Streptococcal Cell Wall Research Articles

Local interleukin-12 gene transfer promotes conversion of an acute arthritis to a chronic destructive arthritis.

To determine whether local overexpression of interleukin-12 (IL-12), a pleiotropic cytokine that promotes the development of naive T cells into Th1 cells, could aggravate murine streptococcal cell wall (SCW)-induced arthritis, a model of acute arthritis. C57BL/6 mice were injected intraarticularly with saline or with 10(7) plaque-forming units of control vector (Ad5del70-3) or IL-12 vector (AdmIL-12.1) into the right knee joint 1 day before intraarticular injection of 25 microg of SCW fragments. The development of joint swelling, changes in chondrocyte proteoglycan (PG) synthesis, and joint destruction were examined thereafter. In normal joints, high levels of IL-12 (20 ng/ml on day 1) could be detected after application of the AdmIL-12.1 vector. After 14 days, expression of IL-12 was still found locally, but IL-12 alone did not induce protracted inflammation. Local expression of IL-12, in combination with SCW, markedly aggravated SCW-induced arthritis, as determined by enhanced joint swelling and prolonged inhibition of chondrocyte PG synthesis. Histologic examination on day 21 showed a chronic inflammatory process, with persistent cartilage PG depletion, cartilage erosion, and VDIPEN neoepitope expression (indicative of metalloproteinase activation). The mixture of IL-12 with SCW fragments did not lead to a chronic destructive process in mice deficient for recombination-activating gene 2, indicating the involvement of lymphocytes. In addition, systemic flare of smoldering SCW arthritis, produced by intravenous injection of SCW fragments, was only seen in the AdmIL-12/SCW group. These results indicate that local overexpression of IL-12 promotes conversion of an acute arthritis to a chronic destructive immune-mediated process, which is more susceptible to flares.

Endogenous regulation of a therapeutic transgene restores homeostasis in arthritic joints

The treatment of chronic inflammatory diseases is complicated by their unpredictable, relapsing clinical course. Here, we describe a new strategy in which an inflammation-regulated therapeutic transgene is introduced into the joints to prevent recurrence of arthritis. To this end, we designed a recombinant adenoviral vector containing a two-component, inflammation-inducible promoter controlling the expression of human IL-10 (hIL-10) cDNA. When tested in vitro, this system had a low-level basal activity and was activated four to five orders of magnitude by various inflammatory stimuli, including TNF-α, IL-1β, IL-6, and LPS. When introduced in joints of rats with recurrent streptococcal cell wall–induced arthritis, the IL-10 transgene was induced in parallel with disease recurrence and effectively prevented the influx of inflammatory cells and the associated swelling of the joints. Levels of inflammation-inducible hIL-10 protein within the joints correlated closely with the severity of recurrence. An endogenously regulated therapeutic transgene can thus establish negative feedback and restore homeostasis in vivo while minimizing host exposure to the recombinant drug.

Endogenous regulation of a therapeutic transgene restores homeostasis in arthritic joints.

The treatment of chronic inflammatory diseases is complicated by their unpredictable, relapsing clinical course. Here, we describe a new strategy in which an inflammation-regulated therapeutic transgene is introduced into the joints to prevent recurrence of arthritis. To this end, we designed a recombinant adenoviral vector containing a two-component, inflammation-inducible promoter controlling the expression of human IL-10 (hIL-10) cDNA. When tested in vitro, this system had a low-level basal activity and was activated four to five orders of magnitude by various inflammatory stimuli, including TNF-alpha, IL-1 beta, IL-6, and LPS. When introduced in joints of rats with recurrent streptococcal cell wall-induced arthritis, the IL-10 transgene was induced in parallel with disease recurrence and effectively prevented the influx of inflammatory cells and the associated swelling of the joints. Levels of inflammation-inducible hIL-10 protein within the joints correlated closely with the severity of recurrence. An endogenously regulated therapeutic transgene can thus establish negative feedback and restore homeostasis in vivo while minimizing host exposure to the recombinant drug.

Suppression of chronic streptococcal cell wall-induced arthritis in Lewis rats by liposomal clodronate.

To investigate the role of macrophages in the pathogenesis of chronic streptococcal cell wall (SCW)-induced arthritis using liposomal clodronate. Female Lewis rats with SCW-induced arthritis received a single intravenous injection of 20 mg of clodronate encapsulated within small unilamellar vesicles (SUVc) 10 days post-arthritis induction. SUVc significantly suppressed the development of chronic SCW-induced arthritis for up to 26 days after treatment. At this time point, ED1(+) macrophages were significantly depleted in the liver and ankle joints, although splenic macrophage numbers were not significantly different from control groups. Macrophage elimination induced a significant reduction in local levels of interleukin (IL)-1beta, IL-6, tumour necrosis factor-alpha (TNFalpha) and matrix metalloproteinase-9 (MMP-9) from ankle joints. Macrophage elimination by SUVc inhibits local production of IL-1beta, IL-6, TNFalpha and MMP-9, and the pathogenesis of inflammatory arthritis.

Aminoethyl-isothiourea inhibits leukocyte production of reactive oxygen species and proinflammatory cytokines induced by streptococcal cell wall components in human whole blood.

The incidence of severe invasive disease caused by serogroup A streptococci (GAS) is increasing, and to elucidate the role of streptococcal cell wall components in the inflammatory response, human whole blood was stimulated with lipoteichoic acid (LTA, 0.005-50 microg/mL) and peptidoglycan (10 and 100 microg/ml) from Streptococcus pyogenes. Both stimulants increased dose dependently the leukocyte release of cytokines many thousand fold: tumor necrosis factor alpha (0 to 158,000+/-4,900 pg/mL), interleukin (IL)-1beta (85+/-56 to 31,000+/-4,600 pg/mL), IL-6 (30+/-11 to 34,800+/-15,000 pg/mL), and IL-8 (300+/-150 to 29,000+/-14,000 pg/mL). Intracellular leukocyte levels of reactive oxygen species (ROS) as measured by flow cytometry increased 15-20 fold, from 25 to 400-500 mean fluorescence intensity. Aminoethyl-isothiourea (AE-ITU), a relatively selective inhibitor of the inducible nitric oxide synthase (iNOS) and a ROS scavenger, reduced the cytokine production by 70-100%, and intracellular leukocyte ROS levels by 50-70% (all P < 0.05). The non-selective NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME) did not affect intracellular ROS levels, but it caused a moderate selective inhibition of IL-8 production. Leukocyte NO production (measured up to 36 h) was not enhanced by LTA, peptidoglycan, inactivated streptococci, or cytokine combinations. The mechanisms for the anti-inflammatory effects of AE-ITU may be through a reduction of intracellular ROS levels, or through a direct effect on signal transduction, whereas NO modulation is an unlikely mechanism.

The discovery of RPR 200765A, a p38 MAP kinase inhibitor displaying a good oral anti-arthritic efficacy

RPR132331, a 2-(2-dioxanyl)imidazole, was identified as an inhibitor of tumour necrosis factor (TNF)α release from lipopolysaccharide (LPS)-stimulated human monocytes. An intensive programme of work exploring the biology, toxicity and physical chemistry of a novel series of inhibitors, derived from RPR132331, has led to the identification of RPR200765A, a development candidate for the treatment of rheumatoid arthritis (RA). RPR200765A is a potent and selective inhibitor of p38 MAP kinase (IC50=50nM). It inhibits LPS-stimulated TNFα release both in vitro, from human monocytes (EC50=110nM), and in vivo in Balb/c mice (ED50=6mg/kg). At oral doses between 10 and 30mg/kg/day it reduces the incidence and progression in the rat streptococcal cell wall (SCW) arthritis model when administered in either prophylactic or therapeutic dosing regimens. The compound, which is a mesylate salt and exists as a stable monohydrate, shows good oral bioavailabiltiy (F=50% in the rat) and excellent chemical stability. The data from the SCW disease model suggests that RPR200765A could exhibit a profile of disease modifying activity in rheumatoid arthritis (RA) patients which is not observed with current drug therapies.

Local interleukin-12 gene transfer promotes conversion of an acute to a chronic destructive murine streptococcal cell wall arthritis

Local interleukin-12 gene transfer promotes conversion of an acute to a chronic destructive murine streptococcal cell wall arthritis

An IFN-gamma-independent proinflammatory role of IL-18 in murine streptococcal cell wall arthritis.

IL-18 is a member of the IL-1 family of proteins that exerts proinflammatory effects. It was formally known as IFN-gamma-inducing factor and is a pivotal cytokine for the development of Th1 responses. Apart from Th1 immune-stimulatory activity, IL-18 induces the production of proinflammatory cytokines such as TNF-alpha and IL-1 in vitro. The goal was to investigate the role of endogenous IL-18 in murine streptococcal cell wall (SCW)-induced arthritis. Furthermore, we investigated whether IL-18 neutralization had an impact on local TNF and IL-1 production. C57BL/6, BALB/c, and IFN-gamma-deficient mice were injected with 2 mg of rabbit anti-murine IL-18 Abs shortly before induction of arthritis by intra-articular injection of 25 microg of SCW fragments into the right knee joint. Suppression of joint swelling was noted on days 1 and 2 of SCW arthritis after blockade of endogenous IL-18. Analysis of local cytokine concentrations showed that IL-18, TNF-alpha, and IL-1ss levels were decreased. Severe inhibition of chondrocyte proteoglycan synthesis was seen in the vehicle-treated control animals, whereas a reversal of the inhibition of chondrocyte proteoglycan synthesis was found in the anti-IL-18-exposed animals. Blockade of endogenous IL-18 in IFN-gamma-deficient mice showed results similar to those found in wild-type animals, identifying a role for IL-18 that is IFN-gamma independent. The present study indicates that IL-18 is a proinflammatory cytokine during the onset of murine SCW arthritis, and this inflammatory role of IL-18 is IFN-gamma independent.

Suppression of streptococcal cell wall-induced arthritis by human chorionic gonadotropin.

To determine whether human chorionic gonadotropin (HCG) contributes to pregnancy-associated immunosuppression, as observed clinically by an amelioration of symptoms in human autoimmune diseases, including rheumatoid arthritis, during pregnancy. Administration of HCG was initiated 2 days prior to an arthritogenic dose of streptococcal cell wall (SCW) in nonpregnant female rats, and the development and severity of SCW-induced arthritis was monitored. Inflammatory mediators, including plasma nitrite/nitrate and cytokine levels, were measured. Inducible nitric oxide synthase (iNOS) protein and cytokine messenger RNA expression in joint tissue were compared between treated and untreated arthritic animals. Systemic administration of HCG resulted in a dose-dependent reduction in the clinical arthritis index. Consistent with the amelioration of clinical symptoms, HCG significantly reduced the inflammatory cell infiltration, pannus formation, and bone and cartilage degradation. Mechanistically, HCG therapy was associated with suppression of the overzealous production of tumor necrosis factor alpha, interleukin-6 (IL-6), and IL-1beta, which contribute to synovial pathology in animals with SCW-induced arthritis. Circulating nitric oxide and the amount of iNOS protein were also reduced. Furthermore, circulating transforming growth factor beta levels were elevated by the HCG, all of which suggest monocytes/macrophages as a potential target. These findings indicate that HCG exerts a protective effect in this experimental arthritis model, through modulation of inflammatory mediators.

Toll-like receptors: molecular mechanisms of the mammalian immune response.

The unrelenting bombardment by microbial pathogens from the environment and their increasing resistance to medical treatments are a constant threat to the survival of all organisms on earth. Microbes are covered by molecular patterns that are common among a broad range of pathogens. These include the lipopolysaccharides (LPS) of Gram-negative bacteria, lipoteichoic acids of Gram-positive bacteria, lipoproteins of bacteria and parasites, glycolipids of mycobacteria, mannans of yeast and double-stranded RNAs of viruses.1,2 Recognition of and responses to these molecules are controlled by a wide variety of cellular receptors. The best characterized receptors are the T-cell receptor and B-cell antibody receptor of the adaptive immune response, the specificity of which is randomly generated and clonally selected during the development of T and B lymphocytes.3 Unlike the receptors of the adaptive immune system, the pattern recognition receptors of the innate immune system have predetermined specificity generated early on in evolution and play an essential role in the determination of self versus non-self during the initial rapid responses to infection.1,2 As described in this review, a family of cell surface receptors, termed Toll-like receptors, are emerging as key regulators of host responses to infection.

Fc gamma R expression on macrophages is related to severity and chronicity of synovial inflammation and cartilage destruction during experimental immune-complex-mediated arthritis (ICA).

STATEMENT OF FINDINGS: We investigated the role of Fc gamma receptors (Fc gamma Rs) on synovial macrophages in immune-complex-mediated arthritis (ICA). ICA elicited in knee joints of C57BL/6 mice caused a short-lasting, florid inflammation and reversible loss of proteoglycans (PGs), moderate chondrocyte death, and minor erosion of the cartilage. In contrast, when ICA was induced in knee joints of Fc receptor (FcR) gamma-chain(-/-) C57BL/6 mice, which lack functional Fc gamma RI and RIII, inflammation and cartilage destruction were prevented. When ICA was elicited in DBA/1 mice, a very severe, chronic inflammation was observed, and significantly more chondrocyte death and cartilage erosion than in arthritic C57BL/6 mice. The synovial lining and peritoneal macrophages of naïve DBA/1 mice expressed a significantly higher level of Fc gamma Rs than was seen in C57BL/6 mice. Moreover, elevated and prolonged expression of IL-1 was found after stimulation of these cells with immune complexes. Zymosan or streptococcal cell walls caused comparable inflammation and only mild cartilage destruction in all strains. We conclude that Fc gamma R expression on synovial macrophages may be related to the severity of synovial inflammation and cartilage destruction during ICA.

Superoxide release and superoxide dismutase expression by human gingival fibroblasts.

Oxygen reactive intermediates released from phagocytic cells are important for microbicidal activity, but they may also be harmful to surrounding cells and matrix components at the inflammation site. In different forms of inflammatory periodontal disease, peripheral and crevicular polymorphonuclear leukocytes, as well as mononuclear phagocytes and gingival fibroblasts, are exposed to bacterial cell wall components and cytokines. The aim of this study was to evaluate if some bacterial components and cytokines induce superoxide release and superoxide dismutase (SOD) expression in gingival fibroblasts. Lipopolysaccharide (LPS), streptococcal cell walls (SCW), and formyl-methionyl-leucyl-phenylalanine were found to stimulate O2- release from gingival fibroblasts, which increased when Ca2+ was added. Phorbol myristate acetate, a potent activator of respiratory burst in phagocytes, was found to be a weak stimulator of O2- release in gingival fibroblasts. Of the cytokines tested, tumor necrosis factor (TNF)-alpha was found to activate superoxide release in gingival fibroblasts. Gene expression for manganese superoxide dismutase (MnSOD), but not for copper/zinc superoxide dismutase (CuZnSOD), was demonstrated in fibroblasts exposed to LPS, SCW and TNF-alpha using Northern blot analysis. The production of MnSOD may be protective for these cells. We conclude that bacterial cell wall components and cytokines modulate O2- release by gingival fibroblasts which may contribute to periodontal pathology.

The Eicosapentaenoic to Docosahexaenoic Acid Ratio of Diets Affects the Pathogenesis of Arthritis in Lew/SSN Rats

Dietary-induced changes in tissue levels of polyunsaturated fatty acids modify inflammatory reactions through changes in the synthesis of lipid and peptide mediators of inflammation. Four semipurified 20% fat diets, based on beef tallow (BT), safflower oil (SFO), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were provided. The DHA and EPA ratios of the (n-3) fatty acid-based diets were 1.1 and 3.4, respectively. The effect of prefeeding diets differing in EPA to DHA ratios prior to the induction of streptococcal cell wall (SCW) arthritis in female Lew/SSN rats was examined. Weanling rats were fed diets for 5 wk before arthritis induction and 5 wk post-arthritis induction. Footpad thickness, hock circumference, plasma and macrophage fatty acids and histological assessment were compared. There were no differences in food intake and final body weights among the groups. Footpad inflammation, reported as percentage change (adjusted for growth) was greatest for rats fed the BT-based diet, intermediate in those fed the SFO-based diet and least for the rats fed the EPA- and DHA-based diets (P < 0.05). Macrophage phospholipids revealed cellular incorporation of EPA and DHA from the fish-oil based diets which modified lipid and peptide mediators of inflammation. Histological sections of rat hocks ranked by severity of arthritis-related changes suggested that the SFO- and EPA-based diets were more successful in ameliorating the destructive arthritic phase in hock joints than the BT- and DHA-based diets (P = 0.09) in this model of arthritis. The course of SCW-induced arthritis can be altered by diet-induced changes in macrophage fatty acid composition. The EPA-based diet is more effective in suppression of inflammation than the DHA-based diet.

Peptidoglycan and lipoteichoic acid, components of the streptococcal cell wall, have marked and differential effects on adhesion molecule expression and the production of reactive oxygen species in human whole blood leukocytes

To elucidate the pathophysiology of infections with Streptococcus pyogenes we applied flow cytometric techniques to study dose-response and time-related effects of the streptococcal cell-wall-derived components lipoteichoic acid (LTA 0.005 to 50 microg/ml) and peptidoglycan (10 and 100 microg/ml) on the expression of leukocyte adhesion molecules, the CD14 receptor, and the production of leukocyte reactive oxygen species (ROS). LTA (50 microg/ml, 1-2 h) markedly increased the expression of CD11b (approximately 5-fold), CD11c (approximately 2-fold) and CD11a. Concomitantly, CD62L was downregulated (60%). Peptidoglycan alone or in combination with LTA had little effect on adhesion molecules, except for an amplification of the downregulation of CD62L to 90%. Monocyte CD14 expression was doubled by LTA. Leukocyte ROS production was 10-fold and 5-fold increased by peptidoglycan in granulocytes and monocytes, respectively. LTA alone had no effect, while the combination of peptidoglycan with LTA doubled the increase in ROS caused by peptidoglycan. LTA and peptidoglycan had marked and differential effects: LTA caused mainly adhesion molecule modulation, whereas peptidoglycan mainly increased ROS production. These changes are important in inflammatory cell activation and recruitment, intracellular microbial killing and adverse tissue injury.

Perturbations of arginine vasopressin secretion during inflammatory stress. Pathophysiologic implications.

Pro-inflammatory cytokines, such as interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF alpha), released from inflammatory foci, can activate the hypothalamus to produce corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP). These hypothalamic peptides in synergy increase ACTH production by the pituitary gland and hence corticosteroid (CS) secretion by the adrenal cortices. CS dampens inflammation. The pituitary also produces prolactin (PRL), which is pro-inflammatory, and macrophage inhibitory factor (MIF), which by counteracting the anti-inflammatory and immunosuppressive effects of CS, is pro-inflammatory. Lewis rats develop a variety of induced-autoimmune inflammatory conditions, such as streptococcal cell wall arthritis, whereas the histocompatible F344 Fisher rats are resistant to this condition. Lewis rats have a defective hypothalamic-pituitary adrenal (HPA) response to a variety of hypothalamic stimuli, but have augmented systemic secretion of AVP. Patients with rheumatoid arthritis (RA) have deficient CS with exaggerated PRL responses to inflammatory stimuli. Within inflammatory foci, CRH is pro-inflammatory. AVP, which augments autologous mixed lymphocyte reactions, can replace the IL-2 requirement for gamma IFN production by T cells via V1a receptors, and potentiates primary antibody responses, is also pro-inflammatory. Lewis rats have significantly high plasma levels, hypothalamic content, and in vitro release of AVP in comparison to the inflammatory disease-resistant Fischer rats. Immunoneutralization of AVP attenuates inflammatory responses. In Sprague-Dawley rats, AVP potentiates PRL secretion. Preliminary studies in patients with RA have shown that the circulating levels of AVP are significantly increased, which might be a compensatory response to low CS levels or a result of elevated levels of IL-6 in these patients but could nevertheless contribute to rheumatoid inflammation. A similar observation has been made in patients with ankylosing spondylitis.

IMMUNE COMPLEXES, BUT NOT STREPTOCOCCAL CELL WALLS OR ZYMOSAN, CAUSE CHRONIC ARTHRITIS IN MOUSE STRAINS SUSCEPTIBLE FOR COLLAGEN TYPE II AUTO-IMMUNE ARTHRITIS

In this study we investigated mechanisms involved in the chronic character of experimental collagen type II induced arthritis (CIA). We compared the knee joints of mouse strains which are prone to develop this autoimmune disease (DBA/1,B10RIII) with other nonsusceptible mouse strains (C57Bl/6,BALB/c) in their reaction to different stimuli: immune complexes (IC), zymosan and streptococcal cell walls (SCW). Inflammation was evaluated by99mTc uptake measurements and in haematoxylin- and eosin-stained knee-joint sections. Passively induced immune complex mediated arthritis (ICA) in knee joints of C57Bl/6 and BALB/c mice, showed moderate cell influx at day 3, whereas at day 7 only minor amounts of inflammatory cells were observed. In contrast, in arthritic DBA/1 and, to a lesser extent, in B10.RIII joints, a tremendous cell influx was observed at day 3 and even at day 14 there was still significant synovitis. In contrast, if arthritis was elicited by intra-articular injection of zymosan or SCW in C57Bl/6 and DBA/1, the course of inflammation was similar in both strains and no chronic inflammation developed. In line with severe arthritis, chemotactic factor production was dramatically enhanced in ICA in DBA/1 mice, and a prolonged production of IL-1 was evident. When IL-1 was neutralized before or during the ICA using specific anti-IL-1α,β antibodies, inflammation could be blocked completely. Single or multiple injection of IL-1 in the knee joint of C57Bl/6 or DBA/1 showed comparable inflammation, indicating that the chemotactic response per se is comparable in both strains. No prolonged production of IL-1 was found during zymosan or SCW arthritis. Selective removal of macrophages from the synovial intima prior to ICA induction (using clodronate-containing liposomes) prevented the onset of inflammation in C57Bl/6 and DBA/1 mice. It can be concluded that immune complexes, but not zymosan or SCW, cause a more severe and chronic arthritis in mouse strains which are susceptible for collagen type II autoimmune arthritis. This is due to higher and prolonged expression of IL-1 and chemotactic factors, caused by stimulation with immune complexes. The interaction of IC with lining macrophages probably plays a dominant role in development of chronicity.

Effects of the phosphodiesterase inhibitor rolipram on streptococcal cell wall-induced arthritis in rats

The phosphodiesterase-IV (PDE-IV) inhibitor, rolipram, is antiinflammatory in a number of animal models and inhibits the release of a variety of cytokines, including TNFα. Arthritis induced in rats by systemic reactivation with streptococcal cell walls (SCW) following intraarticular sensitization is a TNFα-dependent, delayed-type hypersensitivity (DTH) reaction. Rolipram administered during the reactivation phase dose-dependently inhibited hind paw edema through day 24, the day of peak swelling. PMN and T-cell recruitment to the arthritic joint were also attenuated in rolipram-treated rats. Histologic examination of ankle sections from rolipram-treated animals showed a marked attenuation of synovial inflammation. Mechanistic studies to determine the role of glucocorticoids in mediating rolipram action showed that the inhibitory effect of rolipram on swelling was not reversed by RU 486, a glucocorticoid antagonist. In contrast, RU 486 reversed the inhibitory effects of rolipram on TNFα secretion. To further evaluate the role of cAMP in the model, the β-adrenergic receptor (βAR) agonist isoproterenol was tested, and found to inhibit swelling but not the release of TNFα. These results are consistent with the view that the inhibitory effects of rolipram may be partially mediated by cAMP-dependent, but TNFα-independent, mechanisms. The βAR antagonists propranolol and nadolol had no appreciable affect on the antiinflammatory effect of rolipram. However, rolipram reversed the lethal effects of the antagonists observed when either was administered alone. Apparently, β-adrenergic mechanisms moderate the response to challenge, and rolipram treatment, presumably as a result of its effects on cAMP levels, reverses the toxic effect of the antagonists.

Inhibition of Bacterial Cell Wall-Induced Leukocyte Recruitment and Hepatic Granuloma Formation by TGF-β Gene Transfer

Abstract Intraperitoneal injection of streptococcal cell walls (SCW) into Lewis rats results in dissemination of SCW to the liver, spleen, bone marrow, and peripheral joints. The uptake of SCW by Kupffer cells in the liver initiates a chain of events largely mediated by T lymphocytes and macrophages. Local synthesis and secretion of cytokines and growth factors in response to the persistent SCW lead to the evolution and maintenance of a chronic T cell-dependent granulomatous response and result in granuloma formation and irreversible hepatic fibrosis. In an attempt to impede the development of the chronic granulomatous lesions in the liver, we injected a plasmid DNA encoding TGF-β1 i.m. to the SCW animals to determine the effect of TGF-β1 gene transfer on the course of liver inflammation and fibrosis. A single injection of plasmid DNA encoding TGF-β1 resulted in virtual abolition of the development of the SCW-induced hepatic granuloma formation and matrix expansion. TGF-β1 DNA not only reduced key proinflammatory cytokines including TNF-α, IL-1β, IFN-γ, and IL-18, but also inhibited both CXC and CC chemokine production, thereby blocking inflammatory cell recruitment and accumulation in the liver. Moreover, TGF-β1 gene delivery inhibited its own expression in the liver tissue, which is otherwise up-regulated in SCW-injected animals. Our study suggests that TGF-β1 gene transfer suppresses hepatic granuloma formation by blocking the recruitment of inflammatory cells to the liver, and thus may provide a new approach to the control of hepatic granulomatous and fibrotic diseases.

The staphylococcal transferrin-binding protein is a cell wall glyceraldehyde-3-phosphate dehydrogenase.

Staphylococcus aureus and Staphylococcus epidermidis possess a 42-kDa cell wall transferrin-binding protein (Tpn) which is involved in the acquisition of transferrin-bound iron. To characterize this protein further, cell wall fractions were subjected to two-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis blotted, and the N-terminus of Tpn was sequenced. Comparison of the first 20 amino acid residues of Tpn with the protein databases revealed a high degree of homology to the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Analysis of staphylococcal cell wall fractions for GAPDH activity confirmed the presence of a functional enzyme which, like Tpn, is regulated by the availability of iron in the growth medium. To determine whether Tpn is responsible for this GAPDH activity, it was affinity purified with NAD+ agarose. Both S. epidermidis and S. aureus Tpn catalyzed the conversion of glyceraldehyde-3-phosphate to 1,3-diphosphoglycerate. In contrast, Staphylococcus saprophyticus, which lacks a Tpn, has no cell wall-associated GAPDH activity. Native polyacrylamide gel electrophoresis of the affinity-purified Tpn revealed that it was present in the cell wall as a tetramer, consistent with the structures of all known cytoplasmic GAPDHs. Furthermore, the affinity-purified Tpn retained its ability to bind human transferrin both in its native tetrameric and SDS-denatured monomeric forms. Apart from interacting with human transferrin, Tpn, in common with the group A streptococcal cell wall GAPDH, binds human plasmin. Tpn-bound plasmin is enzymatically active and therefore may contribute to the ability of staphylococci to penetrate tissues during infections. These studies demonstrate that the staphylococcal transferrin receptor protein, Tpn, is a multifunctional cell wall GAPDH.

Identification and characterization of a lysis module present in a large proportion of bacteriophages infecting Streptococcus thermophilus.

A lysis module encoded by the temperate bacteriophage phiO1205 was identified. This lysis module contains a lysin gene, designated lyt51, and two putative holin-encoding genes, designated lyt49 and lyt50. lyt51 encodes a lytic enzyme specifically directed against streptococcal cell walls. Similar to other phage-encoded lysins, Lyt51 appears to have a modular design in which the N-terminal portion corresponds to its enzymatic activity while the C-terminal region is responsible for its substrate binding specificity. The two putative holin-encoding genes, lyt49 and lyt50, located immediately upstream of lyt51, were identified on the basis of their homology to other identified holin-encoding genes. Expression of lyt49 or lyt50 in Escherichia coli was shown to cause cell death and leakage of the intracellular enzyme isocitrate dehydrogenase into the growth medium without apparent lysis of the cells. Southern blotting experiments demonstrated that at least one of the three components of the identified lysis module is present in all members of a large collection of bacteriophages, indicating that components of this lysis module are widespread among bacteriophages infecting Streptococcus thermophilus.