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AU662235B2 - Intrinsic factor - horseradish peroxidase conjugates - Google Patents

Intrinsic factor - horseradish peroxidase conjugates Download PDF

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Publication number
AU662235B2
AU662235B2 AU44764/93A AU4476493A AU662235B2 AU 662235 B2 AU662235 B2 AU 662235B2 AU 44764/93 A AU44764/93 A AU 44764/93A AU 4476493 A AU4476493 A AU 4476493A AU 662235 B2 AU662235 B2 AU 662235B2
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Prior art keywords
horseradish peroxidase
oxidized
conjugates
hrp
intrinsic
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AU44764/93A
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AU4476493A (en
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Dean William Schroer
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Becton Dickinson and Co
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Becton Dickinson and Co
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    • CCHEMISTRY; METALLURGY
    • C12BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12NMICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/0004Oxidoreductases (1.)
    • C12N9/0065Oxidoreductases (1.) acting on hydrogen peroxide as acceptor (1.11)
    • CCHEMISTRY; METALLURGY
    • C12BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12NMICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/96Stabilising an enzyme by forming an adduct or a composition; Forming enzyme conjugates
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/82Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving vitamins or their receptors

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  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Urology & Nephrology (AREA)
  • Hematology (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • General Physics & Mathematics (AREA)
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  • Food Science & Technology (AREA)
  • Cell Biology (AREA)
  • Measuring Or Testing Involving Enzymes Or Micro-Organisms (AREA)
  • Enzymes And Modification Thereof (AREA)

Description

S1or
AUSTRALIA
Patents Act 1990 BECTON, DICKINSON AND COMPANY
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT i,
I
A
Invention Title: "Intrinsic factor horseradish peroxidase conjugates" The following statement is a full description of this invention including the best method of performing it known to us:i I i BACKGROUND OF INVENTION Assays for the serum level of Vitamin B12 have proven to be extremely challenging to develop. This is due primarily to the high sensitivity required, on the level of picograms, as well as the fact that normal serum contains endogenous B12 binders. These binders must be treated to release the B12 prior to the assay; such treatment is quite harsh and generally requires a separate step to accomplish it. The treatment involves the use of either heating to elevated temperatures (100 0 commonly termed "boil" assays, or the use of strong chemical agents, "no-boil" assays. One example of a no boil assay is presented in U.S. Patent No. 4,300,907 to Mansbach et al.
Because of these requirements, until quite recently virtually all commercially available assays for B12 have been radioassays which utilize a radioactive isotopic labeled binding protein for detection. A number of other formats have been discussed in the literature including 2Q. the use of chemiluminescent (Clin. Chem., Vol. 35, No. 6, p. 1194, Abst. #609 (1989)), fluorescent (Clin. Chem., Vol. 37, No. 6, p. 978 Abst. #326 (1991)), and color-labelled B12 (available from Ciba Corning) detectors. These assays utilize microbeads coated with B12 binding protein for detection, and, as such, may not be compatible with many automated detection methods.
Additionally, enzyme linked assays utilizing alkaline phosphatase Clin. Chem., Vol. 38, No. 6, p. 1089, -1A- Abst. 40662 (1992), Clin. Chem., Vol. 38, No. 6, p. 1095 Abst. #0691 (1992), Clin. Chem., Vol. 37, No. 6, p. 978, Abst. #320 (1991) and B galactosidase (Clin. Chem., Vol.
33, No. 6, p. 963, Abst. #403, (1987)) have been reported; however, both of these enzymes are quite large. Since the time required for competitive immunoassays is heavily dependent on the diffusion rate, and since the diffusion rate is approximately inversely proportional to the cube root of the molecular weight, the utility of these formats in such assays limited.
SUMMARY OF INVE1TION This invention presents a non-isotopic competitive assay for Vitamin B12 (B12). Briefly, the assay utilizes intrinsic factor (IF) labelled with horse radish peroxidase (HRP). The HRP can be conjugated to the IF by oxidizing surface carbohydrates on the HRP.
This method, it has been found, permits formation of the IF/HRP conjugate without deleteriously affecting the B12 binding sites on the IF. Thus the conjugates can be used in assays for B12. Further, because the IF is labelled with HRP, the assays can be run on automated equipment adapted to utilize the signal generated by the HRP/substrate reaction. Additionally, because the method permits relatively large amounts of HRP to be conjugalt..
to IF a high HRP/IF ratio), the signal generated will also be high, increasing the assay sensitivity.
DETAILED DESCRIPTION OF THE INVENTION The assays of this invention make use of the well known binding affinity of intrinsic factor (IF) for Vitamin B12 (B12). Briefly, in a preferred competitive assay format, the (liquid) sample (which may contain B12) -2i
~II~
is mixed with IF conjugated to horse radish peroxidase (HRP), and permitted to react. An aliquot of this mixture is then placed in contact with a solid phase containing bound B12. Subsequently, the liquid phase is separated from the solid phase, leaving behind any IF/HRP bound to the solid phase B12; any IF/HRP bound to sample B12 remains in the liquid. The amount of IF/HRP conjugate in the sample can then be measured by addition of HRP substrate and measurement of the reaction product. This is directly related to the quantity of B12 in the sample.
Alternatively, the activity of the bound IF/HRP conjugate would be determined to ascertain B12 in the sample indirectly.
The substrate utilized is any amenable to HRP action; preferred substrates include: i tetramethylbenzidine, O-phenylene diamine, luminol/iodophenol, and tyramime Coupling of the HRP to the IF is a critical i' requirement of this assay. Since many coupling methods require treatment with chemicals which can deleteriously affect the IF and/or HRP, the treatment must be .sufficiently mild to permit both of these components to remain unaffected, yet sufficiently strong to permit formation of a conjugate which will not dissociate under storage and/or assay conditions.
One such method utilizes the periodate reaction described by Wilson and Nakane in Immunofluorescence and Related Staining Techniques, Krapp et al North Holland Biomedical Press, Amsterdam, pp. 215-224 (1978), incorporated herein by reference. Briefly, the -3r urn
I
carbohydrate surface of the HRP is oxidized to an aldehyde by addition of NaIO 4 in a dark reaction chamber at room temperature. The HRP is in aqueous solution, at a concentration of 1-50 gm/I, preferably 5-25 gm/l, more preferably 10-15 gm/l; the NaIO 4 is also in aqueous solution at a concentration of 10-50 mM, preferably 15-40 mM, more preferably 20-30 mM. The reactants are mixed at a ratio of 10-20, preferably 12-16 moles NaIO 4 /mole HRP.
Subsequently, the reaction is terminated by the addition of an excess of a glycol, preferably ethylene glycol, and the oxidized HRP is dialyzed against mildly acidic (pH 3-6, preferably 4-5) buffer. About 0.1-3 mg, preferably 0.6-2.4 mg of the purified oxidized HRP is then reacted with about 5-20 ug, preferably 10-15 ug IF, in aqueous solution at a basic pH (8-10, preferably The resultant conjugates are then reduced by an .i aqueous solution of a metallic or non-metallic hydride, preferably sodium borhydride or lithium aluminum hydride.
The final product is then exchanged into a neutral salt solution and glycerol is added to facilitate storage.
The above conjugates can be utilized in the competitive assay for Vitamin B12 as described above. The above procedures are particularly suited for making HRP-IF conjugates as they minimize the use of expensive IF, by utilizing an excess of HRP to assure all IF is reacted, in addition to leaving the HRP and IF relatively intact and functionally unaffected.
Further, the above assay procedure, using HRP-IF conjugates, is particularly suited for use in automated assay instruments, such as the AFFINITY@ analyzer manufactured and marketed by Becton, Dickinson and Company, due to the fact that HRP activity is measured.
-4r I Ip ill c n I II _I_ Since many assays can be formatted to use HRP as the tracer or detector, the versatility of such an assay and, thus, such an instrument is enhanced.
EXAMPLES
The following examples demonstrate certain preferred embodiments of the instant invention, but are not intended to be illustrative of all embodiments.
Example 1 Preparation of HRP-IF Conjugate by Periodate Reaction A 12mg quantity of HRP was dissolved in 1.0 ml water and shielded from light. A total of 164pl aqueous 25 mM NaIO 4 was added and the system was allowed to react for 25 minutes at 25 0 C (ambient temperature water bath).
Immediately thereafter, the reaction was terminated by the addition of 2QOpl of 1% ethylene glycol in water and the system was left undisturbed for 20 minutes at 25 0 C. The resultant solution was buffer exchanged into 1mM aqueous sodium acetate buffer (pH 4.4) using a 20 Centricon® 30 ultrafiltra- tion device to 99.5% carbonate buffer.
The HRP concentration was then determined by absorbance at 403 nm and found to be 9.2 mg/ml. A total of 600pg HRP (66pl) was then admixed with 85pl of 0.5M aqueous sodium carbonate buffer (pH 9.0) and i of IF, and incubated at 25°C for 4 hours, protected from light.
SImmediately thereafter, the tube was placed 4 n an ice bath and 50pl of an aqueous solution of NaBH 4 (4mg/ml) was added to stop the reaction. The solution was incubated at 4 0 C for 40min. and subsequently buffer exchanged into 10mM potassium phosphate in normal saline (pH 7.6) using a Centricon® 30 to 99.5% phosphate buffer. The conjugate was stored in a 50/50 mix of phosphate buffered saline and glycerol.
The conjugate was used in a competitive B12 assay in the AFFINITY® unit wherein bound B12 (in a coated tube) competes with free B12 for IF-HRP. All IF-HRP reacting with sample (free) B12 is removed from the tube, and the B12 concentration is determined by monitoring HRP activity remaining in the coated tube.
It is apparent that many modifications and variations of this invention as hereinabove set forth may be made without departing from the spirit and scope hereof. The S specific embodiments descried are given by way of example Sonly and the invention is limited only by the terms of the appended claims.
I-6- -6-
A

Claims (5)

1. A method for preparing intrinsic factor horseradish peroxidase conjugates comprising: reacting horseradish peroxidase with NaIO 4 to oxidize surface carbohydrates to form an oxidized horseradish peroxidase; (ii) terminating said reaction and concentrating said oxidized horseradish peroxidase; (iii) reacting said concentrated oxidized horseradish peroxidase with intrinsic factor at a basic pH to form an oxidized conjugate; and (iv) subsequently reducing and concentrating said oxidized conjugates, and wherein the ratio of NaIO 4 /horseradish peroxidase (mole/mole) is 10/1 to 20/1. S 15 2. The method of claim 1 wherein the ratio of concentrated oxidized horseradish peroxidase to intrinsic Sfactor is 100-3000/5-20 (wt/wt).
3. The method of claim 1 wherein the oxidized conjugates are reduced by the addition of a metallic or non-metallic hydride.
4. An intrinsic factor/horseradish peroxidase conjugate produced by the method comprising: reacting horseradish peroxidase with NaIO to oxidize surface carbohydrates to form an oxidized horseradish peroxidase; (ii) terminating said reaction and concentrating said oxidized horseradish peroxidase; (iii) reacting said concentrated oxidised Shorseradish peroxidase with intrinsic factor at a basic pH S 30 to form an oxidised conjugate; and (iv) subsequently reducing and concentrating said oxidised conjugates, and wherein the ratio of NaIO 4 /horseradish peroxidase (mole/mole) is 10/1 to 20/1. The conjugates of claim 4 wherein the ratio of concentrated oxidised horseradish peroxidase to intrinsic c 8 factor is 100-3000/5-20 (wt/wt).
6. The conjugates of claim 4 wherein the oxidised conjugates are reduced by the addition of a metallic or non-metallic hydride.
7. In a kit for the competitive assay of Vitamin B12 utilising a horseradish peroxidase-labelled intrinsic factor tracer, the improvement comprising using, as said tracer, the intrinsic/horseradish peroxidase conjugate of claim 4. DATED this 19th day of June 1995 BECTON DICKINSON AND COMPANY Patent Attorneys for the Applicant: F.B. RICE CO. 4 0 1 "4 i 0 I.. I ABSTRACT SThis invention presents a non-isotopic assay for Vitamin B12 (B12), utilizing intri (IF) labelled with horse radish peroxidase conjugation is accomplished by oxidizir carbohydrates on the HRP, and reacting this wit] competitive nsic factor (HRP). The ig surface h IF. Iirtt
AU44764/93A 1992-09-04 1993-08-19 Intrinsic factor - horseradish peroxidase conjugates Ceased AU662235B2 (en)

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US94059992A 1992-09-04 1992-09-04
US940599 1992-09-04

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AU (1) AU662235B2 (en)
CA (1) CA2104413C (en)
DE (1) DE4329530A1 (en)
FR (1) FR2695406B1 (en)
GB (1) GB2270315A (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5350674A (en) * 1992-09-04 1994-09-27 Becton, Dickinson And Company Intrinsic factor - horse peroxidase conjugates and a method for increasing the stability thereof
AU660837B2 (en) * 1992-09-04 1995-07-06 Becton Dickinson & Company Indirect chromatographic antigen sandwich test for detection of specific antibody and device therefor
US7790363B2 (en) 2005-02-07 2010-09-07 Abbott Laboratories Inc. Diagnostic test for vitamin B12
US8288124B2 (en) 2008-11-20 2012-10-16 Abbott Laboratories Cloning, expression and purification of recombinant porcine intrinsic factor for use in diagnostic assay

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU650836B2 (en) * 1991-09-23 1994-06-30 Daramic, Inc. Battery separators with T-shaped ribs
AU659754B2 (en) * 1992-09-04 1995-05-25 Becton Dickinson & Company Chromatographic antigen sandwich test for detection of specific antibody and device therefor
AU660837B2 (en) * 1992-09-04 1995-07-06 Becton Dickinson & Company Indirect chromatographic antigen sandwich test for detection of specific antibody and device therefor

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4256833A (en) * 1979-01-08 1981-03-17 Majid Ali Enzyme immunoassay for allergic disorders
FR2502786B1 (en) * 1981-03-24 1985-06-21 Stallergenes Laboratoire METHOD FOR FIXING ANTIGENS AND ANTIBODIES TO POLYSACCHARIDE SUPPORT, AND USE OF THE PRODUCT OBTAINED THEREFOR FOR IMMUNOASSAYS
JPS6178385A (en) * 1984-09-25 1986-04-21 Toyobo Co Ltd Stable peroxidase composition
DE3525911A1 (en) * 1985-07-19 1987-01-29 Boehringer Mannheim Gmbh CONJUGATE FOR ENZYME IMMUNE DETERMINATION
DE3541186A1 (en) * 1985-11-21 1987-05-27 Boehringer Mannheim Gmbh WATER-SOLUBLE, STABILIZED PEROXIDASE DERIVATIVES, METHOD FOR THE PRODUCTION THEREOF AND USE FOR DETERMINING HYDROGEN PEROXIDE
EP0413001A1 (en) * 1988-06-15 1991-02-20 Beckman Instruments, Inc. Vitamin B12 assay

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU650836B2 (en) * 1991-09-23 1994-06-30 Daramic, Inc. Battery separators with T-shaped ribs
AU659754B2 (en) * 1992-09-04 1995-05-25 Becton Dickinson & Company Chromatographic antigen sandwich test for detection of specific antibody and device therefor
AU660837B2 (en) * 1992-09-04 1995-07-06 Becton Dickinson & Company Indirect chromatographic antigen sandwich test for detection of specific antibody and device therefor

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AU4476493A (en) 1994-03-10
CA2104413C (en) 1996-05-21
GB9317356D0 (en) 1993-10-06
FR2695406A1 (en) 1994-03-11
DE4329530A1 (en) 1994-03-10
CA2104413A1 (en) 1994-03-05
JPH06205673A (en) 1994-07-26
FR2695406B1 (en) 1995-09-29
GB2270315A (en) 1994-03-09

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