Detection of soluble peptidoglycan in urine after penicillin administration

Proinflammatory bacterial peptidoglycan as a cofactor for the development of central nervous system autoimmune disease

Upon stimulation by microbial products through TLR, dendritic cells (DC) acquire the capacity to prime naive T cells and to initiate a proinflammatory immune response. Recently, we have shown that APC within the CNS of multiple sclerosis (MS) patients contain peptidoglycan (PGN), a major cell wall component of Gram-positive bacteria, which signals through TLR and NOD. In this study, we report that Staphylococcus aureus PGN as a single component can support the induction of experimental autoimmune encephalomyelitis (EAE) in mice, an animal model for MS. Mice immunized with an encephalitogenic myelin oligodendrocyte glycoprotein peptide in IFA did not develop EAE. In contrast, addition of PGN to the emulsion was sufficient for priming of autoreactive Th1 cells and development of EAE. In vitro studies demonstrate that PGN stimulates DC-mediated processes, reflected by increased Ag uptake, DC maturation, Th1 cell expansion, activation, and proinflammatory cytokine production. These data indicate that PGN-mediated interactions result in proinflammatory stimulation of Ag-specific effector functions, which are important in the development of EAE. These PGN-mediated processes may occur both within the peripheral lymph nodes as well as in the CNS and likely involve recognition by TLR on DC. Thus, PGN may provide a physiological trigger of DC maturation, and in this way disrupt the normal tolerance to self Ag. As such, PGN signaling pathways may serve as novel targets for the treatment of MS.

Characterization of a monoclonal antibody that binds to an epitope on soluble bacterial peptidoglycan fragments

We employed an inhibition-type enzyme-linked immunosorbent assay (ELISA) to characterize a murine immunoglobulin M monoclonal antibody (MAb) that bound soluble macromolecular peptidoglycan (PG). With this ELISA, the MAb was capable of detecting soluble PG concentrations of less than 10 ng/ml. Enzymatic digestion of PG reduced binding by more than 100-fold, implying that the epitope recognized by this antibody depended on repeating subunits within the glycan backbone. Additionally, the MAb bound to epitopes on both O-acetylated and non-O-acetylated PG fragments from gram-negative bacteria, as well as PG fragments from Staphylococcus aureus and PG fragments released into the medium by a number of gram-positive and gram-negative bacteria.

Induction of proinflammatory cytokines by a soluble factor of Propionibacterium acnes: implications for chronic inflammatory acne

Although many cytokines have been implicated in the development and persistence of inflammatory immune responses, it is unknown if any of these are important in inflammatory acne. This study investigated the production of the proinflammatory cytokines interleukin-8 (IL-8), IL-1 beta, and tumor necrosis factor alpha (TNF-alpha) by human monocytic cell lines, ThP-1 and U937, and by freshly isolated peripheral blood mononuclear cells from acne patients. Both Propionibacterium acnes and supernatants obtained from 72-h P. acnes cultures could induce significant concentrations of IL-1 beta, TNF-alpha, and IL-8 by both cell lines and by peripheral blood mononuclear cells as determined by enzyme-linked immunosorbent assay. There was no significant difference between acne and non-acne subjects. Endotoxin quantification and addition of polymyxin B to assays indicated no lipopolysaccharide (LPS) contamination. P. acnes supernatant was fractionated into components with molecular weights of < 3,000, < 10,000, and < 30,000 and assayed for the ability to induce IL-8 and TNF production in ThP-1 cells. Nearly 90% of the original activity was found in the < 30,000-molecular-weight fraction, 50% was in the < 10,000-molecular-weight fraction, and only 15% remained in the < 3,000-molecular-weight fraction. The effluent from the < 3,000-molecular-weight fraction contained about 70% activity, indicating that the inducing factor was not retained in the membrane. Incubation of P. acnes supernatant with various concentrations of mutanolysin or lysozyme resulted in a loss of 60% of the original activity. The addition of jimson lectin, which binds peptidoglycan, resulted in a loss of 70% of the activity in a dose-response manner, whereas peanut lectin had little or no effect on the activity. Heating of the P. acnes supernatant to 65 degrees C also had no effect on the activity. Blocking of CD14, a receptor for both LPS and peptidoglycan, reduced cytokine production by > 50%, suggesting that the soluble stimulating factor may be a secreted form of peptidoglycan-polysaccharide.

Childhood infections and the risk of inflammatory bowel disease

Adults with inflammatory bowel disease from North Carolina were questioned during 1986 and 1987 to assess risk due to a variety of childhood infections and treatments with antibiotics. Responses were compared with those of neighbor controls. Persons with Crohn's disease were more likely to report an increased frequency of childhood infections in general (odds ratio 4.67, 95% CI 2.65-8.23) and pharyngitis specifically (odds ratio 2.14, 95% CI 1.30-3.51). This was validated by an increased frequency of tonsillectomy (odds ratio 1.53, 95% CI 1.07-2.20). Crohn's cases were more likely to report frequent treatment with antibiotics for both otitis (odds ratio 2.07, 95% CI 1.03-4.14) and pharyngitis (odds ratio 2.14, 95% CI 1.20-3.84). Although Crohn's cases were more likely to report frequent exposure to penicillin (odds ratio 1.81, 95% CI 0.98-3.31), there did not appear to be excess risk conferred by penicillin after controlling for frequency of infections. Persons with ulcerative colitis also reported an excess of infections generally (odds ratio 2.37, 95% CI 1.19-4.71), but not an excess of specific infections or treatments with antibiotics. Persons who reported an increased frequency of infections tended to have an earlier onset of Crohn's disease (P < 0.0001) and ulcerative colitis (P = 0.04). Finally, it was noted that urban living in childhood increased the risk for Crohn's disease. We conclude that childhood infections may be a risk factor for Crohn's disease and may presage the early onset of disease.

Systemic uptake and intestinal inflammatory effects of luminal bacterial cell wall polymers in rats with acute colonic injury

The systemic uptake and local intestinal inflammatory potential of luminal bacterial cell wall polymers in rats with normal and acutely inflamed colons were measured. Rats were injected intracecally with either 125I-labeled group A streptococcal peptidoglycan-polysaccharide complexes or equal amounts of Na125I, after either nonspecific colonic injury with 4% acetic acid or injection with buffer. The colons of rats injected with peptidoglycan-polysaccharide had higher inflammatory scores than Na125I-injected rats, a greater incidence of mucosal ulceration and transmural inflammation after acetic acid injury, and an increased frequency of focal accumulations of inflammatory cells in the lamina propria and submucosa after buffer injection. Radioactivity in the liver, spleen, and mesenteric lymph nodes was higher in the colon-injured rats that received peptidoglycan-polysaccharide 48 h before tissue collection than in the noninjured rats (P less than 0.002). Group A streptococcal polysaccharide antigen concentration within the liver, spleen, and mesenteric lymph nodes, measured by enzyme-linked immunosorbent assay, was significantly higher in the colon-injured rats that received cell wall polymers than in noninjured rats. These results indicate that luminal bacterial cell wall polymers with well-described inflammatory and immunoregulatory potential can cross injured colonic epithelia and are capable of initiating and potentiating intestinal inflammation.

Soluble non-cross-linked peptidoglycan polymers stimulate monocyte-macrophage inflammatory functions

Soluble non-cross-linked peptidoglycan polymers are released by gram-positive bacteria when beta-lactam antibiotics are administered to humans. In this report, we show that this type of peptidoglycan can stimulate monocyte-macrophage functions that cause inflammation. Non-cross-linked peptidoglycan polymers from penicillin-treated Streptococcus faecium were purified and shown to stimulate the production of interleukin 1 by human monocytes and of colony-stimulating factors by a murine macrophage cell line. In addition, the release of plasminogen activator by human monocytes was inhibited by the soluble peptidoglycan. These in vitro results suggest that prolonged treatment with beta-lactam antibiotics, by causing the production of soluble peptidoglycan, may result in interleukin 1-mediated inflammatory reactions, excessive production of monocytes and granulocytes, and increased fibrin deposition.