Immunoassay for homocysteine
AssigneeSyntex (U.S.A.) Inc.
InventorsReuel B. Van Atta, Thomas C. Goodman, Edwin F. Ullman
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Abstract
This invention pertains to methods to detect a compound in the presence of a homolog that is immunologically related to the analyte. The invention is particularly suited for the detection of homocysteine in the presence of cysteine. The methods of this invention involve chemically modifying both the analyte and the homolog to increase their immunogenicity and facilitate antibody recognition. More importantly, this modification is done to make these compounds immunologically distinct. Antibodies to the immunologically distinct compounds are then prepared. An assay protocol comprises chemically modifying the analyte and homolog and then immunochemically detecting the modified analyte by means of the aforementioned antibodies.
Claims29
A method of determining the amount of homocysteine in the presence of cysteine in a sample suspected of containing said homocysteine, comprising the steps of:
- (a) bringing together in an aqueous medium:
- (1) said sample,
- (2) a modifying reagent capable of chemically modifying homocysteine and cysteine to form modified homocysteine and modified cysteine, and
- (3) an antibody capable of specifically binding to said modified homocysteine but not to said modified cysteine to form an immunecomplex;
- and
- (b) measuring the amount of said immunecomplex, the amount thereof being related to the amount of homocysteine in said sample.
A method of determining the amount of homocysteine in the presence of cysteine in a sample suspected of containing said homocysteine, comprising the steps of:
- (a) bringing together in an aqueous medium:
- (1) said sample,
- (2) a modifying reagent capable of chemically modifying homocysteine and cysteine to form modified homocysteine and modified cysteine,
- (3) an analog of said modified homocysteine bound to a detectable label, and
- (4) an antibody capable of specifically binding to said modified homocysteine and to said analog, but not to said modified cysteine;
- and
- (b) measuring the immunecomplex formed by the binding of said analog to said antibody, the amount thereof being related to the amount of homocysteine in said sample.
A method of determining the amount of homocysteine in a sample suspected of containing homocysteine and cysteine, comprising the steps of:
- (a) bringing together in an aqueous medium:
- (1) said sample,
- (2) a modifying reagent capable of chemically modifying homocysteine and cysteine to form modified homocysteine and modified cysteine,
- (3) an antibody capable of specifically binding to said modified homocysteine but not to said modified cysteine to form a first immunecomplex,
- (4) a surface capable of binding said antibody, and
- (5) a labeled analog of said modified homocysteine that is capable of binding said antibody to form a second immunecomplex;
- and
- (b) measuring the amount of said second immunecomplex, the amount thereof being related to the amount of homocysteine in said sample.
A method of determining the amount of homocysteine in a sample suspected of containing homocysteine and cysteine, comprising the steps of:
- (a) bringing together in an aqueous medium:
- (1) said sample,
- (2) a modifying reagent capable of chemically modifying homocysteine and cysteine to form modified homocysteine and modified cysteine,
- (3) an antibody capable of specifically binding to said modified homocysteine but not to said modified cysteine to form an immunecomplex, and
- (4) a receptor capable of binding to a portion of said modifying reagent, wherein said portion is present on said modified homocysteine;
- (b) measuring the amount of said immunecomplex, the amount thereof being related to the amount of homocysteine in said sample.
A method of determining the amount of homocysteine in the presence of cysteine in a serum sample suspected of containing said homocysteine, wherein at least a portion of said homocysteine is in the disulfide form (protein-bound and free-disulfide), comprising the steps of:
- (a) bringing together in an aqueous medium:
- (1) said sample
- (2) a releasing agent to release said homocysteine from the disulfide form,
- (3) a modifying reagent capable of chemically modifying the sulfhydryl groups of homocysteine and cysteine to form modified homocysteine and modified cysteine, and
- (4) an antibody capable of specifically binding to said modified homocysteine but not to said modified cysteine to form an immunecomplex;
- (b) examining said medium for the amount of said immunecomplex, the amount thereof being related to the amount of homocysteine in said sample.
A kit for use in a method for detecting homocysteine, comprising in a packaged combination:
- a modifying reagent capable of chemically modifying homocysteine and cysteine to form modified homocysteine and modified cysteine, and
- an antibody capable of specifically binding to said modified homocysteine but not to said modified cysteine.
Dependencies are inferred from the claim text.