School of Life and Health Sciences, Aston University, Birmingham, UK.
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St, Glasgow G4 0RE, UK.
J Control Release. 2018 Dec 10;291:1-10. doi: 10.1016/j.jconrel.2018.10.002. Epub 2018 Oct 3.
Pattern recognition receptors, including the Toll-like receptors (TLRs), are important in the induction and activation of two critical arms of the host defence to pathogens and microorganisms: the rapid innate immune response (as characterised by the production of Th1 promoting cytokines and type 1 interferons) and the adaptive immune response. Through this activation, ligands and agonists of TLRs can enhance immunotherapeutic efficacy. Resiquimod is a small (water-soluble) agonist of the endosome-located Toll-like receptors 7 and 8 (TLR7/8). However due to its molecular attributes it rapidly distributes throughout the body after injection. To circumvent this, these TLR agonists can be incorporated within delivery systems, such as liposomes, to promote the co-delivery of both antigen and agonists to antigen presenting cells. In this present study, resiquimod has been chemically conjugated to a lipid to form a lipid-TLR7/8 agonist conjugate which can be incorporated within immunogenic cationic liposomes composed of dimethyldioctadecylammonium bromide (DDA) and the immunostimulatory glycolipid trehalose 6,6' - dibehenate (TDB). This DDA:TDB-TLR7/8 formulation offers similar vesicle characteristics to DDA:TDB (size and charge) and offers high retention of both resiquimod and the electrostatically adsorbed TB subunit antigen Ag85B-ESAT6-Rv2660c (H56). Following immunisation through the intramuscular (i.m.) route, these cationic DDA:TDB-TLR7/8 liposomes form a vaccine depot at the injection site. However, immunisation studies have shown that this biodistribution does not translate into notably increased antibody nor Th1 responses at the spleen and draining popliteal lymph node compared to DDA:TDB liposomes. This work demonstrates that the conjugation of TLR7/8 agonists to cationic liposomes can promote co-delivery but the immune responses stimulated do not merit the added complexity considerations of the formulation.
模式识别受体,包括 Toll 样受体(TLRs),在诱导和激活宿主防御病原体和微生物的两个关键途径中起着重要作用:快速的先天免疫反应(以产生 Th1 促进细胞因子和 I 型干扰素为特征)和适应性免疫反应。通过这种激活,TLR 的配体和激动剂可以增强免疫治疗效果。瑞喹莫德是一种小(水溶性)的内体定位的 Toll 样受体 7 和 8(TLR7/8)激动剂。然而,由于其分子属性,它在注射后会迅速分布到全身。为了避免这种情况,可以将这些 TLR 激动剂纳入递药系统中,如脂质体,以促进抗原和激动剂共同递送到抗原呈递细胞。在本研究中,瑞喹莫德已被化学偶联到脂质上,形成脂质-TLR7/8 激动剂偶联物,可掺入由二甲基二辛基溴化铵(DDA)和免疫刺激糖脂海藻糖 6,6'-二硬脂酸酯(TDB)组成的免疫原性阳离子脂质体中。这种 DDA:TDB-TLR7/8 制剂具有与 DDA:TDB 相似的囊泡特征(大小和电荷),并能高度保留瑞喹莫德和静电吸附的 TB 亚基抗原 Ag85B-ESAT6-Rv2660c(H56)。通过肌肉内(i.m.)途径免疫后,这些阳离子 DDA:TDB-TLR7/8 脂质体在注射部位形成疫苗库。然而,免疫研究表明,与 DDA:TDB 脂质体相比,这种生物分布并不能转化为脾和引流的腘淋巴结中明显增加的抗体或 Th1 反应。这项工作表明,TLR7/8 激动剂与阳离子脂质体的偶联可以促进共递药,但刺激的免疫反应不值得考虑制剂的复杂性。
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