Passive immunization against dental caries and periodontal disease: development of recombinant and human monoclonal antibodies

Novel trends, challenges and new perspectives for enamel repair and regeneration to treat dental defects

Dental enamel is the hardest tissue in the human body, providing external protection for the tooth against masticatory forces, temperature changes and chemical stimuli. Once enamel is damaged/altered by genetic defects, dental caries, trauma, and/or dental wear, it cannot repair itself due to the loss of enamel producing cells following the tooth eruption. The current restorative dental materials are unable to replicate physico-mechanical, esthetic features and crystal structures of the native enamel. Thus, development of alternative approaches to repair and regenerate enamel defects is much needed but remains challenging due to the structural and functional complexities involved. This review paper summarizes the clinical aspects to be taken into consideration for the development of optimal therapeutic approaches to tackle dental enamel defects. It also provides a comprehensive overview of the emerging acellular and cellular approaches proposed for enamel remineralization and regeneration. Acellular approaches aim to artificially synthesize or re-mineralize enamel, whereas cell-based strategies aim to mimic the natural process of enamel development given that epithelial cells can be stimulated to produce enamel postnatally during the adult life. The key issues and current challenges are also discussed here, along with new perspectives for future research to advance the field of regenerative dentistry.

Inhibition of experimental periodontitis by a monoclonal antibody against Porphyromonas gingivalis HA2

It is known that complexes of the multi-protein, gingipain, possess heme binding domains (hemagglutinin 2, HA2) that bind hemoglobin to provide heme and iron to the bacterium, Porphyromonas gingivalis. The DHYAVMISK peptide sequence was proposed to act as an inhibitor of hemin binding, and thus, it might be used to control or prevent periodontal disease. In this study, we created a monoclonal antibody (mAb) that targeted the DHYAVMISK peptide, aimed to determine whether it could inhibit the growth of P. gingivalis in vitro, and block its induction of experimental periodontitis and subsequent bone loss. Peptide DGFPG-DHYAVMISK conjugated to KLH (DK-KLH) was synthetic, and injected subcutaneously into BALB/c mice to generate specific mAbs with the hybridoma technique. We isolated mAb 1H11, which showed specific binding to DK. When we incubated these mAbs with P. gingivalis in vitro for 18 h, bacterial growth was significantly lower in cultures treated with mAb 1H11 compared to those treated with control (PBS; P < 0.05). Next, we induced experimental periodontitis in mouse models with a silk ligature and a P. gingivalis infection. When we injected the mAbs into the gingival sulcus, the group treated with mAb 1H11 displayed a reduction in bone loss compared to the other treatment groups. Thus, mAb 1H11 might provide protection against a P. gingivalis infection. Accordingly, this antibody could serve as a candidate therapy for periodontitis or other infections caused by P. gingivalis.

Prevalence of Dental Caries in Adult South Indian Population in Association with Dietary Pattern: A Comparative Study

Background:

Dental caries is considered to be one of the most prevalent dental diseases among humans. It involves cycles of demineralization and remineralization. The etiology and pathogenesis of dental caries are multifactorial. The role of diet plays an important aspect in occurrence and progression of dental caries. Indians have differing dietary habits due to various religious and personal reasons. A substantial number of Indians are vegetarian by choice.

Aim:

The aim of this study was to assess the effect of vegetarian and mixed diet over the prevalence of dental caries.

Materials and Methods:

This observational cross-sectional study was conducted among 104 individuals. Healthy subjects who were 20–40 years of age, with no systemic disease, and not on any medications were included in this study. A thorough dental examination was performed by a single investigator with the help of mouth mirror and probe. The examination of patients involved the sequential assessment of teeth starting from 1 to 32. All the exposed and accessible surfaces of the teeth were examined for dental caries, and the data were recorded.

Statistical Analysis:

The data obtained were statistically analyzed using the Statistical Package for the Social Sciences (SPSS) software, version 11.0, and the results were tabulated. Univariate analysis was performed to find an association between caries and diet.

Results:

Distribution of the respondents according to dietary practices revealed 51% of the population consuming mixed diet and 49% consuming vegetarian diet. Oral hygiene was measured in terms of frequency of brushing tooth. Among the enrolled subjects, 57% brushed their teeth once a day and 42% brushed twice a day. No significant association was found between vegetarian and mixed dietary habits and dental caries. Two-sample independent t test was carried out to find the mean age. The mean age of caries group was 30.93 ± 12.27 and in without caries group, 27.83 ± 11.58, which is statistically not significant (P = 0.218).

Conclusion:

The study did not show any significant association between dietary habits and prevalence of dental caries.

Oral microbiome development during childhood: an ecological succession influenced by postnatal factors and associated with tooth decay

Information on how the oral microbiome develops during early childhood and how external factors influence this ecological process is scarce. We used high-throughput sequencing to characterize bacterial composition in saliva samples collected at 3, 6, 12, 24 months and 7 years of age in 90 longitudinally followed children, for whom clinical, dietary and health data were collected. Bacterial composition patterns changed through time, starting with "early colonizers", including Streptococcus and Veillonella; other bacterial genera such as Neisseria settled after 1 or 2 years of age. Dental caries development was associated with diverging microbial composition through time. Streptococcus cristatus appeared to be associated with increased risk of developing tooth decay and its role as potential biomarker of the disease should be studied with species-specific probes. Infants born by C-section had initially skewed bacterial content compared with vaginally delivered infants, but this was recovered with age. Shorter breastfeeding habits and antibiotic treatment during the first 2 years of age were associated with a distinct bacterial composition at later age. The findings presented describe oral microbiota development as an ecological succession where altered colonization pattern during the first year of life may have long-term consequences for child´s oral and systemic health.

A tissue-dependent hypothesis of dental caries

Current understanding of dental caries considers this disease a demineralization of the tooth tissues due to the acid produced by sugar-fermenting microorganisms. Thus, caries is considered a diet- and pH-dependent process. We present here the first metagenomic analysis of the bacterial communities present at different stages of caries development, with the aim of determining whether the bacterial composition and biochemical profile are specific to the tissue affected. The data show that microbial composition at the initial, enamel-affecting stage of caries is significantly different from that found at subsequent stages, as well as from dental plaque of sound tooth surfaces. Although the relative proportion of Streptococcus mutans increased from 0.12% in dental plaque to 0.72% in enamel caries, Streptococcus mitis and Streptococcus sanguinis were the dominant streptococci in these lesions. The functional profile of caries-associated bacterial communities indicates that genes involved in acid stress tolerance and dietary sugar fermentation are overrepresented only at the initial stage (enamel caries), whereas other genes coding for osmotic stress tolerance as well as collagenases and other proteases enabling dentin degradation are significantly overrepresented in dentin cavities. The results support a scenario in which pH and diet are determinants of the disease during the degradation of enamel, but in dentin caries lesions not only acidogenic but also proteolytic bacteria are involved. We propose that caries disease is a process of varying etiology, in which acid-producing bacteria are the vehicle to penetrate enamel and allow dentin degrading microorganisms to expand the cavity.

Biological plaque control: novel therapeutic approach to periodontal disease

Despite its important role in the control of periodontal disease, mechanical plaque control is not properly practiced by most individuals. Therefore, adjunctive chemical plaque control using chlorhexidine and antibiotics has also been suggested as an additional therapeutic strategy to augment mechanical plaque control. However, the additional effects of adjunctive antibiotic therapy are small, and topical chlorhexidine therapy is not without side effects. Given current limitations, new approaches for the control of biofilm are required. The new therapeutic approaches discussed in this review are divided into two categories: probiotics and vaccines. Probiotics is an interesting new field of periodontology research that aims to achieve biological plaque control by eliminating pathogenic bacteria. In addition, passive immunization using egg yolk antibody raised against periodontal pathogens may be an effective approach for the treatment of periodontitis. Further study to evaluate the possible effects of these biological plaque control methods against periodontal disease is warranted.

Susceptibility to dental caries and the salivary proline-rich proteins

Early childhood caries affects 28% of children aged 2–6 in the US and is not decreasing. There is a well-recognized need to identify susceptible children at birth. Caries-free adults neutralize bacterial acids in dental biofilms better than adults with severe caries. Saliva contains acidic and basic proline-rich proteins (PRPs) which attach to oral streptococci. The PRPs are encoded within a small region of chromosome 12. An acidic PRP allele (Db) protects Caucasian children from caries but is more common in African Americans. Some basic PRP allelic phenotypes have a three-fold greater frequency in caries-free adults than in those with severe caries. Early childhood caries may associate with an absence of certain basic PRP alleles which bind oral streptococci, neutralize biofilm acids, and are in linkage disequilibrium with Db in Caucasians. The encoding of basic PRP alleles is updated and a new technology for genotyping them is described.

Transition metal ions induce carnosinase activity in PepD-homologous protein from Porphyromonas gingivalis

Aminoacylhistidine dipeptidase (EC 3.4.13.3; also Xaa-His dipeptidase, carnosinase, or PepD) catalyzes the cleavage and release of an N-terminal amino acid, which is usually a neutral or hydrophobic residue, from an Xaa-His dipeptide or degraded peptide fragment. PepD enzyme is found extensively in prokaryotes and eukaryotes, and belongs to the metallopeptidase family M20, a part of the metallopeptidase H (MH) clan. Carnosine is a naturally occurring dipeptide (β-alanyl-l-histidine) present in mammalian tissues that has protective functions in addition to anti-oxidant and free-radical scavenging roles. During bacterial infections, degradation of l-carnosine via carnosinase or PepD-like enzymes may enhance the destructive potential of bacteria, resulting in a pathological impact. This process has been proposed to act in an anti-oxidant manner in vivo. In the present study, the recombinant PepD protein encoded by Porphyromonas gingivalis TDC60 pepD was generated and biochemically characterized. In addition, a recombinant dipeptidase enzyme was found to function not only as an alanine-aminopeptidase, but also as a carnosinase. Furthermore, when carnosine was used as substrate for PepD, the transition metals, Mn(2+), Fe(2+), Co(2+), and Ni(2+) stimulated the hydrolyzing activity of rPepD with β-alanine and l-histidine. Based on its metal ion specificity, we propose that this enzyme should not only be termed l-aminopeptidase, but also a carnosinase.

Characterization of human-type monoclonal antibodies against reduced form of hemin binding protein 35 from Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

The gram-negative anaerobe Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. We previously identified a 35 kDa surface protein (hemin binding protein 35; HBP35) from P. gingivalis that exhibited coaggregation activity, while additional analysis suggested that this protein possessed an ability to bind heme molecules. For development of passive immunotherapy for periodontal diseases, human-type monoclonal antibodies have been prepared using HBP35 as an antigen in TransChromo mice. In the present study, we focused on a single antibody, TCmAb-h13, which is known to inhibit heme binding to recombinant HBP35. The aim of our investigation was to clarify the redox-related function of HBP35 and consider the benefits of human-type monoclonal antibodies.

MATERIAL AND METHODS

To examine the antigen recognition capability of TCmAbs with immunoblotting and Biacore techniques, we used the native form as well as several Cys-to-Ser variants of recombinant HBP35.

RESULTS

We found that the redox state of recombinant HBP35 was dependent on two Cys residues, (48) C and (51) C, in the thioredoxin active center (WCGxCx). Furthermore, TCmAb-h13 recognized the reduced forms of recombinant HBP35, indicating its inhibitory effect on P. gingivalis growth.

CONCLUSION

Hemin binding protein 35 appears to be an important molecule involved in recognition of the redox state of environmental conditions. In addition, TCmAb-h13 had an inhibitory effect on heme binding to recombinant HBP35, thereby interfering with P. gingivalis growth.

Dental caries: A complete changeover, PART III: Changeover in the treatment decisions and treatments

Comprehensive management of dental caries should involve the management of disease as well as the lesion. Current decision making process in cariology is influenced by numerous factors such as the size/ depth/ activity of the carious lesion and age/ the caries risk status of the patient. Treatment decisions should involve planning the non-operative/ preventive treatment for non-cavitated or early cavitated lesions and also formulating operative treatment for cavitated lesions. Apart from these two responsibilities, a clinician should also be knowledgeable enough to decide when not to interfere in the caries dynamics and how frequently to recall the patient for follow-ups. The non-operative treatment prescriptions vary in dose, intensity and mode of delivery according to the caries risk status. Minimal invasion and maximal conservation of tooth structure has become the essence of current operative treatments. This part of the series elaborates on the paradigm shift in the management of dental caries.

A monoclonal antibody against fimA type II Porphyromonas gingivalis inhibits IL-8 production in human gingival fibroblasts

The periodontal pathogen Porphyromans gingivalis is classified into six groups (types I-V and Ib) based on the genotype of the fimbriae A (fimA) gene. Among genotypes, fimA type II strains are thought to be most strongly related to advanced periodontitis. The present study was undertaken to develop passive immunotherapy monoclonal antibodies (MAbs) against periodontitis, which are capable of inhibiting virulency and were constructed through the immunization of outer membrane vesicles (OMV) fraction of fimAII strain, TDC60, using mouse hybridoma technology. MAbs that recognized OMV by ELISA assay were identified, and 28 clones were screened by Western blot analysis. After purifying these MAbs using protein G column, the effect of the MAb on IL-8 production from human gingival fibroblasts by OMV was examined. We selected MAb TDC4-33H, which strongly inhibited the IL-8 production with a higher MAb production rate. Since the MAb showed an individual ladder-like profile against OMV by Western blotting, we further examined the reactivity against lipopolysaccharides (LPS) from TDC60, W83 (fimAIV), and ATCC33277 (fimAI). As a result, MAb TDC4-33H recognized all LPSs. Moreover, MAb TDC4-33H significantly inhibited the LPS-stimulated IL-8 production in human gingival fibroblasts. These findings suggest that MAb TDC4-33H reacts with LPS and may be useful for passive immunotherapy through neutralizing IL-8 production in gingival fibroblasts by P. gingivalis LPS.

Functional analysis of the thioredoxin domain in Porphyromonas gingivalis HBP35

Periodontitis is one of the most common oral diseases in humans. This caused by infection by the oral bacterium Porphyromonas gingivalis. Our strategy to prevent this infection is to establish a passive immunization system in which endogenous antibodies can be applied directly to neutralize virulent factors associated with this bacterium. We focused our attention on the P. gingivalis 35 kDa surface protein, or HBP35, since this protein is involved not only in the coaggregation with oral miroflora but also in hemin binding. In addition, nucleotide sequencing of the gene, hbp35, coding for this protein revealed the presence of a catalytic center for thioredoxin, and we further attempted to characterized the protein by amino acid substitution. A total of four Cys residues were substituted for Ser residues by combining the simple method for site-directed mutagenesis and the heterodimer system, an approach designed to construct chimeric plasmids readily. Native and mutagenized hbp35 were introduced into the Eschericha coli dsbA mutant strain, JCB 572, defective in both alkaline phosphatase and motile activities due to inefficient disulfide bond formation. Transformant harboring the native hbp35 could complement the dsbA mutation, suggesting a role of disulfide bond formation of this protein in P. gingivalis cells. Possible roles of the Cys residues in complementation are discussed.

Activity of anti-Porphyromonas gingivalis egg yolk antibody against gingipains in vitro

INTRODUCTION

We investigated the effect of anti-Porphyromonas gingivalis egg yolk antibody against gingipains [immunoglobulin Y (IgY)-GP] on gingipain activity in vitro.

METHODS

IgY-GP was isolated from the yolks of White Leghorn hens immunized with purified gingipains. Control antibody (IgY) was isolated from the yolks of non-immunized hens. Gingipain activity was assessed according to the rate of enzymatic substrate hydrolysis. Human epithelial cells were cultured with or without gingipains and with gingipains pretreated with either IgY-GP or IgY.

RESULTS

Hydrolytic activity decreased in the presence of IgY-GP. Cells incubated with gingipains showed a dose-dependent loss of adhesion activity. Pretreatment of gingipains with IgY-GP was associated with strong inhibition of cell detachment, whereas pretreatment with IgY was not.

CONCLUSION

Our findings suggest that IgY-GP may be an effective immunotherapeutic agent in the treatment of periodontitis.

Inhibition of Porphyromonas gingivalis hemagglutinating activity by IgY against a truncated HagA

Porphyromonas gingivalis has been implicated as an important pathogen in the development of periodontitis. Hemagglutinins have been identified as important adhesion molecules, allowing Porphyromonas gingivalis to adhere to gingival tissue cells, and to attach and lyse erythrocytes in order to uptake Fe ions as essential nutrition. One hemagglutinin, hemagglutinin A (HagA), has been molecularly cloned via functional screening for hemagglutinating activity. We previously cloned the gene encoding the 200-kDa cell-surface antigenic protein that was reacted by sera from periodontitis patients and was identified as a truncated protein of HagA by nucleotide sequence analysis. We further subcloned the gene encoding an 122-kDa protein (122k-HagA) which is a fusion protein composed of an 80-kDa truncated HagA containing the functional motif PVQNLT and a 42-kDa maltose binding protein. Passive immunization against infectious pathogens by specific antibodies produced from hen egg yolk antibody (IgY) has been extensively developed. In the present study, to develop passive immunotherapy against periodontal disease, we purified the recombinant 122k-HagA and used this to immunize hens and produce IgY. The purified IgY reacted with the recombinant 122k-HagA and the synthetic peptide containing PVQNLT, and inhibited hemagglutinating activity of Porphyromonas gingivalis. Thus, the novel IgY may be useful in the development of a passive immunization against periodontal diseases caused by P. gingivalis infection.

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.

Egg yolk-derived immunoglobulin (IgY) against Porphyromonas gingivalis 40-kDa outer membrane protein inhibits coaggregation activity

The anaerobic bacterium Porphyromonas gingivalis, a major pathogen in periodontitis, aggregates with a number of oral bacteria to form dental plaque, which is important for its colonization. We previously cloned the gene coding the 40-kDa outer membrane protein (OMP) of P. gingivalis 381 and produced large amounts of the recombinant (r) protein. Affinity-purified rabbit antiserum against r40-kDa OMP effectively inhibited the coaggregation activity of P. gingivalis to oral bacteria, thus 40-kDa OMP was thought to be an important coaggregation factor of P. gingivalis. Further, since it is conserved among many P. gingivalis strains, this coaggregation factor may be an effective target for passive immunotherapy against P. gingivalis infection. Recently, passive immunization approaches using a specific antibody produced from hen egg yolk (IgY) have been developed for oral infectious diseases, and shown to be convenient and economic. In the present study, we immunized hens intramuscularly with r40-kDa OMP and obtained highly purified IgY from the egg yolks. The purified IgY specifically recognized r40-kDa OMP and also reacted with a functional coaggregation-associated domain peptide of 40-kDa OMP. Our results demonstrated that a ratio of purified IgY as low as 2.5 microg/150 microl significantly inhibited the coaggregation of P. gingivalis with Streptococcus gordonii, which was verified by a visual coaggregation assay and radioactivity-based quantitative micro-coaggregation assay. We concluded anti-r40-kDa OMP IgY may be useful for passive immunization against periodontal diseases caused by P. gingivalis infection.

Protective and destructive immunity in the periodontium: Part 1--innate and humoral immunity and the periodontium

Based on the results of recent research in the field, the present paper will discuss the protective and destructive aspects of the innate vs. adaptive (humoral and cell-mediated) immunity associated with the bacterial virulent factors or antigenic determinants during periodontal pathogenesis. Attention will be focused on: (i) the Toll-like receptors (TLR), the innate immune repertoire for recognizing the unique molecular patterns of microbial components that trigger innate and adaptive immunity for effective host defenses, in some general non-oral vs. periodontal microbial infections; (ii) T-cell-mediated immunity, Th-cytokines, and osteoclastogenesis in periodontal disease progression; and (iii) some molecular techniques developed and used to identify critical microbial virulence factors or antigens associated with host immunity (using Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis as the model species). Therefore, further understanding of the molecular interactions and mechanisms associated with the host's innate and adaptive immune responses will facilitate the development of new and innovative therapeutics for future periodontal treatments.

Candida albicans binds to saliva proteins selectively adsorbed to silicone

Explanted voice prostheses obtained from 5 patients at the time of prosthesis replacement were consistently colonized by yeast, in particular Candida albicans. A simple, reproducible, in vitro model of C. albicans adherence to saliva-coated voice prosthesis silicone was developed. Whole saliva promoted adherence of C. albicans to silicone in a dose-dependent manner. Saliva rinses from voice prosthesis patients also promoted binding of C. albicans to silicone in vitro (mean adherence 14.9% +/- 2.8% of input C. albicans cells). This was significantly higher than C. albicans adherence to silicone in the absence of saliva (P < .001) or adherence promoted by saliva rinses from healthy volunteers (P < .005). Polyacrylamide gel electrophoresis analysis and a blot overlay adherence assay revealed that certain salivary proteins were selectively adsorbed to silicone and that C. albicans yeast cells adhered specifically to the adsorbed salivary proteins.

Antibody responses to Porphyromonas gingivalis hemagglutinin A and outer membrane protein in chronic periodontitis

BACKGROUND

Hemagglutinin and outer membrane protein (OMP) are major virulence factors associated with colonization of Porphyromonas gingivalis in the gingival crevice. The genes for the 200-kDa antigenic protein (200-kDa AP) and 40-kDa OMP of P. gingivalis have been successfully cloned. Additionally, the 200-kDa AP gene has been shown to constitute the hemagglutinin A (hagA) gene of P. gingivalis. Therefore, this study was constructed to evaluate the distributions and serum levels of immnoglobulin G (IgG) antibodies specific for 200-kDa AP and 40-kDa OMP in periodontitis patients.

METHODS

Fifty patients with chronic periodontitis and 59 controls without periodontal destruction were enrolled in this study. We cloned the genes for 200-kDa AP and 40-kDa OMP from P. gingivalis and constructed the purified recombinant proteins. Serum levels of IgG subclass antibodies specific for both recombinant 200-kDa and 40-kDa OMP were determined in patients and controls by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The serum IgG subclass distribution for patients and controls was IgG1>IgG4>IgG2>IgG3 in the anti-200-kDa AP response, which was almost identical to that in the anti-40-kDa OMP response. The patient group showed significantly higher serum IgG responses to the 40-kDa OMP than the control group (P<0.01). In contrast, IgG subclass responses to the 200-kDa AP were not different between the patients and controls. Serum levels of antibodies reactive with both 200-kDa and 40-kDa proteins did not have a significant association with mean probing depth.

CONCLUSION

These results suggested that serum IgG responses against P. gingivalis OMP rather than the hagA may be more active in chronic periodontitis.

A single-chain fragment variable recombinant antibody against F5 fimbria of enterotoxigenic Escherichia coli inhibits agglutination of horse red blood cells induced by F5 protein

Bovine colibacillosis caused by enterotoxigenic Escherichia coli (ETEC) is a worldwide problem. Adhesion of ETEC to intestinal cell receptors mediated by the surface protein F5 fimbriae is the initial step in the establishment of colibacillosis. Prevention of ETEC F5(+) adhesion to enterocytes protects newborn calves against collibacillosis. On the enterocytes, the F5 fimbriae bind to a ganglioside that is also found on horse red blood cells. Thus, the presence of F5 fimbriae induces haemagglutination, which is useful as an indicator in a functional assay system. In this study, recombinant anti-F5 scFv antibody fragment produced in E. coli HB2151 reacted with F5 fimbriae in ELISA and Western immunoblot, and prevented haemagglutination induced by the binding of the F5 fimbriae to its natural host receptors on horse red blood cells. Given the ease with which recombinant antibodies can be mass-produced, the presently described scFv may hold promise as a prophylactic agent for colibacillosis.

Immune responses and vaccination against periodontal infections

BACKGROUND

The infectious aetiology of periodontitis is complex and no curative treatment modality exists. Palliative therapy is available.

AIMS

To review the evidence that active or passive immunization against periodontitis provides immune protection.

MATERIAL AND METHODS

PubMed (Medline), the National Institutes of Health, the Food and Drug Administration, and the Center for Disease Control electronic databases were searched to extrapolate information on immune responses to immunization against periodontitis.

RESULTS

Studies in non-human primate models using ligature-induced experimental periodontitis suggest that antibody responses by active immunization against Porphyromonas gingivalis can safely be induced, enhanced, and obtained over time. Immune responses to whole bacterial cell and purified protein preparations considered as vaccine candidates have been evaluated in different animal models demonstrating that there are several valid vaccine candidates. Data suggest that immunization reduces the rate and severity of bone loss. It is also, temporarily, possible to alter the composition of the subgingival microflora. Natural active immunization by therapeutic interventions results in antibody titre enhancement and potentially improves treatment outcomes. Passive immunization of humans using P. gingivalis monoclonal antibodies temporarily prevents colonization of P. gingivalis. Probiotic therapy may be an alternative approach. Regulatory and safety issues for human periodontal vaccine trials must be considered. Shared infectious aetiology between periodontitis and systemic diseases may enhance vaccine effort developments.

CONCLUSIONS

Proof of principle that active and passive immunization can induce protective antibody responses is given. The impact of natural immunization and passive immunization in humans should be explored and may, presently, be more feasible than active immunization studies.

Sequence Analysis of Two ScFv Genes of MAbs AgainstStreptococcus mutansGlucosyltransferase

Streptococcus mutans glucosyltransferases (GTFs) are considered to be the principal etiological agents of dental caries. Water-insoluble glucans (WIG) synthesized by those GTFs mediate sucrose-enhanced colonization for the bacterium on tooth surfaces and form dental plaque. GTFs have two functional domains, that is, an N-terminal catalytic sucrose-binding domain involved in sucrose hydrolysis and a C-terminal glucan-binding domain involved in the binding of the synthesized glucan polymer. Two hybridomas, each producing a monoclonal antibody (MAb) that inhibits the WIG synthesis by WIG synthesized GTF (GTF-I), were constructed. Those MAbs, P126 and P136, were shown to be able to recognize the different epitope domains in GTF; P126 recognized the N-terminal region, whereas P136 recognized the C-terminal region. We previously constructed two single chain fragments of immunoglobulin variable regions (ScFvs), which are capable of inhibiting GTF activity, from mice hybridomas producing P126 and P136. In the present study, we analyzed the nucleotide sequences of molecularly cloned ScFv genes (named ScFv/P126 and ScFv/P136), compared them in three complementarity- determining regions (CDRs), and also located their gene loci originate. Our results showed no particular relationship between the two ScFvs, and suggested the use of a certain type of VH or VL gene segment as well as possible evidence of the ability of these two MAbs to recognize different epitopes of GTF proteins.

Inhibition of biofilm formation by monoclonal antibodies against Staphylococcus epidermidis RP62A accumulation-associated protein

Staphylococcus epidermidis expresses a 140-kDa cell wall-bound protein accumulation-associated protein (AAP) to adhere to and accumulate as a biofilm on a surface. Potentially blocking AAP with a monoclonal antibody (MAb) could reduce or eliminate S. epidermidis bacterial colonization of biomedical devices. Here, we report on our efforts to (i) isolate AAP, (ii) generate MAbs against AAP, and (iii) determine the efficacy of MAbs to inhibit S. epidermidis biofilm formation. An M7 S. epidermidis mutant, reportedly deficient in AAP expression, was used as a negative control. Postinoculation murine sera, containing polyclonal antibodies against AAP, were able to reduce S. epidermidis biofilm formation by 54%. Select MAbs against AAP were able to reduce S. epidermidis by no more than 66%. Two MAb mixtures, 12C6/12A1 and 3C1/12A1, reduced S. epidermidis accumulation up to 79 and 87%, respectively, significantly more than individual MAbs. Contrary to a previous report, biofilm-deficient S. epidermidis mutant M7 expressed a 200-kDa protein on its cell wall that specifically bound AAP MAbs. Peptide characterization of this M7 protein by microcapillary reversed-phase high-pressure liquid chromatography-nanoelectrospray tandem mass spectrometry resulted in 53% homology with AAP. Ongoing studies will elucidate the dynamic expression of AAP and the M7 200-kDa protein in order to define their roles in biofilm formation.

Targeting of Porphyromonas gingivalis with a bispecific antibody directed to FcalphaRI (CD89) improves in vitro clearance by gingival crevicular neutrophils

Phagocytosis and killing of pathogens by polymorphonuclear neutrophils (PMN) from gingival crevicular fluid (GCF) is diminished in chronic periodontitis patients. As an approach to improve targeting of PMN toward a periodontopathogen, Porphyromonas gingivalis, the efficacy of a bispecific antibody (BsAb) directed against both recombinant 130 kDa hemagglutinin domain (r130k-HMGD) of P. gingivalis, and PMN Fc receptor (FcR) was evaluated. GCF PMN exhibited higher IgA FcR (FcalphaRI) levels, and lower IgG FcR (FcgammaRIIa and FcgammaRIIIb) levels than PB PMN. Functional studies revealed that GCF PMN exhibited a higher capacity to phagocytose and kill P. gingivalis opsonized with a BsAb targeting P. gingivalis r130k-HMGD to FcalphaRI as compared to an anti-r130k-HMGD antibody. However, phagocytosis and killing activity of PB PMN that were incubated with the two antibodies proved comparable. These data support targeting of pathogens toward FcalphaRI as an option to improve antibacterial immunity in chronic periodontitis patients.

The Trans-Chromosomic Mouse-Derived Human Monoclonal Antibody Promotes Phagocytosis ofPorphyromonas gingivalisby Neutrophils

BACKGROUND

As a safe immunotherapeutic approach, human monoclonal antibody (hMAb) may be effective in clearing periodontopathic bacteria. The trans-chromosomic (TC) technology has recently been applied to construction of the TC mouse, which enables us to incorporate entire human chromosome fragments containing immunoglobulin (Ig) gene cluster. The aim of this study is to establish TC mouse-derived hMAb, and to test the in vitro opsonophagocytic activity.

METHODS

Human Ig-producing TC mouse was immunized by recombinant 40-kDa outer membrane protein (r40-kDa OMP) of Porphyromonas gingivalis 381, and the spleen cells were fused with the mouse myeloma cell line. The specificity of antir40- kDa OMP hMAb was evaluated with the enzyme-linked immunosorbent assay (ELISA) and surface plasmon resonance assays. Flow cytometric analyses were performed to assess the opsonophagocytic activity.

RESULTS

We successfully constructed 99 IgG isotype clones (IgG1: 84; IgG2: 11; IgG4: four clones), which were specifically reactive with r40-kDa OMP. The anti-r40-kDa OMP IgG1 hMAbs promoted phagocytosis of P. gingivalis by neutrophils. Futhermore, an increased opsonophagocytic activitity of anti-r40-kDa OMP IgG1 hMAbs was observed not only in P. gingivalis 381, but also in the W50, W83, and Su63 strains.

CONCLUSION

Our results document the TC mouse-derived hMAb to promote neutrophil phagocytosis of P. gingivalis, suggesting an immunotherapeutic option for clearance of P. gingivalis.

Construction of novel human monoclonal antibodies neutralizing Porphyromonas gingivalis hemagglutination activity using transgenic mice expressing human Ig loci

Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. One potential virulence factor, hemagglutinin, may mediate bacteria attachment onto and penetration into host cells, as well as agglutinate and lyses erythrocytes to intake heme, an absolute requirement for growth. Toward the development of passive immunotherapy, the construction of a human type monoclonal antibody, which is capable of inhibiting the hemagglutinating ability, will be significant and important. The human mAbs, both exhibiting a high degree of specificity and affinity against the recombinant 130 kDa hemagglutinin domain protein have been prepared using XenoMouse technology. The constructed Xeno-mAbs, IgG2 subclass, significantly inhibited hemagglutination of P. gingivalis and its vesicles. The newly constructed Xeno-mAbs may prove to be useful for the development of passive immunization against periodontal diseases caused by P. gingivalis infection, pending the results of fertility study in disease mode.

Gene expression profiling of pulpal tissue reveals the molecular complexity of dental caries

High-throughput characterisation of the molecular response of pulpal tissue under carious lesions may contribute to improved future diagnosis and treatment. To identify genes associated with this process, oligonucleotide microarrays containing approximately 15,000 human sequences were screened using pooled total RNA isolated from pulpal tissue from both healthy and carious teeth. Data analysis identified 445 genes with 2-fold or greater difference in expression level, with 85 more abundant in health and 360 more abundant in disease. Subsequent gene ontological grouping identified a variety of processes and functions potentially activated or down-modulated during caries. Validation of microarray results was obtained by a combination of real-time and semi-quantitative PCR for selected genes, confirming down-regulation of Dentin Matrix Protein-1 (DMP-1), SLIT 2, Period-2 (PER 2), Period-3 (PER 3), osteoadherin, Glypican-3, Midkine, activin receptor interacting protein-1 (AIP 1), osteoadherin and growth hormone receptor (GHR), and up-regulation of Adrenomedullin (ADM), Interleukin-11 (IL-11), Bone sialoprotein (BSP), matrix Gla protein (MGP), endothelial cell growth factor-1 (ECGF 1), inhibin beta A and orosomucoid-1 (ORM 1), in diseased pulp. Real-time PCR analyses of ADM and DMP-1 in a panel of healthy and carious pulpal tissue and also in immune system cells highlighted the heterogeneity of caries and indicated increased expression of ADM in neutrophils activated by bacterial products. In contrast, DMP-1 was predominantly expressed by cells native to healthy pulpal tissue. This study has greatly extended our molecular knowledge of dental tissue disease and identified involvement of genes previously unassociated with this process.

Production of functional ScFv inhibiting Streptococcus mutans glucosyltransferase activity from a hybridoma P126

Streptococcus mutans has been considered the principal etiologic agent of dental caries in humans. The glucosyltransferase-I (GTF-I), which synthesized adhesive water-insoluble glucans from sucrose, has been demonstrated to be an important cariogenic property. Water-insoluble glucans (WIG) synthesized by S. mutans GTF-I can mediate sucrose-enhanced colonization on tooth surfaces and form dental plaque. It has been suggested that inhibition of WIG synthesis decreases bacterial colonization and cariogenicity. Indeed, the use of GTF enzymes as a vaccine antigen resulted in protection from experimental dental caries in rodents. However, it is preferable to eliminate unwanted immune response during active immunization of humans. To prevent this incidence, we attempted to produce the single-chain variable fragment (ScFv) antibody against GTF-I to develop passive immunization for dental caries. Hybridomas producing monoclonal antibody (MAb) that inhibited WIG synthesis by GTF-I have been constructed. Using mRNA from an IgG1 hybridoma P126, cDNAs encoding the variable fragments of the L and H chains of IgG1 from the hybridoma P126 were cloned by RT-PCR-based techniques and then transformed into an Escherichia coli expression system. The purified ScFv antibody recognized the recombinant (r) GTF-I proteins and was capable of inhibiting the WIG synthesis of rGTF-I.

Inhibition of Hemagglutinating Activity by Monoclonal Antibody againstPorphyromonas gingivalis40-kDa Outer Membrane Protein

Periodontitis is a chronic inflammatory disease of periodontal tissues that results in alveolar bone loss, and Porphyromonas gingivalis, which has a high hemagglutinating activity, has been implicated as an important pathogen in the development of periodontitis. This bacterium has a high hemagglutinating activity. We previously succeeded in gene cloning the 40-kDa outer membrane protein (OMP) from P. gingivalis 381. Although recombinant (r) 40-kDa OMP itself did not show hemagglutinating activity, its polymeric form, constructed with a cross-linking reagent, significantly expressed that activity. Furthermore, an affinity-purified antibody against r40-kDa OMP inhibited the hemagglutinating activity of P. gingivalis vesicles. In the present study, in order to clarify the pathological role of 40-kDa OMP and develop passive immunotherapy, we examined the inhibitory effect of monoclonal antibodies (MAbs) against r40-kDa OMP on the hemagglutinating activity of P. gingivalis vesicles. The MAbs reacted with r40-kDa OMP, the outer membrane fraction, vesicles, and P. gingivalis cell extracts, and significantly inhibited the hemagglutinating activities of the polymeric r40-kDa OMP as well as of P. gingivalis vesicles. These findings suggest that MAbs against 40-kDa OMP may be useful for the development of passive immunotherapy and for assessing treatment for periodontal diseases caused by P. gingivalis infection.

Subcloning of the 200-kDa Porphyromonas gingivalis antigen gene and inhibition of hemagglutination by an antibody against the recombinant protein

Porphyromonas gingivalis is a major etiologic agent of periodontitis and exhibits hemagglutinating and adherence activities. We previously succeeded in molecular cloning the 200-kDa cell-surface antigenic protein (200-k AP), designated pMD101, that is recognized in sera from periodontitis patients, and identified the 200-k AP as a hemagglutinin A (HagA) derivative. HagA is one of the hemagglutinins known to be a useful vaccine against periodontitis. HagA has four large, contiguous, direct repeats and the repeat unit is believed to contain the hemagglutinin domain. Because production of 200-k AP was low in the Escherichia coli host, it was difficult to obtain large amounts of recombinant protein. In this study, we attempt to subclone the gene encoding the useful antigen from pMD101 in an effort to obtain large quantities. A subclone, designated pMD160, encoding a fusion protein of 80-kDa HagA and maltose-binding protein was successfully constructed, and the novel clone produced relatively large amounts of recombinant protein. DNA nucleotide sequences of the pMD160 insert demonstrated that the 80-kDa protein contained a short hemagglutinin motif and a direct repeat unit region. The recombinant protein was purified to homogeneity and rabbit antiserum was raised. The antibody was capable of inhibiting the hemagglutinating activity of P. gingivalis. These findings suggest that novel 80-kDa HagA derivative proteins can be produced efficiently from E. coli hosts and these may be useful in developing immunotherapy against periodontitis infected by P. gingivalis.

Molecular genetic analysis of the virulence of oral bacterial pathogens: an historical perspective

This review will focus on the impact of molecular genetic approaches on elucidating the bacterial etiology of oral diseases from an historical perspective. Relevant results from the pre- and post-recombinant DNA periods will be highlighted, including the roles of gene cloning, mutagenesis, and nucleotide sequencing in this area of research. Finally, the impact of whole-genome sequencing on deciphering the virulence mechanisms of oral pathogens, along with new approaches to control these organisms, will be discussed.

Production of monoclonal antibody inhibiting dipeptidylaminopeptidase IV activity of Porphyromonas gingivalis

Porphyromonas gingivalis is a Gram-negative anaerobic bacterial species implicated as an important pathogen in the development of adult periodontitis. We previously cloned a gene encoding dipeptydilaminopeptidase IV (DAPIV) from P. gingivalis. In the present study, for immunological diagnosis and development of passive immunization, we produced a mouse monoclonal antibody (MAb) capable of inhibiting the DAPIV activity of P. gingivalis using highly purified recombinant DAPIV as an immunogen. The constructed MAb, designated as MAb-Pg-DAP-1, significantly inhibited DAPIV activity in P. gingivalis, as well as slightly inhibited that in other gram-negative bacteria such as Porphyromonas endodontalis and Prevotella loesheii, whereas no inhibition was seen in the gram-positive bacteria Streptococcus mutans and Actinomyces viscosus. Furthermore, the MAb did not inhibit DAPIV enzyme activity in human serum. This novel MAb may be useful for the development of immunological diagnosis capability and in passive immunization.

Production of a single-chain variable fraction capable of inhibiting the Streptococcus mutans glucosyltransferase in Bacillus brevis: construction of a chimeric shuttle plasmid secreting its gene product

Periodontitis and dental caries are common oral diseases, in these days, and the passive immunization is one of the most effective approaches for prevention. For this purpose, we have constructed mouse and human monoclonal antibodies to inhibit the Porphyromonas gingivalis-associated hemagglutination and coaggregation. In addition, an artificial antibody, single-chain variable fraction, or scFv, which also inhibited the hemagglutination, was constructed. Specifically for dental caries, mouse and human monoclonal antibodies that inhibited the glucosyltransferase (GTF) activity, responsible for biofilm formation, were also constructed. The advantage of scFv over the native antibody is that the former molecule does not induce possible side-effects due to Fc, such as autoimmune disease, because it consists only of variable regions originating from both heavy and light chains. To increase the abilities of the antibody preparations, we attempted to construct an additional scFv using Bacillus brevis, a secretion-proficient gram-positive bacterium, as a host cell. An scFv protein possessing the same biological activity as that of the parental antibody was successfully secreted from a B. brevis transformant following the construction of a chimeric shuttle plasmid, which was accomplished by employing a new heterodimer system.

Human monoclonal antibody inhibits Porphyromonas gingivalis hemagglutinin activity

BACKGROUND

Porphyromonas gingivalis has been implicated as an important pathogen in the development of chronic periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. One potential virulence factor, hemagglutinin, may mediate bacteria attachment onto and penetration into host cells, as well as agglutinate and lyse erythrocytes to intake heme, an absolute requirement for growth. We previously cloned the gene encoding the 130 kDa hemagglutinin domain (130k HMGD) and identified its functional domain. The construction of a human monoclonal antibody that is capable of inhibiting the hemagglutinating ability is significant and important toward the development of passive immunotherapy.

METHODS

Human lymphocytes isolated from a donor, who had high antibody titer against the recombinant 130k HMGD (r130k HMGD), were immortalized by Epstein-Barr virus, and specific antibody-producing B cells were established by panning using the r130k HMGD.

RESULTS

The constructed HuMAb-HMGD1, IgG subclass, recognized the r130k HMGD as well as the 43 and 49 kDa major bands in P. gingivalis cells and vesicles. The HuMAb-HMGD1 significantly inhibited hemagglutinating activity of P. gingivalis vesicles in a dose-dependent manner. Furthermore, the HuMAb-HMGD1 recognized the synthetic peptide, EGSNEFAPVQNLTGSSVG, which contains the functional domain of 130k HMGD.

CONCLUSION

The newly constructed HuMAb-HMGD1 may prove to be useful for the development of passive immunization against periodontal diseases caused by P. gingivalis infection, pending the results of fertility study in disease mode.

Monoclonal antibody againstPorphyromonas gingivalishemagglutinin inhibits hemolytic activity

Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis. This bacterium possesses hemagglutinating and hemolytic activities to attach and lyse erythrocytes. Hemolysis by this oral pathogen functions to provide heme-containing molecules for growth in the periodontal pocket. We previously constructed a monoclonal antibody using P. gingivalis vesicles as the immunogen, designated as MAb-Pg-vc, which inhibited vesicle-associated hemagglutinating activity. Furthermore, we cloned the gene encoding 130-kDa hemagglutinin (130-kDa HAG) and identified its functional motif for attachment to erythrocytes. Generally, bacterial cell attachment to erythrocytes is an important initial step for expressing hemolysis activity. In the present study, we examined the effect of MAb-Pg-vc on the hemolytic activity of P. gingivalis cells. The MAb-Pg-vc significantly inhibited the hemolytic activity and, further, this inhibitory activity was reduced by the synthetic peptide of the 130-kDa HAG functional motif.