Production of interferon-gamma, interleukin-6, and interleukin-1β by human peripheral blood mononuclear cells stimulated with novel lys-gingipain synthetic peptides

Background Periodontitis is a progressive inflammatory process, and its pathogenesis is related to the presence of a dysbiotic subgingival biofilm that elicits the immune response. Porphyromonas gingivalis is a keystone pathogen, and its Lys-gingipain (Kgp) virulence factor is involved in the pathogen-host interaction through the production of cytokines by host cells, but the specific mechanisms of this interaction have not been elucidated. The present study evaluated the in vitro production of interferon-gamma (IFN-gamma), interleukin (IL)-6, and IL-1 beta cytokines in response to antigenic stimulation of peripheral blood mononuclear cells (PBMCs) with novel Kgp synthetic peptides. Methods Our previous in silico study predicted 16 immunogenic peptides from Kgp protein. Nine peptides derived from different regions of the protein were chemically synthesized. The synthetic peptides Kgp12, 17, and 18 were selected based on the immunoglobulin G immunoreactivity in the serum of patients with periodontitis (P) and individuals without periodontitis (WP), and they were used in in vitro stimulation of PBMC derived from groups P and WP. Enzyme-linked immunosorbent assay and microsphere-based flow cytometric assay were used to verify the levels of the cytokines produced in PBMC cultures after 48 hours. Results Kgp12, 17, and 18 peptides induced lower production of IFN-gamma. Kgp12 induced higher levels of IFN-gamma in WP than in P individuals. Kgp12 induced higher production of IL-6 and IL-1 beta compared with the other stimuli. Conclusion The novel Kgp synthetic peptides tested herein are immunogenic peptides (epitopes) since they induced the production of cytokines by PBMC and therefore may be useful tools in evaluating the pathogen-host interaction.