Risk of tuberculosis infection in anti-TNF-α biological therapy: from bench to bedside

A New Venue of TNF Targeting

The first Food and Drug Administration-(FDA)-approved drugs were small, chemically-manufactured and highly active molecules with possible off-target effects, followed by protein-based medicines such as antibodies. Conventional antibodies bind a specific protein and are becoming increasingly important in the therapeutic landscape. A very prominent class of biologicals are the anti-tumor necrosis factor (TNF) drugs that are applied in several inflammatory diseases that are characterized by dysregulated TNF levels. Marketing of TNF inhibitors revolutionized the treatment of diseases such as Crohn’s disease. However, these inhibitors also have undesired effects, some of them directly associated with the inherent nature of this drug class, whereas others are linked with their mechanism of action, being pan-TNF inhibition. The effects of TNF can diverge at the level of TNF format or receptor, and we discuss the consequences of this in sepsis, autoimmunity and neurodegeneration. Recently, researchers tried to design drugs with reduced side effects. These include molecules with more specificity targeting one specific TNF format or receptor, or that neutralize TNF in specific cells. Alternatively, TNF-directed biologicals without the typical antibody structure are manufactured. Here, we review the complications related to the use of conventional TNF inhibitors, together with the anti-TNF alternatives and the benefits of selective approaches in different diseases.

Flow Cytometric Evaluation of Primary Immunodeficiencies

Primary immunodeficiency diseases are genetic disorders that mostly cause susceptibility to infections and are sometimes associated with autoimmune and malignant diseases. For early detection and management of these diseases, flow cytometric procedures allow an encompassing assessment of cellular phenotypes and cellular functions. State-of-the art cytometry is based today on 8- to 10-color staining and includes an assessment of lineage maturation and functional markers.

Tuberculosis associated with tumor necrosis factor-α antagonists, case description and analysis of reported cases in Colombia

Tumor necrosis factor-α (TNF-α) is an important fundamental cytokine during the immune response against cancer and infections such as tuberculosis. This molecule also plays a key pathogenic role in complex and difficult-to-treat diseases such as rheumatoid arthritis, ankylosing spondylitis, Crohn's disease, psoriasis and ulcerative colitis. The treatment of these diseases frequently needs TNF-α antagonists, which has been related to an increased risk of developing tuberculosis, mycoses, and other severe infections.We report the case of a 68-year-old man with Crohn's disease, who developed  disseminated tuberculosis due to anti-TNF-α immunosuppressive therapy. The diagnosis was based on the histopathological findings and molecular biology assays.We discuss the clinical presentation and workup of this case, and we present a comparative analysis of tuberculosis cases associated with anti-TNF-α reported in Colombia during the last 10 years emphasizing on the diagnosis and treatment of latent tuberculosis.

[Tuberculosis in the era of anti-TNF-alpha therapy: Why does the risk still exist?]

Rheumatoid arthritis is an autoimmune systemic disease characterized mainly by inflammatory compromise of diarthrodial joints. Multiple drug therapies have been developed to control the activity of rheumatoid arthritis, among them, the first line of disease-modifying antirheumatic drugs (DMARD), and novel drug therapies such as the anti-TNF alpha therapy, with satisfactory clinical outcomes.Despite this positive fact, the use of this therapy implies the risk of producing negative effects due to its mechanism of action, which has been associated with multiple infections, especially tuberculosis, making it necessary to use screen tests before resorting to this kind of drugs.We present the case of a 58-year-old female patient, with a six-year history of rheumatoid arthritis.The patient developed disseminated tuberculosis with compatible radiological and histological findings after receiving treatment with infliximab (anti-TNF therapy). No test was performed to screen for latent tuberculosis infection prior to the administration of infliximab.The performance of routine screenings tests for tuberculosis prior to anti-TNF alpha therapy plays an essential role in the detection of asymptomatic patients with latent tuberculosis. This is the only way to identify those patients who would benefit from anti-tuberculosis drugs before the initiation of anti-TNF alpha therapy, which makes the difference in the search of a significant reduction in the incidence of tuberculosis and its associated morbidity and mortality.

Protein engineering of the chemokine CCL20 prevents psoriasiform dermatitis in an IL-23-dependent murine model

Psoriasis is a chronic inflammatory skin disease characterized by the infiltration of T cell and other immune cells to the skin in response to injury or autoantigens. Conventional, as well as unconventional, γδ T cells are recruited to the dermis and epidermis by CCL20 and other chemokines. Together with its receptor CCR6, CCL20 plays a critical role in the development of psoriasiform dermatitis in mouse models. We screened a panel of CCL20 variants designed to form dimers stabilized by intermolecular disulfide bonds. A single-atom substitution yielded a CCL20 variant (CCL20 S64C) that acted as a partial agonist for the chemokine receptor CCR6. CCL20 S64C bound CCR6 and induced intracellular calcium release, consistent with G-protein activation, but exhibited minimal chemotactic activity. Instead, CCL20 S64C inhibited CCR6-mediated T cell migration with nominal impact on other chemokine receptor signaling. When given in an IL-23-dependent mouse model for psoriasis, CCL20 S64C prevented psoriatic inflammation and the up-regulation of IL-17A and IL-22. Our results validate CCR6 as a tractable therapeutic target for psoriasis and demonstrate the value of CCL20 S64C as a lead compound.

Efficacy of isoniazid salvage therapy for latent tuberculosis infection in patients with immune-mediated inflammatory disorders - A retrospective cohort study in Taiwan

BACKGROUND

Active tuberculosis (TB) in patients with latent tuberculosis infection (LTBI) was associated with use of biological agents for immune-mediated inflammatory disorders (IMIDs). For decreasing active TB, isoniazid prophylaxis therapy was administered before biologic therapy among IMID patients with LTBI. However, for patients who had been received biologics for a long time with unknown status of LTBI or exposure history of active TB, the prevalence of LTBI and efficacy of isoniazid therapy were unclear.

METHOD

A retrospective cohort study was conducted during 2012-2014 in a tertiary medical center in Taiwan, and the incidence case of active TB was identified by the national TB registration system on October 1, 2015.

RESULTS

All 382 patients with 1532 person-years were followed up, the initial prevalence of LTBI by positive interferon-gamma releasing assay (IGRA+) was 17.5%. The prevalence of LTBI was increased in elder age (>20%, p < 0.05), chronic kidney disease (33%, p < 0.05), metabolic syndrome (26.3%, p < 0.05), but not related to the type of IMIDs or biologics. The crude incidences of TB were increased in elders (53.3/1000 person-year), abnormal chest film (49.6/1000 person-year), administration of tocilizumab (13.6/1000 person-year), and metabolic syndrome (56.1/1000 person-year), respectively. Among patents with LTBI, the incidence of active TB was lower in patients with isoniazid therapy (9.2/1000 person-year, p = 0.02) than without isoniazid therapy (92.2/1000 person-years), regardless the timing of initiating isoniazid therapy (p > 0.05).

CONCLUSION

Isoniazid therapy can prevent active TB from LTBI despite of the timing of biologics administration.

Tuberculosis and biologics in rheumatology: A special situation

India has a huge patient burden of rheumatic diseases (RDs) including rheumatoid arthritis. The use of biologics has transformed the treatment paradigm for RD; however, biologic treatment-related infections (especially tuberculosis [TB]) are an area of potential concern for TB-endemic nations like India. Anti-tumor necrosis factor (TNF) therapy impairs the physiological TNF-mediated signaling and may cause reactivation and dissemination of latent TB infection (LTBI). Careful screening is, thus, crucial in RD patients who are about to commence anti-TNF treatment. To date, there is no consensus available for the screening, evaluation and treatment of LTBI as well as on the drug dosage and duration regimen (monotherapy or combination therapy) in the Indian population. An evidence-based algorithm for LTBI screening and management in RD patients undergoing biologic disease-modifying anti-rheumatic drug therapy is suggested in this review for Indian rheumatologists. The proposed algorithm guides physicians through a step-wise screening approach, including medical history, tuberculin skin test, interferon gamma release assay, chest radiograph and management of LTBI with isoniazid therapy or its combination with rifampicin. Further, the provided algorithm can aid the national bodies (such as National TB Control Program) in formulating recommendations for LTBI in this high-risk population.

The risk of tuberculosis disease in rheumatoid arthritis patients on biologics and targeted therapy: A 15-year real world experience in Taiwan

The objective of this study is to determine the risk of tuberculosis (TB) disease in biologics users among rheumatoid arthritis (RA) patients in Taiwan from 2000 to 2015. This retrospective cohort study enrolled adult RA patients initiated on first biologics at Taichung Veterans General Hospital. TB risks were determined as hazard ratio (HR) with 95% confidence interval (CI) using cox regression. A total of 951 patients were recruited; etanercept (n = 443), adalimumab (n = 332), abatacept (n = 74), golimumab (n = 60), tocilizumab (n = 31) and tofacitinib (n = 11). Twenty-four TB cases were identified; 13 in etanercept and 11 in adalimumab group with the TB incidence rate of 889.3/ 100,000 and 1055.6/ 100,000 patient-years respectively. There was no significant difference in TB risk between adalimumab and etanercept users with an incidence rate ratio of 1.27 (p = 0.556 by Poisson model). Significant 2-year TB risk factors included elderly patient >65 year-old (HR: 2.72, 95% CI: 1.06–6.99, p = 0.037), history of TB (HR: 6.24, 95% CI: 1.77–22.00, p = 0.004) and daily glucocorticoid use ≥5mg (HR:5.01, 95% CI: 1.46–17.21, p = 0.010). Sulfasalazine treatment appeared to be protective (HR: 0.32, 95% CI: 0.11–0.97, p = 0.043). Risk management plan (RMP) for TB before initiation of biologics commenced in 2012. The 2-year TB risks after RMP was compared with that before 2012 (HR:0.67, 95% CI: 0.30–1.49, p = 0.323). Elderly RA patients with a history of previous TB infection and concomitant moderate dose glucocorticoid were at higher risk of TB disease. Concurrent sulfasalazine treatment appeared to be a protective factor against TB disease.

Risk of infections using anti-TNF agents in rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis: a systematic review and meta-analysis

INTRODUCTION

Five anti-tumor necrosis factor (anti-TNF) agents have received regulatory approval for use in rheumatology: adalimumab, golimumab, infliximab, certolizumab, and etanercept. Apart from their well-documented therapeutic value, it is still uncertain to what extent they are associated with an increased risk of infectious adverse events. Areas covered: We conducted a systematic review and meta-analysis of published randomized studies to determine the effect of anti-TNF drugs on the occurrence of infectious adverse events (serious infections; tuberculosis; opportunistic infections; any infection). We searched Medline, Embase, and the Cochrane Library up to May 2014 to identify eligible studies in adult patients with rheumatoid arthritis, psoriatic arthritis, or ankylosing spondylitis that evaluated anti-TNF drugs compared with placebo or no treatment. Expert opinion: Our study encompassed data from 71 randomized controlled trials involving 22,760 participants (range of follow-up: 1-36 months) and seven open label extension studies with 2,236 participants (range of follow-up: 6-48 months). Quantitative synthesis of the available data found statistically significant increases in the occurrence of any infections (20%), serious infections (40%), and tuberculosis (250%) associated with anti-TNF drug use, while the data for opportunistic infections were scarce. The quality of synthesized evidence was judged as moderate. Further evidence from registries and long-term epidemiological studies are needed to better define the relationship between anti-TNF agents and infection complications.

Risk of incident Mycobacterium tuberculosis infection in patients with inflammatory bowel disease: a nationwide population-based study in South Korea

BACKGROUND

The low incidence of Mycobacterium tuberculosis infection and lack of adequate controls have prevented researchers from estimating tuberculosis (TB) risk in inflammatory bowel disease (IBD) patients.

AIM

To evaluate the risk of incident TB among IBD patients.

METHODS

Using the 2011-2013 data of the South Korean National Health Insurance (NHI) system, we calculated the incidence rates (IRs), standardised incidence ratio (SIR) and number needed to screen (NNS) for incident TB in IBD patients compared to the general population in terms of subtype, age, gender and IBD medications.

RESULTS

The IR, SIR and NNS for TB in IBD patients were 223.9/100 000 person-years, 2.64 (2.30-3.01) and 446.6 (392.8-517.6), respectively. The TB IR in Crohn's disease (CD) patients was significantly higher than that in ulcerative colitis (UC) patients (340.1/100 000 person-years vs. 165.5/100 000 person-years, respectively; P < 0.001). The SIR and NNS for TB among CD patients were 4.00 (3.59-4.45) and 604.2 (506.1-749.6), respectively; those among UC patients were 1.95 (1.66-2.27) and 294.0 (246.9-363.4). The TB IRs in IBD patients did not differ significantly by age or gender (P_trend  = 0.505 and P = 0.861, respectively). The TB IRs among IBD patients prescribed 5-ASA, corticosteroids, immunomodulators and anti-TNF-α were 143.5, 208.5, 284.6 and 554.1 per 100 000 person-years, respectively. Among IBD patients treated using anti-TNF-α, the TB IR was significantly higher than that among all IBD patients (P < 0.001); the SIR and NNS for TB were 6.53 (5.99-7.09) and 180.5 (144.6-240.1) respectively.

CONCLUSION

Clinicians should be aware of the increased risk of active tuberculosis in patients with IBD who are receiving anti-TNF-α therapy.

Anti-inflammatory effects of recombinant human PDCD5 (rhPDCD5) in a rat collagen-induced model of arthritis

Programmed cell death 5 (PDCD5) was first identified as a gene upregulated in cells undergoing apoptosis. We recently demonstrated the inhibitory effect of PDCD5 on experimentally induced autoimmune encephalomyelitis. In this study, we investigated the anti-inflammatory effects of recombinant human PDCD5 (rhPDCD5) in a rat collagen-induced arthritis (CIA) model. We find that vaccination of collagen II (CII) induced CIA rats with rhPDCD5 significantly delayed the occurrence and reduced the severity of CIA rats. rhPDCD5 also restored the loss of Foxp3⁺ regulatory T (Treg) cells and decreased the population of Th1 and Th17 in CIA rats. Simultaneously, rhPDCD5 treatment suppressed the production of pro-inflammatory cytokines (interleukin (IL)-6, IL-17A, tumor necrosis factor-α (TNF-α), and interferon gamma (IFN-γ)) and increased the secretion of anti-inflammatory cytokines (transforming growth factor beta 1 (TGF-β1) and IL-10) in CIA rats. In addition, rhPDCD5 inhibited the ability of CII to induce proliferation of splenocytes and lymph node cells (LNCs) and promoted the CII-activated CD4⁺ cell apoptosis. These results of rhPDCD5-treated CIA rats were similar with those of recombinant human TNF-α receptor IgG Fc (rhTNFR:Fc). Thus, to our knowledge, we provide the first evidence that rhPDCD5 may be an efficient approach to diminishing exacerbated immune responses in CIA, indicating its therapeutic potential in the treatment of rheumatoid arthritis and other autoimmune diseases.

Complexity and Controversies over the Cytokine Profiles of T Helper Cell Subpopulations in Tuberculosis

Tuberculosis (TB) is a contagious infectious disease caused by the TB-causing bacillus Mycobacterium tuberculosis and is considered a public health problem with enormous social impact. Disease progression is determined mainly by the balance between the microorganism and the host defense systems. Although the immune system controls the infection, this control does not necessarily lead to sterilization. Over recent decades, the patterns of CD4+ T cell responses have been studied with a goal of complete understanding of the immunological mechanisms involved in the maintenance of latent or active tuberculosis infection and of the clinical cure after treatment. Conflicting results have been suggested over the years, particularly in studies comparing experimental models and human disease. In recent years, in addition to Th1, Th2, and Th17 profiles, new standards of cellular immune responses, such as Th9, Th22, and IFN-γ-IL-10 double-producing Th cells, discussed here, have also been described. Additionally, many new roles and cellular sources have been described for IL-10, demonstrating a critical role for this cytokine as regulatory, rather than merely pathogenic cytokine, involved in the establishment of chronic latent infection, in the clinical cure after treatment and in keeping antibacillary effector mechanisms active to prevent immune-mediated damage.

Recombinant H22(scFv) blocks CD64 and prevents the capture of anti-TNF monoclonal antibody. A potential strategy to enhance anti-TNF therapy

Tumor necrosis factor (TNF) is a pro-inflammatory cytokine that plays a critical role in many inflammatory diseases. Soluble TNF can be neutralized by monoclonal antibodies (mAbs), and this is a widely-used therapeutic approach. However, some patients do not respond to anti-TNF therapy due to the increased expression of CD64 on monocytes and macrophages. A recent study has shown that CD64 captures anti-TNF mAbs via their Fcγ domain, which induces the transcription of pro-inflammatory genes. Specific blocking of CD64 could therefore be a promising strategy to improve the response to anti-TNF therapy. We used the CD64-specific antibody fragment H22(scFv) and tested its activity against the human CD64(+) cell line HL-60. When stimulated with interferon gamma (IFN-γ), these cells represent a pro-inflammatory phenotype of the monocyte/macrophage lineage. We found that H22(scFv) binds selectively to and blocks CD64, preventing the capture of anti-TNF mAb. Importantly, H22(scFv) itself does not induce CD64 activation. We also found that transmembrane TNF on HL-60 cells stimulated with IFN-γ also contributes to the capture of anti-TNF mAb, although via their Fab domain. In conclusion, the specific blocking of CD64 by H22(scFv) could be used a possible anti-inflammatory mechanism for potentiating the effect of anti-TNF antibodies.

Risk of Tuberculosis in Children with Juvenile Idiopathic Arthritis: A Nationwide Population-Based Study in Taiwan

Objective

We aimed to determine the risk of tuberculosis in children with juvenile idiopathic arthritis (JIA) in Taiwan.

Methods

We used the Taiwan National Health Insurance Research Database (NHIRD) to conduct a nested case-control study. We identified a JIA cohort and matched each JIA child with non-JIA children for comparison. Methotrexate (MTX), tumor necrosis factor (TNF) inhibitor administration, and new tuberculosis cases were determined during our study period. To compare tuberculosis (TB) risk among our study groups, Cox proportional regression models were used to determine adjusted hazard ratios (aHRs).

Results

We identified 1495 children with JIA and 11592 non-JIA children. Majority (68.7%) children with JIA had not received MTX or TNF inhibitors; 23.9% used MTX without TNF inhibitors, and 7.4% received TNF inhibitors, irrespective of MTX administration. In total, 43 children developed tuberculosis. The overall tuberculosis infection rate for children with JIA was two times higher than that for non-JIA children. Compared with non-JIA children, children with JIA who used MTX without TNF inhibitors revealed a significantly increased of tuberculosis infection rate (aHR = 4.67; 95% CI: 1.65–13.17; P = 0.004). Children with JIA who either received TNF inhibitors or never used MTX and TNF inhibitors revealed a tuberculosis infection rate comparable to that of non-JIA children.

Conclusions

Analysis of nationwide data of Taiwan suggested that children with JIA were at higher risk of tuberculosis compared with those without JIA.

Follow-up results of isoniazid chemoprophylaxis during biological therapy in Colombia

The use of biological therapy has been linked with an increased risk of tuberculosis (TB) reactivation. The aim of this study was to present the follow-up results for isoniazid (INH) chemoprophylaxis in patients receiving different biological therapies. In this prospective observational study, patients with latent tuberculosis infection (LTBI) were given INH chemoprophylaxis between 2 and 9 months prior to the beginning of biological therapy. All patients were followed up monthly for any signs or symptoms of active TB or INH toxicity. A total of 221 patients, 122 females (55.2 %), with a mean age of 46.8 ± 11.3 years (16-74) were enrolled. LTBI was identified in 218 patients (98.7 %), all of whom received INH chemoprophylaxis. Seven patients (3.2 %) developed active tuberculosis, and 32 (17.2 %) patients developed intolerance or toxicity related to INH. Chemoprophylaxis with INH seems to be effective and safe for the prevention of most TB reactivation in individuals with LTBI, but toxicity must be monitored during follow-up.

Spinal non-Hodgkin's lymphoma mimicking a flare of disease in a patient with ankylosing spondylitis treated with anti-TNF agents: case report and review of the literature

We report the case of a 52-year-old man with long-standing HLAB27-positive ankylosing spondylitis treated with anti-tumour necrosis factor (TNF) alpha therapy who was admitted to our rheumatology department complaining of increasing lumbar and buttock pain radiating to the posterior thigh, associated with numbness in the leg, gait disturbance and low-grade fever. The clinical picture was initially interpreted as a flare of disease but was not responsive to treatment. A contrast-enhanced spinal MRI was performed with evidence of a diffuse signal abnormality involving the sacroiliac joints and the spine, with evidence of spondylodiscitis of L5 and with a lesion causing L5-S1 root compression and infiltrating the iliopsoas muscle. These findings confirmed the possibility of a reactivation of disease associated with an infectious process. The most frequent causes of infectious spondylodiscitis were excluded, and a biopsy was then performed. Histological analysis revealed a high-grade B-cell non-Hodgkin's lymphoma of the spine. This case highlights how a differential diagnosis of low back pain with neurological symptoms can be particularly troublesome in ankylosing spondylitis and that continuous vigilance is warranted in patients treated with long-term immunosuppressive therapies.

Fibrogenesis and fibrosis in inflammatory bowel diseases: Good and bad side of same coin?

Fibrogenesis in inflammatory bowel diseases is a complex phenomenon aimed at mucosal repair. However, it may provoke intestinal fibrosis with the development of strictures which require surgery. Therefore, fibrogenesis may be considered as a “two-faced” process when related to chronic intestinal inflammation. Many types of cells may be converted into the fibrogenic phenotype at different levels of the intestinal wall. A complex interaction of cytokines, adhesion molecules and growth factors is involved in the process. We report an overview of recent advances in molecular mechanisms of stricturizing Crohn’s disease (CD) including the potential role of trasforming growth factor beta, protein kinase C and Ras, Raf and ERK proteins. Fibrotic growth factors such as vascular endothelial growth factor and platelet-derived growth factor, as well as the Endothelial-to-Mesenchymal Transition induced by transforming growth factor-β, are considered. Finally, our experience, focused on tumor necrosis factor α (the main cytokine of inflammatory bowel diseases) and the link between syndecan 1 (a heparan sulphate adhesion molecule) and basic fibroblast growth factor (a strong stimulator of collagen synthesis) is described. We hypothesize a possible molecular pattern for mucosal healing as well as how its deregulation could be involved in fibrotic complications of CD. A final clinical point is the importance of performing an accurate evaluation of the presence of fibrotic strictures before starting anti-tumor necrosis α treatment, which could worsen the lesions.

TNF-alpha neutralizing antibody blocks thermal sensitivity induced by compound 48/80-provoked mast cell degranulation

Background: Neuro-inflammatory circuits in the tissue regulate the complex pathophysiology of pain. Protective nociceptive pain serves as an early warning system against noxious environmental stimuli. Tissue-resident mast cells orchestrate the increased thermal sensitivity following injection of basic secretagogue compound 48/80 in the hind paw tissues of ND4 mice. Here we investigated the effects of pre-treatment with TNF-α neutralizing antibody on compound 48/80-provoked thermal hyperalgesia.

Methods: We treated ND4 Swiss male mice with intravenous anti-TNF-α antibody or vehicle 30 minutes prior to bilateral, intra-plantar compound 48/80 administration and measured changes in the timing of hind paw withdrawal observed subsequent to mice being placed on a 51oC hotplate. We also assessed changes in tissue swelling, TNF-α gene expression and protein abundance, mast cell degranulation, and neutrophil influx in the hind paw tissue.

Findings: We found that TNF-α neutralization significantly blocked thermal hyperalgesia, and reduced early tissue swelling. TNF-α neutralization had no significant effect on mast cell degranulation or neutrophil influx into the tissue, however. Moreover, no changes in TNF-α protein or mRNA levels were detected within 3 hours of administration of compound 48/80.

Interpretation:  The neutralizing antibodies likely target pre-formed TNF-α including that stored in the granules of tissue-resident mast cells. Pre-formed TNF-α, released upon degranulation, has immediate effects on nociceptive signaling prior to the induction of neutrophil influx. These early effects on nociceptors are abrogated by TNF-α blockade, resulting in compromised nociceptive withdrawal responses to acute, harmful environmental stimuli.

TNF-alpha neutralizing antibody blocks thermal sensitivity induced by compound 48/80-provoked mast cell degranulation

BACKGROUND

Neuro-inflammatory circuits in the tissue regulate the complex pathophysiology of pain. Protective nociceptive pain serves as an early warning system against noxious environmental stimuli. Tissue-resident mast cells orchestrate the increased thermal sensitivity following injection of basic secretagogue compound 48/80 in the hind paw tissues of ND4 mice. Here we investigated the effects of pre-treatment with TNF-α neutralizing antibody on compound 48/80-provoked thermal hyperalgesia.

METHODS

We treated ND4 Swiss male mice with intravenous anti-TNF-α antibody or vehicle 30 minutes prior to bilateral, intra-plantar compound 48/80 administration and measured changes in the timing of hind paw withdrawal observed subsequent to mice being placed on a 51oC hotplate. We also assessed changes in tissue swelling, TNF-α gene expression and protein abundance, mast cell degranulation, and neutrophil influx in the hind paw tissue.

FINDINGS

We found that TNF-α neutralization significantly blocked thermal hyperalgesia, and reduced early tissue swelling. TNF-α neutralization had no significant effect on mast cell degranulation or neutrophil influx into the tissue, however. Moreover, no changes in TNF-α protein or mRNA levels were detected within 3 hours of administration of compound 48/80.

INTERPRETATION

  The neutralizing antibodies likely target pre-formed TNF-α including that stored in the granules of tissue-resident mast cells. Pre-formed TNF-α, released upon degranulation, has immediate effects on nociceptive signaling prior to the induction of neutrophil influx. These early effects on nociceptors are abrogated by TNF-α blockade, resulting in compromised nociceptive withdrawal responses to acute, harmful environmental stimuli.