Sequence analysis of kgp in Porphyromonas gingivalis isolates from periodontitis patients

Identification of a new genetic variant (G231N, E232T, N235D) of peptidylarginine deiminase from P. gingivalis in advanced periodontitis

Chronic periodontitis (CP), an inflammatory disease of periodontal tissues driven by a dysbiotic subgingival bacterial biofilm, is also associated with several systemic diseases, including rheumatoid arthritis (RA). Porphyromonas gingivalis, one of the bacterial species implicated in CP as a keystone pathogen produces peptidyl arginine deiminase (PPAD) that citrullinates C-terminal arginine residues in proteins and peptides. Autoimmunity to citrullinated epitopes is crucial in RA, hence PPAD activity is considered a possible mechanistic link between CP and RA. Here we determined the PPAD enzymatic activity produced by clinical isolates of P. gingivalis, sequenced the ppad gene, and correlated the results with clinical determinants of CP in patients from whom the bacteria were isolated. The analysis revealed variations in PPAD activity and genetic diversity of the ppad gene in clinical P. gingivalis isolates. Interestingly, the severity of CP was correlated with a higher level of PPAD activity that was associated with the presence of a triple mutation (G231N, E232T, N235D) in PPAD in comparison to W83 and ATCC 33277 type strains. The relation between mutations and enhanced activity was verified by directed mutagenesis which showed that all three amino acid residue substitutions must be introduced into PPAD expressed by the type strains to obtain the super-active enzyme. Cumulatively, these results may lead to the development of novel prognostic tools to assess the progress of CP in the context of associated RA by analyzing the ppad genotype in CP patients infected with P. gingivalis.

The profile of Porphyromonas gingivalis kgp biotype and fimA genotype mosaic in subgingival plaque samples

Combined analysis of allelic variation of the virulence-associated, strain-specific lys-gingipain gene (kgp) and major fimbrial gene (fimA) of Porphyromonas gingivalis was undertaken in 116 subgingival plaque samples to understand the kgp biotype and fimA genotype profile in a subject-specific manner. Allelic variation in the polyadhesin domain of kgp from P. gingivalis strains 381 (ATCC 33277), HG66 and W83 generated four isoforms corresponding to four biotypes of P. gingivalis. Similarly, variation in the fimA subunit of the fimA gene cluster of P. gingivalis resulted in six fimA genotypes. Strain-specific differential PCR was performed for kgp and fimA using DNA isolated from subgingival plaque samples. Our findings demonstrate that all of the P. gingivalis kgp biotypes detected in this study were predominantly associated with the fimA II genotype. Dominance of kgp biotypes 381 or HG66 combined with fimA II fimbriae could imply an adaptive strategy by P. gingivalis to generate the fittest strains for survival in the host environment.

Genotype variation and capsular serotypes of Porphyromonas gingivalis from chronic periodontitis and periodontal abscesses

Porphyromonas gingivalis is considered an important pathogen in periodontal disease. While this organism expresses a number of virulence factors, no study combining different virulence polymorphisms has, so far, been conducted. The occurrence of combined virulence (Cv) genotypes in 62 isolates of P. gingivalis was investigated from subjects displaying either chronic periodontitis or periodontal abscess. The Cv genotypes, based on gene variation of fimbriae (fimA), Lys-specific cystein proteinase (kgp) and Arg-specific cystein proteinase (prpR1/rgpA), were evaluated by PCR. The isolates were also subjected to capsular polysaccharide K-serotyping. A total of 18 Cv genotype variants based on fimA: kgp: rgpA were identified, of which II:I:A and II:II:A Cv genotypes (53.3%) were the two most frequently detected combinations. Moreover, 36% of the isolates were K-typeable, with the K6 serotype being the most prevalent (23%). Two isolates had the same genotype as the virulent strain W83. The results indicate that chronic periodontitis is not associated with a particularly virulent clonal type. A highly virulent genotype (e.g. strain W83) of P. gingivalis can be found in certain periodontitis patients.

Major outer membrane proteins from Porphyromonas gingivalis: strain variation, distribution, and clinical significance in periradicular lesions

Porphyromonas gingivalis has been implicated in both marginal periodontitis and periapical infection. This study examined the major outer membrane proteins, from P. gingivalis, which related to periradicular lesions. Outer membrane protein profiles of P. gingivalis ATCC 33277 and W83 were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and N-terminal amino acid analysis. Most outer membrane proteins, such as RagA, gingipains, and OmpA-like proteins, were found in both strains in a similar distribution pattern; however, the migration positions of Lys-gingipain and RagB were inverted in SDS-PAGE. Western blot analysis showed that RagA, RagB, and OmpA-like proteins were found in all of the P. gingivalis strains tested. The antiserum of W83 against RagB reacted poorly to some strains, such as ATCC 33277. When strains phylogenetically related to P. gingivalis were examined, RagA and OmpA homologs were immunologically detected in several strains. However, none of the RagB homologs were detected in any strain analyzed, suggesting that RagB is unique to P. gingivalis. To examine immunoreactive antigens in P. gingivalis, sera from patients with periradicular lesions were used. More than half of the sera showed strong reactions to P. gingivalis cell components, especially RagB. Our results indicate that a major outer membrane protein, RagB, is a possible virulence factor in periradicular lesions.

Sequence variations in rgpA and rgpB of Porphyromonas gingivalis in periodontitis

OBJECTIVE

The aim of the present study was to determine sequence variations in the active centre of the Arg-X-specific protease encoding genes rgpA and rgpB of clinical Porphyromonas gingivalis isolates and to analyse their prevalence in periodontitis patients before and 3 months after mechanical periodontal therapy.

BACKGROUND

Genetic diversity at nucleotides 281, 283, 286 and 331 has been shown to result in amino acid substitutions in the catalytic domain of RgpA and RgpB that affect the substrate specificity and thus may influence the efficacy of Arg-X-protease specific inhibitors.

METHODS

Sequence analysis of rgpA and rgpB genes in clinical P. gingivalis strains isolated from subgingival plaque samples of 82 periodontitis patients before and 3 months after mechanical supra- and subgingival debridement was performed.

RESULTS

No specific variation within the rgpA sequence was observed. However, the rgpB sequence in the region of the active centre showed five different rgpB genotypes, which were named NYPN, NSSN, NSSK, NYPK and DYPN according to the derived amino acid substitution. Porphyromonas gingivalis genotype NYPN was detected in 27 patients (32.9%) before and in 8 patients (9.8%) after therapy, NSSN in 26 (31.7%) and 10 (12.2%), NSSK in 22 (26.8%) and 2 (2.4%), NYPK in 5 (6.2%) and 1 (1.2%), and DYPN in 1 patient (1.2%) and 0 patients (0%), respectively. Only one patient (1.2%) harboured two P. gingivalis rgpB genotypes (NSSK/NYPN) before treatment; these were no longer detected after therapy.

CONCLUSION

The results indicate that five rgpB genotypes are maintained in natural populations of P. gingivalis. These data may be of importance with regard to the development of specific rgpB inhibitors.