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的共刺激分子的人抗体，利用抗体建立免疫系统的靶向和控制，并将其应用于DNA疫苗的开发。我们利用人源抗体噬菌体展示文库成功地分离出能抑制ICOS与B7RP-1共刺激信号的抗B7RP-1抗体，目前正在申请专利。所获得的三种抗体均能抑制抗CD3抗体刺激的T细胞增殖。我们还开发了其他针对CD86的人类抗体，CD86是CD28的共刺激配体，目前正在准备申请专利。由于抗原提呈细胞(APC)大量表达CD86和B7RP-1分子，这些抗体不仅可以作为阻断共刺激信号的拮抗剂，而且还可以靶向APC，这种靶向能力对于有效的疫苗开发将抗原有效地引导到APC是非常重要的。我们现在正在研究利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(靶向APC的分子)与人Fc(抗原)的胞外区融合蛋白基因，并将其经皮肤免疫小鼠作为DNA疫苗。因此，在CTLA-4-Fc融合的情况下，与仅使用Fc(抗原)相比，获得了对该抗原的高抗体应答。这些结果表明，针对APC的抗原靶向在疫苗效力方面具有良好的效果。

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.