Radiolabeled humanized anti-CD3 monoclonal antibody visilizumab for imaging human T-lymphocytes

Visilizumab is an IgG2 humanized monoclonal antibody (mAb) characterized by non-FcγR binding and specific to the CD3 antigen, expressed on more than 95% of circulating resting T-lymphocytes and on activated T-lymphocytes homing in inflamed tissues. We hypothesized that the use of a radiolabeled anti-CD3 antibody might serve as a diagnostic tool for imaging T-cell traffic and lymphocytic infiltration of tissues and organs affected by autoimmune diseases. Here we describe the results of in vitro and animal experiments with 99mTc-succinimidyl-6-hydrazinonicotinate hydrochloride (SHNH)-visilizumab. Methods: For mAb labeling, we used a 2-step method with a heterobifunctional linker SHNH. Several titrations were performed to obtain the best labeling efficiency. In vitro quality controls included stability assay, cysteine challenge, sodium dodecyl sulfate polyacrylamide gel electrophoresis, binding assay, and immunoreactivity assay. In vivo studies by high-resolution images were performed at 6 and 24 h after the injection of 99mTc-SHNH-visilizumab. These included cell-targeting experiments in BALB/c mice xenografted subcutaneously with an increasing number of HuT78 cells in the leg and displaced with an excess of cold antibody. We also studied irradiated severe combined immunodeficient (SCID) mice reconstituted with human peripheral blood mononuclear cells (hPBMCs) and injected with 99mTclabeled visilizumab or control mAb. After dynamic imaging for 3 h, major organs were removed, counted, and processed for immunohistologic examination. Results: Visilizumab was labeled with HYNIC with high labeling efficiency (>90%) and high specific activity (SA; 10,360-11,100 MBq/mg), with retained biochemical integrity and in vitro binding activity to CD3-positive cells. The in vivo targeting experiment showed a proportional increase of specific uptake with the number of injected cells, both at 6 and at 24 h, and the in vivo competition study demonstrated more than 60% decreased uptake after an excess of unlabeled antibody. In SCID mice, hPBMCs in different tissues were detected by 99mTc-labeled visilizumab and confirmed by histology. Conclusion: Visilizumab can be efficiently labeled with 99mTc with high efficiency and SA and could be a valuable tool for the study of human T-lymphocyte trafficking and lymphocytic infiltration of tissues and organs. Copyright © 2009 by the Society of Nuclear Medicine, Inc

Thyroid Cancer Imaging In Vivo by Targeting the Anti-Apoptotic Molecule Galectin-3

Background The prevalence of thyroid nodules increases with age, average 4-7% for the U.S.A. adult population, but it is much higher (19-67%) when sub-clinical nodules are considered. About 90% of these lesions are benign and a reliable approach to their preoperative characterization is necessary. Unfortunately conventional thyroid scintigraphy does not allow the distinction among benign and malignant thyroid proliferations but it provides only functional information (cold or hot nodules). The expression of the anti-apoptotic molecule galectin-3 is restricted to cancer cells and this feature has potential diagnostic and therapeutic implications. We show here the possibility to obtain thyroid cancer imaging in vivo by targeting galectin-3. Methods The galectin-3 based thyroid immuno-scintigraphy uses as radiotracer a specific 99mTc-radiolabeled mAb. A position-sensitive high-resolution mini-gamma camera was used as imaging capture device. Human galectin-3 positive thyroid cancer xenografts (ARO) and galectin-3 knockout tumors were used as targets in different experiments in vivo. 38 mice with tumor mass of about 1 gm were injected in the tail vein with 100 ?Ci of 99mTc-labeled mAb to galectin-3 (30 ?g protein/in 100 ?l saline solution). Tumor images were acquired at 1 hr, 3 hrs, 6 hrs, 9 hrs and 24 hrs post injection by using the mini-gamma camera. Findings Results from different consecutive experiments show an optimal visualization of thyroid cancer xenografts between 6 and 9 hours from injection of the radiotracer. Galectin-3 negative tumors were not detected at all. At 6 hrs post-injection galectin-3 expressing tumors were correctly visualized, while the whole-body activity had essentially cleared. Conclusions These results demonstrate the possibility to distinguish preoperatively benign from malignant thyroid nodules by using a specific galectin-3 radio-immunotargeting. In vivo imaging of thyroid cancer may allow a better selection of patients referred to surgery. The possibility to apply this method for imaging and treatment of other galectin-3 expressing tumors is also discussed

Development and Evaluation of a Novel 99mTc-Labeled Annexin A5 for Early Detection of Response to Chemotherapy

99mTc-HYNIC-annexin A5 can be considered as a benchmark in the field of apoptosis imaging. However, 99mTc-HYNIC-annexin A5 has characteristics of high uptake and long retention in non-target tissues such as kidney and liver. To minimize this problem, we developed a novel 99mTc-labeled annexin A5 using a bis(hydroxamamide) derivative [C3(BHam)2] as a bifunctional chelating agent, and evaluated its usefulness as an imaging agent for detecting apoptosis. The amino group of C3(BHam)2 was converted to a maleimide group, and was coupled to thiol groups of annexin A5 pretreated with 2-iminothiolane. 99mTc labeling was performed by a ligand exchange reaction with 99mTc-glucoheptonate. Biodistribution experiments for both 99mTc-C3(BHam)2-annexin A5 and 99mTc-HYNIC-annexin A5 were performed in normal mice. In addition, in tumor-bearing mice, the relationship between the therapeutic effects of chemotherapy (5-FU) and the tumor accumulation of 99mTc-C 3(BHam)2-annexin A5 just after the first treatment of 5-FU was evaluated. 99mTc-C3(BHam)2-annexin A5 was prepared with a radiochemical purity of over 95%. In biodistribution experiments, 99mTc-C3(BHam)2-annexin A5 had a much lower kidney accumulation of radioactivity than 99mTc-HYNIC- annexin A5. In the organs for metabolism, such as liver and kidney, radioactivity after the injection of 99mTc-HYNIC-annexin A5 was residual for a long time. On the other hand, radioactivity after the injection of 99mTc-C3(BHam)2-annexin A5 gradually decreased. In therapeutic experiments, tumor growth in the mice treated with 5-FU was significantly inhibited. Accumulation of 99mTc-C 3(BHam)2-annexin A5 in tumors significantly increased after 5-FU treatment. The accumulation of radioactivity in tumor correlated positively with the counts of TUNEL-positive cells. These findings suggest that 99mTc-C3(BHam)2-annexin A5 may contribute to the efficient detection of apoptotic tumor response after chemotherapy

Diagnosis of vascular prosthesis infection: PET or SPECT?

[No abstract available

Can we produce an image of bacteria with radiopharmaceuticals?

[No abstract available

New radiopharmaceuticals for imaging rheumatoid arthritis

Rheumatoid arthritis (RA) is an incapacitating chronic inflammatory disease of the joints that, because of frequent relapses, requires life-long treatment. in patients affected with RA an important treatment objective is to achieve specific immune suppression in order to extinguish the immune process and arrest the disease, thus preventing or delaying complications and avoiding disease recurrence. The side effects of anti-inflammatory drugs given to improve the quality of life of these patients can be reduced with the use of specific immune therapies that block, as selectively as possible, the pathologic mechanism responsible for the disease. New therapeutic options for specific, targeted therapies for treating RA are being developed, and trials to assess the efficacy and safety of these approaches are underway. However, these therapies rely primarily on clinical assessment to evaluate treatment efficacy. it would be useful, therefore, to have an objective and reliable method that directly highlights the immune processes underlying the disease. Currently available radiopharmaccuticals for imaging RA, with a special emphasis on recently developed agents and their use in therapy decision-making and follow-up are the focus of this article

High resolution small animal single photon emission computed tomography: uptake of [(99m)Tc]bombesin and [(123)I]ioflupane by rat brain.

The aims of this study were: 1) to perform brain single photon emission computed tomography (SPECT) in anesthetized rats with high resolution cameras (HRC) equipped with parallel hole collimation resolution of about 1 mm (HRC1) and 2 mm (HRC2); 2) to assess when and with which radio-tracer HRC1 SPECT shows advantages over HRC2.We used two multicrystal HRCs with parallel square hole collimators, whose pure tungsten septa closely fit the crystals, in turn matched with a 4 inch2 position sensitive photomultiplier. HRC1 showed 1.1 mm and HCR2 2.1 mm resolution at collimator contact. HRCs performed 180 degrees semi-circular orbits around the head of rats: image reconstruction occurred with ordered subsets expectation maximization algorithms. Resolution of SPECT was measured with a Derenzo Phantom, resulting 1.4 mm for HRC1 and 2.3 mm for HRC2. Three rats were studied with [(99m)Tc]HMPAO, 3 rats with [(99m)Tc]bombesin (BN) and 48 h later with [(123)I]ioflupane (DaTSCAN). SPECT studies were reviewed by two experienced operators.Technetium-99m-HMPAO SPECT showed similar images with HRC1 and HRC2. The uptake of BN by amygdale, hippocampus and olfactory tract was detected by both cameras. DaTSCAN SPECT with HRC1 showed detailed image of the tail of the caudatus: this image was not obtained with HRC2. DaTSCAN and BN SPECT showed amygdale with both HRCs. However, only the central nucleus of amygdale takes up DaTSCAN, whereas central, lateral and basolateral amygdaloid nuclei express BN receptors. Only HRC1 SPECT showed amygdale larger with BN than with DaTSCAN.Spatial resolution of 1.4 mm is appropriate to detect selected subcerebral structures