WO2008138783A1 - Agent d'exposition permettant la détection de vitamine d - Google Patents

Agent d'exposition permettant la détection de vitamine d Download PDF

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Publication number
WO2008138783A1
WO2008138783A1 PCT/EP2008/055441 EP2008055441W WO2008138783A1 WO 2008138783 A1 WO2008138783 A1 WO 2008138783A1 EP 2008055441 W EP2008055441 W EP 2008055441W WO 2008138783 A1 WO2008138783 A1 WO 2008138783A1
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WIPO (PCT)
Prior art keywords
vitamin
metabolite
exposure
pamoic acid
assay
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PCT/EP2008/055441
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English (en)
Inventor
Bo Li
Per Qvist
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Nordic Boiscience A/S
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Publication of WO2008138783A1 publication Critical patent/WO2008138783A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/82—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving vitamins or their receptors
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K16/00—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies
    • C07K16/44—Immunoglobulins [IGs], e.g. monoclonal or polyclonal antibodies against material not provided for elsewhere, e.g. haptens, metals, DNA, RNA, amino acids

Definitions

  • the present invention relates to a method of measuring vitamin D or a metabolite of vitamin D present in a sample, to an exposure reagent which can be used in such a method and to a kit which can be used for carrying out such a method.
  • vitamin D 3 The physiological form of vitamin D in the human body is vitamin D 3 (cholecalciferol) .
  • the most important derivatives of vitamin D 3 are 25OHD 3 (25-hydroxy vitamin D 3 , or calcidiol) and l ⁇ , 25 (OH) 2 D 3 ( l ⁇ , 25-dihydroxy-cholecalciferol, or calcitriol) .
  • the primary source of vitamin D 3 is skin where 7- dehydrocholesterol is converted to previtamin D 3 on exposure to ultraviolet radiation (mainly sunlight) and further converted to vitamin D 3 .
  • a further source of vitamin D 3 is food.
  • Fatty fish such as herring, salmon and tuna are rich in vitamin D 3 .
  • vitamin D 2 calciferol or ergocalciferol
  • Vitamin D 2 and vitamin D 3 supplements are other important sources for keeping sufficient vitamin D in the body.
  • Vitamin D is transported through the lymphatic system into the liver bound to vitamin D binding proteins (DBP) , also known as group-specific component or Gc-globulin.
  • DBP vitamin D binding proteins
  • Gc-globulin group-specific component
  • DBP is a multifunctional plasma protein and a member of the albumin gene family. It binds to vitamin D, its metabolites, and fatty acids .
  • Vitamin D undergoes hydroxylation on C-25 in the liver, a reaction catalysed by cytochrome P450 (CYP) enzymes.
  • 25OHD is the major metabolic species in circulation, and its concentration in serum is used as an indication of vitamin D status in humans .
  • Vitamin D is biotransformed into the active form 1,25(OH) 2 D (mainly from 25OHD) . This transformation takes place in the kidneys and in extra-renal tissues.
  • Vitamin D is essential for normal bone structure and the maintenance of blood and cellular calcium.
  • the biologically active metabolite 1,25(OH) 2 D is involved in gene transcription and cell function in multiple tissues.
  • Severe vitamin D deficiency has been identified as the most common aetiology of rickets in children and osteomalacia in adults. The prevalence of mild-to-moderate vitamin D deficiency is very high and increases with age. The pathogenetic role of an insufficient vitamin D supply as an important risk factor for osteoporosis was provided by the results of the first large, placebo-controlled, intervention study showing a significant reduction in nonvertebral fractures after 18 months of supplementation with 800 IU (International Units; 800 IU is equivalent to 20 ⁇ g of
  • Vitamin D of vitamin D and 1200 mg of calcium in vitamin D- deficient elderly women.
  • Vitamin D and its metabolites have been determined both by chromatographic procedures (in particular HPLC, which is considered the gold standard) and immunoassays.
  • chromatographic procedures in particular HPLC, which is considered the gold standard
  • immunoassays For accurate determination via immunoassays vitamin D and its metabolites must not be in the usual DBP-bound form, but must be exposed. This can be achieved by a variety of techniques including precipitation of DBP by organic solvents (e.g. ethanol or methanol), and liquid-liquid organic extraction (e.g. chloroform-methanol followed by phase separation using chloroform and water, or methanol and hexane) .
  • organic solvents e.g. ethanol or methanol
  • liquid-liquid organic extraction e.g. chloroform-methanol followed by phase separation using chloroform and water, or methanol and hexane
  • an exposure agent which allows the immunoassay to be conducted without an initial separation step to remove the DBP and exposure agent from the vitamin D containing sample to be analysed.
  • An assay wherein no such separation step is required is referred to as a "direct" assay.
  • US7087395 discloses methods for determining vitamin D metabolites using a releasing composition, in particular aqueous bases, e.g. NaOH and KOH, cyclo-oligomer components, e.g. cyclodextrin, a metal salicylate, e.g. sodium salicylate, and surfactant.
  • a releasing composition in particular aqueous bases, e.g. NaOH and KOH, cyclo-oligomer components, e.g. cyclodextrin, a metal salicylate, e.g. sodium salicylate, and surfactant.
  • the releasing composition comprises 0.1-1.0 M NaOH, 0.01-5% beta- randomly methylated cyclodextrin, and 0.01-5% sodium salicylate with a pH of about 13.
  • WO98/31580 ( Immunodiagnostic Systems Limited) describes the use of 8-anilino-l-naphthalenesulphonic acid ammonium salt (ANS) as a vitamin D binding protein inhibitor in a method for determining 1,25(OH) 2 D.
  • ANS 8-anilino-l-naphthalenesulphonic acid ammonium salt
  • EP 1352238 Bl (Immunodiagnostic Systems Limited) describes methods for measuring vitamin D metabolites using a non-competitive displacement agent comprising ANS, 3- (acetonylbenzyl) -4-hydroxycoumarin (warfarin) and a water miscible solvent.
  • a non-competitive displacement agent comprising ANS, 3- (acetonylbenzyl) -4-hydroxycoumarin (warfarin) and a water miscible solvent.
  • this method encompasses the simultaneous use of two compounds in addition to the organic solvent in the displacement solution.
  • pamoic acid as an exposure agent.
  • the present invention is based on the surprising discovery that pamoic acid salts (in particular pamoic acid disodium salt (PAD) ) can expose vitamin D and its metabolites from DBP.
  • PAD can be used as an exposure agent in a direct vitamin D assay.
  • the present invention provides a method of measuring vitamin D or a metabolite of vitamin D present in a sample, comprising: adding to the sample an exposure reagent comprising an exposure agent, wherein the exposure agent comprises pamoic acid; and conducting an assay for vitamin D or a metabolite of vitamin D on the sample.
  • pamoic acid includes both pamoic acid in its free form (as shown in Fig. l(a)) and solubilised derivatives of pamoic acid, for example salts or esters of pamoic acid.
  • exposure agent includes agents which when added to DBP-bound vitamin D and/or vitamin D metabolite allow the vitamin D and/or vitamin D metabolite to be detected, in particular by interrupting the binding between the DBP and vitamin D and/or vitamin D metabolite so that the DBP does not interfere with detection of the vitamin D and/or vitamin D metabolite.
  • exposure agent includes displacement agents (that is, agents which release vitamin D and/or and vitamin D metabolites from DBP) and non- displacement agents (that is, agents which expose vitamin D and/or vitamin D metabolites from DBP so that they can be detected but without releasing the vitamin D and/or vitamin D metabolites from the DBP) .
  • the assay for vitamin D or a metabolite of vitamin D is conducted on the mixture of exposure reagent and sample (a direct assay), that is, no step of separating exposure agent and DBP from the mixture is carried out before the assay.
  • a direct assay that is, no step of separating exposure agent and DBP from the mixture is carried out before the assay.
  • the body fluid is selected from serum and plasma.
  • the body fluid may be from a human or an animal.
  • the pamoic acid is present as a pamoic acid salt. More preferably, the pamoic acid salt is selected from sodium salts of pamoic acid and potassium salts of pamoic acid, for example, pamoic acid disodium salt, pamoic acid monosodium salt, pamoic acid dipotassium salt and pamoic acid monopotassium salt.
  • the exposure agent is PAD (as shown in Fig. l(b)).
  • the exposure agent may comprise free pamoic acid.
  • the exposure reagent can be prepared from the exposure agent itself (for example, dissolving PAD in water) or by reaction of a precursor to form exposure agent (for example, dissolving free pamoic acid in aqueous sodium hydroxide solution) .
  • the exposure reagent is an aqueous solution. More preferably, the exposure reagent comprises an aqueous buffer.
  • a suitable buffer is PBS (phosphate buffered saline ) .
  • the exposure agent is present in the exposure reagent at a concentration of 0.001 to 20 mM, more preferably 0.5 to 15 mM, and highly preferably at a concentration of 3 to 12 mM.
  • the effectiveness of the exposure agent is increased by including small amounts of organic solvents, such as ethanol, in the exposure reagent.
  • the exposure reagent further comprises an organic solvent. More preferably, the organic solvent is ethanol and/or methanol.
  • the organic solvent is present in the exposure reagent at a concentration of 0-25% (v/v) , more preferably 2- 20% (v/v) , and highly preferably at a concentration of 6-15% (v/v) .
  • the assay is for the vitamin D metabolite 25- hydroxy vitamin D 3 .
  • the assay is an immunoassay, that is, an assay which relies on binding between a moiety and an immunological binding partner to form an immunocomplex .
  • immunoassay that is, an assay which relies on binding between a moiety and an immunological binding partner to form an immunocomplex .
  • immunological binding partner includes antibodies.
  • immunoassay formats can be used.
  • suitable immunoassay formats include heterogeneous assays, homogeneous assays, sandwich assays, competition assays, enzyme immunoassays, radioimmunoassays, fluorescence polarisation immunoassays, microparticle enzyme immunoassays and chemiluminescent magnetic immunoassays.
  • Several of the above mentioned immunoassays can be performed either as a one step procedure or as a two step procedure .
  • heterogeneous assay refers to assays in which separation of the immunocomplex from other components, for example by washing, is required.
  • homogeneous assay refers to assays in which no separation of the immunocomplex from other components is required.
  • the term "competition assay” refers to assays in which analyte in the sample is measured by its ability to compete with detectable (e.g. labelled) analyte for immunological binding partner.
  • the term “sandwich assay” refers to assays in which analyte is bound (sandwiched) between two immunological binding partner moieties, one of which is detectable (e.g. labelled) .
  • the term “enzyme immunoassay” refers to assays which use an enzyme as a label. Examples of such labels are alkaline phosphatase, horseradish peroxidase and B-galactosidase .
  • ELISA Enzyme Linked Immunosorbent Assay
  • radioimmunoassay refers to assays which use a radioactive isotope as a label.
  • An example of such a label is iodinei25-
  • the assay suitably comprises a detection step.
  • This may comprise label detection.
  • Known labels can be used. Examples of suitable labels include an enzyme label (as discussed above), a radioisotope label (as discussed above), a fluorescent label and a poly-histidine label.
  • analyte or immunological binding partner it is possible to detect the analyte or immunological binding partner by binding with a labelled detection agent.
  • a labelled detection agent for example, unlabelled antibody can be detected using a labelled anti-idiotypic (secondary) antibody .
  • vitamin D or a metabolite of vitamin D is immobilised on a solid surface, and an antibody to vitamin D or a metabolite of vitamin D and a sample mixture (comprising the serum/plasma to be analysed and the exposure reagent) are in solution.
  • a vitamin D antibody is immobilised on a solid surface and the sample mixture and a competing reagent of vitamin D or a metabolite of vitamin D are in solution.
  • Polyclonal antibodies or monoclonal antibodies, as well as fragments of polyclonal antibodies or monoclonal antibodies, can be used.
  • the invention provides an exposure reagent for use in a method as described above, comprising an aqueous solution of pamoic acid and an organic solvent.
  • the invention provides a kit for carrying out a method as described above, comprising: an exposure reagent; and assay reagents for vitamin D or a metabolite of vitamin D.
  • the assay reagents are reagents for an immunoassay. Suitable immunoassay formats are discussed above. More preferably, the assay reagents comprise an immunological binding partner (for example an antibody) recognising the vitamin D or a metabolite of vitamin D. Highly preferably, the assay reagents further comprise a competition agent for the vitamin D or metabolite of vitamin D.
  • an immunological binding partner for example an antibody
  • one of the immunological binding partner and the competition agent is labelled. Suitable labels are discussed above.
  • the kit preferably further comprises an enzyme label substrate.
  • the substrate may be a chromogenic substrate, e.g. 3, 3 ' , 5, 5 ' -tetramethylbenzidine (TMB) .
  • one of the immunological binding partner and the competition agent comprises a binding moiety for binding to a solid surface.
  • a suitable binding moiety is biotin. As is well-known, biotin binds to streptavidin . Therefore, a biotinylated molecule will bind to a streptavidin-coated surface .
  • the kit may contain a coated solid surface, for example a surface coated with vitamin D or its metabolites, or a surface coated with an antibody.
  • the kit may further comprise assay reagents for a second analyte selected from vitamin D and a metabolite of vitamin D.
  • the kit may further comprise one or more standard components, for example a wash reagent, a buffer, a stopping reagent (for stopping the enzyme reaction, e.g. sulphuric acid is a stopping reagent for peroxidase/TMB reaction), calibration standards and instructions.
  • a wash reagent for stopping the enzyme reaction, e.g. sulphuric acid is a stopping reagent for peroxidase/TMB reaction
  • a stopping reagent for stopping the enzyme reaction, e.g. sulphuric acid is a stopping reagent for peroxidase/TMB reaction
  • the assays described herein may be used in the assessment of the vitamin D nutritional status of humans.
  • Fig. 1 (a) shows the structure of pamoic acid and Fig. l(b) shows the structure of pamoic acid disodium salt (PAD) .
  • PAD pamoic acid disodium salt
  • Fig. 2 shows the assay procedure of Example 4.
  • Fig. 3 shows the immunoassay binding of Example 4.
  • Fig. 4 (a) shows a one-step assay procedure
  • Fig. 4(b) shows a two step assay procedure
  • Fig.4(c) shows a one step antibody capture assay procedure
  • Fig. 5 shows the results of Example 4.
  • Fig. 6 shows the results of Example 5.
  • Fig. 7 shows a comparison of vitamin D measurements obtained in Examples 4 and 6.
  • Polyclonal antibody were raised in rabbits against l ⁇ , 25 (OH) 2 D 3 -hemisuccinate (Hoffman-La Roche, Nutley, NJ) coupled to thyroglobulin (Koch-Light Laboratories Ltd, Colnbrook, Berks, UK.).
  • Example 2 Biotinylation of 25OHD 3 25OHD 3 -hemisuccinate (KJ Ross-Petersen, H ⁇ rsholm, DK) was coupled with (+) -Biotinyl-3, 6, 9, -trioxaundecanediamine (Pierce, Rockford, IL) .
  • An exposure reagent was prepared by addition of phosphate buffered saline (PBS buffer, 90 mL) to pamoic acid disodium (PAD, 173 mg) (Sigma). After PAD was dissolved 99.9% ethanol (10 mL) was added. The final exposure reagent contained 4 mM PAD and 10% ethanol.
  • PBS buffer phosphate buffered saline
  • PAD pamoic acid disodium
  • Serum samples A to G were obtained from DEQAS (UK) with pre-determined values of 25OHD 3 .
  • 480 ⁇ L aliquots of exposure reagent (Example 3) were pipetted into glass tubes and 12 ⁇ L of each of serum samples A to G were added to a respective glass tube. The mixtures were vortexed for 10 s and left on the bench top until use.
  • Microtitre plates pre-coated with streptavidin (Roche Diagnostics GmbH, Penzberg, GER) were incubated with 100 ⁇ L of biotinylated 25OHD 3 (Example 2) diluted in PBS buffer containing BSA (final dilution factor 250 000) at room temperature for 30 minutes on a plate shaker (300 rpm) .
  • Example 1 antibody 6505, an in-house antibody
  • exposure reagent final dilution factor from antiserum 12 000
  • PBS buffer containing BSA final dilution factor 1000
  • Example 4 The assay procedure of Example 4 is shown in Fig. 2.
  • the immunoassay binding is shown in Fig. 3.
  • Variant assay procedures are shown in Fig. 4.
  • the range of the standards above is sufficient to measure 25OHD 3 in human serum samples.
  • Example 5 Comparative study of 25(OH)D 3 determined by direct 25-OH vitamin D3 ELISA and by HPLC
  • An exposure reagent was prepared using an alternative method. 77.7 mg pamoic acid, 600 ⁇ L of IM aqueous sodium hydroxide solution and 40 mL of 1 x PBS were combined. IM aqueous hydrochloric acid (about 700 ⁇ L) was added to adjust the pH of the solution to 6.4. PBS was added to increase the volume of the solution to 45 mL, then 5 mL of 99.9% ethanol was added. The final exposure reagent contained 3.6 mM of PAD and 10% ethanol.
  • PAD pamoic acid disodium
  • Raising of antibody to vitamin D 3 was as described previously (Hummer et al . , 1984), except for the present investigation conjugation to thyroglobulin (Koch-Light Laboratories Ltd, Colnbrook, Berks, UK) was used for preparation of the immunogen.
  • a standard curve was constructed using a 4-parameter logistic curve fit, and the concentrations of the 25- hydroxyvitamin D 3 in the samples were determined by interpolation on the curve .

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Abstract

L'invention concerne un procédé de mesure de la vitamine D ou d'un métabolite de la vitamine D présent dans un échantillon de sérum contenant de la vitamine D liée à des protéines de liaison de la vitamine D. Ledit procédé comprend les étapes consistant à ajouter à l'échantillon le sel disodique de l'acide pamoïque comme agent d'exposition et de conduire un dosage immunologique de la vitamine D ou d'un métabolite de la vitamine D sur l'échantillon.
PCT/EP2008/055441 2007-05-15 2008-05-02 Agent d'exposition permettant la détection de vitamine d WO2008138783A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0709322A GB0709322D0 (en) 2007-05-15 2007-05-15 Exposure agent for detection of vitamin d
GB0709322.2 2007-05-15

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WO2008138783A1 true WO2008138783A1 (fr) 2008-11-20

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010100487A1 (fr) * 2009-03-02 2010-09-10 Axis-Shield Diagnostics Limited Dosage pour la détection de la vitamine d et anticorps correspondants
DE102013205055A1 (de) 2013-03-21 2014-09-25 Orgentec Diagnostika Gmbh Verfahren und Reagenz zur Bestimmung von Vitamin D Metaboliten
CN108267602A (zh) * 2010-12-28 2018-07-10 未来诊断有限公司 对于维生素d的释放剂

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002046746A2 (fr) * 2000-12-06 2002-06-13 Immunodiagnostic Systems Ltd Procede de detection de metabolites de la vitamine d
WO2005009356A2 (fr) * 2003-07-15 2005-02-03 Pr Pharmaceuticals, Inc. Procede de preparation de compositions a liberation controlee
WO2007039194A1 (fr) * 2005-09-29 2007-04-12 Roche Diagnostics Gmbh Réactif de liberation pour les composés de vitamine d

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002046746A2 (fr) * 2000-12-06 2002-06-13 Immunodiagnostic Systems Ltd Procede de detection de metabolites de la vitamine d
WO2005009356A2 (fr) * 2003-07-15 2005-02-03 Pr Pharmaceuticals, Inc. Procede de preparation de compositions a liberation controlee
WO2007039194A1 (fr) * 2005-09-29 2007-04-12 Roche Diagnostics Gmbh Réactif de liberation pour les composés de vitamine d

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
LI B ET AL: "An improved immunoassay for the specific measurement of 25-hydroxy-vitamin D-3 with no cross-reactivity to 25-hydroxy-vitamin D-2.", JOURNAL OF BONE AND MINERAL RESEARCH, vol. 21, no. Suppl. 1, September 2006 (2006-09-01), & 28TH ANNUAL MEETING OF THE AMERICAN-SOCIETY-FOR-BONE-AND-MINERAL-RESE ARCH; PHILADELPHIA, PA, USA; SEPTEMBER 15 -19, 2006, pages S236, XP002485795, ISSN: 0884-0431 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010100487A1 (fr) * 2009-03-02 2010-09-10 Axis-Shield Diagnostics Limited Dosage pour la détection de la vitamine d et anticorps correspondants
CN108267602A (zh) * 2010-12-28 2018-07-10 未来诊断有限公司 对于维生素d的释放剂
DE102013205055A1 (de) 2013-03-21 2014-09-25 Orgentec Diagnostika Gmbh Verfahren und Reagenz zur Bestimmung von Vitamin D Metaboliten
WO2014147121A1 (fr) 2013-03-21 2014-09-25 Orgentec Diagnostika Gmbh Procédé et réactif de détermination de métabolites de la vitamine d
US9863963B2 (en) 2013-03-21 2018-01-09 Orgentec Diagnostika Gmbh Method and reagent for determining vitamin D metabolites

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