EP0725933A1 - Dosage immunologique conjugue a une technique fluorimetrique directe pour mesurer l'activation des plaquettes - Google Patents

Dosage immunologique conjugue a une technique fluorimetrique directe pour mesurer l'activation des plaquettes

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Publication number
EP0725933A1
EP0725933A1 EP95902405A EP95902405A EP0725933A1 EP 0725933 A1 EP0725933 A1 EP 0725933A1 EP 95902405 A EP95902405 A EP 95902405A EP 95902405 A EP95902405 A EP 95902405A EP 0725933 A1 EP0725933 A1 EP 0725933A1
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Prior art keywords
sample
platelets
samples
selectin
platelet
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EP95902405A
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German (de)
English (en)
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EP0725933A4 (fr
Inventor
Bruce A. Kottke
Deyong Wen
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Mayo Foundation for Medical Education and Research
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Mayo Foundation for Medical Education and Research
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Priority claimed from PCT/US1994/012369 external-priority patent/WO1995012125A1/fr
Publication of EP0725933A1 publication Critical patent/EP0725933A1/fr
Publication of EP0725933A4 publication Critical patent/EP0725933A4/fr
Withdrawn legal-status Critical Current

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Definitions

  • P-selectin also known as granule membrane protein-140 (GMP- 1 ⁇ 0), or PADGEM protein, is an integral membrane glycoprotein found in secretory granules of both platelets and endothelial cells. See E.I.B.
  • P-selectin belongs to the cell surface during degranulation.
  • P-selectin belongs to the selectin family of vascular cell surface receptors that share sequence similarity and overall domain organization. See G.I. Johnston et al., Cell. 56, 1033 (1989).
  • the other known selectins are ELAM-1, a cytokine-inducible endothelial cell receptor for neutrophils, and a leukocyte surface structure which plays a role in directing the homing of lymphocytes to high endothelial venules of peripheral lymph nodes. It has recently been shown by J.-G. Geng et al., Blood. 74, 65a (1989), that human neutrophils bind in a Ca 2+ -dependent manner to purified P- selectin immobilized on plastic. Furthermore, adhesion of neutrophils to endothelium stimulated with rapid activators such as histamine is mediated at least in part by P-selectin.
  • P-selectin is also involved in binding of activated platelets to monocytes and neutrophils. See, S.A. Hamburger et al., Blood. 75, 550 (1990) and E. Larsen, Cell, &, 305 (1989).
  • PF4 platelet factor 4
  • ⁇ -thromboglobulin ⁇ -TG
  • metabolites of thromboxane A 2 metabolites of thromboxane A 2 .
  • the present invention provides a method to determine the extent of mammalian platelet activation.
  • the platelets preferably are isolated in vitro from a sample of physiological material, such as human blood, saliva, urine, CSF and the like, and divided into two portions, preferably containing equivalent numbers of platelets.
  • One sample is then maximally activated, employing a suitable agonist such as ADP, while the other sample is not treated with exogenous activation agonists.
  • Anti-P-selectin antibody is then added to each sample in an amount effective to bind to the activated platelets in each sample.
  • the antibody-activated platelet complexes in each sample are determined fluorometrically, by means of a fluorescent label that is attached to the anti-P-selectin antibody, or by addition to the complexes of a fluorescent label which binds to a binding site on the bound antibody.
  • a ratio of the fluorescence of the complexed activated platelets in the sample not exogenously activated to the fluorescence of the maximally activated platelets provides a measure of the extent of platelet activation in the mammalian donor of the platelets.
  • the present invention provides a fluorescence-conjugated immunobinding assay (FCIBA), for measuring endogenous platelet activation comprising: (a) isolating m v/tn? a first sample of platelets and a second sample of platelets from a mammal, wherein said sample each contains a preselected number of platelets;
  • the platelets are isolated from a tissue or a physiological fluid such as human blood, e.g., the first and second samples comprise platelet-rich plasma (PRP).
  • PRP platelet-rich plasma
  • the PRP samples can be diluted with a compatible liquid medium such as platelet-poor plasma (PPP), PBS, isotonic saline and the like, so that the samples which are processed contain essentially identical numbers of platelets.
  • a compatible liquid medium such as platelet-poor plasma (PPP), PBS, isotonic saline and the like, so that the samples which are processed contain essentially identical numbers of platelets.
  • the liquid medium can also include an anti-clotting agent.
  • the assay may be performed on whole blood without a pre-isolation step, thus substantially reducing processing time.
  • a sample of whole blood is obtained from a patient whose level of platelet activation is to be determined and divided into two portions.
  • One control sample is treated with an activation agonist to maximally activate the platelets contained therein, employing a suitable agonist such as ADP, while the other sample is hot treated with exogenous activation agonists.
  • both samples are treated with a prefixing solution, such as paraformaldehyde, and allowed to incubate for a period of time sufficient to partially fix the platelets.
  • the term "partially fixed” indicates a state in which the platelets contained in said samples will not be further activated or damaged by vortexing in the subsequent step while the red blood cells in the sample will maintain their ability to react with the lytic agent subsequently employed. hile undergoing vortexing, an eiythrocytic lytic agent is added to the samples. After allowing a sufficient time for the lysis of the erythrocytes to occur, a leukocyte stabilizer is added to stop the lysis reaction. Subsequently, an amount of a cell membrane fixative is added to fully fix and to stabilize the samples.
  • the term "stabilize” indicates a state in which the samples can be stored for up to at least about 72 hours before completing the analysis.
  • Anti-P-selectin antibody is then added to each sample in an amount effective to bind to the activated platelets in each sample.
  • the antibody-activated platelet complexes in each sample are determined fluorometrically, by means of a fluorescent label that is attached to the anti-P- selectin antibody, or by addition to the complexes of a fluorescent label which binds to a binding site on the bound antibody.
  • a ratio of the fluorescence of the complexed activated platelets in the sample not exogenously activated to the fluorescence of the maximally activated platelets provides a measure of the extent of platelet activation in the mammalian donor of the platelets.
  • the present invention further provides a fluorescence- conjugated immunobinding assay (FCIBA), for measuring endogenous platelet activation comprising: (a) obtaining a sample of whole blood from a patient whose platelet activation is to be determined and dividing it into a first sample and a second sample;
  • FCIBA fluorescence- conjugated immunobinding assay
  • step (f) determining the fluorescence of the binary labelled complexes in each sample, wherein a ratio of the fluorescence of said second sample to said first sample provides a measure of the extent of a platelet activation in said second sample.
  • endogenous platelet activation is defined to mean that the activation measured is due to the in vivo activation and is not due to the addition of exogenous activating agents to the sample in vitro.
  • step (d) is performed by placing the samples in a Q-Prep machine (Coulter® Corporation, Hialeah, FL) and performing a 30 second cycle.
  • the Q-Prep instrument consists of a matched, three reagent system that provides a gentle, no-wash erythrocyte lysing and fixing system which maintains leukocyte morphology and cell surface integrity.
  • the Q-prep machine had been used primarily to prepare white blood cells for flow cytometry.
  • the treatment of the platelets in the Q-prep machine fixes them so that the platelets are stable for an extended period of time, the platelets are still able to react with antibodies.
  • the use of whole blood processed in this manner offers an alternative to the use of PRP, since the results obtained using whole blood that has been treated in the Q-prep machine correlate to those obtained using PRP. See Examples 7 and 8.
  • platelet samples were activated with various doses of ADP and fixed platelets were incubated with a fluorescence- conjugated anti-P-selectin antibody in wells of microtiter plates.
  • the fluorescence intensity was read on a fluorescence concentration analyzer.
  • the intra-assay coefficient of variation (CV) was 6.97% the time-based inter-assay CV was 6.17%.
  • the measurement of the available sites for fibrinogen binding on platelets may be used to determine the extent of mammalian platelet activation. This analysis can be carried out on platelets isolated from a tissue or physiological fluid such as human blood, e.g., the first and second samples may comprise whole blood or platelet-rich plasma.
  • the present assays can be used to evaluate, monitor and stage platelet activation-related events associated with acute coronary syndromes, and in restenosis following percutaneous transfemoral coronary angioplasty (PTCA).
  • PTCA percutaneous transfemoral coronary angioplasty
  • Figure 1 is a schematic depiction of one embodiment of the present assay.
  • FIG. 4 Fluorescence intensity was log-transformed and the coefficient r was computed using linear regression.
  • PE phycoerythrin
  • Closed circles represent the fluorescence intensities detected using PE-conjugated CD62, while triangles represent the values detected using unconjugated CD62, and the open circles represent the levels of fluorescence intensity detected by using unconjugated CD62 and PE- conjugated CD62.
  • a dose of 2.5 ⁇ M of ADP was used in the determination of aggregation by aggregometry and by the present assay in platelets in plasma sampled from three normal donors. Values are the means ⁇ standard deviation (SD) of three samples in triplicate.
  • Coefficient r was computed using linear regression.
  • ADP-stimulated platelets in plasma from three normal donors were sampled and assayed by the present assay. Values are the means ⁇ SD of three samples in triplicate.
  • Monoclonal antibodies and polyclonal antibody preparations comprising fluorescent labels or binding sites for ligands comprising fluorescent labels are commercially available, available to the art or preparable by art-recognized procedures.
  • Representative murine anti-P-selectin antibodies are listed in Table I, below.
  • CD62 Phyoerythrin or no label Becton-Dickinson
  • Unlabelled antibodies can be conjugated to fluorescent labels such as fluorescein isocyanate (FITC) by standard techniques. See, for example, S.J. Shattil et al. Blood. 70, 307 (1987) and J.W. Goding et al. Monoclonal Antibodies: Principles and Practice - Production and Application of Monoclonal Antibodies in Cell Biology. Biochemistry anu Immunology. Academic Press, London (1986) at pages 255-280.
  • the antibodies can be prepared as biotinylated conjugates and reacted with phycoerythrin-streptavidin as taught by Goding, ibid.. McEver et al, ibid, and S.J. Shattil et al, J. Biol. Chem.. 260. 11107 (1985).
  • Polyclonal anti-P- selectin antibody preparations can be prepared and detected as taught by P.E. Stenberg, J. Cell Biol.. 101. 880 (1985).
  • ADP is a preferred platelet activation-aggregation agonists
  • other useful agents for platelet activation include thrombin, serotonin, collagen and throboxane, as well as bioactive subunit polypeptides thereof.
  • the erythrocytic lytic agent of step d(i) of the present invention is preferably formic acid
  • the lytic agent may also contain a stabilizer that serves to increase the shelf life of the agent.
  • the leukocyte stabilizer is a combination of sodium carbonate, sodium sulfate and sodium chloride.
  • the three components are in aqueous solution.
  • the leukocyte stabilizer may further comprise a stabilizing agent which serves to extend the shelf life of the solution.
  • the cell membrane fixative employed in step d(iii) is paraformaldehyde. Although paraformaldehyde is the prefered fixative, several other sell membrane fixatives are known to those of skill in the art.
  • the cell membrane fixative may further comprise a buffer solution.
  • step (d) of the assay is carried out using automated instrumentation which vortexes the samples and rapidly adds the recited reagents.
  • automated instrumentation shortens the preparation time of samples by eliminating the cell washing and centrifugation steps and thus allows a more rapid response in urgent clinical siutations.
  • One example of such an instrument is the Q-Prep machine manufactured by Coulter® Corporation, Hialeah, FL.
  • the use of platelets prepared in this manner offers an alternative to the use of PRP, since the results obtained using whole blood that has been treated in the Q-prep machine correlate to those obtained using PRP. See Examples 7 and 8.
  • adenosine diphosphate (ADP, Catalog No. 885-3), paraformaldehyde (Catalog No. 62H0174) and other chemicals were obtained from Sigma (Sigma Chemical Co, St. Louis, MO).
  • Phycoerythrin (PE)-conjugated (Catalog No. 348107) and pure (Catalog No. 348100) murine monoclonal anti-human platelet P-selectin antibodies (CD62) and PE-conjugated isotype specific mouse IgGl (Catalog No. 340013) were purchased from Becton-Dickinson (Mountain View, CA).
  • FITC-conjugated murine monoclonal anti-human platelet GPIIb-IIIa antibody (Catalog No. 0649) was obtained from AMAC (Westbrook, ME).
  • FITC-conjugated sheep anti-human fibrinogen antibody (Catalog No. K90056F) was obtained from BIO-DESIGNE (Kennebun-kport, ME).
  • Antibodies were diluted using 1% fetal calf serum phosphate-buffered saline (PBS) solution.
  • PBS fetal calf serum phosphate-buffered saline
  • Platelet aggregation studies were performed at 37°C on a dual channel aggregometer (Dayton D . Channel Aggregation Module), at a stirring speed of 900 rpm. Optical density for PRP and PPP was set at 10% and 90%, respectively. Adenosine diphosphate (ADP) (0.05 ml) was added to 0.45 ml of stirred suspension of PRP up to the final concentration as shown. The maximal or steepest slope of the aggregation tracing curve was measured.
  • ADP Adenosine diphosphate
  • the fluorescence measurements were obtained using the IDEXX Fluorescence Concentration Analyzer (FCA) machine (TDEXX Laboratories, Inc, Westbrook, ME).
  • FCA Fluorescence Concentration Analyzer
  • This instrument uses a specially designed (96-2311) 2 mm diameter filter membrane-bottomed plate (Fluoricon assay plate) that separates antibody-bound cells from non-bound antibody in solution by applying a vacuum (0-25 mmHg) from below the membrane.
  • the total cell/antibody-bound fluorescence is determined by front-surface fluorimetry.
  • the instrument has a fluorimeter capable of exciting and reading at several wavelengths (400/450 nm-590/620 nm).
  • PRP and of fluorescence-conjugated antibodies the same total volume, with varying dilutions of PRP and the antibodies, was used.
  • PRP was stored at room temperature in the centrifuge tubes after being diluted to a constant concentration with PPP. At each time point, PRP was withdrawn from the stock tubes and added to test tubes and the activation and aggregation assays performed as described above.
  • samples were prepared as described in flow cytometric analysis example, and 100 ⁇ l of the samples were placed in Fluoricon plates and read on the FCA instrument.
  • the intra-assay CVs for the means of ten replicates ranged from 3.45% to 10.78% (mean: 6.97%).
  • the time-based interassay CVs for the means of triplicates ranged from 5.93% to 12.39% (mean: 8.11%).
  • the sample-based inter-assay CVs for the means of triplicates ranged from 2.82% to 13.99% (mean: 6.17%).
  • Platelet concentrates were obtained from the Mayo Clinic blood bank within 24 hours of collection of blood from volunteer donors.
  • Platelet concentrate (PC) was prepared by collecting blood (450 ⁇ 45 ml) from random donors in 63 ml of CPD in a pyrogen-free (Fenwal Laboratories, Morton Grove, IL) quad blood collection pack with an attached satellite bag containing 100 ml of ADSOL solution. After blood collection, whole blood was centrifuged for 5.2 minutes at 1400 g"s at 20-24°C The platelet-rich plasma was pressed into an empty satellite bag, leaving approximately 50 ml of PC. The PC was left undisturbed for 1 hour, was resuspended on a platelet rotator, and stored on a horizontal flatbed shaker. Twenty individual PC units were sampled after 24 hours of storage.
  • Samples were prepared for analysis by fixing 100 ⁇ l of platelets with 1 ml cold 1% paraformaldehyde for 1 hour at 4°C.
  • the platelets were washed (x2) with phosphate-buffered saline EDTA (PBS/EDTA), the pellet was resuspended in 1 ml PBS/EDTA and stored at 4°C in the dark.
  • the following day (within 24 hours) 50 ⁇ l of the resuspended platelets were labeled with 10 ⁇ l of monoclonal antibody CD41 (AMAC, Inc, Westbrook, ME).
  • the percentage of platelets expressing P- selectin was determined as described by R. Funbeer et al. Transfusion. 30, 20 (1990).
  • the mean GPIIb-IIIa surface density was determined for the subsets of P-selectin-negative platelets and P- selectin-positive platelets. See, H.M Rinder et al. Transfusion, 31, 409 (1991); Anesthesiology. 25, 963 (1991).
  • Quantitative expression of P-selectin as fluorescence intensity or as the ratio of P-selectin positively stained platelets in one-day stored platelets in platelet con ntrates from 20 normal don * , -s were determined simultaneously by the present assay and by flow cytometric analysis, respectively.
  • Reactivity of platelets in plasma to ADP as measured by aggregation or by expression of P-selectin from three healthy donors were measured both by an aggregometer and by the procedure of Example 1, at time intervals ranging from 1.5 to 10 hours after blood was drawn. Platelets in plasma aggregated in response to increasing stimulating doses of ADP in parallel with the expression of P-selectin at time intervals ( Figure 9). The reactivity of platelets to ADP was increased at time intervals, and reached similar peak levels at the seventh hour ( Figure 9).
  • Example 5 Relation of ADP-induced Aggregation and Expression of P-selectin in Platelets Data from Examples 3-4 were analyzed using linear regression. This showed that the expression of P-selectin in platelets in plasma as measured by the present assay was correlated positively with platelet aggregation of platelets in plasma as determined by aggregometry in response to ADP both on the basis of stimulating doses of ADP ( Figure 10) and on the basis of time intervals ( Figure 11).
  • Example 6 Relation of Expression of P-selectin and Exposure of P T h-IIIa and Fibrinogen in Platelets in Response to ADP
  • platelets in plasma from two healthy subjects were sampled and tested in the assay of Example 1 simultaneously by using monoclonal antibodies to GPIIb-IIIa as well as with monoclonal antibodies to P-selectin, and a polyclonal antibody to fibrinogen.
  • Detectable GPIIb-IIIa complex in platelets showed little change in response to stimulation with ADP ( Figure 12).
  • Detection of P-selectin translocation to the platelet surface as determined by the present method is a sensitive and specific measure of platelet activation, which correlates well with more complex traditional measures of this phenomenon.
  • simpler cells could be employed for fluorometry, the methodology using microtiter plates with filters and the measurement of front-surface fluorimetry to measure this translocation permits measurements to be made in 96 wells as a single semiautomated procedure.
  • a fluorescence analyzer with the ability to read 10 plates (960 wells) as an even more automated procedure (screen machines, IDEXX, Portland, ME) is also available.
  • a 6 ml sample of whole blood was isolated, divided into twenty 100 ⁇ l samples, and added to round-bottomed polystyrene tubes. Thirty ⁇ l of phosphate buffered saline (PBS, 0.01 M, pH 7.4, as baseline) or ADP (2.5 ⁇ M) were added to each sample and all were allowed to incubate at room temperature for five minutes. One hundred ⁇ l of 1% of paraformaldehyde PBS solution was added to each tube, and the samples were incubated at room temperature for fifteen minutes. Following this incubation, each sample was placed in a Q-Prep machine (Coulter® Corporation, Hialeah, FL) for a 30-second cycle.
  • PBS phosphate buffered saline
  • ADP 2.5 ⁇ M
  • the sample was vortexed while a series of three reagents was added.
  • the first reagent added was a solution of formic acid at a concentration of 1.2 mlJL.
  • a solution of sodium carbonate (6.0 g/L), sodium chloride (14.5 gL) and sodium sulfate (31.3 gT-,) was added.
  • a solution of paraformaldehyde was added (10.0 g/L).
  • the fixed samples were then washed twice by centrifugation in a microcentrifuge using PBS solution.
  • the washed platelets were diluted to 8.5 x 10 e-7/ml in PBS solution. All samples were analyzed within 72 hours of fixing.
  • ADP PBS ADP PBS
  • a 6 ml sample of whole blood was isolated, divided into twelve 100 ⁇ l samples, and added to round-bottomed polystyrene tubes. Thirty ⁇ l of fibrinogen, labeled with FITC (1:100 dilution) were added to each sample. Subsequently, 30 ⁇ l of either ADP (2.5 ⁇ M) or phosphate buffer saline (PBS, 0.01 M, pH 7.4, as baseline) was added to each tube and the samples were allowed to incubate at room temperature for five minutes. One hundred ⁇ l of 1% of paraformaldehyde PBS solution was added to each tube, and the samples were incubated at room temperature for fifteen minutes.
  • ADP 2.5 ⁇ M
  • PBS phosphate buffer saline
  • each sample was placed in a Q-Prep machine (Coulter® Corporation, Hialeah, FL) for a 30-second cycle. During this cycle, the sample was vortexed while a series of three reagents was added. The first reagent added was a solution of formic acid at a concentration of 1.2 m-L/L. Next, a solution of sodium carbonate (6.0 g/L), sodium chloride (14.5 g/L) and sodium sulfate (31.3 g/L) was added. Finally, a solution of paraformaldehyde was added (10.0 g/L). The fixed samples were then washed twice by centrifugation in a microcentrifuge using PBS solution. The washed platelets were diluted to 8.5 x 10 e "7 /ml in PBS solution. All samples were analyzed within 72 hours of fixing.
  • Q-Prep machine Coulter® Corporation, Hialeah, FL
  • Antibody-bound fluorescence was determined by reading plates at a gain of 10 for CD62 on the FCA instrument at the appropriate wavelength. Data was recorded as relative fluorescence units (FU), after subtracting the blank and is shown in Table HI along with the results obtained from Example 6 wherein PRP was used. Table IV shows the data that was obtained by following the above protocol employing FITC labeled fibrinogen as a 1:50 dilution. Table UL
  • Sample 1 (PRP) 4226 0
  • Sample 2 (PRP) 3972 0
  • Sample 3 (PRP) 4208 12
  • Sample 4 (Whole Blood) 3624 0
  • Sample 5 (Whole Blood) 3454 0
  • Sample 6 (Whole Blood) 3640 0

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Abstract

L'invention concerne un procédé pour mesurer l'activation des plaquettes. Ce dosage est effectué en déterminant par fluorimétrie l'expression de la P-sélectine dans un échantillon de plaquettes in vitro, en utilisant comme étalon de référence un échantillon de plaquettes activées au maximum. La figure est une représentation schématique d'un mode de réalisation de ce dosage.
EP95902405A 1993-10-26 1994-10-26 Dosage immunologique conjugue a une technique fluorimetrique directe pour mesurer l'activation des plaquettes Withdrawn EP0725933A4 (fr)

Applications Claiming Priority (5)

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US14276693A 1993-10-26 1993-10-26
US142766 1993-10-26
US32847594A 1994-10-25 1994-10-25
US328475 1994-10-25
PCT/US1994/012369 WO1995012125A1 (fr) 1993-10-26 1994-10-26 Dosage immunologique conjugue a une technique fluorimetrique directe pour mesurer l'activation des plaquettes

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EP0725933A1 true EP0725933A1 (fr) 1996-08-14
EP0725933A4 EP0725933A4 (fr) 1998-04-29

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Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, vol. 121, no. 19, 1 September 1994 Columbus, Ohio, US; abstract no. 225667, XP002056597 & D. WEN ET AL.: "A fluorescence-conjugated immunobinding assay for the detection of P-selectin on platelets." JOURNAL OF LABORATORY AND CLINICAL MEDICINE, vol. 124, no. 3, 1 September 1994, BETHESDA MD USA, pages 447-454, *
See also references of WO9512125A1 *

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