抗PSA/抗CD3两种双特异性单链抗体的活性研究

目的:研究并比较已成功构建的抗PSA/抗CD3两种双特异性单链抗体的生物学活性。方法:利用流式细胞仪和51Cr释放试验评价抗PSA/抗CD3双特异性单链抗体的抗原亲和活性和体外介导杀伤靶细胞的效果。建立前列腺癌裸鼠模型,分为非治疗组、对照组、双特异性单链抗体(BsAb)组和多价双特异性单链抗体(mBsAb)组,分析两种双特异性单链抗体在体内介导细胞毒T细胞对肿瘤细胞杀伤的能力。结果:流式细胞仪结果显示:BsAb与LNCaP细胞和Jurkat细胞的阳性结合率分别为56.3%和55.4%;mBsAb与LNCaP细胞和Jurkat细胞的阳性结合率分别为74.0%和83.0%。在体外,有细胞毒T细胞存在时两种抗体均可引起前列腺癌细胞的裂解,裂解效率分别与抗体浓度和T细胞与靶细胞比例呈正相关。与对照组比较,接种前列腺癌细胞的裸鼠在体内注射激活的细胞毒T细胞的同时分别接受两种抗体的治疗后,肿瘤生长均明显受到抑制(P<0.05)。在亲和力、体外杀伤和体内抑制肿瘤生长等方面,mBsAb的活性明显优于BsAb。结论:抗PSA/抗人CD3 BsAb及其四聚体均具有良好的生物学活性,单链抗体四聚体的形成可以明显改善抗体的生物学活性。

Comparison of Biologic Activity of Two Anti-PSA/Anti-CD3 Bispecific Single-chain Antibodies

OBJECTIVE: To study and compare the biologic activity of two anti-PSA/anti-CD3 bispecific single-chain antibodies. METHODS: Flow cytometry (FCM) was used to detect the binding activity of two antibodies to CD3-positive cell line Jurkat and prostate carcinoma cell line LNCaP. The effect of the two antibodies in mediating tumor cell lysis in vitro was determined by using the 51Cr-release test. For in vivo evaluation of the two antibodies activity, a nude mouse model was used. The mice were inoculated with LNCaP prostate cancer cells. RESULTS: FCM showed that both the antibodies could bind Jurkat and LNCaP cells with high specificity. The percentages of the cells bond by the bispecific single-chain antibodies were 56.3% and 55.4%, and those by the multivalent antibodies were 74.0% and 83.0% respectively. Both the antibodies mediated a specific lysis of LNCaP cells in vitro, with activated CTLs as effector cells, and significantly reduced tumor growth of nude mice in vivo as compared with the untreated controls and the group treated with CTLs only (P <0.05). The experiment also showed that the multivalent antibody had a better activity than the bispecific antibody in binding antigens, mediating lysis of LNCaP cells and reducing tumor growth (P < 0.05). CONCLUSION: Both the anti-PSA/anti-CD3 bispecific single-chain antibody and multivalent antibody have good biologic activity, and the formation of the tetramerization of single-chain antibody can improve its biologic activity.