Porphyromonas gingivalis (Pg) is one of the main pathogens in chronic periodontitis (CP). Studies on the immunogenicity of its virulence factors may contribute to understanding the host response to infection. The present study aimed to use in silico analysis as a tool to identify epitopes from Lys-gingipain (Kgp) and neuraminidase virulence factors of the Pg ATCC 33277 strain. Protein sequences were obtained from the NCBI Protein Database and they were scanned for amino acid patterns indicative of MHC II binding using the MHC-II Binding Predictions tool from the Immune Epitope Database (IEDB). Peptides from different regions of the proteins were chemically synthesized and tested by the indirect ELISA method to verify IgG immunoreactivity in serum of subjects with CP and without periodontitis (WP). T cell epitope prediction resulted in 16 peptide sequences from Kgp and 18 peptide sequences from neuraminidase. All tested Kgp peptides exhibited IgG immunoreactivity whereas tested neuraminidase peptides presented low IgG immunoreactivity. Thus, the IgG reactivity to Kgp protein could be reaffirmed and the low IgG reactivity to Pg neuraminidase could be suggested. The novel peptide epitopes from Pg were useful to evaluate its immunoreactivity based on the IgG-mediated host response. In silico analysis was useful for preselecting epitopes for immune response studies in CP.Electronic supplementary materialThe online version of this article (10.1186/s13568-019-0757-x) contains supplementary material, which is available to authorized users.

This study aimed at evaluating the transcriptional profile of apoptosis-related genes after in vitro stimulation of peripheral blood mononuclear cells (PBMCs) derived from individuals with periodontitis (P) and healthy nonperiodontitis (NP) control subjects with P. gingivalis HmuY protein. PBMCs from the P and NP groups were stimulated with HmuY P. gingivalis protein, and the expression of genes related to apoptosis was assessed by custom real-time polymerase chain reaction array (Custom RT2 PCR Array). Compared with the NP group, the P group showed low relative levels of apoptosis-related gene expression, downregulated for FAS, FAS ligand, TNFSF10 (TRAIL), BAK1, CASP9, and APAF1 after P. gingivalis HmuY protein stimulation. Furthermore, the P group exhibited low levels of relative gene expression, downregulated for CASP7 when the cells were not stimulated. Our data suggest that P. gingivalis HmuY protein might participate differently in the modulation of the intrinsic and extrinsic apoptosis pathways.

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 interferongamma (IFN-), interleukin (IL)-6, and IL-1 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-. Kgp12 induced higher levels of IFN-in WP than in P individuals. Kgp12 induced higher production of IL-6 and IL-1 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. K E Y W O R D Scytokines, immunology, microbiology, periodontitis J Periodontol. 2019;90:993-1001.

A periodontite é multifatorial e acomete tecidos circundantes dos dentes. Sua etiologia inclui microrganismos como Porphyromonas gingivalis, Tannerella forsythia e Aggregatibacter actinomycetemcomitans. Este trabalho objetivou discutir o papel de Porphyromonas gingivalis na periodontite crônica. Foram pesquisadas as bases eletrônicas PubMed, BIREME e SciELO, buscando aspectos históricos e estudos publicados entre 2000 e 2015, usando, em português e inglês, os descritores: “Periodontite Crônica”, “Porphyromonas gingivalis” e “Fatores de virulência”. Foram encontrados 205 artigos e 24 foram incluídos. Foram selecionados registros sobre doenças periodontais dos primórdios civilizatórios até os dias atuais. Sua prevalência na população mundial permanece alta e diversas pesquisas abordam a etiopatogenia da doença. P. gingivalis é capaz de induzir resposta humoral e celular nos indivíduos infectados. Estudos sobre seus mecanismos de escape e fatores de virulência relatam dano tecidual consequente à resposta imuno-inflamatória exacerbada do hospedeiro que pode evoluir para edentulismo. Estudos da resposta imune a P. gingivalis sugerem seu papel na perpetuação do estado inflamatório por interferir na produção de citocinas e em mecanismos de morte celular em tecidos do hospedeiro, resultando em destruição tecidual. Os conhecimentos atuais sobre mecanismos de infecção e fatores de virulência de P. gingivalis indicam seu papel como componente-chave na periodontite crônica.

Introduction: Periodontitis is a multifactorial disease, characterized by an inflammatory response of the periodontal tissues to a dysbiotic biofilm in the subgingival surface. The presence of keystone pathogens, such as Porphyromonas gingivalis, is one of the main causes of dysbiosis, although the host response is preponderant in the beginning and the progression of the disease. The periodontal treatment is based on the mechanic scaling of the biofilm but using of chemicals adjuvants has been preconized. However, there are many restrictions related to the antibiotics and other chemical adjuvants usage, which makes the use of herbal medicines for this purpose very promising. In addition, many herbal medicines have been used in the folk medicine, with various biologic effects.