systemic biochemical parameters. Thus the saliva is an useful tool to follow the systemic health status in these patients.

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.

Application ofIn VitroMutagenesis to Identify the Gene Responsible for Cold Agglutination Phenotype ofStreptococcus mutans

A previously unidentified protein with an apparent molecular mass of 120 kDa was detected in some Streptococcus mutans strains including the natural isolate strain Z1. This protein was likely involved in the cold-agglutination of the strain, since a correlation between this phenotype and expression of the 120 kDa protein was found. We have applied random mutagenesis by in vitro transposition with the Himar1 minitransposon and isolated three cold-agglutination-negative mutants of this strain from approximately 2,000 mutants screened. A 2.5 kb chromosomal fragment flanking the minitransposon in one of the three mutants was amplified by PCR-based chromosome walking and the minitransposon insertion in the other two mutants occurred also within the same region. Nucleotide sequencing of the region revealed a 1617 nt open reading frame specifying a putative protein of 538 amino acid residues with a calculated molecular weight of 57,192. The deduced eight amino acid sequence following a putative signal sequence completely coincided with the N-terminal octapeptide sequence of the 120 kDa protein determined by the Edman degradation. Therefore, the 1617 nt gene unexpectedly encoded the 120 kDa protein from S. mutans. Interestingly, this gene encoded a collagen adhesin homologue. In vitro mutagenesis using the Himar1 minitransposon was successfully applied to S. mutans.

A therapeutic anti-Streptococcus mutans monoclonal antibody used in human passive protection trials influences the adaptive immune response

The adhesin known as Antigen I/II, P1 or PAc of the cariogenic dental pathogen Streptococcus mutans is a target of protective immunity and candidate vaccine antigen. Previously we demonstrated that immunization of mice with S. mutans complexed with anti-AgI/II monoclonal antibodies (MAbs) resulted in changes in the specificity, isotype and functionality of elicited anti-AgI/II antibodies in the serum of immunized mice compared to administration of bacteria alone. In the current study, an anti-AgI/II MAb reported in the literature to confer unexplained long term protection against S. mutans re-colonization following passive immunization in human clinical trials (MAb Guy's 13), and expressed in tobacco plants (MAb Guy's 13 plantibody), was evaluated for its potential immunomodulatory properties. Immunization of BALB/c mice with immune complexes of Guy's 13 plantibody bound to S. mutans whole cells resulted in a similar change in specificity, isotype, and functionality of elicited anti-AgI/II antibodies as had been observed for other immunomodulatory MAbs. This new information, coupled with the recently solved crystal structure of the adhesin, now provides a rational explanation and plausible mechanism of action of passively administered Guy's 13/Guy's 13 plantibody in human clinical trials, and how long-term prevention of S. mutans carriage well past the application period of the therapeutic antibody could have been achieved.

[Effects of the cell wall of Streptococcus mutans on the expression of TLR4, IL-6 and IL-8 by EAhy926 cells]

OBJECTIVE

To investigate the effects of the cell wall of Streptococcus mutans on the expression of Toll-like receptor 4 (TLR4), IL-6 and IL-8 in EAhy926 cells (The human endothelial hybridoma of human umbilical vein endothelial cells (HUVEC) and the human epithelial cell line A549, characterized by endothelial phenotype and biology).

METHODS

EAhy926 cells were treated with different concentrations of the cell wall of Streptococcus mutans. The proliferation of EAhy926 cells was determined by MTT assay. The mRNA expression of TLR4, IL-6 and IL-8 in EAhy926 cells was detected by reverse transcription polymerase chain reaction (RT-PCR). TLR4 was analyzed by flow cytometry. The production of IL-6 and IL-8 in the cultured supernatants was measured by biochemical method and ELISA respectively. TLR4 blocking assay was used to investigate the relationship between IL-6, IL-8 and TLR4 mRNA expression.

RESULTS

The proliferation of EAhy926 cells was significantly enhanced by the cell wall of Streptococcus mutans at 6 h (P<0.05), and inhibited after 12 h (P<0.05), both time- and dose-dependent. The expression of mRNA and protein for TLR4 in EAhy926 cells was increased after stimulated by the cell wall of Streptococcus mutans, peaking at 16 h (P<0.05), and then decreased. The expression of IL-6 and IL-8 mRNA was significantly induced when exposed to the cell wall, reaching the maximal level at 16 h and 24 h, respectively (P<0.05). Meanwhile, the cell wall of Streptococcus mutans induced the production of IL-6 and IL-8 (P<0.05). The expression of IL-6 and IL-8 mRNA in EAhy926 cells was blocked by anti-human TLR4 antibodies significantly.

CONCLUSION

The cell wall of Streptococcus mutans upregulated the expression of TLR4 and induced the production of inflammatory cytokines IL-6 and IL-8, indicating that the expression of TLR4 of EAhy926 cells may elicit a TLR4-mediated innate immune response and contribute to production of inflammatory cytokines IL-6 and IL-8.

Streptococcus mutans autolysin AtlA is a fibronectin-binding protein and contributes to bacterial survival in the bloodstream and virulence for infective endocarditis

Streptococcus mutans, a commensal of the human oral cavity, can survive in the bloodstream and cause infective endocarditis (IE). However, the virulence factors associated with this manifestation of disease are not known. Here, we demonstrate that AtlA, an autolysin of S. mutans is a newly identified fibronectin (Fn) binding protein and contributes to bacterial resistance to phagocytosis and survival in the bloodstream. Interestingly, prior exposure to plasma at low concentrations was sufficient to enhance bacterial survival in the circulation. Calcium ions at physiological plasma concentrations induced maturation of AtlA from the 104-90 kDa isoform resulting in increased Fn binding and resistance to phagocytosis. An isogenic mutant strain defective in AtlA expression exhibited reduced survival and virulence when tested in a rat model of IE compared with the wild-type and complemented strains. The data presented suggest that plasma components utilized by S. mutans enhanced survival in the circulation and AtlA is a virulence factor associated with infective endocarditis.

[Protective efficacy of a new fusion anti-caries DNA vaccine encoding antigens of both Streptococcus mutans and Streptococcus sobrinus]

OBJECTIVE

To construct a new fusion anti-caries DNA vaccine pGJGAC/VAX encoding antigens of both S. mutans and S. sobrinus so as to enhance the protective effect of DNA vaccine against S. sobrinus infection.

METHODS

The CAT fragment of S. sobrinus OMZ176 gtf-I was amplified by semi-nest PCR and then inserted into the plasmid pGJA-P/VAX to construct the recombinant plasmid pGJGAC/VAX. The CHO cell was transfected and the expression of fusion protein detected using cellular immunohistochemistry and Western blot. Mice were immunized with pGJGAC/VAX and control plasmids via the intramuscular (i.m) or intranasal (i.n) routes. During the experiment, blood and saliva samples were collected at a 2-week interval for antibody assay by ELISA. Rats were orally challenged with S. mutans Ingbritt or S. sobrinus 6715 and then immunized i.n with pGJGAC/VAX, pGJA-P/VAX or pVAX1. The Keyes method was used to determine the caries activity.

RESULTS

(1) CAT sequence was identical to the related sequence of gtf-I (OMZ176) in GenBank. The recombinant plasmid pGJGAC/VAX encoded the genes of antigens of both S. mutans and S. sobrinus. The expressed protein could respond to specific anti-PAc, anti-GLU and anti-CAT antibodies respectively. (2) As for antibody reactions, mice in the experiment group had significantly higher levels of anti-PAc, anti-GLU and anti-CAT IgG antibodies than those in the pVAX1 group (P < 0.01). The peak responses of specific anti-CAT antibodies were observed at 8 weeks (GAC/i.m) and 10 weeks (GAC/i.n) and were approximately 62.13 microg/ml and 11.43 microg/ml respectively. The peak responses of specific anti-CAT IgA antibodies were seen at 8 weeks (GAC/i.m) and 10 weeks (GAC/i.n) and were approximately 0.67% and 0.80% respectively. (3) In the group infected with S. mutans or S. sobrinus, the pGJGAC/VAX-immunized rats showed significantly fewer E, Ds and Dm lesions than pVAX1-immunized rats (P < 0.05) and decreased Ds and Dm levels than pGJA-P/VAX-immunized rats (P < 0.05) while there was no obvious difference in E lesions between the two groups (P > 0.05).

CONCLUSION

A new fusion anti-caries DNA vaccine pGJGAC/VAX encoding antigens of both S. mutans and S. sobrinus is constructed successfully and expressed correctly in eukaryotic cells. It induces effective mucosal and systematic humoral responses so as to provide a better protection against S. sobrinus.

Production of monoclonal antibodies against Streptococcus mutans antigens

Several studies have been conducted in the last decades aiming to obtain an anti-caries vaccine, however some studies have demonstrated cross reactivity between Streptococcus mutans surface antigens and the human cardiac tissue. In this work, the reactivity of five anti-Streptococcus mutans monoclonal antibodies (MoAb) (24A, 56G, C8, E8 and F6) was tested against oral streptococci, cardiac antigens and skeletal and cardiac myosins, aiming to evaluate the specificity of these MoAb. The hybrid producers of immunoglobulins of the IgG2b class were cloned by limit dilution and expanded in vivo. MoAb were tested by ELISA. The hybrid 24A reacted with S. mutans CCT 1910, S. salivarius CCT 0365 and S. pyogenes T23. No reactivity difference was observed among the tested species. Cross reactivity with heart and cardiac myosin was not confirmed and only reaction with myosin of skeletal muscle was observed (p = 0.0381). The hybrid 56G reacted with all the tested microorganisms and there was statistically significant difference between S. mutans and S. pyogenes T23 (p < 0.001). This hybrid also reacted with myosin of skeletal muscle (p = 0.0095). C8, E8 and F6 presented low reactivity against oral streptococci strains and no reactivity against cardiac antigens. The data of this study showed that the 24A and 56G anti-S. mutans MoAb presented reactivity with S. pyogenes and S. salivarius, reinforcing the occurrence of common antigens between these species. The tested MoAb presented low cross-reactivity with myosin of skeletal muscle, but anti-heart activity could not be confirmed.

Interaction forces between salivary proteins and Streptococcus mutans with and without antigen I/II

The antigen I/II family of surface proteins is expressed by oral streptococci, including Streptococcus mutans, and mediates specific binding to, among others, salivary films. The aim of this study was to investigate the interaction forces between salivary proteins and S. mutans with (LT11) and without (IB03987) antigen I/II through atomic force microscopy (AFM) and to relate these interaction forces with the adhesion of the strains to saliva-coated glass in a parallel plate flow chamber. Upon approach of the bacteria toward a saliva-coated AFM tip, both strains experienced a similar repulsive force that was significantly smaller at pH 6.8 (median 3.0 and 3.1 nN for LT11 and IB03987, respectively) than at pH 5.8 (median 4.6 and 4.7 nN). The decay length of these repulsive forces was between 19 and 37 nm. Upon retraction at pH 6.8, the combined specific and nonspecific adhesion forces were significantly stronger for the parent strain LT11 (median -0.4 nN) than for the mutant strain IB03987 (median 0.0 nN), whereas at pH 5.8 the median of the adhesion forces measured was 0.0 nN for both strains. Moreover, at pH 6.8, the parent strain LT11 adhered in significantly higher numbers (9.6 x 106 cm-2) to a salivary coating than the mutant strain IB03987 (2.5 x 106 cm-2). Similar to the difference in adhesion forces between both strains at pH 5.8, the difference in adhesion between both strains also disappeared at pH 5.8, which suggests the involvement of attractive electrostatic forces in the interaction between antigen I/II and salivary coatings. In summary, this study shows that antigen I/II at the surface of S. mutans LT11 is responsible for its increased adhesion to salivary coatings under flow through an additional attractive electrostatic force.

Enhanced efficacy of CTLA-4 fusion anti-caries DNA vaccines in gnotobiotic hamsters

AIM

To evaluate the comparative immunogenicity and protective efficacy of the cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) fusion anti-caries DNA vaccines pGJA-P/VAX1, pGJA-P, and non-fusion anti-caries DNA construct pGLUA-P in hamsters. In addition, the ability of CTLA-4 to target pGJA-P/VAX1-encoding antigen to dendritic cells was tested in vitro.

METHODS

All DNA constructs contain genes encoding the A-P regions of a cell surface protein (PAc) and the glucan binding (GLU) domain of glucosyltransferases (GTFs) of cariogenic organism Streptococcus mutans. Human dendritic cells were mixed with the CTLA-4-Ig-GLU-A-P protein expressed by pGJA-P/VAX1-transfected cells and analyzed by flow cytometry. Gnotobiotic hamsters were immunized with anti-caries DNA vaccines by intramuscular injection or intranasal administration. Antibody responses to a representative antigen PAc were assayed by ELISA, and caries protection was evaluated by Keyes caries scores.

RESULTS

A flow cytometric analysis demonstrated that CTLA-4-Ig-GLU-A-P protein was capable of binding to human dendritic cells. pGJA-P/VAX1 and pGJA-P induced significantly higher specific salivary and serum anti-PAc antibody responses than pGLUA-P. Significantly fewer caries lesions were also observed in hamsters immunized with pGJA-P/VAX1 and pGJA-P. There was no significant difference in the anti-PAc antibody level or caries scores between pGJA-P/VAX1 and pGJA-P-immunized groups.

CONCLUSION

Antigen encoded by CTLA-4 fusion anti-caries DNA vaccine pGJA-P/VAX1 could specifically bind to human dendritic cells through the interaction of CTLA-4 and B7 molecules. Fusing antigen to CTLA-4 has been proven to greatly enhance the immunogenicity and protective efficacy of anti-caries DNA vaccines.

Age-dependent deficiency in saliva and salivary antibodies secretion in Down's syndrome

OBJECTIVE

Down's syndrome (DS) individuals suffer from an increased susceptibility to infections. Here, we assessed age-related changes in the salivary-specific humoral immunity of DS subjects.

DESIGN

Parotid and whole saliva were collected from a young group of DS (YDS, n=30, 23.3+/-4 years), an older group of DS individuals (ODS, n=10, 51.9+/-8 years) and compared to two age-matched groups of healthy volunteers--a young group (YC, n=29, 22.8+/-5 years) and an older group (OC, n=10, 48.4+/-9 years). The levels of total IgA, and specific antibodies to three common oral pathogens (Porphyromonas gingivalis, Actinobacillus (Aggregatibacter) actinomycetemcomitans and Streptococcus mutans) were analysed.

RESULTS

The limited increases in IgA concentrations could not compensate the dramatic reduction in the salivary flow rate observed in DS individuals. Therefore, the median secretion rates of the specific antibodies in whole and parotid saliva were 70-77% and 34-60% (respectively) lower in YDS individuals as compared to YC and farther 77-100% and 75-88% (respectively) lower in ODS compared to YDS. In contrast, the antibody secretion rates were similar for parotid saliva, or even increased for whole saliva of OC, compared with YC. Consequently, a dramatic cumulative extreme reduction (>92%) in the bacterial specific salivary antibodies differentiated the adult DS individuals from to their age-matched controls.

CONCLUSIONS

Our results indicate a severe immunodeficiency in the secretion rate of the specific salivary IgA response of in DS individuals which intensifies with age.

Basis of beneficial immunomodulation by monoclonal antibodies against Streptococcus mutans adhesin P1

We previously identified five monoclonal antibodies (MAbs) against Streptococcus mutans adhesin P1 that modulate the humoral response when bound to whole bacteria and immune complexes (ICs) are administered to BALB/c mice. The two MAbs that redirected the response towards increased efficacy recognize discontinuous epitopes involving pre-alanine-rich domain sequence; therefore, to evaluate whether epitope specificity contributes to a desirable outcome a further MAb with this characteristic was tested. A beneficial immune response was promoted. None of the three MAbs that promoted a beneficial response was opsonic, suggesting that increased uptake of ICs by phagocytes does not mediate the improvement of the IC-elicited antibodies to inhibit bacterial adherence. Finally, two of the six anti-P1 MAbs activated complement but did not partition according to desirable vs. nondesirable effects.

[Construction and identification of an immune single chain antibody library derived from a chicken]

AIM

To develop a method for constructing an immune single chain antibody library derived from a chicken.

METHODS

According to the principle of phage display and the character of chicken antibody genes, an immune single chain antibody library was constructed by using the spleen B cells which were extracted from a chicken immunized with streptococcus mutans as antibody gene sources. According to the principle of immobilized panning the specific chicken single chain phage antibody was selected from the single chain antibody library to identify the immune antibody library.

RESULTS

The repertoire of the chicken heavy-chain and light-chain variable regions was obtained from the total intact RNA of chicken spleen. The phage antibody library was generated and its size was determined to be 1.6x10(7). A specific chicken single chain phage antibody against streptococcus mutans was selected and its DNA was sequenced.

CONCLUSION

An immune single chain antibody library derived from a chicken can be constructed successfully based on the principle of phage antibody library and the character of chicken antibody genes.

Characterization of epitopes recognized by anti-Streptococcus mutans P1 monoclonal antibodies

Sequences contributing to epitopes recognized by a panel of monoclonal antibodies (mAbs) against the Streptococcus mutans surface protein P1 were delineated by Western blot and enzyme-linked immunosorbent assay using a battery of deletion constructs and recombinant polypeptides. mAbs that recognize complex discontinuous epitopes reconstituted by combining the alanine-rich and proline-rich repeat domains and varying degrees of flanking sequence were identified as well as mAbs that bound epitopes contained within contiguous segments of P1. Cross-reactivity with SspA and SspB from Streptococcus gordonii is also reported. This information enables insight into the structure and function of a streptococcal adhesin and its correlates of protection and furthers our understanding of the immunomodulatory and bacterial-adherence inhibition activities of anti-P1 mAbs.

Enhancement of salivary IgA response to a DNA vaccine against Streptococcus mutans wall-associated protein A in mice by plasmid-based adjuvants

A specific salivary IgA (sIgA) response was obtained in mice by intranasal immunization with a naked DNA vaccine consisting of the Streptococcus mutans wall-associated protein A gene (wapA) inserted into the mammalian expression vector pcDNA3.1/V5/His-TOPO. In the present study, the vaccine, referred to as pcDNA-wapA, was administered with or without the cationic lipid DMRIE-C. No mucosal response was observed in mice immunized with the vaccine alone, whereas a weak and temporal sIgA response was obtained when the vaccine was mixed with DMRIE-C. To investigate the use of pcDNA containing the interleukin 5 (IL-5) gene (pcDNA-il-5) or the cholera toxin B gene (pcDNA-ctb) as genetic adjuvants, these constructs were used in co-immunization studies. The enhancement effect was transient with pcDNA-il-5, but longer lasting with pcDNA-ctb, thus supporting the use of the latter as a genetic adjuvant to DNA vaccine.

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.

Relationships of anti-PAc (361-386) peptide salivary IgA antibody, eosinophils and basophils with periodontal status in the elderly

The amino acid residues 361-386 of Streptococcus mutans PAc includes an important region associated with the interaction between S. mutans and salivary components. We investigated the relationships between levels of the anti-PAc (361-386) peptide antibody (PPA) in saliva and periodontal status in 281 elderly subjects (mean age 77 years; 118 females, 163 males) by assessing dental calculus (CA), attachment loss (AL), pocket depth (PD), bleeding on probing (BOP) and various blood parameters. Enzyme-linked immunosorbent assay results revealed that subjects with a PPA level of greater than 0.1 (PPA detected group) showed a lower average value for number of sites with more than 6 mm of AL/6 points x 100/tooth (rAL6) than those with a PPA level of less than 0.1 (PPA not detected group). Furthermore, average values for rAL6 were significantly lower in the PPA detected group, and BOP, AL and rAL6 correlated positively and significantly with the percentage of eosinophils present in leukocytes in female subjects in both groups. PPA level had a negative correlation with percentages of basophils and eosinophils. The results indicate that systemic increases in numbers of eosinophils and basophils are associated with the development of periodontal diseases, while PPA level may be a useful indicator of periodontal status.