Treatment with a Toll-like Receptor 7 ligand evokes protective immunity against atherosclerosis in hypercholesterolaemic mice.

BACKGROUND: The interplay between innate and adaptive immunity is central in life-threatening clinical complications of atherosclerosis such as myocardial infarction and stroke. The specific mechanisms involved and their protective versus detrimental effects in the disease process remain poorly understood. We have previously shown that higher levels of Toll-like receptor 7 (TLR7) expression in human atherosclerotic lesions are correlated with better patient outcome. OBJECTIVE: In this study, we explored whether TLR7 activation can ameliorate disease in experimental atherosclerosis in mice. METHODS: Apolipoprotein E deficient mice (Apoe-/- ) with established disease were injected for five weeks intraperitoneally with the TLR7 ligand R848. Local effects were evaluated by characterization of the lesion. Systemic effects of the treatment were investigated by immune composition analysis in the spleen and plasma measurements. RESULTS: The in vivo treatment arrested lesion progression in the aorta. We also detected expansion of marginal zone B cells and Treg in the spleen together with increased plasma IgM antibodies against oxidized low-density lipoprotein (oxLDL) and reduced plasma cholesterol levels. These changes were accompanied by increased accumulation of IgM antibodies, decreased necrosis and fewer apoptotic cells in atherosclerotic lesions. CONCLUSIONS: Our findings show that TLR7 stimulation could ameliorate atherosclerotic lesion burden and reduce plasma cholesterol in Apoe-/- mice. TLR7 stimulation was associated with an atheroprotective B-cell and Treg response, which may have systemic and local effects within lesions that could prevent arterial lipid accumulation and inflammation.

Expression of type III interferons (IFNλs) and their receptor in Sjögren's syndrome.

Type III interferons (IFNs) or IFN-λs (IFN-λ1/IL29, IFN-λ2/interleukin (IL)-28A and IFN-λ3/IL-28B) consist of a recently identified group of IFNs, implicated initially in several human diseases, including cancer and autoimmunity. In this study, we sought to investigate the expression of type III IFNs and their common receptor IFN-λR1/IL-28Ra in Sjögren's syndrome (SS). Type III IFN expression was examined in minor salivary gland tissues (MSG), peripheral blood mononuclear cells (PBMCs), sera and resting or Toll-like receptor (TLR)-stimulated salivary gland epithelial cells (SGEC) from SS patients and sicca-complaining controls. All type III IFN family members were detected in ductal and acinar epithelia of MSGs from both SS patients and sicca controls. IFN-λ2/IL-28A and IFN-λ3/IL-28B were also expressed in infiltrating mononuclear cells. In SS patients with intermediate MSG lesions, the epithelial expression of IFN-λ2/IL-28A was more intense compared to sicca controls (P < 0·05). The receptor IFN-λR1/IL-28Ra was detected in all types of cells except fibroblasts, and was exceptionally strong in plasmatocytoid dendritic cells, indicating that they are susceptible to type III IFN-mediated regulation. In the periphery, only IFN-λ1/IL-29 was detected in the sera and was elevated significantly in SS patients with intermediate MSG inflammatory lesions compared to sicca controls (P = 0·0053). None of the type III IFNs was expressed constitutively in resting SGECs; they were all induced readily by TLR-3 stimulation, suggesting that the in-situ epithelial expression can be attributed to local microenvironment. Type III IFNs are expressed in MSGs in a similar pattern to type I IFNs and their expression is probably subjected to micro-environmental regulation, suggesting that they are implicated in the inflammatory processes occurring in the affected exocrine glands.

Evidence for a DC-specific inhibitory mechanism that depends on MyD88 and SIGIRR.

Dendritic cells (DC) are an essential link between the innate and adaptive immune response. To become effective antigen-presenting cells DC need to undergo maturation, during which they up-regulate co-stimulatory molecules and produce cytokines. There is great interest in utilizing DC in vaccination regimes. Over recent years, Toll-like receptor (TLR) signalling has been recognized to be one of the major inducers of DC maturation. This study describes a mutant version of the TLR adaptor molecule MyD88 (termed MyD88lpr) as a novel adjuvant for vaccination regimes. MyD88lpr specifically activates DC by disrupting a DC intrinsic inhibitory mechanism, which is dependent on single immunoglobulin IL-1R-related. Moreover, MyD88lpr was able to induce an IgG2a-dominated response to a co-expressed antigen, suggesting Th1 immunity. However, when used as a vaccine adjuvant for Influenza nucleoprotein there was no significant difference in the lung viral titres during the infection. This study describes MyD88lpr as a potential adjuvant for vaccinations, which would be able to target DC specifically.

Targeting intracellular mediators of pattern-recognition receptor signalling to adjuvant vaccination.

PRR (pattern-recognition receptor) signalling is involved early in the immune response and therefore would be attractive to target during vaccination. The use of PRR ligands has shown some success; however, toxicity and non-specificity are issues with this strategy. The targeting of PRR intracellular signalling networks would allow for greater specificity and reduced systemic toxicity. The present review examines the successes seen with overexpression or repression of PRR signalling molecules.

Activation of NF-kappaB by the intracellular expression of NF-kappaB-inducing kinase acts as a powerful vaccine adjuvant.

There is a pressing need for adjuvants that will enhance the effectiveness of genetic vaccines. This is particularly important in cancer and infectious disease such as HIV and malaria for which successful vaccines are desperately needed. Here, we describe an approach to enhance immunogenicity that involves the activation of NF-kappaB by the transgenic expression of an intracellular signaling molecule, NF-kappaB-inducing kinase (NIK). In vitro, NIK increases dendritic cell antigen presentation in allogeneic and antigen-specific T cell proliferation assays by potently activating NF-kappaB and consequently up-regulating the expression of cytokines (TNF-alpha, IL-6, IL-12, IL-15, and IL-18), chemokines [IL-8, RANTES (regulated on activation, normal T cell expressed and secreted), macrophage inflammatory protein-1alpha, monocyte chemoattractant protein-1, and monocyte chemoattractant protein-3], MHC antigen-presenting molecules (class I and II), and costimulatory molecules (CD80 and CD86). In vivo, NIK enhances immune responses against a vector-encoded antigen and shifts them toward a T helper 1 immune response with increased IgG2a levels, T cell proliferation, IFN-gamma production, and cytotoxic T lymphocyte responses more potently than complete Freund's adjuvant, a very efficacious T helper 1-inducing adjuvant. These findings define NIK, and possibly other inducers of NF-kappaB activation, as a potent adjuvant strategy that offers great potential for genetic vaccine development.

Evolving radiological features of hypothalamo-pituitary lesions in adult patients with Langerhans cell histiocytosis (LCH).

Langerhans cell histiocytosis (LCH) is a rare, systemic disease caused by monoclonal expansion of dendritic cells that shows a particular predilection for the hypothalamic-pituitary system (HPS). We studied the function (anterior and posterior pituitary hormonal secretion) and morphology using magnetic resonance imaging (MRI) of the HPS in 17 adult patients (seven males, median age 35 years, range 18-59 years) with multisystem LCH. We also evaluated the evolution of structural HPS abnormalities in relation to pituitary function and response to treatment in 12 of these patients during a median follow-up period of 3.75 years (range 1.5-10 years). Of the 17 patients, 14 (82%) had abnormal HPS imaging, and 12 (70%) had more than one area involved. Lack of the bright spot of the posterior pituitary lobe was typically found in all patients with the diagnosis of diabetes insipidus (DI). Eight patients (47%) had infundibular enlargement, six (35%) pituitary infiltration, four (24%) partially or completely empty sella, three (18%) hypothalamic involvement, and two (12%) infundibular atrophy. DI was found in 16 patients (94%) and anterior pituitary hormonal deficiency (APHD) in 10 patients (59%); two patients had single (12%) and 8 (47%) multiple APHD. During the follow-up period there was improvement of the initially demonstrated HPS pathology in seven (47%) patients, and five (33%) of them had received at least one form of treatment. APHD and DI persisted in all patients except in one in whom established gonadotrophin deficiency recovered. In summary, DI and APHD are very common in patients with multisystem LCH and are almost always associated with abnormal HPS imaging.

Common and uncommon features of rheumatoid arthritis and chronic obstructive pulmonary disease: clues to a future therapy.

Over the last decade it has become apparent that common pathogenic mechanisms are shared between many human chronic inflammatory diseases of unrelated pathology and manifestation. These mechanisms include common inflammatory networks that control tissue destructive and repair processes and their study is of major therapeutic potential as recently demonstrated for TNFalpha. Thus, early studies in rheumatoid arthritis defined TNFalpha as a major therapeutic target, the blockade of which was subsequently proved to be of great efficacy in the clinic. This paved the way for the successful blockade of TNFalpha in various other diseases including Crohn's disease, psoriasis, spondyloarthropathies and juvenile arthritis, although no similar networks with anti-TNFalpha at their apex had previously been demonstrated. In this article, we review the current knowledge of the pathogenic mechanisms involved in rheumatoid arthritis and chronic obstructive pulmonary disease with particular emphasis on the role of inflammatory cytokines, chemokines, and tissue degrading enzymes as revealed by studies in the laboratory and the clinic. Direct comparison of these mechanisms may provide clues for a future therapy for these painful and incurable diseases.

TNF autovaccination induces self anti-TNF antibodies and inhibits metastasis in a murine melanoma model.

TNF is a proinflammatory cytokine involved in the pathogenesis of chronic inflammatory diseases, but also in metastasis in certain types of cancer. In terms of therapy, TNF is targeted by anti-TNF neutralising monoclonal antibodies or soluble TNF receptors. Recently, a novel strategy based on the generation of self anti-TNF antibodies (TNF autovaccination) has been developed. We have previously shown that TNF autovaccination successfully generates high anti-TNF antibody titres, blocks TNF and ameliorates collagen-induced arthritis in DBA/1 mice. In this study, we examined the ability of TNF autovaccination to generate anti-TNF antibody titres and block metastasis in the murine B16F10 melanoma model. We found that immunisation of C57BL/6 mice with TNF autovaccine produces a 100-fold antibody response to TNF compared to immunisation with phosphate-buffered saline vehicle control and significantly reduces both the number (P<0.01) and size of metastases (P<0.01) of B16F10 melanoma cells. This effect is also observed when an anti-TNF neutralising monoclonal antibody is administered, confirming the essential role TNF plays in metastasis in this model. This study suggests that TNF autovaccination is a cheaper and highly efficient alternative that can block TNF and reduce metastasis in vivo and trials with TNF autovaccination are already underway in patients with metastatic cancer.

Is NF-kappaB a useful therapeutic target in rheumatoid arthritis?

There is increasing evidence that NF-kappaB is a major, if not the major transcription factor regulating inflammation and immunity. While this implies that blocking NF-kappaB might be therapeutically beneficial, it raises clear questions regarding the balance between efficacy and safety. In this brief review we discuss the effects of NF-kappaB blockade in rheumatoid arthritis, inflammation and immunity, and consider possible therapeutic targets within the NF-kappaB family.

NF-kappaB-inducing kinase is dispensable for activation of NF-kappaB in inflammatory settings but essential for lymphotoxin beta receptor activation of NF-kappaB in primary human fibroblasts.

The transcription factor NF-kappaB is of major importance in the biology of pro-inflammatory cytokines, such as TNF-alpha and IL-1alpha, and thereby is intimately involved in the process of inflammation. Understanding the mechanisms by which NF-kappaB is activated in response to inflammatory stimuli has become a major goal of inflammation research. The discovery of NF-kappaB-inducing kinase (NIK) as a TNFR-associated factor-interacting enzyme and a potential activator of the IkappaBalpha-kinase complex appeared to have identified an important element of the NF-kappaB activation pathway, a view that was supported by several subsequent studies. However, recent experiments in the alymphoplasia (aly/aly) mouse, which has missense point mutation (G885R) in NIK, has challenged that view. The reasons for the discrepancy between the different studies is unclear and could be due to multiple factors, such as cell type, species of cell, or primary vs transformed cell lines. One system that has not been investigated is primary human cells. Using an adenoviral vector encoding kinase-deficient NIK, we have investigated the role of NIK in LPS, IL-1, TNF-alpha, and lymphotoxin (LT) betaR signaling in primary human cells and TNF-alpha expression from rheumatoid tissue. These data show that, in the primary systems tested, NIK has a restricted role in LTbetaR signaling and is not required by the other stimuli tested. Also, there is no apparent role for NIK in the process of TNF-alpha production in human rheumatoid arthritis. These data also highlight the potential problems in extrapolating the function of signaling pathways between primary and transfected cell lines.

The nonpsychoactive cannabis constituent cannabidiol is an oral anti-arthritic therapeutic in murine collagen-induced arthritis.

The therapeutic potential of cannabidiol (CBD), the major nonpsychoactive component of cannabis, was explored in murine collagen-induced arthritis (CIA). CIA was elicited by immunizing DBA/1 mice with type II collagen (CII) in complete Freund's adjuvant. The CII used was either bovine or murine, resulting in classical acute CIA or in chronic relapsing CIA, respectively. CBD was administered after onset of clinical symptoms, and in both models of arthritis the treatment effectively blocked progression of arthritis. CBD was equally effective when administered i.p. or orally. The dose dependency showed a bell-shaped curve, with an optimal effect at 5 mg/kg per day i.p. or 25 mg/kg per day orally. Clinical improvement was associated with protection of the joints against severe damage. Ex vivo, draining lymph node cells from CBD-treated mice showed a diminished CII-specific proliferation and IFN-gamma production, as well as a decreased release of tumor necrosis factor by knee synovial cells. In vitro effects of CBD included a dose-dependent suppression of lymphocyte proliferation, both mitogen-stimulated and antigen-specific, and the blockade of the Zymosan-triggered reactive oxygen burst by peritoneal granulocytes. It also was found that CBD administration was capable of blocking the lipopolysaccharide-induced rise in serum tumor necrosis factor in C57/BL mice. Taken together, these data show that CBD, through its combined immunosuppressive and anti-inflammatory actions, has a potent anti-arthritic effect in CIA.