The antibody response against human and chimeric anti-TNF therapeutic antibodies primarily targets the TNF binding region.

BACKGROUND: In a subset of patients, anti tumour necrosis factor (TNF) therapeutic antibodies are immunogenic, resulting in the formation of antidrug antibodies (ADAs). Neutralising ADAs compete with TNF for its binding site and reduces the effective serum concentration, causing clinical non-response. It is however unknown to which extent ADAs are neutralising. OBJECTIVES: To study which proportion of antibodies to human(ised) anti-TNF (adalimumab, golimumab, certolizumab) as well as chimeric anti-TNF (infliximab) is neutralising. METHODS: Neutralising capacity of ADAs was assessed using a TNF competition assay in ADA-positive sera of patients treated with adalimumab (n=21), golimumab (n=4), certolizumab (n=9) or infliximab (n=34) sent in to our diagnostic department. RESULTS: In 34 sera with ADAs to adalimumab, golimumab or certolizumab, >97% of the antibodies were neutralising. In 34 sera with ADAs to infliximab >90% of the antibodies were neutralising. Further characterisation of the broader antibody response to infliximab revealed that non-neutralising antibodies to infliximab do not target murine domains, but may bind infliximab-unique domains not involved in TNF binding (located outside the paratope). CONCLUSIONS: Our study shows that ADAs to human(ised) as well as chimeric anti-TNF therapeutic antibodies are largely neutralising. This highly restricted ADA response suggests an immunodominant role for the paratope of anti-TNF therapeutics.

Patients non-responding to etanercept obtain lower etanercept concentrations compared with responding patients.

OBJECTIVE: To investigate the relationship between serum etanercept levels and clinical response. METHODS: In 292 etanercept-treated patients with rheumatoid arthritis clinical and pharmacological data were determined at baseline and after 1, 4 and 6 months of etanercept treatment. Differences in etanercept levels between good, moderate and European League Against Rheumatism (EULAR) non-responders were assessed after 6 months of therapy. RESULTS: After 6 months of therapy etanercept levels were significantly higher in good responders (median (IQR) 3.78 (2.53-5.17)) compared with both moderate 3.10 (2.12-4.47) and EULAR non-responders 2.80 (1.27-3.93) (all p<0.05). There was a significant association between clinical response and serum etanercept levels (regression coefficient 0.54, 95% CI 0.21 to 0.86, p=0.001). When patients were categorised into quartiles according to the height of etanercept levels, the lowest quartile (etanercept level <2.1 mg/l) comprised 40% of all non-responders. The highest quartile (etanercept level >4.7 mg/l) comprised 35% of all good EULAR responders. Anti-etanercept antibodies were detected in none of the sera. CONCLUSION: The authors demonstrated that lower etanercept levels were associated with non-response. Therapeutic drug monitoring and the possibility of the adjusted dosing regimes in the selected groups of patients should be investigated further as a possible tool to optimise treatment with etanercept.

Mannan binding lectin in febrile adults: no correlation with microbial infection and complement activation.

AIMS: To study the role of the mannan binding lectin (MBL) pathway of complement activation in the host defence to microbial infection in vivo, and the role of MBL in infectious mortality in non-selected patients. METHODS: A prospective observational study on 177 hospitalised medical patients with new onset fever. The presence, origin, and microbial cause of infection, the circulating MBL and complement activation product 3a (C3a), and the 28 day hospital course were determined. RESULTS: The patients had median MBL values similar to healthy blood donors: 18% of the patients and 14% of the blood donors had MBL deficiency, with values below 0.1 microg/ml. Median C3a was higher in patients with microbiologically confirmed infection than in those without, whereas there was no difference in MBL values or frequency of deficiency among patient groups with or without positive local cultures or bacteraemia. The mortality rate was 8% and the outcome groups did not differ in MBL. In febrile adults hospitalised in internal medicine wards, microbial infection induces complement activation, independently of MBL. CONCLUSIONS: The results argue against a predominant role for the MBL pathway of complement activation and a deficiency of MBL predisposing to serious and invasive microbial infection in non-selected adults.

Complicated PEG-to-skin level gastrostomy conversions: analysis of risk factors for tract disruption.

BACKGROUND: PEG disruptions during conversions to skin-level gastrostomy devices have been described, but specific risk factors have not been reported. In this study, possible risk factors for tract disruption in a pediatric population were identified, and management of complications described. METHODS: The medical records of patients who underwent gastrostomy conversions during 1994 were reviewed. Statistical analysis was performed using two-tailed student's t test, and risk ratios with 95% confidence limits were calculated. RESULTS: Gastrostomy tract disruption occurred in 6 to 30 (20%) of tube conversions. Complicated and uncomplicated cases did not differ with regard to age, sex, primary or associated diagnoses, pregastrostomy or postgastrostomy nutritional status, tract maturity, or percutaneous gastrostomy tube type. The use of an 18F obturator-type skin-level gastrostomy tube increased the risk for gastric separation 4.8-fold. Tract disruptions were managed by fluoroscopic gastrostomy tube replacement, repeat PEG, or exploratory laparotomy with open gastrostomy. CONCLUSIONS: The use of obturator-type skin-level gastrostomy tubes was associated with an increased risk of tract disruption. Fluoroscopic verification of intragastric placement is warranted after initial conversions to skin-level gastrostomy tubes.

Peritoneal interleukin-8 in acute appendicitis.

Interleukin-8 (IL-8) is a chemoattractant that is highly selective for neutrophils. This study was designed to investigate the presence of IL-8 in peritoneal fluid of patients with acute appendicitis. The clinical circumstances underlying the secretion of IL-8 by mesothelium and its mechanism of activation have not been defined. In an in vitro model for bacterial peritonitis the role of bacteria in activating human mesothelial cells to secrete IL-8 was studied. Cultured human mesothelium was incubated with various species of pathogenic bacteria, isolated from peritoneal exudate fluids of patients with appendicitis. The amount of IL-8 secreted by the cultured mesothelial cells was determined in an IL-8 ELISA, as IL-8 was present in the original peritoneal fluid of these patients. Peritoneal fluids from patients with a perforated appendix were found to contain a significantly higher concentration of IL-8 compared to peritoneal fluids from patients with nonperforating appendicitis (121.6 (57.8) ng/ml versus 0.2 (0.07) ng/ml, respectively; mean (SEM), P < or = 0.01). Species of Bacteroïdes and Fusobacterium necrophorum induced IL-8 secretion from cultured mesothelial monolayers to levels comparable to those found in peritoneal fluids in vivo. Heat-killed bacteria and bacterial supernatant were also able to stimulate mesothelium to secrete IL-8. The results suggest that in the early phase of bacterial peritonitis the influx of PMN is regulated by bacteria-induced IL-8 secretion by the mesothelium lining the peritoneal cavity.

Purification and characterization of the soluble interleukin-6 receptor from human plasma and identification of an isoform generated through alternative splicing.

The soluble human interleukin-6 receptor (shIL6R) was purified from human plasma. In a single immunoaffinity purification step a 140000-fold enrichment with a yield of 95% was achieved. A subsequent IL-6 affinity chromatography resulted in a homogeneous receptor preparation but only in a yield of less than 5%. The biological activity of the soluble receptor was clearly demonstrated by its ability to induce the synthesis of the acute-phase protein 1-antichymotrypsin in HepG2 cells stably transfected with IL-6. Upon gel filtration, the native shIL6R showed an apparent molecular mass of 93 kDa. Analysis by SDS/PAGE revealed an apparent molecular mass of 65 kDa for the soluble receptor. Deglycosylation with peptide N-glycosidase F led to a shift in molecular mass from 65 kDa to 45 kDa. It has previously been shown that the shIL6R can be generated by shedding the membrane-bound form or by expression of an alternatively spliced mRNA. Here we show that the shIL6R isolated from human plasma is recognized by an affinity-purified peptide antibody raised against an amino acid sequence unique for the alternatively spliced isoform. Thus, the shIL6R isoform generated through alternative splicing which has been previously detected in supernatants of cultured cell lines is also an in vivo product circulating in human plasma.

Soluble human interleukin-6 receptor. Expression in insect cells, purification and characterization.

The extracellular domain of the human interleukin-6 (IL-6) receptor, comprising 339 amino acids following the signal peptide, has been expressed in baculovirus-infected insect cells (Sf158). When the soluble receptor secreted into the culture medium was purified by affinity chromatography, using IL-6 immobilized on Sepharose, 6 mg soluble receptor was isolated from 1 l conditioned medium of Sf158 suspension cultures. A molar absorption coefficient of 9.3 x 10(4) l.mol-1.cm-1 was calculated from the ultraviolet spectrum of the soluble IL-6 receptor. After SDS/PAGE and silver staining, an apparent molecular mass of 48 kDa was estimated for the purified protein. Deglycosylation with peptide N-glycosidase F resulted in an increase in electrophoretic mobility and a decrease in the apparent molecular mass from 48 kDa to about 41-44 kDa. As expected, the soluble human IL-6 receptor bound human 125I-labeled IL-6 with low affinity (Kd = 500 pM). Furthermore, the binding of soluble human IL-6 receptor to immobilized IL-6 was studied using real-time interaction analysis. The recombinant soluble receptor showed biological activity on HepG2 cells stably transfected with a cDNA coding for IL-6 (HepG2-IL-6 cells). Haptoglobin mRNA synthesis was induced by the soluble IL-6 receptor at concentrations as low as 10 ng/ml. Five monoclonal antibodies were generated. Two groups of antibodies were identified mapping to amino acids 1-67 and 68-143 of the soluble IL-6 receptor, respectively. The plasma clearance of soluble 125I-labeled IL-6 receptor in the absence and presence of IL-6 was studied in rats as a model system. The kinetics was biphasic. Soluble IL-6 receptor/IL-6 complexes were cleared more rapidly than the soluble receptor alone. Intravenously injected soluble 125I-labeled IL-6 receptor, as well as complexes with IL-6, rapidly accumulated in liver and to a lesser extent in skeletal muscle, skin and kidneys. Subsequently, the radioactivity appeared in the gut content.

The release of interleukin-8 during intravenous bolus treatment with interleukin-2.

OBJECTIVE: To study the role that interleukin-8 might play in the activation of polymorphonuclear neutrophils during interleukin-2 therapy and the relationship of these phenomena to interleukin-2 induced toxicity. DESIGN: A cohort study with measurements before and after the administration of interleukin-2. SETTING: Medical oncology department of a large teaching hospital. PATIENTS: Fourteen patients with metastatic renal cell carcinoma and 10 with metastatic melanoma being treated in a phase 2 study of the sequential combination of interferon-gamma and interleukin-2. MEASUREMENTS: Plasma levels of tumour necrosis factor-alpha, interleukins-6 and 8 and markers of neutrophil activation (neutrophil elastase and lactoferrin) were measured in patients receiving 5 daily injections of interferon-gamma (100 micrograms/m2/day) followed by 5 days of interleukin-2 (18 x 10(6) IU/m2/day). MAIN RESULTS: Tumour necrosis factor-alpha rose from baseline levels of 32 (range, 12 to 56) to 343 (103 to 787) pg/ml 3 hours after interleukin-2 administration returning to baseline values 21 hours later. Interleukins-6 and -8 rose from baseline levels of 6 (5 to 10) and 75 (35 to 100) to 2151 (152 to 7259) and 1283 (490 to 2500) pg/ml, respectively, at 4 hours after interleukin-2 with both returning to baseline values by 24 hours. Peak levels of neutrophil elastase and lactoferrin, both markers of neutrophil activation, occurred 6 hours after interleukin-2 administration. CONCLUSIONS: These data indicate that following administration of interleukin-2 tumour necrosis factor-alpha is released followed sequentially by rises in interleukins-6 and -8. It is hypothesised that these events result in activation of polymorphonuclear neutrophils. These activated neutrophils may play an important role in initiating endothelial cell damage leading to the haemodynamic toxicity and the capillary leak syndrome which is typically seen following the administration of interleukin-2.

Interleukin-8 (IL-8) in synovial fluid of rheumatoid and nonrheumatoid joint effusions.

IL-8 was measured in knee joint synovial fluid of 60 patients with rheumatoid arthritis, 8 with gout, 6 with osteoarthritis and 4 with meniscus lesions. IL-8 could be demonstrated in most SF samples. The highest levels were observed in rheumatoid joint effusions, yet mean levels were not significantly different between the different subgroups (mean +/- SE; RA 1537 +/- 3049 pg/ml, gout 570 +/- 952 pg/ml, OA/ML 178 +/- 188 pg/ml). In RA patients, IL-8 levels could not be related to various serological, clinical or radiological parameters. However, a correlation was observed between SF levels of IL-8 with those of lactate, LDH, beta 2-microglobulin and glucose. These observations suggest that next to the laboratory parameters IL-8 will be a parameter of the activity of the local inflammatory process. The results also demonstrate that IL-8 is not a disease-specific marker of joint inflammation.

Neutrophil migration across monolayers of cytokine-prestimulated endothelial cells: a role for platelet-activating factor and IL-8.

In a previous study we observed that neutrophils respond with a rapid rise in [Ca2+]i during adherence to cytokine-activated endothelial cells (EC), caused by EC membrane-associated platelet-activating factor (PAF). In the present study, we investigated whether this form of PAF was important in neutrophil adherence and migration across monolayers of rIL-1 beta- or rTNF alpha-prestimulated EC. PAF receptor antagonists prevented neutrophil migration across cytokine-pretreated EC by approximately 60% (P less than 0.005) without interfering with the process of adherence. The antagonists WEB 2086 and L-652,731 had no effect on neutrophil migration across resting EC induced by formylmethionyl-leucyl-phenylalanine (FMLP). A murine anti-IL-8 antiserum was found to also partially inhibit the neutrophil transmigration across cytokine-activated EC. When the anti-IL-8 antiserum was used in combination with a PAF receptor antagonist, neutrophil migration across cytokine-pretreated monolayers of EC was completely prevented. During transmigration, LAM-1 and CD44 on the neutrophils were down-modulated; both WEB 2086 and anti-IL-8 antiserum partially prevented this down-modulation caused by cytokine-prestimulated EC. Our results indicate that human neutrophils are activated and guided by EC-associated PAF and EC-derived IL-8 during the in vitro diapedesis in between cytokine-stimulated EC.

The intestinal absorption of 3-O-methyl-D-glucose in methotrexate-treated rats: an in vivo study of small bowel function.

The in vivo absorption of 3-O-methyl-D-glucose (3MG) as a marker of intestinal function has not been studied in an animal model. We evaluated the use of 3MG as a marker of intestinal absorption when given enterally to rats recovering from small bowel mucosal injury induced by methotrexate (MTX). Radiolabeled 3MG was administered into the duodenum of control (CON) and MTX-treated rats and blood samples were obtained at specified intervals. Mucosal permeability was also assessed using radiolabeled mannitol and polyethylene glycol 900 (PEG). Concentration time points were plotted, and area under the curve was calculated as an approximation of absorbed dose. Mucosal weight, maltase activity, and protein content were determined on mucosal scrapings. During the acute phase (day 5), 3MG absorption and maltase-specific activity were significantly decreased in the MTX group when compared to the CON group (p less than 0.001). The MTX group showed a trend toward greater permeability to mannitol when compared to the CON group; however, this was not statistically significant. Mucosal permeability to PEG was similar in both groups. During a later stage in the recovery process (day 12), the area under the curve calculations for 3MG absorption were the same for both CON and MTX animals, with maltase activity in the MTX group recovering to control values. Changes in 3MG absorption paralleled total maltase activities following severe injury. These results suggest that the combined active and passive transport of 3MG in vivo could be of use as a marker of intestinal absorption in states where the small intestine has sustained major damage resulting in compromised absorption as well as brush border digestion.

Neonatal hepatitis and extrahepatic biliary atresia associated with cytomegalovirus infection in twins.

Prenatally acquired cytomegalovirus infection in twins was temporally associated with a discordant development of neonatal hepatitis and extrahepatic biliary atresia. This case presents evidence suggesting an association between perinatal cytomegalovirus infection and selected extrahepatic biliary atresia and neonatal hepatitis. Congenital cytomegalovirus infections and cytomegalovirus hepatitis are also discussed.

Elevated plasma aluminum levels in normal infants receiving antacids containing aluminum.

Aluminum toxicity is a documented cause of encephalopathy, anemia, and osteomalacia. Excretion is primarily renal; therefore, patients with renal insufficiency are at risk for aluminum accumulation and toxicity. This has been demonstrated in uremic children treated with aluminum-containing antacids. The purpose of this study was to determine whether plasma aluminum levels were elevated in infants with normal renal function during prolonged aluminum-containing antacid use. Ten study infants (mean age = 5.8 months), who had been receiving antacids for at least 1 week, were compared with 16 control infants (mean age = 9.8 months) not receiving antacids. The study patients consumed 123 +/- 16 mg/kg per day (mean +/- SEM) of elemental aluminum for an average of 4.7 weeks. Their plasma aluminum level (37.2 +/- 7.13 micrograms/L) was significantly greater than that of the control group (4.13 +/- 0.66 micrograms/L) (P less than .005). It is concluded that plasma aluminum levels may become elevated in infants with normal renal function who are consuming high doses of aluminum-containing antacids. The safety of antacids containing aluminum should not be assumed and they should be used judiciously in infants, with careful monitoring of the aluminum dose and plasma level.

Suppression of diamine oxidase activity enhances postresection ileal proliferation in the rat.

To assess the influence of diamine oxidase activity on the adaptive process of the small bowel after resection, we administered aminoguanidine, a potent diamine oxidase inhibitor, to rats for 10 days after either small bowel transection (n = 5) or 80% jejunoileal resection (n = 7). Five or more additional animals from each group received saline as controls. Ileal mucosal homogenates from the resection group receiving aminoguanidine, when compared with those from resection controls, showed no diamine oxidase activity with increased putrescine content and ornithine decarboxylase activity. Mucosal proliferation, as measured by mucosal mass, protein content, and deoxyribonucleic acid content, was greater in the resected animals receiving aminoguanidine when compared with that of resection controls. Sucrase activity per gram of mucosa was almost identical in both resection groups. These results show that the suppression of diamine oxidase during the postresection adaptive period results in enhanced mucosal proliferation with no effect on mucosal functional differentiation. Diamine oxidase may play a regulatory role in adaptive intestinal proliferation.

Acute self-limited colitis associated with Cryptosporidium in an immunocompetent patient.

A case report of acute self-limiting colitis associated with enteric Cryptosporidium infection in an immunocompetent child is presented. This case broadens the spectrum of symptoms and manifestation of Cryptosporidium infection in a normal human host.

Effects of dietary linoleic acid on mucosal adaptation after small bowel resection.

We have shown that dietary long-chain triglycerides and 16,16-dimethyl prostaglandin E2 enhance and aspirin impairs postresection mucosal adaptation in rats. The present studies examined the hypothesis that supplemental linoleic acid (LA) above the minimum requirement may enhance postresection mucosal adaptation through altered prostaglandin (PG) synthesis. Forty male Sprague-Dawley rats (105 +/- 5 g) were fed purified diet containing either 5% LA or 4% palmitic acid and 1% LA. After 2 weeks, 12 rats from each dietary group underwent 70% proximal jejunoileal resection and the remainder were sham-operated. Dietary regimens were continued for an additional 13 days. Mucosal fatty acid analysis of 1% LA group revealed a ratio of 20:3 n-9/20:4 n-6 lower than 0.2, indicating normal essential fatty acid status. Mucosal protein per centimeter bowel was higher in the 5% LA group compared to the 1% group, but mucosal DNA, maltase, and ex vivo PG synthesis were not affected. These results indicate that LA stimulates postresection mucosal hypertrophy, which does not appear to be related to PG synthesis.