開發具有誘發特異性免疫反應之微脂體複合體與其特性研究

Abstract

抗原呈現細胞 (antigen presenting cell; APC) 利用MHC分子將病源體之抗原和T細胞細胞膜表面的TCR交互作用後，並配合共同刺激因子，可有效地開啟專一性的T細胞免疫反應。目前了解樹突細胞 (dendritic cell; DC) 是抗原呈現細胞中，呈現抗原之能力最具有效率的。根據一些相關樹突細胞的研究，利用樹突細胞能有效吞噬抗原、呈現抗原，及活化T細胞的能力，研究人員藉此已將其發展成為一個很好的疫苗平台。但是，在其他研究中也發現到樹突細胞會受到病源體相關因子影響，降低了樹突細胞之免疫功能。於是便發展人工化抗原呈現細胞來解決樹突細胞所遭遇到問題。本篇論文研究成功建立了一個具有免疫調節功能的新穎之微脂體。LPPC (Lipo-PEI-PEG Complex) 是本實驗室開發出來的微脂體，因為它具有穩定吸附蛋白的能力，並且能維持該蛋白的活性。因此，利用LPPC新穎的特性，將具有可以調節免疫反應的單株抗體或MHC分子給予LPPC吸附後，賦予LPPC擁有抗原呈現細胞的能力。

研究結果顯示，LPPC吸附anti-CD3和anti-CD28單株抗體後，仍保有原來活性可刺激老鼠脾臟細胞和人類周邊單核球在細胞增生及細胞激素 (cytokine)有較高表現。此外LPPC本身可以促進抗原呈現細胞對抗原之吞噬反應，也可以刺激免疫細胞在前發炎反應激素表現及呈現抗原能力。因此LPPC在免疫功能上具有佐劑一樣效應，可增強免疫細胞對抗原的反應。而當LPPC吸附來自於樹突細胞富含許多MHC分子和共同刺激分子的膜蛋白時，一樣也保有該蛋白分子的活性可誘發動物體內專一性的免疫反應。此外LPPC吸附帶有特定抗原的人類MHC I (HLA-A2) 分子和anti-CD28單株抗體後，蛋白分子在LPPC平台上仍然可以誘發動物體內專一性免疫反應。因此LPPC在本研究中，可以靈活變動地賦予免疫功能之優勢去引發專一性的免疫反應，LPPC未來將可以發展成一個很好的免疫調控平台。

Antigen presenting cells (APCs) can efficiently elicit specific T cell immune responses by presenting pathogen-derived peptides on the major histocompatibility complexs (MHCs) to T cell receptor (TCR) on the surface of T cells. Currently, dendritic cells (DCs) have been discovered as the most efficient APCs. Based on these findings, DCs have been developed as a good bio-reagent to activate host’s adaptive immunity by up-taking antigen, presenting antigen and stimulating T-cells. However, DCs would be inactivated in vivo by certain pathogen-derived antigens. Thus, artificial antigen presenting cells were developed to resolve this problem. In this study, a novel immuno-regulatory liposome was developed. Lipo-PEI-PEG-complex (LPPC) was a novel liposome could strongly absorb proteins on its surface and the bound proteins could maintain their activities. By these characters, LPPC was designed to adsorb certain monoclonal antibodies or MHC molecules which have the abilities to regulate immune responses and the immuno-LPPCs were used as APC. The results showed that the LPPC adsorbed anti-CD3 and anti-CD28 monoclonal antibodies could increase the proliferation and cytokine secretions (IL-2, IFN-γ and TNF-α) of mouse splenocytes and human peripheral blood mononuclear cells (PBMC). In addition, LPPC can promote the abilities of APCs to up take antigen, induce the proinflammatory cytokine expressions, and present antigen. Thus, LPPC could provide a good adjuvant effect. Besides, the LPPC coated with membrane proteins of DCs performed as APCs to stimulate specific T-cell immune responses. Moreover, antigen-loaded HLA-A2 molecules and anti-CD28 monoclonal antibody were adsorbed on LPPC and they also maintained their specific activities, and induced the specific immune responses. The immuno-LPPC displays its flexible character and advantage to regulate immunity by combining certain immuno-regulatory antibodies and specific-antigen MHC molecules. Therefore, the immuno-LPPC may be developed as a good immunoregulatory platform.