Degradation of immunoglobulins A2, A2, and G by suspected principal periodontal pathogens

Modification of cystatin C activity by bacterial proteinases and neutrophil elastase in periodontitis

AIM

To study the interaction between the human cysteine proteinase inhibitor, cystatin C, and proteinases of periodontitis associated bacteria.

METHODS

Gingival crevicular fluid samples were collected from discrete periodontitis sites and their cystatin C content was estimated by enzyme linked immunosorbent assay (ELISA). The interaction between cystatin C and proteolytic enzymes from cultured strains of the gingival bacteria Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans was studied by measuring inhibition of enzyme activity against peptidyl substrates, by detection of break down patterns of solid phase coupled and soluble cystatin C, and by N-terminal sequence analysis of cystatin C products resulting from the interactions.

RESULTS

Gingival crevicular fluid contained cystatin C at a concentration of approximately 15 nM. Cystatin C did not inhibit the principal thiol stimulated proteinase activity of P gingivalis. Instead, strains of P gingivalis and P intermedia, but not A actinomycetemcomitans, released cystatin C modifying proteinases. Extracts of five P gingivalis and five P intermedia strains all hydrolysed bonds in the N-terminal region of cystatin C at physiological pH values. The modified cystatin C resulting from incubation with one P gingivalis strain was isolated and found to lack the eight most N-terminal residues. The affinity of the modified inhibitor for cathepsin B was 20-fold lower (Ki 5 nM) than that of full length cystatin C. A 50 kDa thiol stimulated proteinase, gingipain R, was isolated from P gingivalis and shown to be responsible for the Arg8-bond hydrolysis in cystatin C. The cathepsin B inhibitory activity of cystatin C incubated with gingival crevicular fluid was rapidly abolished after Val10-bond cleavage by elastase from exudate neutrophils, but cleavage at the gingipain specific Arg8-bond was also demonstrated.

CONCLUSIONS

The physiological control of cathepsin B activity is impeded in periodontitis, owing to the release of proteinases from infecting P gingivalis and neutrophils, with a contribution to the tissue destruction seen in periodontitis as a probable consequence.

Endopeptidase activities of selected Porphyromonas spp., Prevotella spp. and Fusobacterium spp. of oral and non-oral origin

The ability of three Porphyromonas spp., seven Prevotella spp., seven Fusobacterium spp. and two related Bacteroides spp. (B. levii and B. macacae) to degrade an extensive range of synthetic endo-, amino- and diamino peptidase substrates linked to the fluorescent leaving group 7-amido-4-methylcoumarin (NHMec) was investigated. Many more species than was previously recognized exhibited peptidase activities, albeit at lower levels than those already described for Porphyromonas gingivalis. Detection of chymotrypsin-like activity was dependent on which of three NHMec-linked substrates was used, but all species exhibited degradative activity with at least one of these substrates. Elastase-like activity was detected in all species though not all species reacted with each of the elastase substrates. Glycylprolyl peptidase activity was detected in all of the species tested with the exception of F. mortiferum, F. gonidiaformans, F. naviforme and F. necrophorum. While the detection of peptidase activities does not appear to be useful for the differentiation of species within the genera Bacteroides and Prevotella, its ability to differentiate species of the genus Porphyromonas or Fusobacterium warrants further investigation.

Comparative analysis of immunoglobulin A1 protease activity among bacteria representing different genera, species, and strains

Immunoglobulin A1 (IgA1) proteases cleaving human IgA1 in the hinge region are produced constitutively by a number of pathogens, including Haemophilus influenzae, Neisseria meningitidis, Neisseria gonorrhoeae, and Streptococcus pneumoniae, as well as by some members of the resident oropharyngeal flora. Whereas IgA1 proteases have been shown to interfere with the functions of IgA antibodies in vitro, the exact role of these enzymes in the relationship of bacteria to a human host capable of responding with enzyme-neutralizing antibodies is not clear. Conceivably, the role of IgA1 proteases may depend on the quantity of IgA1 protease generated as well as on the balance between secreted and cell-associated forms of the enzyme. Therefore, we have compared levels of IgA1 protease activity in cultures of 38 bacterial strains representing different genera and species as well as strains of different pathogenic potential. Wide variation in activity generation rate was found overall and within some species. High activity was not an exclusive property of bacteria with documented pathogenicity. Almost all activity of H. influenzae, N. meningitidis, and N. gonorrhoeae strains was present in the supernatant. In contrast, large proportions of the activity in Streptococcus, Prevotella, and Capnocytophaga species was cell associated at early stationary phase, suggesting that the enzyme may play the role of a surface antigen. Partial release of cell-associated activity occurred during stationary phase. Within some taxa, the degree of activity variation correlated with degree of antigenic diversity of the enzyme as determined previously. This finding may indicate that the variation observed is of biological significance.

Characterization of protease activities in Capnocytophaga spp., Porphyromonas gingivalis, Prevotella spp., Treponema denticola and Actinobacillus actinomycetemcomitans

Protease activities in cell sonicates of defined bacterial strains were examined using peptide substrates and class-specific inhibitors. Capnocytophaga spp. all produced serine dipeptidyl peptidase activity and arginine/lysine, elastase- and chymotrypsin-like enzymes with some metalloprotease characteristics. The elastase-like activity was strongest in Capnocytophaga sputigena, but the others were greatest in Capnocytophaga gingivalis. The latter also had a separate arginine-specific enzyme which appeared not to be present in the other two species. Porphyromonas gingivalis showed serine dipeptidyl peptidase activity and very strong arginine and lysine cysteine protease activities. Prevotella spp. had inhibitor-resistant dipeptidyl peptidase activity and arginine cysteine protease activity that was much weaker but biochemically similar to P. gingivalis. Treponema denticola possessed a strong trypsin-like serine protease activity as well as very weak dipeptidyl peptidase and chymotrypsin-like activities that were sensitive to some cysteine protease reagents. Actinobacillus actinomycetemcomitans showed a novel alanine- and lysine-specific activity, but its nature was unclear.

Inhibition of Prevotella and Capnocytophaga immunoglobulin A1 proteases by human serum

Oral Prevotella and Capnocytophaga species, regularly isolated from periodontal pockets and associated with extraoral infections, secret specific immunoglobulin A1 (IgA1) proteases cleaving human IgA1 in the hinge region into intact Fab and Fc fragments. To investigate whether these enzymes are subject to inhibition in vivo in humans, we tested 34 sera from periodontally diseased and healthy individuals in an enzyme-linked immunosorbent assay for the presence and titers of inhibition of seven Prevotella and Capnocytophaga proteases. All or nearly all of the sera inhibited the IgA1 protease activity of Prevotella buccae, Prevotella oris, and Prevotella loescheii. A minor proportion of the sera inhibited Prevotella buccalis, Prevotella denticola, and Prevotella melaninogenica IgA1 proteases, while no sera inhibited Capnocytophaga ochracea IgA1 protease. All inhibition titers were low, ranging from 5 to 55, with titer being defined as the reciprocal of the dilution of serum causing 50% inhibition of one defined unit of protease activity. No correlation between periodontal disease status and the presence, absence, or titer of inhibition was observed. The nature of the low titers of inhibition in all sera of the IgA1 proteases of P. buccae, P. oris, and P. loescheii was further examined. In size exclusion chromatography, inhibitory activity corresponded to the peak volume of IgA. Additional inhibition of the P. oris IgA1 protease was found in fractions containing both IgA and IgG. Purification of the IgG fractions of five sera by passage of the sera on a protein G column resulted in recovery of inhibitory IgG antibodies against all three IgA1 proteases, with the highest titer being for the P. oris enzyme. These finding indicate that inhibitory activity is associated with enzyme-neutralizing antibodies.

Cloning and characterization of a Prevotella melaninogenica hemolysin

Hemolysins have been proven to be important virulence factors in many medically relevant pathogenic organisms. Their production has also been implicated in the etiology of periodontal disease. Hemolytic strain 361B of Prevotella melaninogenica, a putative etiologic agent of periodontal disease, was used in this study. The cloning, sequencing, and characterization of phyA, the structural gene for a P. melaninogenica hemolysin, is described. No extensive sequence homology could be identified between phyA and any reported sequence at either the nucleotide or amino acid level. As predicted from sequence analysis, this gene produces a 39-kDa protein which has hemolytic activity as measured by zymogram analysis. Unlike many Ca2+-dependent bacterial hemolysins, both the cloned and native PhyA proteins were enhanced by the presence of EDTA in a dose-dependent fashion with 40 mM EDTA allowing maximum activity. Ca2+ and Mg2+ were found to be inhibitory. The hemolytic activity also was found to have a dose-dependent endpoint. Through recovery of hemolytic activity from a spent reaction, this endpoint was shown to be the result of end product inhibition. This is the first report describing the cloning and sequencing of a gene from P. melaninogenica.

Biochemical characterization of the arginine-specific proteases of Porphyromonas gingivalis W50 suggests a common precursor

Extracellular proteases of Porphyromonas gingivalis specific for arginyl peptide bonds are considered to be important virulence factors in periodontal disease. In order to determine the number, inter-relationship and kinetic properties of these proteases, extracellular enzymes with this peptide-bond specificity were purified and characterized from P. gingivalis W50. Three forms, which we denote RI, RI-A and RI-B, accounted for all of the activity in the supernatant. All three enzymes contain an alpha chain of approximately 54 kDa with the same N-terminal amino acid sequence. RI is a heterodimer of non-covalently linked alpha and beta chains which migrate to the same position on SDS/PAGE but which can be resolved by 8 M urea/PAGE. RI-A and RI-B are both monomeric, but the molecular mass of RI-B (70-80 kDa) is significantly increased due to post-translational modification with lipopolysaccharide. All forms show absolute specificity for peptide bonds with Arg in the P1 position and are also capable of hydrolysing N-terminal Arg and C-terminal Arg-Arg peptide bonds. Thus they show limited amino- and carboxy-peptidase activity. For the hydrolysis of Nalpha-benzoyl-L-Arg-p-nitroanilide, the pH optimum is 8.0 at 30 degrees C. The Vmax for all three enzymes is controlled by ionization of two residues with apparent pKas at 30 degrees C of 6. 5+/-0.05 and 9.7+/-0.05, and DeltaH values of approximately 29 kJ/mol and approximately 24 kJ/mol in the enzyme-substrate complex. By analogy with papain, the pKa of 6.5 could be ascribed to a Cys and the pKa of 9.7 to a His residue. E-64 [L-trans-epoxysuccinyl-leucylamide-4-(4-guanidino)butane] is a competitive inhibitor of RI, RI-A and RI-B. Based on physical properties and kinetic behaviour, RI-A appears to be analogous to gingipain from P. gingivalis HG66. However the alpha/beta structure of RI differs significantly from that of the high-molecular-mass multimeric complex of gingipain containing four haemagglutinins described by others. Since the genes for RI and high-molecular-mass gingipain are identical, the data indicate that an alternative processing pathway is involved in the formation of RI from the initial precursor. Furthermore, the identical N-termini and enzymic properties of the catalytic component of RI, RI-A and RI-B suggest that the maturation pathway of the RI precursor may also give rise to RI-A and RI-B. The physiological functions of these isoforms and their role in the disease process may become more apparent through examination of their interactions with host proteins.

Protein degradation by Prevotella intermedia and Actinomyces meyeri supports the growth of non-protein-cleaving oral bacteria in serum

The proteolytic activities of oral bacteria are thought to play an important role in the aetiology of dental abscesses. Bacteria-derived proteases may contribute to tissue destruction, and are likely to impair host defence by degrading immunoglobulins and complement. Degraded periodontal tissue and tissue fluid are likely to constitute essential sources of nutrients in the abscess. Tissue fluid, which is derived from serum, is rich in protein and poor in carbohydrate, suggesting that breakdown of protein and fermentation of amino acids is a crucial step to generate energy for growth of the microflora. The number of oral bacterial species that perform hydrolytic cleavage of protein into polypeptides, the first step in protein degradation, is relatively small compared to the large majority of peptidase-producing species. In this study, we therefore investigated the growth-promoting effect of proteinase-producing species like Prevotella intermedia and Actinomyces meyeri on the growth of some non-proteinase producing bacteria in mixed cultures. We used serum as a substitute for the supposed natural substrate of the abscess microflora. The breakdown of serum proteins was investigated using capillary electrophoresis. Poor growth was found in mono- and mixed cultures of non-proteinase producing species Eubacterium lentum, Fusobacterium nucleatum. Peptostreptococcus micros, and Streptococcus intermedius. The presence of P. intermedia in mixed cultures strongly enhanced growth of these 4 species, according to the hypothesis that the growth of the mixed cultures was peptide-limited. The enhanced growth of P. intermedia in pronase-digested serum indicated peptide-limited growth of this organism in serum, despite its production of proteinase. We found that growth of monocultures of Actinomyces meyeri was poor. In contrast, A. meyeri grew well in mixed cultures and its presence stimulated growth of F. nucleatum and P. micros, suggesting a synergistic relationship. The growth of mono- and mixed cultures was investigated using one representative strain of each species. Thus, there is a small risk of having selected unique strains. Proteinase inhibitors reduced the growth of Porphyromonas gingivalis, Prevotella nigrescens, and P. intermedia in trypticase peptone-yeast extract medium with, and without, IgG. Our study indicated that proteinase-producing organisms play a key role in mixed cultures of oral bacteria in human serum by providing polypeptides for growth. This may explain their association with dental abscesses.

Levels of specific immunoglobulin G to Porphyromonas gingivalis in gingival crevicular fluid are related to site disease status

Titers of immunoglobulin G (IgG) directed against Porphyromonas gingivalis in gingival crevicular fluid of 40 periodontitis patients were measured at three sites in each patient (healthy, gingivitis and periodontitis) by enzyme-linked immunosorbent assay. When paired analyses were performed using Wilcoxon signed-rank tests, periodontitis sites were found to have lower median titers than gingivitis sites. Both systemic and locally-produced antibodies contribute to the overall gingival crevicular fluid antibody profile. Albumin, in contrast, is derived only from serum, and thus this protein serves as an indicator of serum contribution to gingival crevicular fluid. Correction was therefore made for systemic input to the gingival crevicular fluid IgG profile by expressing the results per unit of albumin. When this was done, periodontitis sites were also found to have significantly lower antibody levels than gingivitis sites. These findings suggest that a failure of local antibody production or reduction in quantities, by, for example, degradation by bacterial proteases, may contribute to the change from a gingivitis to a periodontitis lesion.

Inducible expression of a Porphyromonas gingivalis W83 membrane-associated protease

The Tpr protease of Porphyromonas gingivalis W83 is a membrane-associated enzyme capable of hydrolyzing a chromogenic bacterial collagenase substrate. An isogenic mutant lacking a functional tpr gene had a greatly reduced ability to hydrolyze the collagenase substrate. Activity was restored to the tpr mutant by introducing a shuttle plasmid containing the tpr gene. Expression of the gene is induced by nutrient limitation, as shown by enzymatic and Northern analyses.

Are bacterial proteases important virulence factors?

The contribution of bacterial proteases to virulence has been relatively understudied. It is a simple matter to argue that bacterial proteases have the potential to destroy the structural and functional proteins that constitute host tissues as well as to destroy proteins important in host defense. Systematically demonstrating that such interactions occur during disease pathogenesis is more difficult, although a few studies have suggested that the ability of a pathogen to use proteases to cross proteinaceous barriers within the host contributes to bacterial virulence. This manuscript reviews concepts of bacterial virulence. Next, it describes how the host regulates the activities of its own proteases to maintain a state of health, and examines evidence suggesting that dysregulation of host proteases results in disease. Finally, evidence supporting a role for endogenous microbial proteases or acquisition of host proteases by microbes as virulence determinants is discussed as are suggestions for future directions for research in this area.

The potential role of alpha 2-macroglobulin in the control of cysteine proteinases (gingipains) from Porphyromonas gingivalis

Porphyromonas gingivalis is closely associated with the development of some forms of periodontitis. The major cysteine proteinases released by this bacterium hydrolyze peptide bonds only after arginyl (gingipain R) or lysyl residues (gingipain K). No target protein inhibitors have been identified for either enzyme, leading us to investigate their inhibition by human plasma alpha 2-macroglobulin (alpha 2M). Both 50- and 95 kDa gingipain R were efficiently inhibited by alpha 2M, whereas the catalytic activity of gingipain K could not be eliminated. All 3 enzymes were, however, inhibited by a homologous macroglobulin from rat plasma, alpha 1-inhibitor-3 (alpha 1I3). alpha-Macroglobulins must be cleaved in the so-called "bait region" in order to inhibit proteinases by a mechanism involving physical entrapment of the enzyme. A comparison of the amino acid sequences of the 2 macroglobulins indicates that the lack of lysyl residues within the bait region of alpha 2M protects Lys-specific proteinases from being trapped. On this basis, other highly specific proteinases might also not be inhibited by alpha 2M, possibly explaining the inability of the inhibitor to control proteolytic activity in some bacterially induced inflammatory states, despite its abundance (2-5 mg/ml) in vascular fluids.

Growth inhibition of a human oral bacterium Porphyromonas gingivalis by rat cysteine proteinase inhibitor cystatin S

Agar diffusion analysis demonstrated that rat cystatin S, a cysteine proteinase inhibitor, inhibited the growth of all tested strains of a human oral, Gram-negative anaerobic periodontopathogen Porphyromonas gingivalis. Its specific inhibitory activity against this tissue-invasive bacterium but not against other tested oral bacterial species emphasized the importance of specific cysteine proteinases for growth of P. gingivalis.

Putative periodontal pathogens, antibody titres and avidities to them in a longitudinal study of patients with resistant periodontitis

OBJECTIVE

To study changes in antibody titres and antibody avidities to putative periodontal pathogens in patients with resistant periodontitis and to compare these findings with the result of culture of these pathogens.

SUBJECTS AND METHODS

Patients meeting strict clinical criteria in whom periodontal therapy had failed to prevent disease progression were studied microbiologically and immunologically over a 75-week period. Particular reference was made to the isolation of Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) together with changes in antibody titres and avidities to these organisms between baseline examination and week 75.

RESULTS

Pg was eliminated following antibiotic treatment but metronidazole and amoxycillin therapy failed to remove Aa in all cases. Antibody avidities to these pathogens were higher in patients than in matched controls but no change in avidity was noted during the course of treatment. Most antibody titres were not significantly higher in patients than in controls.

CONCLUSIONS

Continued disease progression characterised these patients who, nevertheless, mounted an immune response to the periodontal pathogens but this appeared to be inadequate to stop the disease.

Characterization of the immunodominant antigens of Porphyromonas gingivalis 381 in high-responder patients

The immunodominant antigens of Porphyromonas gingivalis 381 whole cells that reacted with sera from high-responder patients were examined in this study. Whole cells, phenol-water extracted lipopolysaccharide, and fimbriae from P. gingivalis 381 were analyzed using sera from 14 patients with adult periodontitis, rapidly progressive periodontitis or juvenile periodontitis as well as from two healthy subjects. Western blot analysis and enzyme-linked immunosorbent assay (ELISA) were performed. On Western blots, among many prominent protein bands, a smear was observed which was removed after adsorption of the sera with P. gingivalis phenol-water extracted lipopolysaccharide. Two major protein bands of 43 kDa and 41 kDa were found to be prominent even at very high dilutions of sera, the latter of which showed the same molecular weight as the fimbrilin band. These two bands were resistant to treatment by papain and trypsin. ELISA titers remained high after adsorption of the sera with P. gingivalis phenol-water extracted lipopolysaccharide. The results of this study suggest that the 43-kDa and the fimbrilin (41 kDa) proteins may play an important role as immunodominant antigens of P. gingivalis 381.

The importance of immunoglobulin-breakdown supporting the growth of bacteria in oral abscesses

Oral bacteria play an important rôle in the causation of oro-facial abscesses. However, they can also be involved in brain, liver and lung abscesses. To persist, it is essential that these bacteria can grow on those sites. The main source of nutrients for growth in abscesses is likely to be tissue exudate, which is rich in serum-derived proteins, and relatively poor in free amino acids and carbohydrates. Degradation of intact proteins seems a crucial step in providing the peptides necessary for energy generation. The aim of this study was to investigate the capacity of microorganisms from asscesses to degrade serum proteins, in particular immunoglobulins. To this end, samples were taken by aspiration from 16 odontogenic abscesses. It was found that pus from abscesses differed strongly in the concentration of viable bacterial cells. The ability of the abscess microflora to degrade serum proteins was investigated after growth of the sample in heat-inactivated human serum. The microflora from abscesses with a high concentration (n = 10) of bacteria strongly degraded immunoglobulins, whereas breakdown of immunoglobulins was virtually absent after growth of the microflora from low-bacterial concentration (n = 6) abscesses. Bacteriological analyses revealed the presence of at least one proteinase-producing species, like Porphyromonas, black-pigmented Prevotella species, or Actinomyces meyeri, in abscesses with a high density of bacteria, but not in those with low bacterial density. The results indicate that the capacity to degrade intact proteins, in particular immunoglobulins, is a major determinant of bacterial growth in abscesses.

Correlation between gingivain/gingipain and bacterial dipeptidyl peptidase activity in gingival crevicular fluid and periodontal attachment loss in chronic periodontitis patients. A 2-year longitudinal study

The aim of this study is to determine whether either gingival crevicular fluid (GCF) bacterial gingivain/gingipain or dipeptidyl peptidase (DPP) levels, total activity (TA) and concentration (EC), predict progressive attachment loss (AL) in 75 patients with moderate periodontitis. GCF was collected from 16 molar and premolar mesiobuccal sites and then clinical attachment level (CAL) and probing depth (PD) were measured with an electronic constant pressure probe. Lastly, gingival, gingival bleeding, and plaque indices were scored. Prior to the baseline visit, patients were given basic periodontal treatment after which the above procedures were repeated. In addition, carefully localized radiographs were taken of the test teeth and repeated annually. Patients were then seen every 3 months for 2 years and the clinical measurements repeated at each visit. In 48 patients, 124 AL sites, 91 rapid AL (RAL), and 33 gradual AL (GAL) were detected. Gingivain/gingipain and bacterial DPP levels (TA and EC) at RAL sites were significantly higher (P < or = 0.0001) than at paired control sites at the attachment loss time (ALT) and prediction time (PT). Mean levels over the study period of both proteases (TA and EC) at GAL sites were significantly higher (P < or = 0.0001) than those at paired control sites. The GCF levels of gingivain/gingipain were always higher than those of DPP. Critical values (CV) of 5 microU/30 seconds (TA) and 30 microU/microL (EC) for both proteases showed high sensitivity and specificity values for TA and EC, which were the same at both ALT and PT. The positive predictive values were higher for gingivain/ gingipain. Mean site levels, over the course of the study, of both proteases (TA and EC) were significantly higher (P < or = 0.0001) at AL, RAL, and GAL sites than non-attachment loss (NAL) sites in AL patients and mean patient levels were significantly higher (P < or = 0.0001) in AL, RAL, and GAL patients than NAL patients. These results indicate that both of these bacterial proteases in GCF may be predictors of periodontal attachment loss.

A method for titration of inhibiting antibodies to bacterial immunoglobulin A1 proteases in human serum and secretions

Bacterial IgA1 proteases specifically cleave IgA1, including S-IgA1, molecules into Fab alpha and Fc alpha fragments. Hereby these enzymes interfere with the protective functions of antibodies belonging to this isotype. Antibodies inhibiting IgA1 proteases have been detected in humans, but the titration of such antibodies is a matter of methodological concern. Because human serum and secretions contain IgA1 substrate, it is impossible to provide uniform substrate conditions for samples of IgA1 protease incubated with inhibitors differing in their origin and state of dilution. This study demonstrates that such variations in substrate are not prohibitive for a reliable titration of inhibiting antibodies. This was evident from experiments demonstrating that the variations do not interfere with the quantification of residual IgA1 protease activity provided the activity is measured in terms of the proportion of IgA1 substrate cleaved during incubation. Proportions of cleaved IgA1 were measured by exploiting the differential reactivity of cleaved and intact IgA1 molecules in an ELISA using anti-Fc alpha and enzyme-conjugated anti-light chain antibodies for catching and development, respectively. A protocol for the titration of IgA1 protease-inhibiting antibodies based on this ELISA is described. By application of the protocol to chromatographic fractions of saliva, IgA1 protease-inhibiting activity was found to co-purify with salivary S-IgA.

Biological significance of IgA1 proteases in bacterial colonization and pathogenesis: critical evaluation of experimental evidence

IgA1 protease activity, which allows bacteria to cleave human IgA1 in the hinge region, represents a striking example of convergent evolution of a specific property in bacteria. Although it has been known since 1979 that IgA1 protease is produced by the three leading causes of bacterial meningitis in addition to important urogenital pathogens and some members of the oropharyngeal flora, the exact role of this enzyme in bacterial pathogenesis is still incompletely understood owing to lack of a satisfactory animal model. Cleavage of IgA1 by these post-proline endopeptidases efficiently separates the monomeric antigen-binding fragments from the secondary effector functions of the IgA1 antibody molecule. Several in vivo and in vitro observations indicate that the enzymes are important for the ability of bacteria to colonize mucosal membranes in the presence of S-IgA antibodies. Furthermore, the extensive cleavage of IgA sometimes observed in vivo, suggests that IgA1 protease activity results in a local functional IgA deficiency that may facilitate colonization of other microorganisms and the penetration of potential allergens. It has been hypothesized that IgA1 protease activity of Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae, under special immunological circumstances, allows these bacteria to take advantage of specific IgA1 antibodies in a strategy to evade other immune factors of the human body. The decisive factor is the balance between IgA antibodies against surface antigens of the respective bacteria and their IgA1 protease. Recent studies have shown that serine-type IgA1 proteases of H. influenzae, meningococci, and gonococci belong to a family of proteins used by a diverse group of Gram-negative bacteria for colonization and invasion.

Differentiation of human Capnocytophaga species by multilocus enzyme electrophoretic analysis and serotyping of immunoglobulin A1 proteases

As part of a larger taxonomic investigation of the genus Capnocytophaga, 50 strains, including reference strains as well as clinical isolates, were subjected to multilocus enzyme electrophoretic (MLEE) analysis of 12 intracellular metabolic enzymes and characterization of their immunoglobulin A1 (IgA1) proteases by enzyme-neutralizing antibodies raised in rabbits. The dendrogram derived from cluster analysis of the MLEE data discriminated between the five known human Capnocytophaga species and separated the strains into two major divisions. Division A comprised C. gingivalis and C. granulosa strains, and division B comprised C. ochracea, C. sputigena and C. haemolytica strains. Immunoglobulin A1 (IgA1) protease activity, a known feature of C. ochracea, C. sputigena and C. gingivalis, was present in all strains except the type strain of C. haemolytica and two clinical isolates. Inhibition typing of IgA1 proteases of all active strains with enzyme-neutralizing antibodies against protease preparations of the type strains of C. ochracea, C. sputigena and C. gingivalis separated the strains into two major groups identical to the two divisions based on the MLEE data. Thus, the IgA1 proteases of C. granulosa and C. gingivalis seemed to be antigenically similar to one another, and different from the IgA1 proteases of C. ochracea and C. sputigena, which had similar characteristics. The clustering of the clinical isolates based on the MLEE analyses, which was confirmed by the antigenic characterization of IgA1 proteases, was in good agreement with the results of previous studies.

Construction and characterization of arginine-specific cysteine proteinase (Arg-gingipain)-deficient mutants of Porphyromonas gingivalis. Evidence for significant contribution of Arg-gingipain to virulence

Arginine-specific cysteine proteinase (Arg-gingipain; formerly, argingipain) is one of the major extracellular proteinases produced by the oral anaerobic bacterium Porphyromonas gingivalis. To determine whether Arg-gingipain is important for periodontopathogenicity of the organism, Arg-gingipain-deficient mutants were constructed via gene disruption by use of suicide plasmid systems. First, Southern hybridization analyses suggested that two separate Arg-gingipain-encoding genes designated rgpA and rgpB existed on 12.5- and 7.8-kilobase pair HindIII chromosomal fragments of P. gingivalis ATCC33277, respectively. rgpA and rgpB single mutants were constructed by mobilization of a suicide plasmid. Then, an rgpA rgpB double mutant was isolated by electroporation with a second suicide plasmid. No proteolytic activity for Arg-gingipain was observed in either the cell extract or the culture supernatant of the rgpA rgpB mutant. The chemiluminescence response of polymorphonuclear leukocytes, which is closely related to their bactericidal function, was not inhibited by the culture supernatant of the rgpA rgpA mutant, while the wild type parent showed a significant inhibition of the response. The result suggests that Arg-gingipain is responsible for disruption of the function of polymorphonuclear leukocytes. In addition, the rgpA rgpB double mutations caused a marked decrease in the hemagglutination of P. gingivalis, indicating that a major part of the hemagglutinin activity of the organism is associated with the two genes. These findings demonstrate that Arg-gingipain makes a significant contribution to the virulence of P. gingivalis.

In vivo cleavage of immunoglobulin A1 by immunoglobulin A1 proteases from Prevotella and Capnocytophaga species

Immunoglobulin A1 (IgA1) proteases secreted by oral Prevotella and Capnocytophaga species specifically cleave IgA1 at the same peptide bond in the hinge region, leaving intact monomeric Fab and Fc fragments. Assuming that Prevotella- and Capnocytophaga-induced Fab fragments of IgA1 expose a specific immunogenic neoepitope at the cleavage site, we established an enzyme-linked immunosorbent assay to measure human serum antibodies to this neoepitope as indirect evidence of in vivo activity of Prevotella and Capnocytophaga IgA1 proteases. The assay used a monoclonal antibody with specificity for the neoepitope, and the ability to block binding of the monoclonal antibody to the neoepitope was investigated. Absorption of sera with Prevotella melaninogenica-induced Fab fragments of IgA1 resulted in removal of antibodies blocking binding of the monoclonal antibody, whereas absorption with Fab fragments induced by bacterial IgA1 proteases of other cleavage specificities did not remove blocking antibodies. Consequently, we assume that the antibodies detected had been induced by a neoepitope an the Fab fragment of IgA1 exposed exclusively after cleavage with IgA1 proteases from Prevotella and Capnocytophaga, indicating in vivo activity of these IgA1 proteases. Evidence, though indirect, of in vivo activity of Prevotella and Capnocytophaga IgA1 proteases was present in 42 of 92 sera examined and in a significantly higher proportion of sera from adults with periodontal disease compared with control individuals. No correlation with disease was observed for the juvenile periodontitis groups.

Microflora in adult periodontitis

The subgingival microflora of adult periodontitis was studied in 8 adults (36-47 years) and compared with that of 10 periodontally healthy individuals (36-43 years). A total of 64 periodontal lesions were examined, and classified according to the attachment level in three categories: attachment loss > 6 mm, attachment loss 4-6 mm and attachment loss < 4 mm. Also for comparative purposes 20 gingival sulci were evaluated. Samples were taken using three standardized paper points and were incubated anaerobically in selective and non-selective media. The results showed a statistically significant association of Capnocytophaga gingivalis and Capnocytophaga sputigena with moderate periodontal lesions, while Haemophilus segnis has been correlated to severe periodontal lesions. We concluded that C. gingivalis, C. sputigena and H. segnis might be potentially conductive to periodontal deterioration in adult periodontitis.

Initial serum antibody titer to Porphyromonas gingivalis influences development of antibody avidity and success of therapy for chronic periodontitis

This study assessed the effect of periodontal therapy on specific serum antibody concentration, expressed as titer, and antibody binding strength, expressed as relative avidity. The immune responses to Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans were investigated. Antibody titer was assayed by enzyme-linked immunosorbent assay (ELISA) and relative avidity was measured by thiocyanate elution in 17 adult periodontitis patients before and after therapy. Immunoglobulin G (IgG) avidities (expressed as thiocyanate molarity) to P. gingivalis increased from 1.01 to 1.38 M (P = 0.05) and IgA titers (expressed as ELISA units [EU]) increased from 89 to 237 EU (P = 0.012). There were no significant changes in avidity to A. actinomycetemcomitans, but the titer of all three immunoglobulin classes increased significantly (P < 0.03). More specifically, when patients were divided into subgroups which had originally been either IgG seropositive (i.e., having an IgG titer to this organism > 2 times the control median) or seronegative for P. gingivalis, only patients who were initially seropositive showed a significant increase in antibody avidity (P = 0.026; mean difference, 0.69 M). Patients who were originally seropositive in terms of IgG and IgA titer to P. gingivalis had demonstrably better treatment outcomes in terms of a reduced number of deep pockets and sites which bled on probing (P < 0.05). These findings suggest that periodontal therapy affects the magnitude and quality of the humoral immune response to suspected periodontopathogens, that this effect is dependent on initial serostatus, and that initial serostatus may have a bearing on treatment outcome.

Recovery of uncommon bacteria from blood: association with neoplastic disease

Table 6 is a summary of the organisms discussed with a listing of the environmental source, the endogenous source, the predisposing factors including neoplasms, and the postulated mechanisms by which the organism can gain access to the circulation. The evidence considered indicates that the entrance of one of these microorganisms into the bloodstream of a human being depends on the presence of multiplicity of predisposing factors. In the majority of cases of bacteremia due to one of these unusual organisms, two or more predisposing factors are present. Certain predisposing factors, such as cancer chemotherapy or intravenous catheterization, often provide a barrier break, while others, such as liver disease, may render the host immune system less capable of clearing organisms from the circulation. For organisms such as Campy-lobacter, Listeria, and Salmonella spp., attributes that allow the invasion of a healthy host are present and seem to be enhanced by the simultaneous presence of a predisposing condition, such as liver disease, in the host. Although somewhat fragmentary, a number of individual case reports describe bacteremia due to one of these organisms occurring weeks to years after surgery and after other therapeutic measures had effected a supposed cure of a cancer. It may be speculated that cancer patients, even after a cure, are still susceptible to bloodstream invasion by one of the aforementioned organisms by virtue of the presence of one or more predisposing metabolic, physiologic, or immunologic factors, even though these factors may be cryptic. The predominance of hematologic malignancies among cases of bacteremia due to these unusual organisms is also apparent. Although, as pointed out by Keusch (169), the reduction in the performance of immune function in hematologic malignancies compared with solid tumors is likely to be responsible, other associations of certain organisms with specific neoplasms warrant further examination. The frequency of bloodstream infections of Salmonella typhimurium and Capno-cytophaga canimorsus in Hodgkin's disease patients seems likely due to a particular mechanism which infection by these species is favored. The specific nature of these mechanisms remains to be determined. The recovery of any unusual bacterium from blood should warrant a careful consideration of the possibility of underlying disease, especially cancer. Microbiologists should advise clinicians of the unusual nature of the identified organism and provide the counsel that certain neoplastic processes, often accompanied by neutropenia, render the human host susceptible to invasion by almost any bacterium. The recovery of such organisms as C. septicum or S. bovis should prompt the clinician to aggressively seek to identify an occult neoplasm if one has not yet been diagnosed.

Characterization of immunoglobulin G-degrading proteases of Prevotella intermedia and Prevotella nigrescens

Degradation of immunoglobulins is thought to be an important factor in the causation of periodontal diseases by hindering local host defenses and by providing nutrients to the periodontal microflora. In this study, we characterized the proteolytic activity against human immunoglobulin G (IgG) of 20 strains of Prevotella intermedia and Prevotella nigrescens isolated from periodontal pockets and oral abscesses. IgG degradation was studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. All strains degraded IgG within 48 h after growth in trypticase-yeast extract medium (TY) supplemented with 0.3% IgG. Incorporating IgG in TY broth enhanced bacterial growth. Protease profiles (zymography), which revealed the presence of 1-4 IgG-degrading proteolytic bands in bacterial cell extracts, became more complex after growth in the presence of IgG. A 38-kDa protease capable of degrading IgG nonspecifically was present in almost all strains. The proteolytic activity was mainly located on the surface of the cell envelope. Two strains of P. intermedia and P. nigrescens ATCC 33563 were selected for further studies. Bacterial cell suspensions in phosphate-buffered saline completely degraded human IgG, IgA and IgM within 24 h. This activity depended on reducing conditions and was inhibited at temperatures above 50 degrees C. The pH optimum of immunoglobulin degradation was at pH 7. Strains cultured at 42 degrees C showed a markedly reduced capacity to degrade IgG. Inhibition studies revealed that breakdown of IgG was caused by a cysteine protease(s). The capacity of P. intermedia and P. nigrescens to degrade immunoglobulins may explain their association with polymicrobial oral diseases.

The multiple forms of trypsin-like activity present in various strains of Porphyromonas gingivalis are due to the presence of either Arg-gingipain or Lys-gingipain

Porphyromonas gingivalis contains high concentrations of numerous cysteine proteinases with trypsin-like activity which have been implicated as important virulence factors in adult-onset periodontitis. We have analyzed the subfractions of six P. gingivalis strains for the presence of arginine-X- and lysine-X-specific proteinases (Arg-gingipain [RGP] and Lys-gingipain [KGP]) previously purified from P. gingivalis H66. Western blot (immunoblot) analysis using antibodies produced against RGP and the N-terminal peptides of RGP or the catalytic subunit of KGP indicated that these enzymes are synthesized by the strains studied and exist as multiple molecular mass species. The major forms of RGP were identified as 110-, 95-, 70- to 90-, and 50-kDa proteins, the first two being a complex of the 50-kDa catalytic subunit with hemagglutinins, with or without an added membrane anchorage peptide. The other forms are single-chain enzymes. While the 95- and 50-kDa RGP were found predominantly in culture medium, the 110- and 70- to 90-kDa forms associated with membranous fractions of the bacteria. The predominant form of KGP in all strains was a complex of the 60-kDa catalytic domain with hemagglutinins, and vesicle- and membrane-associated KGP was about 15 kDa larger than the 105-kDa enzyme present in culture media. These data explain the apparent complexity of P. gingivalis proteinases and indicate that in all strains tested there are two identical enzymes, one with arginine-X specificity and the other with lysine-X specificity, which, working in concert, are responsible for the trypsin-like activity associated with this bacterium.

IgA nephropathy

IgAN is the most common type of glomerulonephritis worldwide, and is found more in men and distinctly less in blacks. It presents with macroscopic hematuria in about 40 to 45% of patients, with microscopic hematuria and proteinuria in about 35 to 40%, and with nephrotic syndrome or acute renal failure in the remainder. The diagnosis continues to rely on the finding of the dominant or codominant mesangial deposition of IgA on immunohistologic examination of the kidney. No blood or urine test is sufficiently reliable for diagnosis. While the pathogenesis remains unknown, accumulating evidence suggests that polyclonal stimulation of immunoglobulins perhaps coupled with structural abnormalities of IgA play pivotal roles. These defects may account for the variety of autoantibodies detected in patients with both IgAN and HSP. While IgAN has an indolent course, about 30% of patients will reach ESRD after 20 years, particularly in those who present with hypertension, heavy proteinuria or renal insufficiency. At present, therapy is disappointing, but immunoglobulin supplementation and newer agents that interrupt the pathways of mesangial proliferation and sclerosis hold promise for the future. Kidney transplantation has shown excellent allograft survival.

Molecular cloning and structural characterization of the Arg-gingipain proteinase of Porphyromonas gingivalis. Biosynthesis as a proteinase-adhesin polyprotein

The identification of proteinases of Porphyromonas gingivalis that act as virulence factors in periodontal disease has important implications in the study of host-pathogen interactions as well as in the discovery of potential therapeutic and immunoprophylactic agents. We have cloned and characterized a gene that encodes the 50-kDa cysteine proteinase gingipain or Arg-gingipain-1 (RGP-1) described previously (Chen, Z., Potempa, J., Polanowski, A., Wikstrom, M., and Travis, J. (1992) J. Biol. Chem. 267, 18896-18901). Analysis of the amino acid sequence of RGP-1 deduced from the cloned DNA sequence showed that the biosynthesis of this proteinase involves processing of a polyprotein that contains multiple adhesin molecules located at its carboxyl terminus. This finding corroborates previous evidence (Pike R., McGraw, W., Potempa, J., and Travis, J. (1994) J. Biol. Chem. 269, 406-411) that RGP-1 is closely associated with adhesin molecules, and that high molecular weight forms of the proteinase are involved in the binding of erythrocytes.

In vitro cleavage of serum complement protein C3: a comparison between patients with adult periodontitis and periodontally healthy persons

This study tested the hypothesis that in vitro cleavage of C3 could be triggered with similar case in serum samples from patients with adult periodontitis (n = 26) as in samples from periodontally healthy subjects (n = 13). A lipoteichoic acid, a lipopolysaccharide and an aggregated IgG served as activators of complement. On the average, the periodontitis group generated significantly (p < 0.01) more C3d activation fragments than did the healthy group, as judged from rocket immunoelectrophoresis measurements. Cleavage of C4 and factor B were then assayed through immunoblotting, without prior purification of the sera. C4c fragments were seen in all activated samples, the healthy group causing significantly (p < 0.05) more C4 conversion than did the periodontitis group. Cleavage of factor B, taken as a measure of soluble amplification convertase formation, was about equal between the groups. We inferred therefore that the 2 groups produced comparable amounts of C3b. The results suggested, however, that periodontitis sera favour breakdown of the opsonin C3b, most likely by activating the regulatory proteins factor H and I. Lipoteichoic acid, causing moderate depletion of C4 and factor B, produced significantly (p < 0.01) more C3d fragments than the other two activators examined. It may be that complement activation is down-regulated in periodontitis sera, perhaps at the expense of adequate local opsonic function.

Capnocytophaga (Capnocytophaga ochracea group) bacteremia in hematological patients with profound granulocytopenia

The clinical and microbiological features of 7 cases of bacteremia due to Capnocytophaga (Capnocytophaga ochracea group) are reported. They were diagnosed during 1991-93 at three hospital clinics. Five patients were < 10 years old and all had hematological disorders, 4 acute lymphoblastic leukemia and 1 each had aplastic anemia, non-Hodgkin lymphoma, and myelodysplastic syndrome. All were profoundly granulocytopenic with an absolute granulocyte count < 0.13 x 10(9)/l, and all but 1 had oral lesions as a possible portal of entry. A favourable response to antibiotic therapy was recorded in all patients but one who, being profoundly granulocytopenic, rapidly succumbed to Pseudomonas aeruginosa septicemia. None of the isolates were beta-lactamase producers. In addition to penicillin the isolates were susceptible to broad-spectrum cephalosporins and ciprofloxacin, but resistant to aminoglycosides.

Proteolytic activity of Aeromonas caviae

Aeromonas strains produce a variety of virulence factors including proteases. Studies on the kinetics of growth of Aeromonas caviae NRRL B-966 and its proteases suggest that the proteolytic activities are produced throughout the growth phase, with peak level occurring at stationary phase. A. caviae synthesize both intracellular and extracellular proteases with the latter account for major portion of the total activity. Optimum pH for the A. caviae proteolytic activity is at 7.0. A. caviae produces a thermoresistant protease, whose activity is dependent on Mg++ and Ca++ ions. Inhibition of proteolytic activity by phenyl methyl sulfonyl fluoride suggest the presence of a serine protease in A. caviae. Nitrogenous compounds enhance the proteolytic activity while carbohydrates tested in this study inhibit the activity.

Carbohydrate depletion of immunoglobulin A1 by oral species of gram-positive rods

Bacterial deglycosylation of immunoglobulin Al (IgA1), the dominant isotype of antibody in the oral cavity, probably provides both nutrition as well as protection to the oral bacterial community. Representative strains of oral gram-positive rods were tested for their ability to remove carbohydrates from IgA1. Detection of sialic acids was performed by means of high-performance liquid chromatography (HPLC) separation (Aminex HPX-87H) and ultraviolet light absorption at 190 nm, and neutral carbohydrates were measured by HPLC separation (Capcell Pak C-18 SG 120) and ultraviolet light absorption at 245 nm after derivatization. Four strains of Actinomyces naeslundii, two strains of Corynebacterium matruchotii and one of two strains of Actinomyces odontolyticus partially or totally removed sialic acid, while two strains of Propionibacterium propionicus and the other strain of A. odontolyticus did not. Complete correlation was observed between sialic acid removal, neuraminidase activity measured with fluorogenic substrate and with one exception, altered immunoelectrophoretic mobility of IgA1. Only limited removal of other carbohydrates was observed with poor correlation to exoglycosidase activities measured with chromogenic substrates. Desialylation increases the susceptibility of glycoproteins, including IgA1, to proteolysis. Therefore, the desialylation of IgA1 by oral gram-positive rods may facilitate the proteolytic activities of other oral bacteria, and the concerted action may positively influence the survival of the bacteria in the oral community.

Degradation of immunoglobulin G by periodontal bacteria

Several subgingival microorganisms were tested for their ability to utilize human immunoglobulin G (IgG) as a substrate for growth. This was done using a protein-free chemically defined medium, supplemented with IgG. Stimulation of growth was observed for Capnocytophaga ochracea, Porphyromonas asaccharolytica, Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella oralis, Lactobacillus catenaforme and Streptococcus intermedius. Immunoelectrophoresis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a protein assay demonstrated that P. intermedia and P. endodontalis completely degraded the protein chains of IgG. Partial breakdown of IgG was observed for P. asaccharolytica and C. ochracea, whereas P. oralis cleaved the IgG heavy chain, yielding Fc and Fab fragments. All these bacteria utilized IgG as a substrate for growth. Binding studies using an enzyme-linked immunosorbent assay, revealed complete loss of in vitro antigen-antibody binding capacity after incubation of specific IgG with P. endodontalis and partial loss of binding with P. intermedia, P. gingivalis, C. ochracea or Fusobacterium nucleatum. Degradation or inactivation of IgG by oral bacteria is thought to be important in the causation of polymicrobial infections.

Taxonomy, ecology, and pathogenicity of the root canal flora

The bacteria present in infected root canals include a restricted group of species compared with the total flora of the oral cavity. Conditions exist in the root canal that permit the growth of anaerobic bacteria capable of fermenting amino acids and peptides, whereas bacteria that mainly obtain energy by fermenting carbohydrates are restricted by lack of available nutrients. During the course of infection interrelationships develop between microbial species and population shifts are produced as a result of these interactions. Strong associations between certain species are present. These associations are most likely based on nutritional demands and nutritional relationships. The pathogenicity of the polymicrobial root canal flora is dependent on bacterial synergy.

Physiopathology of primary periodontitis associated with plaque. Microbial and host factors. A review. Part 1

Microbial factors involved in the genesis of periodontitis include colonization, bacterial penetration of the epithelium, multiplication and invasive-destructive capacity. Colonization of the gingival sulcus is related, to a certain extent, to supragingival plaque. Bacterial multiplication is induced by nutrients in the gingival fluid, and nutrients produced by degradative and excretory microbial activity. Invasion and destruction are mediated by exotoxins, structural elements of the bacteria, enzymes, metabolites, polyclonal lymphocyte activity, fibroblastic cytotoxicity, and leukocyte chemotactic inhibition.

Pathogenic mechanisms in periodontal disease

Periodontal diseases have been considered as "infections" in which micro-organisms initiate and maintain the destructive inflammatory response. Host-mediated tissue destruction occurs via complement activation and the release of lysosomal enzymes, and connective tissue matrix metalloproteinases. Microbial enzymes may damage connective tissues directly, and, together with toxic metabolites and structural materials, are thought to disrupt the reparative activities of fibroblasts and cells of the immune defenses. The significance and relative contributions of host and microbial factors to the disease process remain unresolved. Environmental changes in the gingival sulcus and periodontal pocket and tissues, the degree of the host response and nutrient availability, concomitant with disease progression, compromise tissue metabolism and repair, and allow for enhanced or de novo expression of microbial virulence factors, such as proteases, which alter microbial pathogenicity. Proteolytic destruction of specific antibodies and complement by both viable and non-viable bacterial cells may retard phagocytic killing and removal of pathogens, thus prolonging the inflammatory response. Bacterial products may indirectly mediate tissue destruction by stimulating release of matrix metalloproteinases or by proteolytically inactivating the specific inhibitors of these enzymes.

Vascular permeability enhancing activity of Porphyromonas gingivalis protease in guinea pigs

Porphyromonas gingivalis protease, which had been isolated from a culture supernatant, caused vascular permeability enhancement in a dose-dependent manner when injected into guinea pig skin. The permeability-enhancing reaction caused by the protease was not affected by treatment with antihistamine, but was greatly augmented by simultaneous injection of a kinin potentiator, carboxypeptidase N inhibitor. However, the reaction was inhibited by soybean trypsin inhibitor or alpha 2-antiplasmin, although both of these inhibitors could not inhibit P. gingivalis protease at all by themselves. A bradykinin-degrading enzyme, carboxypeptidase B, weakened this vascular reaction. Results described indicate that the permeability-enhancing reaction induced by the protease is caused by activation, of the kallikrein-kinin cascade in the tissue.

Purification and partial characterization of a lysine-specific protease of Porphyromonas gingivalis

A lysine-specific protease hydrolysing peptide bonds at the carboxyl side of lysine residues in Porphyromonas gingivalis was purified from culture supernatant by a combination of ion-exchange chromatography, gel filtration, and affinity chromatography. The molecular mass was 48 kDa and the pI value was 7.3. The enzyme hydrolysed the peptide bonds at the carboxyl side of lysine residues in synthetic substrates and natural proteins.

Characterization of the tpr gene product and isolation of a specific protease-deficient mutant of Porphyromonas gingivalis W83

The previously described protease gene (tpr) of Porphyromonas gingivalis W83 was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the recombinant protein and in vitro translation to encode a 50-kDa protein whose active form migrates with an apparent molecular mass of 90 kDa. The 50-kDa protein was expressed at high levels by using a T7 RNA polymerase/promoter system. The NH2-terminal sequence of the protein was identical to the amino acid sequence deduced from the DNA sequence of the protease gene. Affinity-purified antibody to the 90-kDa recombinant protease reacted with an 80-kDa P. gingivalis protein. A specific protease (Tpr)-deficient isogenic mutant of P. gingivalis was generated by homologous recombination between P. gingivalis chromosomal DNA and a suicide plasmid carrying the cloned gene disrupted by insertion of an erythromycin resistance gene. Gelatin substrate zymography showed that cell extracts of the mutant lacked a protease band that migrated with an apparent molecular mass of 80 kDa. Western immunoblots of the cell extracts indicated the loss of an antigen with a similar mass.

Eubacterium yurii subspecies margaretiae is resistant to nonopsonic phagocytic ingestion

We have previously shown that strains of Eubacterium yurii are hydrophobic, as compared with human polymorphonuclear leukocytes (PMNs), possibly because of a crystalline surface layer (S-layer) covering the cell envelope of this potential endo-perio pathogen. The aim of the present study was to investigate the phagocytic ingestion by PMNs of the three E. yurii subspecies, with special attention to bacterial surface structures and hydrophobicity. Type strains of subspp. margaretiae, yurii, and schtitka, together with three clinical isolates from necrotic root canals, were studied. All strains were hydrophobic when tested by a two-phase partition method. E. yurii subspp. margaretiae strains ATCC43715T, ES4C, and ES14B-8E were resistant to PMN ingestion in the absence of opsonins, whereas strains of the two other subspecies were readily ingested. The presence of a resistant strain (subsp. margaretiae ATCC43715T) did not inhibit the ingestion of a sensitive strain (subsp. schtitka ATCC43716T). Ingestion of E. yurii subsp. margaretiae strains required opsonization by normal human serum or specific antibodies. Electron microscopy revealed an S-layer in all strains and fimbria-like structures in the subspp. margaretiae and yurii strains. The antiserum prepared against the S-protein of E. yurii subsp. margaretiae ATCC43715T showed only slight cross-reactivity with other E. yurii strains and indicated the presence of strain-specific rather than species- or subspecies-specific antigens in the S-protein of E. yurii subsp. margaretiae ATCC43715T. The results suggest that the mere presence of the S-layer or fimbria-like structures cannot explain the susceptibility to ingestion by the PMNs.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific antibodies and their potential role in periodontal diseases

Periodontal diseases are thought to result from inflammatory responses to bacterial challenges in the gingival crevicular area. Antibodies are a major host-protective mechanism in many bacterial infections. Consequently, the antibody responses to suspected periodontal pathogenic bacteria have been extensively measured as to their relationship to diseases and specificity for suspected pathogens associated with progressing disease sites. Recently, studies on the bacterial immunogen characterization, antibody-subclass identification, and antibody biological capabilities have been reported. Although increased antibody levels to certain suspected periodontal pathogens were associated with periodontal diseases in humans, little evidence exists as to the role of these antibodies in the infectious process. In vivo experiments in animals indicated that specific antibodies against certain suspected periodontal pathogens were associated with suppression of bacterial colonization, limiting the spread of infection, and a decrease in alveolar bone loss. However, in vitro as well as in vivo experiments suggested that phagocytic cells are required for efficient bactericidal activity of antibodies and that the presence of other sensitized immune cells may either have inhibited or enhanced the infectivity of certain periodontal pathogens. Possible explanations for the observed inconsistencies are presented and the potential for utilization of specific anti-periodontal pathogen responses in the understanding and prevention of diseases is discussed.

Changes in complement and immunoglobulin G receptor expression on neutrophils associated with Porphyromonas gingivalis-induced inhibition of phagocytosis

We examined the phagocytic capacity and receptor expression on neutrophils stimulated with Porphyromonas gingivalis soluble products. Stimulated neutrophils had decreased phagocytic capacities and altered expression of CR1, CR3, Fc gamma RII, and Fc gamma RIII. For cases in which TLCK (N-alpha-p-tosyl-L-lysine chloromethyl ketone) neutralized the effects of the stimuli, the P. gingivalis-derived factors causing the phenomena seem to be trypsin-like proteases.

Local and systemic antibody response to putative periodontopathogens in patients with chronic periodontitis: correlation with clinical indices

Specific immunoglobulin G (IgG), IgA and IgM antibody titres to Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans were measured by enzyme-linked immunosorbent assay in serum and gingival crevicular fluid at 5 sites in each of 20 chronic periodontitis patients. Specific serum antibody titres correlated with mean gingival crevicular fluid titres. The 3 immunoglobulin subclass responses (IgA, IgG and IgM) to P. gingivalis correlated. A comparison of sites with probing depth < 4 mm and > or = 4 mm showed that the latter group had significantly lower gingival crevicular fluid IgG titres to P. gingivalis. Sites with a gingival index of 3 had significantly lower gingival crevicular fluid IgG titres to this organism than those with a gingival index of less than 3. These findings support the concept that the humoral immune response is protective, as chronic periodontitis patients with greater pocket depths and more gingival inflammation had paradoxically lower antibody titres to suspected periodontopathogens.