生物素-亲和素预定位技术在抗CEA单抗放免显像中的实验研究

Experimental study of biotin-avidin pretargeting technique for anti-CEA McAb radioimmunoimaging

为提高抗CEA单抗(McAb)放免显像(RII)的诊断效果,应用二步法(生物素化CEA McAb-^(131)I标链霉亲和素)和三步法(生物素化CEA McAb-链霉亲和索-^(111)In螯合DTPA生物素)预定位于荷人结肠癌裸鼠,分别在注射放射性标记物后2～120小时进行γ显像和体内分布测定。结果表明,二步法:实验组各脏器靶/非靶(T/NT)比值较对照组明显增高,血T/NT比值实验组和直接法组之比24小时为1.11:0.42,120小时为8.55:3.51;各时相各脏器的%ID/g均低于相应直接法组。γ显像实验组24小时已见肿瘤有放射性浓聚,96小时和120小时更为清晰;而对照组肿瘤仅见稍有显影或不显影。三步法:实验组2小时血T/NT比值达4.19,而对照组各时相均小于1.37,其他脏器T/NT比值也以实验组为高;肿瘤%ID/g 2小时为9.72%,48小时为3.65%;对照组各时相均小于3.07%。γ显像2小时肿瘤已有明显放射性浓聚,48小时更清晰;对照组肿瘤早期稍显示,随后不显影。故生物素-亲和素预定位技术能提高T/NT比值,降低血本底,获得早期显影,改善图像质量。

PURPOSE Biotin-avidin pretargeting technique was used in promoting the diagnostic efficacy of anti-CEA MeAb radioimmunoimaging. METHODS CEA McAb was conjugated with biotin MeAb(B-McAb), streptoavidin(SA) was labeled with ^(131)I ((131)I-SA) and DTPA-biotin with (111) In ((111)In-DTPA-B). Experimental human colonic tumor bearing nude mice were used. Two step method: B-McAh was preinjected, followed by ^(131)I SA 48h later, 24, 48, 96 and 120h postinjection, γ-imaging and biodistribution were studied. Three step method: B-McAb was preinjected, followed by cold SA 24h later and ^(111)In-DTPA-B another 24h later. 2, 6, 24 and 48h postinjection, γ-imaging and biodistribution were also studied. RESULTS Two step method: T/NT of all organs in experimental group was significantly increased compared with controls. The blood T/NT in experimental group and control group at 24 and 120h was 1.11: 0.42 and 8.58: 3.51, respectively. Tumor % ID/g in all organs slightly decreased compared with direct group. In γ-imaging radioactivity has been accumulated in tumor site as early as 24h, while only slightly visualized or nonvisualized in controls. Three step method: in experimental group the blood T/NT reached 4.19 at 2h, whileas all was < 1.37 at each phase of controls, the T/NT of all organs was also higher in experimental group than in controls. The tumor % ID/g in experimental group was 9.72% at 2h and 3.65 96 at 48h whileas % ID/g in controls in all phases was<3.07. The tumor clearly visualized at 2h and clearer at 48h in γ-imaging. In controls, the tumor was slightly visualized also at early stage, but faded away later on. CONCLUSIONS Biotin-avidin pretargeting technique can elevate the T/NT ratio and decrease the blood background. Early imaging was obtained with better imaging quality.