Periodontal Bacterial DNA Suppresses the Immune Response to Mutans Streptococcal Glucosyltransferase

Abstract

Certain CpG motifs found in bacterial DNA enhance immune responses through Toll-like receptor 9 (TLR-9) and may also demonstrate adjuvant properties. Our objective was to determine if DNA from bacteria associated with periodontal disease could affect the immune response to other bacterial antigens in the oral cavity. Streptococcus sobrinus glucosyltransferase (GTF), an enzyme involved in dental caries pathogenesis, was used as a test antigen. Rowett rats were injected with aluminum hydroxide (alum) with buffer, alum-GTF, or alum-GTF together with either Escherichia coli DNA, Fusobacterium nucleatum DNA, or Porphyromonas gingivalis DNA. Contrary to expectation, animals receiving alum-GTF plus bacterial DNA (P. gingivalis in particular) demonstrated significantly reduced serum immunoglobulin G (IgG) antibody, salivary IgA antibody, and T-cell proliferation to GTF compared to animals immunized with alum-GTF alone. A diminished antibody response was also observed after administration of alum-GTF with the P. gingivalis DNA either together or separately, indicating that physical complexing of antigen and DNA was not responsible for the reduction in antibody. Since TLR triggering by DNA induces synthesis of prospective suppressive factors (e.g., suppressor of cytokine signaling [SOCS]), the effects of P. gingivalis DNA and GTF exposure on rat splenocyte production of SOCS family molecules and inflammatory cytokines were investigated in vitro. P. gingivalis DNA significantly up-regulated SOCS1 and SOCS5 expression and down-regulated interleukin-10 expression by cultured splenocytes. These results suggested that DNA from periodontal disease-associated bacteria did not enhance, but in fact suppressed, the immune response to a protein antigen from cariogenic streptococci, potentially through suppressive SOCS components triggered by innate mechanisms.

Involvement of SOCS3 in Regulation of CD11c + Dendritic Cell-Derived Osteoclastogenesis and Severe Alveolar Bone Loss

“…1A and B), based on previously reported results (27,49,54). These findings are consistent with those of Taubman's and Garlet's, in which rat SOCS1 and SOCS5 mRNA and protein levels versus human SOCS1, -2, and -3 mRNA levels were increased in vivo postchallenge by DNA of Porphyromonas gingivalis in diseased periodontal tissues compared to healthy controls (12,47). Given the suppressive nature of SOCS family molecules and their roles in controlling cytokine receptor signaling, it is conceivable that SOCS1, -3, and -5 are likely engaged in modulating the inflammatory responses during periodontal infections.…”

“…Our data are also in accordance with the recent study by Wormald et al, in which higher levels of SOCS expression (i.e., 1, 3, or 5) were strongly associated with the diseased periodontal tissues in the presence of (pro)inflammatory cytokines (e.g., RANKL, IL-1, and IL-6) (12,35,47). Further, particular SOCS molecules can be "hard-wired" to specific cytokine signaling pathways, thereby allowing them to modulate the kinetics of downstream effects (61).…”

“…Replicate membranes were blotted for the phosphorylated protein species with antibodies against phospho-Erk (Thr202/ Tyr204), phospho-Jnk1/2 (Tyr183/185), phospho-p38 (Thr180/Tyr182), and phospho-Akt (Ser473) (Cell Signaling Technology and Santa Cruz Biotechnology). Later, horseradish peroxidase-or allophycocyanin-conjugated anti-mouse or rabbit/rat IgG was used as secondary Ab at a 1/2,000 dilution (47,48). Bound protein complexes were detected with the enhanced chemiluminescence kit (Amersham) and then visualized with the Kodak-2000 mm Image Station for quantification and comparisons (50,51).…”

Porphyromonas gingivalis Exacerbates Ligature-Induced, RANKL-Dependent Alveolar Bone Resorption via Differential Regulation of Toll-Like Receptor 2 (TLR2) and TLR4

“…P. gingivalis (strain ATCC 33277) was grown on anaerobic blood agar plates (NHK agar; Northeast Laboratory Services, Waterville, ME) in an anaerobic chamber with 85% N 2 , 5% H 2 , and 10% CO 2 . A single colony of P. gingivalis was isolated from the plate and grown in Trypticase soy broth (BD Biosciences, San Diego, CA) containing 1% yeast extract, 5 g/ml hemin, and 2.5 g/ml menadione as previously described (29). Bacterial numbers in culture broth were determined by reading absorbance values, using a spectrophotometer, and comparing them to a curve derived from a standard plate count.…”

The Role of Chemokines and Cytokines in the Pathogenesis of Periodontal and Periapical Lesions: Current Concepts

“…This control can be exerted by the suppressors of cytokine signaling (SOCS), which act to attenuate signal transduction as part of a negative feedback loop to inhibit the response to subsequent stimuli (Yoshimura et al, 2007). Accordingly, a recent study demonstrates that the upregulation of SOCS expression after the challenge with DNA from PD-associated bacteria significantly suppressed the response to a subsequent bacterial challenge (Taubman et al, 2007). Aside from the suppression of innate immunity cytokines, IL-10 interferes directly with IFN- and IL-17 production by T cells, demonstrating a broad role for this immunoregulatory cytokine (Jovanovic et al, 1998, Naundorf et al, 2009.…”