Impact of increased Porphyromonas gingivalis peptidylarginine deiminase (PPAD) T2 variant allele on oral microbiota composition and severity of chronic periodontitis.

Abstract

Background: Porphyromonas gingivalis (Pg) is a keystone pathogen in periodontitis, encoding a unique peptidyl arginine deiminase (PPAD) linked to protein citrullination, a process associated with rheumatoid arthritis (RA). Recently, we identified a super-active PPAD variant (T2) in Pg isolates. Here, we evaluated if the presence of the super-active T2 variant of PPAD affects the salivary microbiome, the severity of chronic periodontitis (CP), and subsequently CP's causative association with RA onset/progression.

Patients/materials and methods: We examined 56 CP patients and 36 healthy volunteers. Pg and Tannerella forsythia counts were measured via RT-PCR, and PPAD variant was typed via PCR. 16S rRNA from salivary DNA sequencing characterized microbiota composition, while CP severity was assessed through bleeding on probing (BoP), clinical attachment loss (CAL), and pocket depth (PD) parameters.

Results: CP patients exhibited higher Pg and T. forsythia counts, with 30.7% harbouring the PPAD-T2 variant, compared to only one healthy volunteer. Clinical CP parameters were unaffected by the PPAD variant. However, PPAD-T2 influenced oral microbiota composition, enriching certain genera.

Conclusion: While the PPAD variant did not affect CP severity, it influenced oral microbiota composition. Further research is needed to understand citrullination's role in oral microbiota and chronic inflammatory disease development.