ABSTRACT
Cysteine proteinases, termed gingipains, of Porphyromonas gingivalis are able to inactivate a broad range of host proteins involved in cellular responses and have been implicated as key virulence factors in the onset and progression of adult periodontitis. In the present study, the high molecular weight Arg-gingipain, RgpA, produced a time- and concentration-dependent hydrolysis of the tumour necrosis factor (TNF)-alpha receptor family member CD27 on resting T cells. As a consequence of CD27 degradation, a reduction in CD27-ligation dependent co-stimulatory CD40L expression was observed. Concomitantly, RgpA activated the protease-activated receptors (PAR)-1, PAR-2 and PAR-4 and induced CD69 and CD25 expression on T cells, thereby demonstrating T cell activation. The Lys-gingipain Kgp demonstrated a low capacity to degrade CD27 but the ability to affect CD27 expression and biological activity was increased when T cells were pretreated with blocking peptide against PAR-2. CD70, the ligand for CD27 induced on activated B cells, was significantly reduced by RgpA treatment and weakly affected by Kgp. These findings suggest that while RgpA can activate T cells through PARs, the parallel action of direct hydrolysis of membrane CD27 as well as CD70 indicates a potential down-regulatory effect through inhibition of CD27/CD70-mediated cell activation in periodontitis.
Subject(s)
Adhesins, Bacterial/pharmacology , CD4-Positive T-Lymphocytes/immunology , Cysteine Endopeptidases/pharmacology , Porphyromonas gingivalis/immunology , Receptors, Proteinase-Activated/antagonists & inhibitors , Tumor Necrosis Factor Receptor Superfamily, Member 7/metabolism , Antigens, CD/metabolism , Antigens, Differentiation, T-Lymphocyte/metabolism , CD27 Ligand/metabolism , CD4-Positive T-Lymphocytes/drug effects , CD40 Ligand/metabolism , Cell Cycle/drug effects , Cells, Cultured , Dose-Response Relationship, Immunologic , Extracellular Fluid/immunology , Formaldehyde/pharmacology , Gingipain Cysteine Endopeptidases , Humans , Interleukin-2 Receptor alpha Subunit/metabolism , Lectins, C-Type , Lymphocyte Activation/immunology , Polymers/pharmacology , Receptors, Proteinase-Activated/metabolism , Serum , SolubilityABSTRACT
Porphyromonas gingivalis cysteine proteinases (gingipains) have been associated with virulence in destructive periodontitis, a disease process that has been linked with Th2 pathways. Critical in maintaining Th2 activity is the response of B lymphocytes to environmental interleukin (IL)-4, a cytokine that also counteracts Th1-cell differentiation. Here we demonstrate that while the gingipains effectively degrade interleukin (IL)-4 under serum-free conditions, limited hydrolysis was observed in the presence of serum even after prolonged incubation. Gingipains up-regulated CD69 expression directly in purified peripheral blood B cell preparations. Further, the induction of IL-4 receptor expression on B cells by gingipains correlates with B cell activation, which is also manifested by a mitogenic response. These results suggest that the gingipains of P. gingivalis act during the early stage of B-cell growth as a competence signal, whereby sensitized B cells might become more responsive to further challenge in the disease-susceptible individual.
