Preparation and characterization of conjugates of (modified) human serum albumin and liposomes: drug carriers with an intrinsic anti-HIV activity.
Human serum albumin (HSA) derivatized with cis-aconitic anhydride (Aco-HSA) that was earlier shown to inhibit replication of human immunodeficiency virus type 1 (HIV-1), was covalently coupled to conventional liposomes, consisting of phosphatidylcholine, cholesterol and maleimido-4-(p-phenylbutyryl)phosphatidylethanolamine, using the heterobifunctional reagent N-succinimidyl-S-acetylthioacetate (SATA). The amount of HSA that could be coupled to the liposomes depended on derivatization of the HSA and ranged from 64.2 +/- microgram HSA/micromol total lipid for native HSA to 29.5 +/- 2.7 microgram HSA/micromol total lipid for HSA in which 53 of the epsilon amino groups of lysine were derivatized with cis-aconitic anhydride (Aco53-HSA). Incorporation of 3.8 mol% of total lipid of a poly(ethylene glycol) derivative of phosphatidylethanolamine (PEG-PE) in the liposomes resulted in a lower coupling efficiency of Aco-HSA. The elimination and distribution of the liposomal conjugates in rats in vivo was largely dependent on the modification of the HSA coupled to the liposomes. With native HSA-liposomes, more than 70% of the conjugate was still found in the blood plasma 30 min after i.v. injection in rats, while at this time Aco-HSA-liposomes were completely cleared from the circulation. The rapid clearance of conventional Aco-HSA-liposomes was due to a rapid uptake into the liver and could be considerably decreased by incorporating PEG-PE in the liposomal bilayer. After 3 h 60% of Aco-HSA-PEG-liposome conjugates were found in the blood. In an in vitro anti-HIV-1 assay, the 50% inhibitory concentrations (IC50) for Aco39-HSA-liposomes and Aco53-HSA-liposomes expressed as protein weight, were 2.87 microgram/ml and 0.154 microgram/ml, respectively. When PEG-PE was incorporated, the Aco53-HSA-liposomes retained anti HIV-1 activity (IC50:3.13 microgram/ml). The possibility to modulate the residence time in the bloodstream of Aco-HSA-liposomes and the potent anti-HIV-1 activity of these conjugates, may allow the development of an intrinsically active drug carrier system. By incorporating anti HIV-1 drugs such as AZT into such liposomes a drug delivery system can be designed that might act simultaneously on the virus/cell binding by virtue of the coupled Aco-HSA and on the RNA/DNA transcription of the HIV-1 replication cycle through the nucleoside analogue.
Kamps
J A
JA
Groningen Institute for Drug Studies, Department of Physiological Chemistry, Groningen University, Groningen, The Netherlands.
Swart
P J
PJ
Morselt
H W
HW
Pauwels
R
R
De Béthune
M P
MP
De Clercq
E
E
Meijer
D K
DK
Scherphof
G L
GL
D000156:Aconitic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D000838:Anions; D000998:Antiviral Agents / Q000494:pharmacology*; D004337:Drug Carriers; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D007700:Kinetics; D008081:Liposomes; D008099:Liver / Q000378:metabolism; D010714:Phosphatidylethanolamines; D011092:Polyethylene Glycols; D012709:Serum Albumin / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D014018:Tissue Distribution
D000838:Anions; D000998:Antiviral Agents; D004337:Drug Carriers; D008081:Liposomes; D010714:Phosphatidylethanolamines; D012709:Serum Albumin; D011092:Polyethylene Glycols; C064873:aconitic anhydride; D000156:Aconitic Acid