Human immune responses to oral microorganisms. II. Serum antibody responses to antigens from Actinobacillus actinomycetemcomitans and the correlation with localized juvenile periodontitis

Aggregatibacter (Actinobacillus) actimycetemcomitans leukotoxin and human periodontitis - A historic review with emphasis on JP2

Aggregatibacter (Actinobacillus) actimycetemcomitans (Aa) is a gram-negative bacterium that colonizes the human oral cavity and is causative agent for localized aggressive (juvenile) periodontitis (AgP). In the middle of 1990s, a specific JP2 clone of belonging to the cluster of serotype b strains of Aa with highly leukotoxicity (leukotoxin, LtxA) able to kill human immune cells was isolated. JP2 clone of Aa was strongly associated with in particularly in rapidly progressing forms of aggressive periodontitis. The JP2 clone of Aa is transmitted through close contacts. Therefore, AgP patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontitis lesions are relatively high. Furthermore, timely periodontal treatment, including periodontal surgery supplemented by the use of antibiotics, is warranted. More importantly, periodontal attachment loss should be prevented by early detection of the JP2 clone of Aa by microbial diagnosis testing and/or preventive means.

Contemporary concepts in the diagnosis of periodontal disease

Periodontitis is an inflammatory disease of bacterial origin that results in the progressive destruction of the tissues that support the teeth, specifically the gingiva, periodontal ligament, and alveolar bone. The diagnosis of periodontal disease currently relies almost exclusively on clinical parameters and traditional dental radiography. In this article, the authors review current diagnostic techniques and present new approaches and technologies that are being developed to improve assessment of this common condition.

Adaptive immune response in osteoclastic bone resorption induced by orally administered Aggregatibacter actinomycetemcomitans in a rat model of periodontal disease

There is mounting evidence that innate and adaptive immunity are critical for periodontal disease-mediated bone resorption. These studies examined the role of B and CD4 T cells in adaptive immunity of rats infected with Aggregatibacter actinomycetemcomitans (Aa). Sprague-Dawley male rats were fed Aa-containing mash or control-mash for 2 weeks. B and CD4 T cells were obtained from draining lymph nodes at 2, 4 and 12 weeks, postinoculation. Quantitative polymerase chain reaction-based messenger RNA expression was conducted for 89 cytokine family genes. Disease-relevance of the differentially expressed genes was assessed using a biological interaction pathway analysis software. B and CD4 T cells of Aa-infected rats increased and were activated, resulting in enhanced isotype-switched serum immunoglobulin G by 2 weeks postinoculation. Bone resorption was evident 12 weeks after Aa-feeding. In B cells, interleukin-2 (IL-2), macrophage-inhibiting factor, IL-19, IL-21, tumor necrosis factor (TNF), CD40 ligand (CD40L), CD70, bone morphogenetic protein 2 (BMP2), BMP3, and BMP10 were upregulated early; while IL-7, Fas ligand (FasL), small inducible cytokine subfamily E1, and growth differentiation factor 11 (GDF11; BMP11) were upregulated late (12 weeks). BMP10 was sustained throughout. In CD4 T cells, IL-10, IL-16, TNF, lymphotoxin-beta (LTbeta), APRIL, CD40L, FasL, RANKL and osteoprotegerin were upregulated early, whereas IL-1beta, IL-1RN, IL-1F8, IL-24, interferon-alpha1, GDF11 (BMP11), and GDF15 were upregulated late (12 weeks). Adaptive immunity appears crucial for bone resorption. Several of the deregulated genes are, for the first time, shown to be associated with bone resorption, and the results indicate that activated B cells produce BMP10. The study provides a rationale for a link between periodontal disease and other systemic diseases.

Infection patterns in chronic and aggressive periodontitis

BACKGROUND

We revisited the postulate that localized aggressive periodontitis (LAP) patients have robust serum antibody (ab) responses to periodontal pathogens while patients with generalized aggressive periodontitis (GAP) show weak responses. We also studied ab responses in localized chronic (LCP) and generalized chronic periodontitis (GCP).

METHODS

Fifty-seven patients (14-74 years, 25% male, 70% Hispanic, 26% African American) were studied (15 LAP, 19 GAP, 11 LCP, 12 GCP patients). Three plaque samples/subject were analysed with respect to 15 species, and serum immunoglobulin G (IgG) responses to the same bacteria were determined. Ab responses were expressed as log-transformed titres, and "infection ratios", i.e., log-transformed ratios of ab titre over the subject-based mean bacterial load for the homologous species.

RESULTS

The results failed to corroborate the postulate that LAG patients have robust responses to infecting agents while GAP subjects exhibit weak responses. This held true for ab to "red complex", "orange complex", and health-associated species, and for both titres and infection ratios. Similarly, no differences were found between ab titres or infection ratios in chronic and aggressive periodontitis, or their extent-based subdivisions.

CONCLUSIONS

A distinction between the two principal categories of the current periodontitis classification cannot be established by the study of infection patterns.

Three case reports of aggressive periodontitis associated with Porphyromonas gingivalis in younger patients

The terms 'early onset periodontitis' (EOP) and 'juvenile periodontitis' (JP) were replaced by that of 'aggressive periodontitis' in a recent international workshop for the classification of periodontal diseases and conditions. The chief etiologic agent for aggressive periodontitis is considered to be Actinobacillus actinomycetemcomitans in localized juvenile periodontitis. Porphyromonas gingivalis is also mentioned as the etiologic agent of the aggressive periodontitis, although to date its role remains questionable. This communication describes three cases of aggressive periodontitis found to be associated with P. gingivalis but not A. actinomycetemcomitans by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Our findings clarify the role of P. gingivalis as an etiologic agent in this type of periodontitis and confirm its inclusion in the current definition of aggressive periodontitis.

Identification of six major outer membrane proteins from Actinobacillus actinomycetemcomitans

We have identified six major sarcosyl-insoluble outer membrane proteins (Omp) of Actinobacillus actinomycetemcomitans Y4, and designated them as Omp100, Omp64, Omp39, Omp29, Omp18 and Omp16 according to the molecular mass. A similar N-terminal sequence was found in the first 15 amino acid residues of Omp16 and Omp18. The N-terminal sequence of Omp29 matched perfectly with the sequence previously identified. We cloned and determined the DNA sequences of three complete genes encoding Omp100, Omp64 and Omp18/16, and one incomplete gene encoding Omp39. Each Omp revealed homologies with some bacterial virulence factors responsible for adhesion, invasion, serum resistance, or protein antigenicity. Serum from patients with periodontitis suspected to be related to A. actinomycetemcomintans infection strongly reacted with Omp100, Omp29 and Omp16 as did serum from mice immunized with A. actinomycetemcomitans Y4 whole bacteria. These findings suggest that Omps of A. actinomycetemcomitans can be associated with periodontal disease.

Periodontal disease as a specific, albeit chronic, infection: diagnosis and treatment

Periodontal disease is perhaps the most common chronic infection in adults. Evidence has been accumulating for the past 30 years which indicates that almost all forms of periodontal disease are chronic but specific bacterial infections due to the overgrowth in the dental plaque of a finite number of mostly anaerobic species such as Porphyromonas gingivalis, Bacteroides forsythus, and Treponema denticola. The success of traditional debridement procedures and/or antimicrobial agents in improving periodontal health can be associated with the reduction in levels of these anaerobes in the dental plaque. These findings suggest that patients and clinicians have a choice in the treatment of this overgrowth, either a debridement and surgery approach or a debridement and antimicrobial treatment approach. However, the antimicrobial approach, while supported by a wealth of scientific evidence, goes contrary to centuries of dental teaching that states that periodontal disease results from a "dirty mouth." If periodontal disease is demonstrated to be a risk factor for cardiovascular disease and stroke, it will be a modifiable risk factor since periodontal disease can be prevented and treated. Since the antimicrobial approach may be as effective as a surgical approach in the restoration and maintenance of a periodontally healthy dentition, this would give a cardiac or stroke patient and his or her physician a choice in the implementation of treatment seeking to improve the patient's periodontal condition so as to reduce and/or delay future cardiovascular events.

Immunodominant antigens in periodontal disease: a real or illusive concept?

The humoral arm of the immune system provides protection from many medically significant pathogens. The antigenic epitopes of the pathogens which induce these responses, and the subsequent characteristics of the host response, have been extensively documented in the medical literature, and in many cases have resulted in the development and implementation of effective vaccines or diagnostic tests. There is a substantial body of literature on the humoral immune response in periodontal disease, which is targeted at micro-organisms present within periodontal pockets. However, the significance and specificity of the immune response in periodontal disease have proved difficult to elucidate, due to the large number of potential pathogens in the plaque biofilm and the apparent commensal nature of many of these opportunistic pathogens. This review addresses our current knowledge of the approaches and strategies which have been used to elucidate and examine the concept of immunodominant antigens in medical infections and, more recently, periodontal disease. An identification/understanding of the immunodominant antigens would be informative with respect to: (i) the relative importance of the implicated pathogens, (ii) new approaches to immunological diagnosis, (iii) specific bacterial virulence determinants, (iv) natural protective responses, and (v) the selection of potential vaccine candidate antigens. We conclude that immunodominance of antigens in periodontal disease may be relevant to our understanding of periodontal disease pathogenesis, but due to the complexity and diversity of the 'pathogenic microbial ecology', it is currently an enigmatic topic requiring a multidisciplinary approach linking clinical, microbiological, and immunological investigations. We also conclude, after assessing the literature available on the topic of immunodominance, that it is a term that, if used, must be clearly defined and understood, since it is often used loosely, leading to a general misinterpretation by readers of oral and medical literature.

Detection rate of Actinobacillus actinomycetemcomitans on the permanent 1st molars of primary school children in Taiwan by polymerase chain reaction

BACKGROUND, AIMS

Actinobacillus actinomycetemcomitans (Aa) has been implicated as the putative micro-organism for localized juvenile periodontitis (LJP). The most distinct clinical features of LJP include severe angular bony defects of the mesial sides of permanent first molars and the onset of disease during puberty. Currently, no large-scale studies have been performed which address the change in detection rates of Aa on the mesial sides of permanent 1st molars following eruption and up to puberty.

METHOD

In this study, subgingival plaque samples were taken from the mesial pockets of 2 randomly selected permanent 1st molars from 328 primary school children and 50 adult staff, and analyzed by polymerase chain reaction (PCR) to detect Aa.

RESULTS

The results showed a 5.5% prevalence rate of Aa which increased after the eruption of 1st molars and peaked near puberty. There were no significant differences in the detection rates of Aa among different groups in terms of gender, plaque index (PII), and gingival index (GI); however, the higher detection rates of Aa were significantly associated with increased probing depths at p<0.05.

CONCLUSION

PCR analysis of the subgingival plaques demonstrated a prevalence of Aa which peaked near puberty, suggesting that Aa may be important for LJP in Taiwan.

"Checkerboard" assessments of periodontal microbiota and serum antibody responses: a case-control study

BACKGROUND

We explored the association between subgingival microbial profiles and serum IgG responses to periodontal microbiota in relation to clinical periodontal status.

METHODS

One hundred thirty-one (131) periodontitis patients aged 29 to 74 years (mean 51.8) were age- and gender-matched with 74 periodontally intact controls (range 26 to 77, mean 49.3). Smoking habits and health history were recorded and assessments of plaque, bleeding on probing, probing depth, and attachment level were performed at 6 sites per tooth on all present teeth, excluding third molars. Subgingival plaque samples were obtained from each tooth in one upper and one lower quadrant (maximum 14 samples/subject; 2,440 samples total) and analyzed with respect to 19 species by means of whole genomic DNA probes. Serum IgG antibodies against the same 19 species were assessed by an immunoassay.

RESULTS

Cases displayed an average of 22.7 teeth, 20.3 sites with probing depth > or =6 mm, and 18.9 sites with attachment loss > or =6 mm. Corresponding figures for controls were 27.1, 0.1, and 1.0, respectively. Heavy smoking was 3 times more frequent among cases than controls (32.1% versus 9.6%). Higher levels of Porphyromonas gingivalis, Porphyromonas endodontalis, Prevotella intermedia, Prevotella nigrescens, Prevotella melaninogenica, Bacteroides forsythus, Fusobacterium nucleatum, Treponema denticola, Eubacterium nodatum, Peptostreptococcus micros, and Campylobacter rectus were found in cases and higher levels of Eikenella corrodens, Veillonella parvula, and Actinomyces naeslundii in controls. Cases displayed higher IgG levels against P. gingivalis and Actinobacillus actinomycetemcomitans, while controls displayed higher levels against F. nucleatum, T. denticola, E. nodatum, and Capnocytophaga ochracea. Positive correlations between bacterial colonization and antibody responses were identified for 9 species in controls. In cases, however, statistically significant correlations were observed for only 3 species out of which only one was positive (V. parvula). Both bacterial levels and antibody responses declined in ages over 55 years. A logistic regression employing selected elements of bacterial colonization and antibody responses as independent variables resulted in 81.1% correct diagnosis, with sensitivity of 83.1%, specificity of 77.8%, positive predictability of 86%, and negative predictability of 73.7%. Smoking did not reach statistical significance in this model.

CONCLUSION

A combined microbial colonization/antibody response profile can effectively discriminate between periodontitis patients and periodontally intact controls.

Early-onset periodontitis

In 1993, the 1st European Workshop on Periodontology explicitly recognized that there was insufficient knowledge to differentiate truly different forms of periodontal disease from differences in the presentation/severity of the same disease. In spite of recent progress in our understanding of periodontal diseases, the issue is far from having been resolved. Classification of periodontal diseases, therefore, remains based upon the definition of specific clinical syndromes. Early-onset periodontitis (EOP) is one such syndrome and comprises a group of pathological conditions leading to loss of periodontal tissues early in life. The notion that classifies periodontitis syndromes as "early-onset" or "adult" is primarily epidemiological in nature and is based on the observation that periodontitis is rather infrequent in children and young adults. Nevertheless, considerable epidemiological evidence indicates that periodontitis does affect children and young adults to a level of severity that may lead to premature exfoliation of primary and/or permanent teeth. Clinical presentation of periodontitis early in the life of an individual is thought to indicate that the etiologic agents have been able to cause considerable tissue damage over a relatively short period of time. It also implies either infection with highly virulent bacteria and/or a highly susceptible subject. The purpose of this review is to discuss the criteria generally utilized to classify EOP, provide the rationale to designate EOP as a distinct disease entity, and to review the evidence justifying a subclassification into particular subgroups of EOP.

Evidence-based care in orthodontics and periodontics: a review of the literature

BACKGROUND

In this article, the author reviews the evidence-based literature in the fields of periodontics and orthodontics to clarify the relationship between orthodontic tooth movement and various types of common periodontal disorders.

TYPES OF STUDIES REVIEWED

The first section is a review of the literature on common periodontal disorders. The second is a review of evidence-based studies in the combined fields of orthodontics and periodontics, with a focus on orthodontic treatment possibilities, limitations and risks inherent in patients with periodontal disorders, particularly active periodontal disease.

RESULTS

The literature on orthodontic tooth movement as it relates to periodontal disease shows that proper orthodontic treatment in patients with excellent oral hygiene and the absence of significant periodontal disorders should not pose any significant periodontal risk. In the presence of poor oral hygiene, however, and under circumstances of certain types of periodontal disorders, fixed orthodontic appliances and tooth movement can contribute to significant deleterious periodontal consequences.

CLINICAL IMPLICATIONS

This review provides a clear understanding of what is known about orthodontic treatment possibilities, limitations and inherent risks in patients who may have certain types of periodontal disorders. It also underscores the importance of teamwork among the restorative dentist, periodontist and orthodontist when planning treatment for these patients. The author also offers a specific patient management protocol for this interdisciplinary dental team to follow.

Rapid evaluation of serum and gingival crevicular fluid immunoglobulin G subclass antibody levels in patients with early-onset periodontitis using checkerboard immunoblotting

A method was developed to evaluate the presence of immunoglobulin G (IgG) subclass (1-4) antibody to Actinobacillus actinomycetemcomitans, serotype b (strain Y4) in patients with early-onset periodontitis on a single nitrocellulose membrane. Sera from 30 early-onset periodontitis patients and gingival crevicular fluid samples from 2 patients were collected and tested with four different preparations of A. actinomycetemcomitans (Y4). The principle steps of the assay are: a) binding of the bacterial antigen (Y4) and the anti-human IgG antibody (capture antibody) in parallel lanes on nitrocellulose membranes; b) incubation of known concentrations of the IgG subclasses 1, 2, 3 and 4, as well as a dilution of serum and/or gingival crevicular fluid from patients in lanes perpendicular to the antigen lanes; c) incubation of the membranes with the corresponding peroxidase conjugated anti-human IgG subclass secondary antibody; d) detection of positive signals by enhanced chemiluminescence. The blots were evaluated by visual comparison to a series of blots containing known concentrations of IgG subclasses. The method was used to rapidly screen a relatively large number of patient sera and gingival crevicular fluid samples for IgG subclasses in a cost-effective assay. The predominant IgG subclass found in early-onset periodontitis was IgG2.

Principles of evaluation of the diagnostic value of subgingival bacteria

This paper describes steps in the process of evaluating subgingival bacteria assays for the diagnosis of periodontal disease. The first step examines the infectious etiology of periodontal disease in pointing to specific oral bacteria as periodontal pathogens. Second is characterization of the laboratory test to detect and quantitate these pathogens as to sensitivity, specificity, and positive and negative predictive value. Third is the role of the laboratory test in the diagnosis of the different forms of periodontal disease which is related to the current clinical rather than microbiological definition of these diseases. The fourth and most important step is an analysis of the significance of subgingival bacterial tests in clinical decision-making.

Immunogenicity of Actinobacillus actinomycetemcomitans serotype b-specific polysaccharide-protein conjugate

To enhance the immunogenicity of capsular-like serotype b-specific polysaccharide antigen (SPA) of Actinobacillus actinomycetemcomitans, the purified antigen was coupled with bovine serum albumin via an adipic acid hydrazide functional group. The conjugate (SPA-bovine serum albumin) or the native SPA was administered subcutaneously or intranasally to BALB/c mice. Neither subcutaneous immunization with SPA emulsified in Freund adjuvant nor intranasal immunization with SPA and cholera toxin B subunit elicited any antibody responses to the polysaccharide antigen. High serum immunoglobulin M (IgM) and IgG responses to SPA were induced by subcutaneous immunization with SPA-bovine serum albumin in Freund adjuvant. Serum and salivary IgA responses to SPA in addition to IgM and IgG responses were induced by intranasal immunization with the conjugate and cholera toxin B subunit. To investigate the functional activity of SPA-specific antibodies, the opsonic activity of sera from BALB/c mice immunized with the conjugate was assessed by chemiluminescence assay using human polymorphonuclear leukocytes. Murine antisera efficiently opsonized A. actinomycetemcomitans serotype b in the assay, suggesting that antibodies to SPA of the organism might serve as a protective role.

Longitudinal changes in antibody avidity to Actinobacillus actinomycetemcomitans in periodontitis

Longitudinal investigations concerning immunological responses and periodontal disease activity support a relationship between serum antibody levels and the micro-organisms associated with dental plaque. To define this host response further, we studied the relationship of antibody avidity to Actinobacillus actinomycetemcomitans (Aa) in 11 adult periodontitis and 6 localized juvenile periodontitis (LJP) patients with Aa infections. Patients were monitored every 3-4 months for immunological and clinical variables including probing pocket depths (PD), bleeding on probing (BOP), plaque index (PLI), and the number of disease active sites (DA). Avidity indices were determined using an ELISA and significant changes from each patients' baseline level were determined. The results showed different response patterns between and within the patient groups. A subset of the subjects experienced significant changes in antibody avidity over time. Between group comparisons yielded no significant differences in the number of positive or negative avidity index changes, although there were more frequent changes in the disease active adult periodontitis group. There were also no significant correlations between clinical parameters and antibody avidity, although there were changes in the clinical parameters between baseline and significant avidity change points, and also between baseline and the determination of active disease. Further studies will be necessary to define fully the role of antibody avidity and its relationship to the pathogenesis of periodontal diseases.

Current concepts in diagnosis and treatment of periodontitis

This article describes some areas of periodontal research and current opinions regarding detection of disease progression, as well as risk indicators and risk factors associated with disease progression. Longitudinal probing of periodontal attachment level is considered the gold standard for detection of disease activity although there are problems with this concept. Digital subtraction radiography can assist in the detection of minor changes of alveolar bone height and density. Risk factors such as composition of subgingival plaque and gingival crevicular fluid, as well as the effect of smoking are discussed. Adjunctive treatment with both antibiotics and nonsteroidal anti-inflammatory drugs, systemic or local, seems to be helpful in some forms of disease. Immunization to prevent colonization of tooth surfaces and pockets by periodontal pathogens does not seem to be feasible in the near future.

Role of the capsular polysaccharide-like serotype-specific antigen in resistance of Actinobacillus actinomycetemcomitans to phagocytosis by human polymorphonuclear leukocytes

Serotype b-specific polysaccharide antigen (SPA) of Actinobacillus actinomycetemcomitans Y4 consists of D-fucose and L-rhamnose. To clarify the role of SPA in phagocytosis of the organism by human polymorphonuclear leukocytes (PMNs), monoclonal antibodies (MAbs) against SPA and SPA-defective mutants, which were constructed by inserting the transposon Tn916 into strain Y4, were used in a chemiluminescence (CL) assay and a phagocytic killing assay. The CL responses of human PMNs to strain Y4 were very low, and the organism was not killed by PMNs. In contrast, SPA-defective mutants induced strong CL responses. The addition of immunoglobulin G MAbs against Y4 SPA enhanced significantly both the CL responses to strain Y4 and the killing of the organism in the presence of complement. The CL responses to SPA-defective mutants were little affected by the addition of these MAbs. We conclude that SPA of A. actinomycetemcomitans plays an important role in the resistance to host defenses by PMNs.

Immunoglobulin G subclass response of juvenile periodontitis subjects to principal outer membrane proteins of Actinobacillus actinomycetemcomitans

The cell envelope of Actinobacillus actinomycetemcomitans includes a number of outer membrane proteins (OMPs) which appear to be important targets for immunoglobulin G (IgG) antibodies in sera from localized juvenile periodontitis (LJP) patients. In this study, we examined the subclass distribution of IgG antibodies reactive to the 16.6- and 29-kDa OMPs of A. actinomycetemcomitans in sera from LJP patients and periodontally healthy individuals. Antibody responses were determined in a quantitative enzyme-linked immunosorbent assay that employed human IgG subclass-restricted monoclonal antibodies. High-titer LJP sera (93% black; geometric mean titer, 32,673) were found to contain significantly elevated levels of IgG1, IgG2, and IgG3 antibodies to the 29-kDa OMP of A. actinomycetemcomitans, compared with those of low-titer LJP sera (mean titer, 1,421) and sera from periodontally healthy, race-matched control subjects. The concentration of IgG2 antibody to this protein was greater than or equal to the corresponding IgG1 concentration in 7 of 14 high-titer sera, although mean IgG1 and IgG2 concentrations were not significantly different. The concentrations of IgG1 and IgG2 antibodies to the 16.6-kDa protein were also significantly elevated in LJP sera, although of considerably lesser magnitude than that observed for the 29-kDa protein. The IgG2 response to the 29-kDa protein could not be attributed to the presence of IgG2 antibodies to lipopolysaccharide contaminants or to Fc-binding activity, nor does this molecule appear to be a glycoprotein. Hence, LJP subjects produce IgG2 antibodies, as well as IgG1 and IgG3 antibodies, directed to at least one of the major OMPs of A. actinomycetemcomitans.

Adoptive transfer of cloned T helper cells ameliorates periodontal disease in nude rats

We have previously described a T helper cell 2-type clone, A3, of rat T cells that provides help for antibody production to Actinobacillus actinomycetemcomitans in vitro and in vivo in normal (euthymic) isogeneic Rowett strain recipient rats. Adoptive transfer of this T helper cell clone to euthymic rats also protects them from periodontal bone loss induced by oral infection with A. actinomycetemcomitans. In the present study, to assess the cell requirement for protection, A3 clone T lymphocytes (10(6)) or naive lymph node (6 x 10(4)) T cells, or A3 plus naive lymph node T cells (6 x 10(4)) were adoptively transferred to groups (n = 7-9) of 30-day-old Rowett athymic nude (rnu/rnu) rats. All recipients were also immunized (intraperitoneally) with 10(7) killed A. actinomycetemcomitans on the day of T cell transfer and orally infected with these bacteria on each of the next 5 days. Recipients of the combined A3+lymph node T cell transfer showed significantly increased serum immunoglobulin G (IgG) and IgM antibody to A. actinomycetemcomitans and in vitro proliferation of spleen lymphocytes to A. actinomycetemcomitans as antigen compared with nude animals receiving lymph node T cells only. Although other possibilities are discussed, we inferred that these differences might be due to successful population of the congenitally athymic rats by A3 clone cells given with a small number of normal autologous naive lymph node T cells. The result of this co-transfer of naive T cells with the A3 clone cells seemed to be greatly increased antibody production and protection from periodontal bone loss.

Macaca nemestrina: a non-human primate model for studies of periodontal disease

The non-human primate Macaca nemestrina was evaluated for use as a potential model in periodontal research by study of 16 animals. Using one incisor, premolar, and molar per quadrant, we measured supragingival plaque, severity of gingival inflammation, and pocket depth, and analyzed the subgingival flora. Serum IgG titers and avidities to antigens of Porphyromonas gingivalis (Pg) and Actinobacillus actinomycetemcomitans (Aa) were also assessed. Ten animals were between 13 and 24 years old, and six were between 4 and 5 years old. While mean gingival inflammation scores were significantly higher for older than for younger animals (2.2 vs 1.8, p < 0.05), mean plaque index scores and mean probing depths did not differ significantly. The animals harbored a subgingival microflora considered to be pathogenic for humans including Aa, Pg, Bacteroides forsythus, Prevotella intermedia I and II, Campylobacter recta and Fusobacterium nucleatum. Aa, however, was found only in the younger animals. All of the animals had serum IgG antibodies reactive with antigens of Pg and Aa, and titers for Pg but not for Aa were significantly higher in the older relative to the younger animals (t test p < 0.02). In contrast, antibody avidity did not significantly differ between the two groups. A combined clinical assessment index based on maximum probing depth, gingival index score, and tooth loss was used to assess the overall disease severity. Titers were positively associated with disease severity (Spearman's rank correlation 0.57, p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Titer and subclass distribution of serum IgG antibody reactive with Actinobacillus actinomycetemcomitans in localized juvenile periodontitis

Most patients with localized juvenile periodontitis (LJP) manifest serum IgG antibodies specifically reactive with antigens of Actinobacillus actinomycetemcomitans serotype b (Aa-b). Whether these antibodies are protective, destructive, or irrelevant to the progress of the disease remains unclear. We report results of studies aimed at assessing the subclass IgG responses in 35 LJP patients and 35 periodontally normal control subjects using well-characterized monoclonal antibody subclass reagents in an enzyme-linked immunosorbent assay. Our data show that the mean value for total IgG reactive with antigens of Aa-b was more than sevenfold higher for patients than for normal control sera (2349.6 micrograms/ml for patients vs 332.2 micrograms/ml for controls). Individual patients and control subjects were classified as high- or low-titer, using twice the median value for total anti-Aa-b IgG in control sera as the cutoff. Of 35 patients, 26 (74%) were high-titer, and 9 (26%) were low-titer. This compares to 5 normal control subjects (14%) high-titer and 30 (86%) low-titer. IgG2 accounted for the major quantitative response in both patients and control subjects. Indeed, the mean IgG2 values for both concentration and percentage of total specific IgG were greater than the combined values for specific anti-Aa-b IgG1, IgG3, and IgG4. Of the 26 high-titer sera, IgG2 predominated in 24, with IgG1 and IgG3 predominating in 1 each; IgG2 predominated in only 2 of the low-titer sera.

Longitudinal monitoring of humoral antibody in subjects with destructive periodontal diseases

Fifty-one subjects (16-61 years old) with evidence of prior destructive periodontal disease were monitored clinically and immunologically at bi-monthly intervals for up to 5 yr. Periodontal disease activity, determined as new attachment loss, was detected in 33 of these subjects. Only 4 of 51 subjects failed to show an elevated serum antibody level to any of the 18 subgingival species tested. The antibody level threshold established for periodontally healthy subjects was exceeded most often in diseased subjects with serum antibody to Actinobacillus sp., P. gingivalis, E. corrodens, C. concisus, F. nucleatum and P. intermedia in that order. In general, most serum antibody levels to subgingival species remained relatively consistent for periods as long as 5 yr. However, major increases and decreases in antibody could be detected to at most one or two species in individual subjects. In addition, prolonged, steady increases and decreases in antibody to specific species could be detected in certain subjects. These findings suggest that major changes occurring in serum antibody may reflect fluctuations in the nature of the infection. Differences were observed in the antibody level to specific species when subjects were divided into subsets on the basis of clinical criteria. These included high levels of antibody to A. actinomycetemcomitans Y4 in LJP and RPP subjects and to A. actinomycetemcomitans 29523 in LJP and GJP subjects.

Immunoglobulin G subclass response of localized juvenile periodontitis patients to Actinobacillus actinomycetemcomitans Y4 lipopolysaccharide

Sera from patients with localized juvenile periodontitis (LJP) often contain markedly elevated immunoglobulin G (IgG) antibody titers to serospecific determinants of the lipopolysaccharide (LPS) from Actinobacillus actinomycetemcomitans. The objective of the present study was to define the subclass distribution of the IgG antibody response of LJP patients to this key cell envelope antigen. IgG subclass antibody responses to A. actinomycetemcomitans LPS were quantified in an enzyme-linked immunosorbent assay with human IgG subclass-restricted monoclonal antibodies. Serum antibody concentrations were calculated by heterologous interpolation of a dose-response curve constructed by using human-mouse chimeric antibodies. Sixteen of 17 LJP serum samples tested contained significantly greater concentrations of IgG2 than IgG1 antibodies reactive toward A. actinomycetemcomitans LPS. Geometric mean antibody concentrations of IgG1 and IgG2 were 7.8 and 136.5 micrograms/ml, respectively, among LJP patients with elevated IgG titers to LPS (94% of whom were black). However, both IgG1 and IgG2 antibody concentrations were significantly greater than the corresponding values obtained from sera from LJP patients with low IgG titers to LPS. Among LJP patients with elevated IgG titers to A. actinomycetemcomitans LPS, serum IgG2 concentration and total IgG concentration were also significantly elevated compared with both low-titered LJP sera and sera from periodontally healthy race-matched controls. The results of this study indicate that the humoral response of a predominantly black population of LJP patients to A. actinomycetemcomitans includes the production of LPS-reactive IgG antibodies which are primarily of the IgG2 subclass.

The bacterial etiology of destructive periodontal disease: current concepts

The interpretation of diagnostic tests for the detection of subgingival bacterial species is dependent on knowledge of the microbial etiology of destructive periodontal diseases. Specific etiologic agents of these diseases have been sought for over 100 years; however, the complexity of the microbiota, an incomplete understanding of the biology of periodontal diseases, and technical problems have handicapped this search. Nonetheless, a number of possible pathogens have been suggested on the basis of their association with disease, animal pathogenicity, and virulence factors. The immunological response of the host to a species and the relation of successful therapy to the elimination of the species have also been used to support or refute suspected periodontal pathogens. Current data suggest that pathogens are necessary but not sufficient for disease activity to occur. Factors which influence activity include susceptibility of the individual host and the presence of interacting bacterial species which facilitate or impede disease progression. Recent studies have attempted to distinguish virulent and avirulent clonal types of suspected pathogenic species and seek transmission of genetic elements needed for pathogenic species to cause disease. Finally, the local environment of the periodontal pocket may be important in the regulation of expression of virulence factors by pathogenic species. Thus, in order that disease result from a pathogen, 1) it must be a virulent clonal type; 2) it must possess the chromosomal and extra-chromosomal genetic factors to initiate disease; 3) the host must be susceptible to this pathogen; 4) the pathogen must be in numbers sufficient to exceed the threshold for that host; 5) it must be located at the right place; 6) other bacterial species must foster, or at least not inhibit, the process; and 7) the local environment must be one which is conducive to the expression of the species' virulence properties.

Antibodies in normal and diseased pulps reactive with microorganisms isolated from deep caries

Immunoglobulin molecules in the supernatant fluids (SF) from pulpal explant cultures have been observed to react with microorganisms implicated in infections of root canals. In this study, the reactivity of immunoglobulin molecules in the SF from normal and irreversible pulpitis pulps to six strains of predominant microorganisms isolated from the immediate layer of carious lesions above the pulps used for explant cultures was investigated using an enzyme-linked immunosorbent assay. Two ATCC strains of Eubacterium were also included in this assay. Specific antibodies to Lactobacillus casei subsp. casei, Lactobacillus casei subsp. rhamnosus, Lactobacillus acidophilus (I), (II), Streptococcus mutans, Bacteroides intermedius, Eubacterium brachy, and Eubacterium alactolyticum in the SF from the normal and irreversible pulpitis tissues were observed with a large variation of antibody levels in both groups. Immunodiffusion assays of the SF revealed that IgG was the major class of immunoglobulin in the normal as well as the irreversible groups. The presence of natural antibodies in the normal pulps suggested a possible protective role of antibodies during the invasive process of caries.

The immunodominant outer membrane antigen of Actinobacillus actinomycetemcomitans is located in the serotype-specific high-molecular-mass carbohydrate moiety of lipopolysaccharide

Most patients with juvenile periodontitis manifest serum antibodies, sometimes at very high titers, to antigens of Actinobacillus actinomycetemcomitans, but the antigens inducing the immune response have been only partly characterized. We separated A. actinomycetemcomitans serotype b cells into protein, lipopolysaccharide (LPS), and soluble polysaccharide fractions and characterized them. Coomassie blue- and silver-stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels were used to detect protein and LPS components, and gas-liquid chromatography was used to determine their carbohydrate and fatty acid composition. Western blots, dot blots, and enzyme-linked immunosorbent assay inhibition with high-titer sera from juvenile periodontitis patients revealed which components were highest in antibody binding activity. These results showed that the major portion of the immunoglobulin G binding activity resides in the purified mannan-free LPS, with lesser amounts in the total protein fraction. Using Sephacryl S-300 chromatography, we separated LPS into high-molecular-mass components with high carbohydrate contents by gas-liquid chromatography and a low-molecular-mass component consisting mainly of lipid A and the inner core sugar heptulose. The results of quantitative dot blot assays and enzyme-linked immunosorbent assay inhibition show that the serotype-specific antibody binding activity is highly concentrated in the high-molecular-mass carbohydrate-rich LPS fraction and is almost completely absent in the low-molecular-weight lipid-rich fraction. Our observations contrast with previous reports that the predominant serotype antigen of A. actinomycetemcomitans resides in a mannan-rich polysaccharide isolated from spent culture medium. These observations support the conclusion that the immunodominant antigen of the outer membrane is the O antigen of the LPS.

Serum antibody in Actinobacillus actinomycetemcomitans-infected patients with periodontal disease

This study was designed to (i) delineate the characteristics of serum antibody responses to Actinobacillus actinomycetemcomitans in patients with periodontitis who are infected with A. actinomycetemcomitans; irrespective of disease classification; (ii) assess the relationship of the elevated antibody levels to colonization of the oral cavity by A. actinomycetemcomitans; and (iii) describe the serotype distribution of A. actinomycetemcomitans and antibodies to the microorganism in infected patients with various clinical classifications. To compare the levels of various isotype-specific antibodies to the different antigens, studies were performed that allowed quantitation of each isotype-specific antibody in a human reference standard. By using this reference standard, it was shown that the levels of immunoglobulin G (IgG), IgM, and IgA responses to A. actinomycetemcomitans were similar among the infected patients, irrespective of disease classification. Also, we demonstrated that the serum antibody response to serotype b was quantitatively greater in all isotypes. Our findings indicate that b was the most frequent A. actinomycetemcomitans serotype detected in the patients and appears to be capable of initiating a substantial serum IgG antibody response that may contain cross-reactive antibodies to other serotypes of A. actinomycetemcomitans. Generally, in cases in which the response to a single serotype was elevated, only that type of A. actinomycetemcomitans was detected in the plaque. Individuals exhibiting elevated antibodies to multiple serotypes were most consistently colonized by the serotype b microorganism. This study represents the first report detailing the distribution of IgG subclass antibodies to A. actinomycetemcomitans in periodontal disease. The results demonstrated that the primary responses of patients with periodontitis to A. actinomycetemcomitans were of the IgG1 and IgG3 subclasses, which is consistent with elicited responses to protein antigens. In contrast, the primary subclass response in normal subjects was limited to the IgG2 subclass and may represent broader cross-reactivity to polysaccharide antigens-lipopolysaccharide from the bacteria.

Effect of adoptive transfer of cloned Actinobacillus actinomycetemcomitans-specific T helper cells on periodontal disease

Previously we isolated several Actinobacillus actinomycetemcomitans-specific T-cell clones from the spleens and lymph nodes of immunized Rowett rats. These clones were characterized as W3/13+, W3/25+, OX8-, and OX22-, suggesting a T helper (Th) phenotype. In the current experiments, 10(6) cells from a single A. actinomycetemcomitans-specific clone (A3) were adoptively transferred to a group (AaTh; n = 13) of normal heterozygous rats (rnu/+) at 28 days of age. A second group received no T cells (AaNT; n = 15), and a third group also received no T cells (NAaNT, n = 11). Beginning 1 day after transfer, the first and second groups were infected orally with A. actinomycetemcomitans for 5 consecutive days. The presence of infection was confirmed immediately after challenge and after 5 months, when the experiments were ended. Significantly higher numbers of lymphocytes were recovered from the gingival tissues of the first group than from those of either of the other groups. Also, this group showed significantly elevated (P less than 0.01) serum immunoglobulin G and immunoglobulin M antibody to A. actinomycetemcomitans in an enzyme-linked immunosorbent assay when compared with both other groups. Bone loss was significantly lower (P less than 0.01) in recipients of A. actinomycetemcomitans-specific cloned cells when compared with the other infected group and was approximately equal to the bone loss of the uninfected group. These results are consistent with the hypothesis that T-cell regulation can affect periodontal disease. In this regulation, T helper cells appear to interfere with periodontal bone loss.

Evidence that the serotype b antigenic determinant of Actinobacillus actinomycetemcomitans Y4 resides in the polysaccharide moiety of lipopolysaccharide

A high-molecular-weight polysaccharide-containing antigen was isolated from a phenol-water extract of Actinobacillus actinomycetemcomitans ATCC 43718 (formerly Y4) by gel permeation chromatography in lipopolysaccharide (LPS)-disaggregating buffer. The polysaccharide antigen formed a precipitin band with rabbit serotype b-specific antiserum but not with rabbit antisera to serotype a or c. Electroblotted serotype b antigen was probed with serum from a patient with localized juvenile periodontitis (LJP), resulting in a diffuse "smear" in the upper region of the lane. By utilizing an enzyme-linked immunosorbent assay, it was demonstrated that the geometric mean immunoglobulin G antibody titer to the serotype b polysaccharide was significantly higher in sera from LJP patients than in sera from periodontally healthy individuals. Moreover, LJP antibody titers to the serotype b polysaccharide exhibited age-dependent variation. Double immunodiffusion analysis revealed that the serotype b antigen formed a line of identity with low-molecular-weight LPS following reaction with serotype b-specific antiserum. Incubation of LJP serum in the presence of a lipid-free polysaccharide moiety obtained by mild acid hydrolysis of LPS from A. actinomycetemcomitans Y4 markedly reduced immunoglobulin G titer to the serotype b antigen. In contrast, solubilized lipid A was only weakly inhibitory. The results of this study indicate that the serotype b-specific determinant of A. actinomycetemcomitans resides in the polysaccharide moiety of LPS and represents a major target for immunoglobulin G antibody in serum of LJP subjects colonized by this organism.

Antigens of Actinobacillus actinomycetemcomitans recognized by patients with juvenile periodontitis and periodontally normal subjects

Most juvenile periodontitis patients respond to infection by Actinobacillus actinomycetemcomitans by producing serum antibodies. Specific antigens inducing the humoral immune response have not been identified, nor has the role of the resulting antibodies in disease progression been determined. Adsorbed and unadsorbed sera from juvenile periodontitis patients and normal subjects were analyzed by enzyme-linked immunosorbent assay and Western blots (immunoblots), using digested and undigested bacterial sonicates and French pressure cell fractions to determine the biochemical class, cross-reactivity, and cellular location of the antigens in different A. actinomycetemcomitans serotypes. Antigens detected by using high-titer sera included the following: (i) serotype-specific nonprotein material located on the cell surface, (ii) soluble-fraction proteins showing highly variable antibody binding, (iii) cross-reactive proteins, and (iv) a protein present in soluble and cell wall fractions and immunopositive for all sera tested. In addition, one apparently nonprotein component that was enriched in the cell wall fraction was observed. Sera with high immunoglobulin G titers to one, two, three, or none of the three A. actinomycetemcomitans serotypes were observed. There was a high degree of variation from one patient to another in the humoral immune response to serotype-specific and cross-reactive antigens. As demonstrated by whole-cell adsorption experiments, the serotype-specific surface antigen accounted for approximately 72 to 90% of the total antibody-binding activity for sera with titers greater than 100-fold above background, while cross-reactive antigen accounted for less than 28%. Antibody binding the whole-cell sonicate for high-titer sera was inhibited 90% by lipopolysaccharide from the same serotype, strongly suggesting that lipopolysaccharide is the immunodominant antigen class.

Periodontitis associated with Papillon-Lefèvre syndrome

The predominant subgingival microflora, host immune response, and genetic history of a 14-year-old girl with Papillon-Lefèvre Syndrome (PLS) are reported. The patient had high counts of Actinobacillus actinomycetemcomitans and surface translocating bacteria. She had significantly raised levels of antibodies to five of the bacterial species studied with the levels to A. actinomycetemcomitans remaining high after antibiotic therapy. The polymorphonuclear leukocytes (PMN) also released significantly increased amounts of O2 compared to controls. The data presented support a role for A. actinomycetemcomitans and PMN dysfunction in the pathogenesis of PLS.

Molecular approaches to leucotoxin as a virulence component in Actinobacillus actinomycetemcomitans

A strategy has been developed to examine the hypothesis that leucotoxin is a critical virulence factor of Actinobacillus actinomycetemcomitans in a non-human primate (Macaca fascicularis). Firstly the leucotoxin gene from A. actinomycetemcomitans was cloned and sequenced. This DNA contained a functional leucotoxin gene, as protein extracts of Escherichia coli with the cloned sequences lysed appropriate human cell lines. The protein encoded by lktA shared at least 42% identity with P. haemolytica leucotoxin and with the alpha-haemolysins from E. coli and A. pleuropneumoniae. The lktA gene of A. actinomycetemcomitans was linked to another gene, lktC, which is thought to be related to the LktC proteins from these other bacteria and with which it shared at least 49% amino acid identity. Despite the overall homology to the other leucotoxins/haemolysins, the LktA from A. actinomycetemcomitans has several unique properties including a very basic pI of 9.7, as compared to pIs approx. 6.2 for lktA proteins in other bacteria. Using the cloned genes as probes produced evidence that a TOX- strain contains the leucotoxin gene but fails to transcribe it at high levels. The second avenue of investigation was to develop methods for examining the humoral immune responses in the monkey to bacterial toxins such as lktA. A. actinomycetemcomitans was detected in subgingival plaque samples from approx. 40% of the animals. A. actinomycetemcomitans comprised less than 1% to 9% of the flora. Most A. actinomycetemcomitans isolates were serotype b and each of the monkeys had serum IgG antibody to A. actinomycetemcomitans serotype b (generally considered to be lktA-producing strains). An ELISA was developed to examine the isotype/subclass distribution, level and avidity of serum antibody in the monkey following parenteral immunization with a prototype bacterial exotoxin (tetanus toxoid). IgG1 and IgG3 antibody predominated over IgG2 and IgG4 after primary immunization. Secondary immunization elicited enriched IgG1 and IgG4 responses. Primary immunization increased avidity indices of IgG to tetanus toxoid from approx. 0.9 (baseline) to a mean of 1.72 and secondary immunization significantly increased the avidity index to 2.56.