Immune Activation of <em>P. gingivalis</em>—Infected Gingiva Fibroblasts Is Determined by Heterogeneity of Peptidylarginine Deiminase Gene and Biochemical Properties of Produce Variant(s)

<jats:p>This study compared immune activation of gingival fibroblasts (GFs) by Porphyromonas gingivalis strains carrying different variants of peptidylarginine deiminase (PPAD). To this aim, GFs from donors with periodontitis (PD) (n=4) and healthy controls (CTRL) (n=2) were infected with P. gingivalis strains expressing either ppad with missense mutations (A390T + T421I) (n=2, moderate PD) or clusters of specific polymorphic variants (S203P + G231N, E232T, N235D) and (S203P + G231N, E232T, N235D + N291D + A515V + S528G) (n=2, advanced PD). Enzymatic activity of PPAD from these strains was determined using a colorimetric assay. Immune activation of infected GFs was analysed using qRT-PCR. P. gingivalis strains carrying clusters of specific polymorphic variants of ppad induced ~two-fold increase of PPAD activity and upregulated TNF-α, IL-6, and COX-2 expression by infected GFs compared to the reference ATCC 33277 strain. Contrary, P. gingivalis strains containing missense mutations showed decreased PPAD activity and elicited inflammatory response comparable to that presented by the ATCC 33277 strain. This study demonstrated that the inflammatory outcome of P. gingivalis infection results from the interplay between bacterial virulence driven by PPAD sequence diversity and enzymatic activity, and the intrinsic hyperreactivity of host GFs associated with PD.</jats:p>