Thansfection of oncogenes into dendritic cells utilizing receptor-mediated endocytosis of liposomes

脂质体是一种很有前途的载体，可将外源性抗原递送至树突状细胞（DC）用于肿瘤免疫治疗。已经显示将外源性抗原靶向DC上的Fcγ受体导致抗原衍生肽在MHC I类以及II类分子上的有效呈递。在这里，我们研究了内吞物理化学优化的含有抗原的脂质体与IgG缀合的DC是否有效地在MHC I类和II类分子上呈递抗原，从而诱导强烈的抗肿瘤免疫应答。直径为200 nm的IgG偶联脂质体（未连接聚乙二醇）最有效地被DC内吞。通过CD 32内吞含破伤风类毒素（TT）IgG脂质体的人单核细胞来源的DC比含TT裸脂质体或可溶性TT的DC刺激的CD 4 ^+ T细胞更强。用内吞含有卵清蛋白（OVA）的IgG-脂质体，但不含OVA的裸脂质体或可溶性OVA的DC免疫小鼠，完全阻止了表达OVA的淋巴瘤细胞的生长。重要的是，给予具有已建立的表达OVA的肿瘤的小鼠内吞含有OVA的IgG脂质体的DC强烈抑制肿瘤生长。本研究证明了IgG-脂质体具有适合于将抗原递送至DC的理化性质，并为IgG-脂质体用于使用DC的肿瘤免疫治疗铺平了道路。

Liposomes represent a promising vehicle to deliver exogenous antigens to dendritic cells (DCs) for tumor immunotherapy. Targeting exogenous antigens to Fcγ receptors on DCs has been shown to result in efficient presentation of antigen-derived peptides on MHC class I as well as class II molecules. Here we investigated whether DCs that endocytosed physicochemically optimized, antigen-containing liposomes conjugated with IgG efficiently present antigens on MHC class I and class II molecules, and consequently induce strong anti-tumor immune responses. IgG-conjugated liposomes with 200 nm in diameter without attaching polyethylene glycol were most efficiently endocytosed by DCs. Human monocyte-derived DCs that endocytosed tetanus toxoid (TT)-containing IgG-liposomes via CD32 stimulated CD4^+ T cells more strongly than DCs pulsed with TT-containing bare liposomes or with soluble TT. Immunization of mice with DCs that endocytosed ovalbumin (OVA)-containing IgG-liposomes, but not OVA-containing bare liposomes or soluble OVA, completely prevented the growth of OVA-expressing lymphoma cells. Importantly, administration of DCs that endocytosed OVA-containing IgG-liposomes to the mice with established OVA-expressing tumors strongly suppressed tumor growth. This study demonstrates an IgG-liposome with physicochemical properties suitable for delivering antigens to DCs, and paves the way to the application of IgG-liposomes for tumor immunotherapy using DCs.