title: An enzyme immunoassay for the quantification of plasma and intracellular lopinavir in HIV-infected patients.
abstract: The protease inhibitor lopinavir (LPV; [1S-[1R*(R*), 3R*,4R*]]-N-[4-[[(2,6-dimethylphenoxy)-acetyl]amino]-3-hydroxy-5-phenyl-1-(phenylmethyl) pentyl] tetrahydro-alpha-(1-methylethyl)-2-oxo-1(2H)-pyrimide acetamide) is widely used in anti-human immunodeficiency virus (HIV) therapy. Knowledge of the plasma and intracellular concentrations of the drug would be useful for a better understanding of LPV action and for therapeutic monitoring. The aim of this study was to develop a sensitive and specific immunoassay for LPV in plasma and cells. Anti-LPV polyclonal antibodies were raised in rabbits using a synthetic LPV derivative coupled to keyhole limpet hemocyanin (KLH) as immunogen. The enzyme tracer was prepared by chemically coupling the LPV derivative with acetylcholinesterase. These reagents were used to develop a competitive enzyme immunoassay (EIA) performed in microtitration plates. The assay was performed on a minimum of 50 microl of plasma or 2 x 10(6) cells. It showed good precision and efficiency in as much as recovery from human plasma and cell extracts spiked with LPV ranged between 87% and 104%, with coefficients of variation of less than 10%. The limit of detection (LOD) was 100 pg/ml, i.e., a value at least 10 times lower than those currently achieved using previously described techniques. Cross-validation with high-performance liquid chromatography (HPLC) revealed a good correlation between methods (r2=0.96). Intracellular concentrations of LPV were measured in cultured human T lymphoblastoid cells (CEM). A pharmacokinetic analysis of plasma and intracellular LPV was performed on a healthy volunteer, and measurements were done in patients infected with HIV. The results obtained indicated a high intracellular/extracellular concentration ratio in cultured cells (19.3) but not in cells from HIV patients (1.3). In contrast, in peripheral blood mononuclear cells (PBMC) the accumulation of ritonavir (RTV) was six times higher than LPV. To date, this is the first reported immunoassay for LPV, and this method is sensitive enough for monitoring plasma and intracellular LPV levels in HIV-infected patients and for intracellular studies.
authors.affiliation: Laboratoire de Chimie Bio-Organique UMR 6001, Faculté des Sciences, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Azoulay
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Nevers
authors.forename: Christophe
authors.initials: C
authors.lastname: Créminon
authors.forename: Laurence
authors.initials: L
authors.lastname: Heripret
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Garraffo
authors.forename: Jacques
authors.initials: J
authors.lastname: Durant
authors.forename: Pierre
authors.initials: P
authors.lastname: Dellamonica
authors.forename: Jacques
authors.initials: J
authors.lastname: Grassi
authors.forename: Roger
authors.initials: R
authors.lastname: Guedj
authors.forename: Danièle
authors.initials: D
authors.lastname: Duval
mesh_terms: D000328:Adult; D000906:Antibodies / Q000276:immunology; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D015658:HIV Infections / Q000188:drug therapy; D017320:HIV Protease Inhibitors / Q000032:analysis* / Q000493:pharmacokinetics / Q000627:therapeutic use; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000737:chemistry*; D061466:Lopinavir; D008297:Male; D011744:Pyrimidinones / Q000032:analysis* / Q000493:pharmacokinetics / Q000627:therapeutic use; D012680:Sensitivity and Specificity
chemical_list: D000906:Antibodies; D017320:HIV Protease Inhibitors; D011744:Pyrimidinones; D061466:Lopinavir