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Neuroblastoma is the most frequent tumour of the childhood under the age of 5. The staging and the follow up are achieved by MIBG scintigraphy, considered as the method of reference, but sometimes difficult to interpret . The availability of monoclonal antibodies against the ganglioside GD2, expressed on the cell membrane of neuroblastoma and neuro-endocrine cancers offers novel tools that deserve to be carefully explored. We investigated four mouse monoclonal antibodies (3 IgG3: BW704, 7A4, 60C3, and the IgG1 variant of BW704: MAK704), on nude mice xenografted with a human neuroblastoma (REM). Sixty one nude mice were included. The three former MAbs provided tumour imaging, the best results being obtained with BW704, followed by 7A4 and 60C3. MAK704 was disappointing. A control antiphosphorylcholine antibody (P51-1) did not give any tumour image in the three tested mice. Scintigraphy ratios tumour/liver and tumour/muscle reached 20 and 100 with BW704, respectively, on the 10th day. Good imaging quality was already obtained from the 24th h. The tumour uptake, calculated from radioactivity countings of resected samples, reached 22 +/- 3% of injected dose per gramme. These results let us hope that these antibodies could also provide highly contrasted images in humans and could open the way for therapeutic applications.

Immunoscintigraphy (IS) using the HRS-3 Hodgkin associated monoclonal antibody (MoAb) was performed in 18 patients with Hodgkin's Disease (HD) at staging or restaging. Either F(ab')2 fragments (14 patients) or whole HRS-3 (4 patients) labeled with 77-260 Mbq 131-I were used. Whole body images, including anterior and posterior views, were taken from a digital gamma camera, within 4 to 8 hours after injection and then daily for 5 days. In one patient IS was discontinued due to iodine intolerance. Seventeen patients were evaluable: 14 showed a true positive result including 2 cases which were reviewed as anaplastic large cell lymphoma (ALCL). Nodal, splenic, bone marrow and muscle involvements were imaged, many of these sites were previously unsuspected. In 7 patients with true positive findings the Pressman Specificity Index, as measured from biopsied material, ranged from 1.5-3 in 4 patients and from 5 to greater than 100 in 3 patients. Imaging was equivocal or failed in 1 patient (lymph nodes). In 2 patients, IS imaging was truly negative due to the absence of active HD, and a false negative result occurred once (inguinal node). In none of the patients a false positive image was observed. In order to rule out non-specific iodine uptake a control, anti-ACE MoAb, labeled with 125-Iodine was injected simultaneously in 10 patients. The evaluation of the study gave a sensitivity of 87% and a good specificity. IS using radioiodine labeled MoAbs is feasible and represents a reliable non-invasive diagnostic method for the staging and follow-up of HD and ALCL.

Protocols for purification of mouse monoclonal antibodies (MAbs) from nude mice ascites were investigated in order to assess the yield and to compare the purified products in two-dimensional gel electrophoresis (2DGE). Three MAbs (one IgG2 and two IgG1), selected for their differing behaviours towards protein A, were purified by ammonium sulphate precipitation and/or gel filtration, anion exchange (DEAE), hydroxylapatite and affinity (protein A) chromatography, or by a combination of these methods. Protein A constantly provided the highest purity whatever the IgG subclass. The best results in terms of yields and purity were a function of the optimization of the protein A protocol. In our study, they were obtained in a 3 h protocol (IgG2), a 16 h protocol with discontinuous pH gradient method (IgG1 with sufficiently high affinity for protein A) or a multi-step protocol involving DEAE and protein A (IgG1 with low affinity for protein A). DEAE chromatography alone provided a slightly better yield, but only moderate purity. Hydroxylapatite chromatography appeared to be less potent in terms of yield, purity and day-to-day reproducibility. Salt precipitation and gel filtration enabled only relative enrichment of the MAb solution. Some degradation products of both heavy and light chains clearly appeared in the 2DGE patterns of antibodies purified by different protocols, and seem to be partly related to the elution pH and to the duration of the purification procedure. Finally, this work highlights considerable heterogeneity not only between two different MAbs of the IgG1 subclass but also within a monoclonal population of immunoglobulins.