Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving antigen-antibody binding – specific binding protein...
Patent
1989-01-05
1992-12-22
Saunders, David
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving antigen-antibody binding, specific binding protein...
435 79, 435966, 435968, 435975, 436528, 436537, 436800, 436805, 436821, 436829, G01N 33542, G01N 33544
Patent
active
051734060
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a liposome immunoassay method and kit therefor.
2. Background Art
In the medical field, immunoassay methods involving an antigen-antibody reaction are now often used for the diagnosis of diseases, etc. Although conventional immunoassays are generally classified as heterogeneous assays and homogeneous assays, the homogeneous assay, in which a washing operation is unnecessary, has become increasingly important due to the suitability to diseases and the ease of diagnosis obtained thereby. Nevertheless, most homogeneous assays do not have a satisfactory sensitivity.
Accordingly, various liposome immunoassay methods have been proposed, with the intention of improving this sensitivity. In these methods, an antigen-antibody complex is formed by a reaction of an antigen as an analyte and a liposome bearing antibody comprising an antibody to the analyte antigen and a liposome encapsulating a marker therein linked to the antibody, the marker is released from the liposome in a complementdependent manner, and the released marker is measured to determine the analyte antigen.
As an embodiment of such a liposome immunoassay, a method is known wherein three entities, i.e., an antigen as an analyte, a liposome bearing antibody comprising a first antibody to the antigen and a liposome encapsulating a marker therein linked to the antibody, and a second antibody to the analyte antigen are reacted to form an antigen-antibody complex of three components, a complement is added to this complex of three components to release the marker from the complexed liposome, and the released marker is measured to determine the analyte antigen. As an embodiment of such an liposome immunoassay, Japanese Unexamined Patent Publication No. 60-138465 discloses a method which uses antibodies derived from different species as the first and second antibodies. Japanese Unexamined Patent Publication No. 61-250558 describes a method similar to the above-method, wherein a hydrophilic marker is encapsulated in a liposome comprising at least one of phospholipide and glycolipide and cholesterol, and the liposome to which at least a part of an antibody to a test substance is used. Japanese Unexamined Patent Publication No. 61-269070 describes a general method similar to the above method. Moreover, Japanese Unexamined Patent Publication No. 61-250560 discloses a liposome immunoassay characterized by reacting four entities, i.e., a first antibody to an analyte antigen, a conjugate of a second antibody to the first antibody and a liposome encapsulating a marker substance, a third antibody to the analyte antigen, and a complement.
In all of the above methods, an antibody, which satisfies two requirements, i.e., (1) is capable of specifically reacting with the analyte antigen, and (2) is capable of activating the complement, must be used as the second or third antibody, but it is not easy to obtain an antibody which satisfies these requirements.
Accordingly, the present invention is intended to resolve the above problems by using different antibodies; one responsible for the first requirement, i.e., the reactivity with the analyte antigen, and another responsible for the second requirement, i.e., ability to activate the complement, and binding these antibodies specifically to each other.
DISCLOSURE OF THE INVENTION
The above-mentioned problems are resolved by the present liposome immunoassay comprising the steps of reacting an analyte antigen, a liposome bearing antibody comprising a first antibody to the analyte antigen and a liposome encapsulating a marker therein linked to the antibody, and a second antibody to the analyte antigen, to form an antigen-antibody complex, releasing the marker from the liposome in an amount depending on an amount of the analyte antigen in the presence of a complement, and measuring the released marker to determine the analyte antigen, characterized in using a third antibody capable of binding directly or indirectly to the second antibody and having an ability to ac
REFERENCES:
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patent: 4971916 (1990-11-01), Jou et al.
"Homogeneous Immunoassay for .alpha..sub.2 Plasmin Inhibitor (.alpha..sub.2 PI) and .alpha..sub.2 PI-plasmin Complex", by K. Hosoda et al., Journal of Immunological Methods, vol. 121, (1989), pp. 121-128.
Umada et al., J. Immunol. Meth., 95:15, 1986.
Bio-Industry, vol. 3, No. 7, 1986, pp. 566-571, T. Yasuda.
Hosoda Kenji
Suzuki Hideaki
Yasuda Tatsuji
Saunders David
Teijin Limited
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