Demonstration of specific antibodies against infliximab induced during treatment of a patient with ankylosing spondylitis

The value of contrast-enhanced ultrasonography to detect the sacroiliac joint for predicting relapse after discontinuation of anti-tumor necrosis factor therapy in patients with ankylosing spondylitis

BACKGROUND

Ankylosing spondylitis (AS) is a chronic inflammatory disease characterized by high relapse. Therefore, the present study aimed to investigate the ultrasonographic features of contrast-enhanced ultrasonography (CEUS) in the sacroiliac joint (SIJ) in patients with AS in remission after discontinuation of anti-tumor necrosis factor (TNF) therapy, and also examined the role of CEUS in predicting relapse.

METHODS

In this prospective observational study, 130 SIJs in 65 patients with AS (according to modified New York criteria) satisfying Ankylosing Spondylitis Disease Activity Score (ASDAS) inactive disease after discontinuation of anti-TNF therapy were investigated on color Doppler ultrasonography (CDUS) and CEUS. Vascularization and the resistive index (RI) of the SIJ were observed and measured. We defined no blood flow, high RI of arterial blood flow (RI ≥0.7), the reversed phase in the diastolic phase or venous blood flow in the bilateral SIJs, as negative CDUS/CEUS; meanwhile, low RI of arterial blood flow (RI <0.7) in the unilateral or bilateral SIJs was defined as positive CDUS/CEUS. All the patients were followed up for 52 weeks until relapse. Relapse was defined as an increase of two or more items in comparison with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) at the time of anti-TNF withdrawal.

RESULTS

After 52 weeks, 46 of the 65 patients (70.8%) had relapse. The mean time to relapse was 31.4 weeks (±8.4 weeks, range 20 to 52). After discontinuation of anti-TNF therapy, positive CEUS accounted for 61.5%; this was significantly more than positive CDUS (13.8%). The vascularization detected by CEUS for patients of relapse was significantly different from that of patients with remission (P<0.05). In addition, patients with negative CEUS had a longer duration of remission than the patients with positive CEUS (P=0.005). A Cox proportional hazards regression analysis found that the disease duration could also be regarded as a factor predictive of relapse in patients with AS.

CONCLUSIONS

The use of CEUS distinctly improved the detection of vascularization in the SIJ in patients with AS in remission after anti-TNF withdrawal. The presence of vascularization in the SIJ detected by CEUS at the time of anti-TNF withdrawal could yield a valuable predictor of relapse in patients with AS. A significant limit of this study is the lack of magnetic resonance imaging (MRI) as the standard reference.

Prevalence of TNF-α Blocker Immunogenicity in Psoriatic Arthritis

Objective.

The longterm use of tumor necrosis factor (TNF)-α blockers is limited by the formation of neutralizing antibodies. To the best of our knowledge, immunogenicity in psoriatic arthritis (PsA) has not been investigated in depth. Our objective was to evaluate the prevalence and significance of TNF-α blocker immunogenicity in PsA.

Methods.

Consecutive patients with PsA treated with either infliximab (IFX), adalimumab (ADA), or etanercept (ETN) > 3 months participated in our cross-sectional study. Their demographic and clinical characteristics, skin and joint disease activity, and records of use of methotrexate (MTX) and other medications were collected. Drug levels (ELISA) and antidrug antibodies (ADAb; Bridging ELISA) were evaluated before the next injection or infusion.

Results.

A total of 93 patients with PsA were recruited (48 receiving ADA, 24 IFX, and 21 ETN), with a mean age of 53 years (range 21–83 yrs), composed of 53% women. One-fourth of the patients were concomitantly treated with MTX. Altogether, 77% of the patients demonstrated therapeutic drug levels. High levels of ADAb were found in 29% of patients taking ADA, 21% taking IFX, and 0% taking ETN. ADAb significantly correlated with lower drug levels, higher 28-joint Disease Activity Scores, and higher global assessments. MTX use correlated significantly with a lower prevalence of ADAb.

Conclusion.

Significant levels of ADAb were present in up to 29% of patients with PsA treated with ADA or IFX. ADAb clearly correlated with low therapeutic drug levels and higher disease activity variables. The use of MTX significantly decreased ADAb prevalence, and its use should be strongly considered in combination with TNF-α blocker antibodies in patients with PsA.

The immunogenicity to the first anti-TNF therapy determines the outcome of switching to a second anti-TNF therapy in spondyloarthritis patients

Introduction

Anti-TNF drugs have proven to be effective against spondyloarthritis (SpA), although 30% of patients fail to respond or experience adverse events leading to treatment discontinuation. In rheumatoid arthritis, the presence of anti-drug antibodies (ADA) against the first TNF inhibitor influences the outcome after switching. Our aim was to assess whether the response to a second anti-TNF drug is related to the previous development of ADA to the first anti-TNF drug SpA patients.

Methods

Forty-two SpA patients began a second anti-TNF drug after failing to respond to the first anti-TNF therapy. Clinical activity was assessed by the Ankylosing Spondylitis Disease Activity Score (ASDAS) at baseline (at the beginning of the first and second anti-TNF therapy) and at 6 months after switching. The drug and ADA levels were measured by ELISA before each administration.

Results

All patients were treated with anti-TNF drugs and mainly due to inefficacy were switched to a second anti-TNF drug. Eleven of 42 (26.2%) developed ADA during the first biologic treatment. At baseline, no differences in ASDAS were found in patients with or without ADA to the first anti-TNF drug (3.52 ± 1.03 without ADA vs. 3.14 ± 0.95 with ADA, p = 0.399) and to the second anti-TNF drug (3.36 ± 0.94 without ADA vs. 3.09 ± 0.91 with ADA, p = 0.466). At 6 months after switching, patients with previous ADA had lower disease activity (1.62 ± 0.93 with ADA vs. 2.79 ± 1.01 without ADA, p = 0.002) and most patients without ADA had high disease activity state by the ASDAS (25 out of 31 (80.6%) without ADA vs. 3 out of 11 (27.3%) with ADA, p = 0.002).

Conclusions

In SpA the failure to respond to the first anti-TNF drug due to the presence of ADA predicts a better clinical response to a second anti-TNF drug.

An efficient method for variable region assembly in the construction of scFv phage display libraries using independent strand amplification

Phage display library technology is a common method to produce human antibodies. In this technique, the immunoglobulin variable regions are displayed in a bacteriophage in a way that each filamentous virus displays the product of a single antibody gene on its surface. From the collection of different phages, it is possible to isolate the virus that recognizes specific targets. The most common form in which to display antibody variable regions in the phage is the single chain variable fragment format (scFv), which requires assembly of the heavy and light immunoglobulin variable regions in a single gene. In this work, we describe a simple and efficient method for the assembly of immunoglobulin heavy and light chain variable regions in a scFv format. This procedure involves a two-step reaction: (1) DNA amplification to produce the single strand form of the heavy or light chain gene required for the fusion; and (2) mixture of both single strand products followed by an assembly reaction to construct a complete scFv gene. Using this method, we produced 6-fold more scFv encoding DNA than the commonly used splicing by overlap extension PCR (SOE-PCR) approach. The scFv gene produced by this method also proved to be efficient in generating a diverse scFv phage display library. From this scFv library, we obtained phages that bound several non-related antigens, including recombinant proteins and rotavirus particles.

Systematic review: antibodies and anti-TNF-α levels in inflammatory bowel disease

BACKGROUND

The associations between clinical efficacy and infusion reactions with anti-TNF-α drug levels and the presence of antibodies against the drug have been described. However, the clinical utility of these tests in routine clinical practice remains unclear.

AIMS

To examine the clinical significance of the development of antibodies against anti-TNF-α drugs and the relationship between the efficacy of these drugs and their serum levels. We also studied the clinical utility of testing for anti-TNF-α antibodies and measuring drug serum levels to optimise treatment of patients with inflammatory bowel disease (IBD) receiving these agents.

METHODS

A systematic review was undertaken based on electronic searches of the PubMed database from the earliest record to February 2012. The reference lists of all relevant articles and abstracts from meetings were also consulted.

RESULTS

We observed a close relationship between trough levels of anti-TNF-α drug and maintenance of response to these drugs. The role of antibodies in loss of response seems to be limited to their effect favouring the clearance of the drug. The risk of infusion reactions, but not of delayed hypersensitivity reactions, is higher in patients with antibodies against the anti-TNF-α drug. Testing anti-TNF-α drug and antibody levels, together with clinical and endoscopic or radiological assessment, seems useful when attempting to optimise therapy and prevent inappropriate management of IBD patients.

CONCLUSION

Measurement of serum anti-TNF-α trough levels and antibody titres could prove useful in therapeutic drug monitoring in IBD patients treated with anti-TNF-α agents.

Anti-infliximab antibody status and its relation to clinical response in psoriatic patients: A pilot study

Although the mechanisms underlying the loss of response to infliximab are not completely understood, the formation of antibodies to infliximab (ATI) are thought to play a role. The aim of this study was to investigate the presence of ATI in psoriatic patients and to evaluate its relationship to the clinical response. Fifteen patients with psoriasis were treated with infliximab (5 mg/kg) every 8 weeks after an initial three-dose induction treatment. An enzyme linked immunosorbent assay kit was used for analyzing the presence of ATI in sera. Effectiveness assessments included the change in Psoriasis Area and Severity Index (PASI) compared with study entry. Five (33.3%) patients developed ATI. While 5.9 +/- 3.2 infliximab infusions achieved a fall in the PASI score from a mean of 20.4 +/- 8.3 to 5.3 +/- 2.4 in ATI-negative patients, these values changed from 23.3 +/- 11 to 10 +/- 4.9 after 9 +/- 5.2 infusions in ATI-positive patients. Our results suggested that ATI measured in psoriatic patients are of clinical importance. Therefore, monitoring for the induction of ATI and rescue strategies should be developed to avoid or to maintain a delay in ATI development.

Monitoring functional serum antitumor necrosis factor antibody level in Crohn's disease patients who maintained and those who lost response to anti-TNF

BACKGROUND

Infliximab (IFX) is an antitumor necrosis factor (TNF)-α antibody used to treat Crohn's disease (CD). However, antibodies to IFX (ATI) emerge, which can impair its efficacy. A fluid-phase enzyme immunoassay (FP-EIA) was established for measuring serum functional IFX (f-IFX) in CD patients receiving maintenance IFX.

METHODS

In 31 patients, 16 had maintained response (GI) and 15 had lost response to IFX despite good initial response (GII) were selected. Serum f-IFX was measured just before and immediately after IFX infusion and the values together with CD activity index (CDAI) and C-reactive protein (CRP) were compared.

RESULTS

IFX therapy in GI and GII were 1.8 ± 1.2 years and 2.7 ± 1.5 years, respectively, while the median dose frequency was 56 days in GI and 29 days in GII. Our FP-EIA for f-IFX showed TNF-α binding increasing with the IFX dose, which was suppressed by antibodies to IFX. On the infusion day, CRP and CDAI in GII were significantly higher than in GI, while median trough f-IFX for GI and GII were 4.7 μg/mL and 6.3 μg/mL, respectively. The median f-IFX immediately after IFX infusion for GI and GII were 149.5 μg/mL and 126.3 μg/mL, respectively (P = 0.0488), and binary logistic regression showed conditional maximum likelihood estimate to be -0.0258 (P = 0.0395), supporting association of low postinfusion f-IFX to the loss of response.

CONCLUSIONS

FP-EIA could accurately measure f-IFX. High serum ATI strongly impacted f-IFX levels immediately after an infusion. The postinfusion f-IFX level was associated with clinical response. f-IFX level should be valuable in decision-making to optimize treatment efficacy.

A novel homogeneous Biotin-digoxigenin based assay for the detection of human anti-therapeutic antibodies in autoimmune serum

Electrochemiluminescence (ECL) assays have been widely used for the detection of anti-therapeutic antibodies (ATAs) against biotherapeutics. With the discontinuation of BioVeris (BV) ECL platform, an alternative technology was needed to replace BV assays to ensure continuous support of multi-year clinical studies. After evaluation of several immunoassay platforms, a novel homogeneous Biotin-digoxigenin (DIG) based bridging ELISA format was selected to develop an anti-rhuMAbX antibody screening assay to test serum samples from rheumatoid arthritis (RA) patients. With a homogeneous overnight sample incubation, the Biotin-DIG ELISA achieved comparable relative sensitivity and free drug tolerance to the previous BV ATA assay for rhuMAbX. To abrogate potential auto-antibody interference in RA sera, various assay conditions were thoroughly evaluated and a horseradish peroxidase (HRP)-conjugated chicken anti-DIG antibody was selected as the detection conjugate. Other potential interferences from serum Biotin, naturally occurring anti-avidin antibodies, and concomitant medications such as digoxin and hydrocortisone, which have similar structures to digoxigenin, were also investigated. Under optimized final assay conditions, the Biotin-DIG assay showed a relative sensitivity of approximately 11 ng/mL using a polyclonal anti-complementarity determining region (CDR) enriched positive control; the assay could detect 500 ng/mL of the positive control in the presence of approximately 27 μg/mL of rhuMAbX in RA serum. In addition, a confirmatory step was optimized for the assay based upon pre-incubating serum samples with an excess of free drug. Overall, the Biotin-DIG assay met the performance requirements for an ATA screening assay and had comparable sensitivity and drug tolerance to the BV assay; therefore this assay was a suitable replacement for the BV assay used for previous clinical studies of rhuMAbX. The Biotin-DIG based assay format can be broadly used as an effective screening platform for the detection of anti-therapeutic antibodies.

Immunogenicity of Anti-TNF-alpha agents in autoimmune diseases

Prognosis of several autoimmune diseases, especially rheumatoid arthritis (RA), ankylosing spondylitis, Crohn's disease (CD), and psoriasis, usually refractory to conventional treatment improved considerably with the introduction of tumor necrosis factor alpha (TNF-alpha) antagonistic agents, which is now available (infliximab, etanercept, and adalimumab). However, a portion of patients persists with active disease, infusion reactions, and relapses even during current biological therapy. One of the reasons for this is the associated immunogenicity to these drugs. The incentive for induction of antibodies against anti-TNF-alpha agent depends mainly on its constitution. Chimerical drugs have a higher capacity of inducing immunogenicity compared to completely human drugs. Among the three anti-TNF-alpha agents, this phenomenon has been studied mainly in patients using infliximab, especially in RA and CD. The prevalence of anti-infliximab antibodies in RA varies from 12% to 44% and seems to be inversely proportional to the level of seric infliximab and therapeutic response. The use of etanercept was associated to the development of anti-etanercept antibodies in 0% to 18% of patients, without apparent effect on effectiveness or adverse events. Studies with RA and CD patients show prevalence of anti-adalimumab antibodies from 1% to 87%. Immunosuppressive drug addiction can reduce the induction of anti-TNF-alpha antibodies.

Influence of anti-infliximab antibodies and residual infliximab concentrations on the occurrence of acquired drug resistance to infliximab in rheumatoid arthritis patients

BACKGROUND

Infliximab (IFX) can be immunogenic for humans and lead to the formation of antibodies against IFX (anti-IFX Ab), which could induce acquired IFX resistance.

OBJECTIVE

To test whether the presence of anti-IFX Ab and residual circulating IFX levels are associated with acquired IFX resistance in RA.

METHODS

A multivariate logistic regression was used to analyze the relationship between anti-IFX Ab, residual IFX concentrations, and acquired IFX resistance in a nested cohort within the Swiss RA registry (SCQM-RA).

RESULTS

Sixty-four RA patients on longstanding IFX therapy were included; 24 with an acquired therapeutic resistance to IFX and 40 with continuous good response to IFX. The two groups had similar disease characteristics, but patients with acquired IFX resistance required significantly higher dosage of IFX (5.4 mg/kg versus 4.3 mg/kg, p=0.02) and shorter infusion intervals (7.1 versus 8.7 weeks, p=0.01) than long-term good responders. The presence of residual IFX tended to be associated with a decreased risk of acquired therapeutic resistance (OR 0.4 [95% CI: 0.1-1.5]), while the presence of anti-IFX Ab tended to be associated with an increased risk of acquired therapeutic resistance (OR: 1.8 [95% CI: 0.4 - 9.0]). The presence of either high anti-IFX Ab levels or low residual IFX concentrations was strongly associated with acquired therapeutic resistance to IFX (OR 5.9, 95% CI 1.3 - 26.6). However, just 42% of patients with acquired IFX resistance had either low IFX or high anti-IFX Ab levels.

CONCLUSION

These results suggest that the assessment of anti-IFX Ab and residual IFX levels is of limited value for individual patients in routine clinical care.

Circulating concentration of infliximab and response to treatment in ankylosing spondylitis: results from a randomized control study

OBJECTIVE

A minority of patients with ankylosing spondylitis (AS) fail to respond to infliximab treatment. This study compared the circulating infliximab concentration and the presence of clinical symptoms in patients continuously treated with infliximab or after treatment interruption.

METHODS

Patients with active AS were randomly assigned at week 0 to receive infliximab either at weeks 4, 6, 10, and then every 6 weeks (continuous treatment), or at weeks 4, 6, and 10 and then upon symptom recurrence (on-demand treatment). The circulating concentration of infliximab was determined early during treatment and at weeks 46 and 52 for the continuous treatment group or upon relapse for the on-demand group. Response in the continuous treatment group was defined at week 58 using the ASsessment in AS International Working Group Criteria for 20% improvement.

RESULTS

Among the 93 patients in the continuous treatment group, treatment failure was not associated with a low circulating concentration of infliximab, either during early treatment or at 1 year. Eleven (39.2%) of the 28 nonresponders had an infliximab concentration of >10 microg/ml at week 52, whereas 9 (13.8%) of the 65 responders had an infliximab concentration of <1 microg/ml. In the on-demand group, the infliximab concentration at relapse closely correlated with the time to relapse. However, 24 (36.9%) of 65 patients had a resurgence of clinical symptoms at an infliximab concentration of >10 microg/ml, whereas 25 patients (38.4%) had a relapse at an infliximab concentration of <0.5 microg/ml.

CONCLUSION

Responsiveness to infliximab treatment is highly heterogeneous among individuals with AS, and this parameter overcomes the circulating infliximab concentration to explain treatment success or failure.

Maintenance of infliximab treatment in ankylosing spondylitis: results of a one-year randomized controlled trial comparing systematic versus on-demand treatment

OBJECTIVE

Continuous treatment with the anti-tumor necrosis factor alpha (anti-TNFalpha) antibody infliximab is efficacious in ankylosing spondylitis (AS), whereas treatment discontinuation results in disease relapse, with variable delay. This study was undertaken to compare the efficacy of continuous treatment with infliximab with that of a treatment regimen adapted to symptom recurrence. Methotrexate (MTX) in combination with infliximab was also tested.

METHODS

Patients with active AS were randomly assigned at week 0 to receive infliximab every 6 weeks (continuous treatment) or upon symptom recurrence (on-demand treatment), following infusions at weeks 4, 6, and 10. Patients in the on-demand group were randomly assigned to receive either MTX in combination with infliximab or infliximab alone. Patients were monitored for 1 year. The primary end point was the proportion of patients who met the ASsessment in AS International Working Group criteria for 20% improvement (ASAS20) at week 58.

RESULTS

Of 247 patients, 124 were assigned to receive infliximab every 6 weeks and 123 to receive on-demand treatment. Among the latter, 62 received MTX, and 61 received infliximab alone. A greater proportion of patients receiving infliximab every 6 weeks fulfilled ASAS20 response criteria at week 58 than did patients receiving on-demand treatment (75% versus 46%; P<0.0001). Patients in the continuous treatment group received more infliximab infusions after week 10 than did those in the on-demand group (mean+/-SD 5.8+/-2.2 versus 3.5+/-2; P<0.0001). Addition of MTX did not significantly affect the proportion of patients with an ASAS20 response at week 58, nor the number of infliximab infusions administered.

CONCLUSION

These findings indicate that continuous treatment of AS with infliximab is more efficacious than on-demand treatment, and that the addition of MTX to infliximab provides no significant benefit.

Autoantibody production in anti-TNF-alpha-treated patients

Targeting tumor necrosis factor alpha (TNF-alpha) has offered an additional therapeutic strategy against several rheumatic inflammatory disorders. The current use of TNF-alpha inhibitors allows physicians who manage these diseases and patients themselves to testify to an extraordinary efficacy, even though caution for possible adverse events must be maintained. Among these, the occurrence of autoimmune phenomena, encompassing new autoantibody formation and triggering of clinical manifestations, continues to be noted in published reports. Here, we review the current knowledge regarding the autoimmune phenomena linked to anti-TNF-alpha therapy in patients with rheumatic inflammatory disorders.

Clinical pharmacokinetics and use of infliximab

Tumor necrosis factor-alpha (TNFalpha) is a key proinflammatory cytokine involved in chronic inflammatory diseases. Infliximab, a chimeric (human-murine) monoclonal IgG1 anti-TNFalpha antibody, is used in the treatment of Crohn's disease (including fistulising disease) and rheumatoid arthritis (in combination with methotrexate) if standard treatments have failed. The indications for infliximab have recently been expanded to include ankylosing spondylitis, psoriatic arthritis, psoriasis and ulcerative colitis. The biological agent infliximab is given by multiple intravenous infusions in a dosage of 3-5 mg/kg (initially at weeks 0, 2 and 6; subsequently in intervals of 4-8 weeks). In controlled trials, clinical response rates of 20-40% have been achieved with such regimens in Crohn's disease and rheumatoid arthritis. However, the therapeutic benefits must be balanced against the risks of a variety of severe adverse events (e.g. severe infections including tuberculosis, hepatotoxicity, infusion reactions, serum sickness-like disease and lymphoma). Following single and multiple infusions of infliximab, no relevant differences in median concentration-time profiles have been observed between patients with Crohn's disease, patients with rheumatoid arthritis and patients with psoriasis. The apparent volume of distribution of the high-molecular-weight infliximab (149.1 kDa) is low (3-6L) and represents the intravascular space. The long persistence in this compartment (elimination half-life 7-12 days, mean residence time 12-17 days) is due to the very low systemic clearance of about 11-15 mL/hour (0.18-0.25 mL/minute). Elimination of infliximab is most probably accomplished through degradation by unspecific proteases. During multiple infusions (every 4-8 weeks), no accumulation was observed, and serum concentrations and the area under the plasma concentration-time curve of infliximab increased in proportion to the infused dose, indicating linear pharmacokinetics. Co-medication with methotrexate delayed the decline in the serum concentrations of infliximab. When relating serum concentrations to the clinical response in patients with rheumatoid arthritis and patients with Crohn's disease, it can be assumed that trough concentrations above 1 microg/mL could be used as a kind of therapeutic target. In the future, identification of biomarkers for (non-)response and risk factors for adverse drug reactions would be very helpful. Furthermore, combined biological, pharmacokinetic, pharmacogenomic and clinical studies have not yet been performed and are needed to optimise the therapeutic potential of infliximab, which is currently established as a rescue treatment in refractory patients.

Vaccination with IL-6 analogues induces autoantibodies to IL-6 and influences experimentally induced inflammation

IL-6 is involved in inflammation and a therapeutic target. 0.1% of Danish blood donors have nanomolar plasma concentrations of polyclonal, picomolar affinity and in vitro as well as in vivo neutralizing IgG autoantibodies to IL-6 (aAb-IL-6). Such donors are assumed to be severely IL-6 deficient; yet they appear healthy and do not exhibit overt clinical or laboratory abnormalities. We induced comparable levels of aAb-IL-6 in different mouse strains by vaccination with immunogenic IL-6 analogues. We observed that the induced aAb-IL-6 protected against collagen-induced arthritis and experimental allergic encephalitis. Furthermore, aAb-IL-6 carrying mice displayed increased plasma TNFalpha concentrations upon challenge with LPS. Taken together, induction of IL-6 autoantibodies was possible in different mouse strains. The autoantibodies influenced experimental inflammation. This immunotherapeutic principle might be a viable alternative in immune competent humans suffering from disorders driven by IL-6.

Investigation of the functional characteristics of antibodies to therapeutic anti-human tumor necrosis factor alpha monoclonal antibody

Humanized antibody-based treatment modalities represent an active area of investigation. Included in these strategies are passive administrations of monoclonal antibodies, which recognize tumor necrosis factor alpha (TNF-alpha). However, several problems associated with these types of treatment strategies have been reported in the literature. We attempted to address the issue related to unresponsiveness to infliximab that might be induced by anti-idiotype response to the passively administered humanized monoclonal antibody. The characteristics and functional importance of antibodies to infliximab (ATI) were investigated in human sera. We studied the binding characteristics of ATI to infliximab, TNF-alpha Receptor-I (RI, p55) and Receptor-II (RII, p75). In addition, cytotoxicity effect on L929 cells and blocking effects on the binding of TNF-alpha with infliximab and etanercept were also analyzed. On the basis of the results obtained from the experiments, it seems that the target epitope for ATI is related with somewhere else not residing in the region capable of generating "mirror image". The results presented indicate that ATI does not mimic the functional characteristics of TNF-alpha. However, ATI inhibited the binding properties of infliximab to TNF-alpha.