Cohen S, Bernstein H, Hewes C, Chow M, Langer R
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge 02139.
Proc Natl Acad Sci U S A. 1991 Dec 1;88(23):10440-4. doi: 10.1073/pnas.88.23.10440.
The feasibility of creating a s.c. depot for sustained protein delivery with the goal of enhancing antigen immunogenicity was investigated. The depot was designed as antigen-laden liposomes of hydrogenated egg phosphatidylcholine and cholesterol (1:1 molar ratio) encapsulated in alginate-poly(L-lysine) microcapsules and evaluated using iodinated bovine serum albumin (BSA) as a model antigen. The in vivo release behavior of the liposomes and microencapsulated liposomes (MELs) was evaluated from the BSA serum concentration profiles after s.c. injection into rats and the pharmacokinetic parameters of 125I-labeled BSA appearance after s.c. or i.v. injections of BSA in saline. Maximal BSA concentrations were detected 11 h after s.c. injection in all rats. The BSA serum concentrations decreased rapidly in rats injected with BSA in saline or Freund's adjuvant and less rapidly in rats injected with BSA in liposomes or MELs. Four to 5 weeks after injection, BSA-associated radioactivity was detected only in sera of rats injected with BSA in liposomes or MELs. Fifty days after injection, 50% of the originally injected BSA was recovered form the s.c. sites of rats injected with BSA in MELs; no radioactivity was recovered from the other three groups of rats. The antigen-reactive antibody levels induced in rats immunized with BSA in MELs were 2- to 3-fold higher than those obtained in rats immunized with BSA in liposomes, saline, or Freund's adjuvant. More significantly, high antibody levels were maintained for more than 150 days after a single injection of BSA in MELs, suggesting that MELs can serve as a long-term single-dose immunization vehicle.
研究了构建皮下贮库以实现蛋白质持续递送从而增强抗原免疫原性的可行性。该贮库设计为负载抗原的氢化卵磷脂和胆固醇（摩尔比1:1）脂质体，包裹于海藻酸钠-聚（L-赖氨酸）微胶囊中，并使用碘化牛血清白蛋白（BSA）作为模型抗原进行评估。通过皮下注射到大鼠体内后BSA血清浓度曲线评估脂质体和微囊化脂质体（MEL）的体内释放行为，以及皮下或静脉注射生理盐水溶液中BSA后125I标记的BSA出现的药代动力学参数。所有大鼠皮下注射后11小时检测到最大BSA浓度。在注射生理盐水溶液或弗氏佐剂中BSA的大鼠中，BSA血清浓度迅速下降，而在注射脂质体或MEL中BSA的大鼠中下降较慢。注射后4至5周，仅在注射脂质体或MEL中BSA的大鼠血清中检测到与BSA相关的放射性。注射后50天，从注射MEL中BSA的大鼠皮下部位回收了50%最初注射的BSA；其他三组大鼠未回收放射性。用MEL中BSA免疫的大鼠诱导的抗原反应性抗体水平比用脂质体、生理盐水或弗氏佐剂中BSA免疫的大鼠高2至3倍。更显著的是，单次注射MEL中BSA后，高抗体水平维持超过150天，表明MEL可作为长期单剂量免疫载体。
