| Objective: To study the (125)~Ⅰlabeling method and immunoreactivity and stability of (125)~Ⅰ-2F5 antibody against CD28; To evaluate the feasibility of specific tumor radioimmunoimaging (RII)using (125)~Ⅰ-2F5.Methods: 1. Iodogen method was used for (125)~Ⅰlabeling 2F5 monoclonal antibody. Labeling efficiency was calculated and the radiochemical purity was measured by using paper chromatography method. Immunoreactivity of (125)~Ⅰ-2F5 to CD28-T cell ( transfected with full-length human CD28 cDNA ) was determined. The stability of (125)~Ⅰ-2F5 in sodium chloride and human serum was analyed respectively, and the radiochemical purity was determined from 0h to 48h after adding to the medium. 2. After the normal nude mice were injected with (125)~Ⅰ-2F5 through tail veil, mice were sacrificed by cutting off carotid artery at different time points. The interested organs were excised, washed with saline, weighed, and counted on a gamma counter for calculating dose per gram of tissue (%ID/g). In the same way, organs and tumor tissue of BALB/c nude mice bearing a lymphoma(CD28-T) at 16h,24h,48h were excised for calculating %ID/g and tumor/non-tumor (T/NT) ratio. 3.Animal models including BALB/c nude mice bearing a lymphoma(CD28-T) and a non small cell lung cancer(A549) were established using 4～6 weeks female BALB/c nude mice. 11.1-14.8MBq/200μL (300-400μCi/200μL) (125)~Ⅰ-2F5 were injected intravenously and radioimmunoimages underwent using SPECT. In order to block thyroid, l%KI 200μL/d were administrated intragastricly three days before imaging. T/B (tumor/background) was analyzed by ROI (region of intest) technique.Results: 1.The Labeling efficiency of (125)~Ⅰ-2F5 was (68.12±6.19)%, and its radiochemical purity was (97.67±0.59)%. The radioactivity of (125)~Ⅰ-2F5 was 756.13 MBq/mg. The highest total binding efficiency of (125)~Ⅰ-2F5 with CD28-T cell was (37.31±0.85)%,and the specific binding efficiency was (34.44±0.93)%. The radiochemical purity of (125)~Ⅰ-2F5 was still above 90% after incubated both at 4℃and 37℃for 24h in control and 4h in sodium chloride.2. (125)~Ⅰ-2F5 in the normal nude mice and nude mice bearing tumor was eliminated mainly through the liver and kidney in vivo; After injection of (125)~Ⅰ-2F5, The distribution of radiotracer in tumor tissue and T/NT ratio increased gradually with the time, the highest value reached at 24h 3. After injection of (125)~Ⅰ-2F5, the tumor can be seen clearly in radioimmunoimages in BALB/c nude mice bearing a lymphoma(CD28-T). However, no high radioactive uptake was observed in tumor tissues of non small cell lung cancer (A549).Conclusion: 1. The high labeling efficiency and radiochemical purity were obtained.The stability of (125)~Ⅰ-2F5 is fine in vitro and (125)~Ⅰ-2F5 keeps its immune activity after Iodogen labeling.2.In nude mice bearing a lymphoma imaging, the tumor uptook (125)~Ⅰ-2F5 highly and can be seen clearly in RII. 3. Our study had laid basic experimental foundation for lymphoma radioimmunoimage and target therapy using different radioisotope iodine (123I,(125)~Ⅰ,131I) labeled mAb 2F5 . |
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