Isolation of human antibodies targeting to immunocytes from phage library and regulation of immune response

本研究的目的是分离针对淋巴细胞上共刺激分子的人源抗体，建立抗体对免疫系统的靶向和控制，以及它们在DNA疫苗开发中的应用。我们利用噬菌体抗体库技术成功地分离到了能够抑制ICOS与B7 RP-1共刺激信号的抗B7 RP-1抗体，并正在申请专利。所获得的三种抗体均能抑制抗CD 3抗体刺激诱导的T细胞增殖。我们还开发了其他对CD 86（CD 28的共刺激配体）具有特异性的人类抗体，目前正在准备专利。这里提到的抗体不仅可以作为阻断共刺激信号的拮抗剂，而且还可以作为抗原呈递细胞（APC）的靶向分子，因为APC大量表达这样的CD 86和B7 RP-1分子，并且这种靶向能力对于有效疫苗开发以将抗原有效地引导至APC是非常重要的。我们现在正在研究通过使用我们的人类抗体开发新疫苗的研究。作为初步实验，我们构建了CTLA-4胞外区（APC靶向分子）与人Fc（抗原）融合蛋白基因，并将其作为DNA疫苗经皮肤免疫小鼠。因此，与仅施用Fc（抗原）相比，在施用CTLA-4-Fc融合物的情况下获得了对抗原的高抗体应答。这些结果表明，将抗原靶向APC在疫苗效力方面给出了有希望的效果。

The aims of this study are the isolation of human antibodies directed to the costimulatory molecules on the lymphocytes, the establishment of the targeting and the control of the immune system by using antibodies, and their applications for DNA vaccine development. We succeeded in the isolation of anti B7RP-1 antibodies which could inhibit the costimulatory signal between ICOS and B7RP-1 by human antibody phage display library and are now applying for a patent. The obtained three antibodies could actually repress the T cell proliferation which was induced by anti CD3 antibody stimulation. We also developed other human antibodies that were specific to CD86, a costimulator ligand for CD28 and are now under preparation for a patent. The antibodies mentioned here can function as not only antagonist blocking the costimulatory signal but also targeting molecule to the antigen presenting cells (APC), because APC express abundantly such CD86 and B7RP-1 molecules, and such targeting ability is very important for the effective vaccine development to lead the antigens efficiently to the APC. We are now investigating the new vaccine developing studies by use of our human antibodies. As a preliminary experiment, we constructed a gene of fusion protein of extracellular domain of CTLA-4 (targeting molecule to APC) and human Fc (antigen) and immunized it through skin on mice as DNA vaccine. Consequently high antibody response to the antigen was obtained in the case of the administration of CTLA-4-Fc fusion, as compared with the administration of Fc (antigen) only. These results indicate that the targeting of the antigen to the APC give the promising effect in the vaccine efficacy.