RESUMEN
Rheumatoid arthritis is a chronic autoimmune disorder resulting in synovial inflammation. Fibroblast activation protein (FAP) is overexpressed by fibroblastlike synoviocytes in arthritic joints. Radioimmunoimaging with an anti-FAP antibody might be used to monitor the response to therapy, thus enabling tailored therapy strategies and therapeutic outcomes. The aim of this study was to assess whether a radiolabeled anti-FAP antibody could be used to monitor the efficacy of treatment with long-circulating liposomes (LCL) containing prednisolone phosphate (PLP-LCL) in a mouse model of arthritis. METHODS: Collagen-induced arthritis (CIA) was induced in male DBA/1J mice. Mice were treated with a single injection (10 mg/kg) of PLP-LCL or empty LCL as a control. SPECT and CT images were acquired 24 h after injection of 99mTc-labeled succinimidyl-hydrazinonicotinamide (99mTc-S-HYNIC)-conjugated anti-FAP antibody 28H1 at 2, 5, and 9 d after treatment. The uptake of 99mTc-S-HYNIC-28H1 in all joints was quantified and correlated with macroscopic arthritis scores. RESULTS: Treatment of CIA with PLP-LCL significantly suppressed joint swelling. At just 1 d after treatment, the macroscopic arthritis scores had decreased by 50%. Scores decreased further, to only 10% of the initial scores, at 5 and 9 d after treatment. In contrast, macroscopic arthritis scores had increased up to 600% in untreated mice at 9 d after the injection of empty LCL. 99mTc-S-HYNIC-28H1 uptake ranged from 1.5 percentage injected dose per gram in noninflamed joints to 22.6 percentage injected dose per gram in severely inflamed joints. The uptake of radiolabeled 28H1 in inflamed joints (percentage injected dose) correlated with the arthritis score (Spearman ρ, 0.77; P < 0.0001). Moreover, the uptake of 99mTc-S-HYNIC-28H1 was slightly increased at 9 d after therapy but was not seen macroscopically, indicating that SPECT/CT imaging might be more sensitive than the macroscopic arthritis scoring method. CONCLUSION: SPECT/CT imaging with 99mTc-S-HYNIC-28H1 specifically monitored the response to therapy, and tracer accumulation correlated with the severity of inflammation. In addition, SPECT/CT imaging was potentially more sensitive than the macroscopic arthritis scoring method. This study showed that SPECT/CT with 99mTc-S-HYNIC-28H1 could be used to noninvasively monitor the course of CIA in mice.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Artritis Reumatoide/diagnóstico por imagen , Artritis Reumatoide/tratamiento farmacológico , Monitoreo de Drogas/métodos , Gelatinasas/inmunología , Proteínas de la Membrana/inmunología , Serina Endopeptidasas/inmunología , Tomografía Computarizada por Tomografía Computarizada de Emisión de Fotón Único/métodos , Animales , Artritis Reumatoide/inmunología , Preparaciones de Acción Retardada/administración & dosificación , Endopeptidasas , Glucocorticoides/administración & dosificación , Marcaje Isotópico/métodos , Liposomas/administración & dosificación , Masculino , Ratones , Ratones Endogámicos DBA , Imagen Molecular/métodos , Prednisolona/administración & dosificación , Prednisolona/análogos & derivados , Radiofármacos/inmunología , Tecnecio/inmunología , Resultado del TratamientoRESUMEN
AIM: Crohn's disease (CD) is a chronic inflammatory bowel disease characterized by a cellular-mediated immune response driven by cytokines secreted mainly by T helper 1 cells (Th1). In active phases of the disease, an increased production and release of tumor necrosis factor a (TNFalpha) by macrophages and monocytes of the lamina propria has been described. The aim of this study was to detect the presence of TNFalpha within the gut mucosa in patients with active CD by using (99m)Tc-labelled chimeric human/mouse monoclonal antibody anti-TNFalpha (Infliximab, Remicade). METHODS: Infliximab has been labeled with (99m)Tc after reduction of disulfide bound by 2-ME method. In vitro binding assay and biodistribution in animal of [(99m)Tc]Infliximab has been performed to evaluate the retention of its biological activity. Ten patients with active CD refractory to conventional medical therapies were studied. Images of the abdomen were acquired at 6 to 20 h after i.v. injection of about 10 mCi of [(99m)Tc]Infliximab and a week later, all patients were also studied with [(99m)Tc]HMPAO-labeled autologous white blood cells (WBC). RESULTS: A product with high labeling efficiency (>95%) and stability has been obtained. In vitro tests with stimulated T-cells expressing TNFalphalpha indicated that [(99m)Tc] Infliximab retains its binding activity to cell bound TNFalpha as compared to unlabelled Infliximab. The degree of [(99m)Tc]Infliximab uptake by the inflamed bowel evaluated at 20 h postinjection was much less than that seen with labeled WBC and with a different distribution. Three of these patients received anti-TNFalpha (Infliximab) for therapeutic purposes with good clinical results despite the scintigraphy with (99m)Tc-Infliximab was negative in 2 of them. CONCLUSION: Scintigraphy with [(99m)Tc]Infliximab shows the presence of little TNFalpha in the affected bowel of patients with active CD. Therefore, the clinical benefit that patients have from Infliximab therapy is unlikely the consequence of a local a reduction of TNFalpha and the mechanism of action of Infliximab, in therapeutic doses, deserves further investigations.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales/uso terapéutico , Enfermedad de Crohn/inmunología , Enfermedad de Crohn/radioterapia , Tecnecio/inmunología , Tecnecio/uso terapéutico , Factor de Necrosis Tumoral alfa/inmunología , Animales , Células Cultivadas , Humanos , Linfocitos/inmunología , Ratones , Especificidad de Órganos , Radiofármacos/farmacocinética , Distribución TisularRESUMEN
The myocardial uptake of radioiodinated (Fab')2 fragments of antimyosin antibody [125I-(Fab')2] was compared with simultaneously administered 99mTc-pyrophosphate (Tc-PYP) in dogs undergoing coronary occlusion for 24 (N=6) or 72 hours (N=5). Relative concentrations of both agents in normal and infarcted myocardium were related to regional blood flow as determined by distribution of 55Sr-labeled microspheres in the same animals. There was an inverse exponential relationship between 125I-(Fab')2 localization and regional blood flow in 24 hr (r=-0.64) and 72 hr (r=-0.80) occluded animals. The greatest uptake of 125I-(Fab')2 was observed in subendocardial layers of the center of the infarct where regional flow was most severely impaired (1-10% of normal flow). Maximal localization of Tc-PYP was observed in subepicardial layers in samples from the periphery of the infarct where flow was only moderately reduced (31-50% of normal). Differences in distribution of these two agents in ischemic myocardium are probably related to differences in kinetics of exit from the blood pool.