Tumor necrosis factor-alpha blockade: a novel therapy for rheumatic disease

Pharmacological treatment of established rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory condition of unknown aetiology that affects about 1% of the general population. Although the optimal care of RA patients requires various modalities, pharmacotherapy remains the cornerstone of treatment for established RA. The current therapeutic model encourages a step-up approach that safely incorporates several currently available classes of agents: non-steroidal anti-inflammatory drugs, selective cyclo-oxygenase-2 inhibitors, glucocorticoids, disease-modifying anti-rheumatic drugs, and biological agents (tumour necrosis factor-alpha inhibitors and interleukin-1 receptor antagonist). Non-steroidal anti-inflammatory drugs, selective cyclo-oxygenase-2 inhibitors and glucocorticoids, which offer a quick onset of symptom relief, are used mainly as adjunctive therapies. Disease-modifying anti-rheumatic drugs and biologicals have been successful in altering disease outcome and slowing radiographic progression. The indications, efficacy and safety of these agents in clinical trials and practice are reviewed in this chapter.

Reactivation of latent tuberculosis infection in TNF-deficient mice

TNF-deficient mice are highly susceptible to Mycobacterium tuberculosis H37Rv infection. Here we asked whether TNF is required for postinfectious immunity in aerosol-infected mice. Chemotherapy for 4 wk commencing 2 wk postinfection reduced CFU to undetectable levels. While wild-type mice had a slight rise in CFU, but controlled infection upon cessation of chemotherapy, TNF-deficient mice developed reactivation of infection with high bacterial loads in lungs, spleen, and liver, which was fatal within 13-18 wk. The increased susceptibility of TNF-deficient mice was accompanied by diminished recruitment and activation of T cells and macrophages into the lung, with defective granuloma formation and reduced inducible NO synthase expression. Reduced chemokine production in the lung might explain suboptimal recruitment and activation of T cells and uncontrolled infection. Therefore, despite a massive reduction of the mycobacterial load by chemotherapy, TNF-deficient mice were unable to compensate and mount a protective immune response. In conclusion, endogenous TNF is critical to maintain latent tuberculosis infection, and in its absence no specific immunity is generated.

Latent tuberculosis: mechanisms of host and bacillus that contribute to persistent infection

Most people infected with Mycobacterium tuberculosis contain the initial infection and develop latent tuberculosis. This state is characterised by evidence of an immune response against the bacterium (a positive tuberculin skin test) but no signs of active infection. It can be maintained for the lifetime of the infected person. However, reactivation of latent infection occurs in about 10% of infected individuals, leading to active and contagious tuberculosis. An estimated 2 billion people worldwide are infected with M tuberculosis--an enormous reservoir of potential tuberculosis cases. The establishment and reactivation of latent infection depend on several factors, related to both host and bacterium. Elucidation of the host immune mechanisms that control the initial infection and prevent reactivation has begun. The bacillus is well adapted to the human host and has a range of evasion mechanisms that contribute to its ability to avoid elimination by the immune system and establish a persistent infection. We discuss here current understanding of both host and bacterial factors that contribute to latent and reactivation tuberculosis.

Secondary immune deficiencies associated with biological therapeutics

Biological therapeutics have been utilized in the past several years for the treatment of various autoimmune, cardiovascular, and neoplastic conditions. As these agents target both pathologic and physiologic components of inflammatory and immune systems, the scientific community has been challenged to identify potential secondary immune deficiencies associated with their use. This article will focus on biological agents used for the treatment of rheumatoid arthritis, including tumor necrosis factor-a inhibitors, cytotoxic T lymphocyte-associated antigen-4 (CTLA-4 Ig), rituximab, and interleukin-1 receptor agonist (IL-1Ra). Both clinical and in vitro studies have been done to explore the potential immunomodulatory and immunosuppressive effects of these agents.

Role of tumor necrosis factor-alpha in graft-versus-host disease and graft-versus-leukemia responses

Tumor necrosis factor-alpha (TNF-alpha) antagonist therapy has proven effective in inflammatory conditions such as rheumatoid arthritis and Crohn's disease. There is substantial evidence that TNF-alpha also plays a role in the development of graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation, which along with leukemia relapse remains one of the 2 major impediments to success of the approach. Using a recently developed potent rat/mouse chimeric monoclonal antibody directed against murine TNF-alpha (CNTO2213), the authors investigated the effect of TNF-alpha blockade on GVHD mediated by either CD4(+) or CD8(+) donor T cells. The results indicated that the treatment had only a moderate effect on both a CD8(+) T cell-mediated major histocompatibility complex-matched GVHD model involving multiple minor histocompatibility antigens and a p-->F(1) acute GVHD model directed against a haplo-mismatched major histocompatibility complex barrier involving both CD4(+) and CD8(+) T cells. In contrast, treatment with the anti-TNF-alpha antibody had a highly significant effect (100% survival rate) on the CD4(+) T cell-mediated component of this latter model. Importantly, anti-TNF-alpha antibody did not block the development of a graft-versus-leukemia effect against a murine myeloid leukemia challenge in either a syngeneic or allogeneic p-->F(1) setting. This suggests that the inhibition of TNF-alpha during allogeneic hematopoietic cell transplantation may be able to diminish the inflammatory GVHD reaction without hindering effective graft-versus-leukemia responses.

High-density lipoproteins protect isolated rat hearts from ischemia-reperfusion injury by reducing cardiac tumor necrosis factor-alpha content and enhancing prostaglandin release

The incidence and severity of primary cardiac events are inversely related to the plasma concentration of high-density lipoproteins (HDLs). We investigated whether HDLs may exert a direct cardioprotection in buffer-perfused isolated rat hearts, which underwent a 20-minute low-flow ischemia followed by a 30-minute reperfusion. The administration of HDLs at physiological concentrations (0.5 and 1.0 mg/mL) during the 10 minutes immediately before ischemia rapidly and remarkably improved postischemic functional recovery and decreased creatine kinase release in the coronary effluent. Reconstituted HDLs containing apolipoprotein A-I (apoA-I) and phosphatidylcholine, but not lipid-free apoA-I or phosphatidylcholine liposomes, were also effective in protecting the heart from ischemia-reperfusion injury. HDLs at reperfusion were less effective than when given before ischemia. HDLs caused a dose-dependent reduction of ischemia-induced cardiac tumor necrosis factor-alpha (TNF-alpha) expression and content, which correlated with the improved functional recovery. A parallel increase of TNF-alpha release in the coronary effluent was observed, due to a direct binding of cardiac TNF-alpha to HDLs. Taken together, these findings argue for a cause-effect relationship between the HDL-mediated removal of TNF-alpha from the ischemic myocardium and the HDL-induced cardioprotection. Indeed, etanercept, a recombinant TNF-alpha-blocking protein, caused a dose-dependent improvement of postischemic functional recovery. HDLs also enhanced ischemia-induced prostaglandin release, which may contribute to the cardioprotective effect. A low plasma HDL level may expose the heart to excessive ischemia-reperfusion damage, and HDL-targeted therapies may be helpful to induce immediate or delayed myocardial protection from ischemia-reperfusion injury.

Lucigenin chemiluminescence assay as an adjunctive tool for assessment of various stages of inflammation: a study of quiescent inflammatory cells

A simple, fast, precise and biologically relevant toxicity assay for screening cytotoxicity of minerals would have distinct advantages due to its cost benefits and relative savings in time. Furthermore, a bioassay to differentiate acute and chronic in vivo pulmonary reactions could have potential value as predictors of fibrogenicity and pathogenicity. In this study we examined the potential use of lucigenin as a probe to evaluate the correlation between chemiluminescence (CL) generated by alveolar macrophages with the known cytotoxicity and patho genicity by conventional bioassays. In this study, we used small doses of dust (20 microg) to minimize cellular overload and to maintain homeostasis. Crystalline silica a highly fibrogenic dust was used as positive control and results are compared with those for bentonite, kaolin and talc. Among the three minerals compared with silica, bentonite was more reactive (27%) in CL assay and declined sharply compared to other minerals. This sudden decline in bentonite CL is caused by cytotoxicity leading to cell death. CL-induced by talc was comparable to silica and declines slowly. Kaolin on the other hand produced relatively a weaker (25%) CL compared to silica. Our data using relatively low doses of dust suggest that the CL assay may have a better predictive value in cytotoxicity evaluations compared to conventional toxicity assays.

Inflammation and cancer

Recent data have expanded the concept that inflammation is a critical component of tumour progression. Many cancers arise from sites of infection, chronic irritation and inflammation. It is now becoming clear that the tumour microenvironment, which is largely orchestrated by inflammatory cells, is an indispensable participant in the neoplastic process, fostering proliferation, survival and migration. In addition, tumour cells have co-opted some of the signalling molecules of the innate immune system, such as selectins, chemokines and their receptors for invasion, migration and metastasis. These insights are fostering new anti-inflammatory therapeutic approaches to cancer development.

Inflammation and cancer

Recent data have expanded the concept that inflammation is a critical component of tumour progression. Many cancers arise from sites of infection, chronic irritation and inflammation. It is now becoming clear that the tumour microenvironment, which is largely orchestrated by inflammatory cells, is an indispensable participant in the neoplastic process, fostering proliferation, survival and migration. In addition, tumour cells have co-opted some of the signalling molecules of the innate immune system, such as selectins, chemokines and their receptors for invasion, migration and metastasis. These insights are fostering new anti-inflammatory therapeutic approaches to cancer development.

Inflammation and cancer

Recent data have expanded the concept that inflammation is a critical component of tumour progression. Many cancers arise from sites of infection, chronic irritation and inflammation. It is now becoming clear that the tumour microenvironment, which is largely orchestrated by inflammatory cells, is an indispensable participant in the neoplastic process, fostering proliferation, survival and migration. In addition, tumour cells have co-opted some of the signalling molecules of the innate immune system, such as selectins, chemokines and their receptors for invasion, migration and metastasis. These insights are fostering new anti-inflammatory therapeutic approaches to cancer development.