Chemistry: analytical and immunological testing – For preexisting immune complex or auto-immune disease
Reexamination Certificate
2000-11-13
2002-08-06
Chin, Christopher L. (Department: 1641)
Chemistry: analytical and immunological testing
For preexisting immune complex or auto-immune disease
C435S007100, C435S007240, C435S007920, C435S007930, C436S507000, C436S513000, C436S528000, C436S531000, C436S534000, C436S811000, C530S326000, C530S330000
Reexamination Certificate
active
06429024
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a novel test method for IgA nephropathy. More particularly, the present invention pertains to a rapid and simple test method for IgA nephropathy and a determination method of antibody, which has low risks in emotional distress, peripheral hemorrhage in the kidney and financial burden to the patient, by determining antibody recognizing IgA1 hinge region core peptide in the specimen.
2. Description of Related Art
IgA (immunoglobulin A) nephropathy is a disease concept provided by Berger et al. (J. Urol., 74, pp. 694-695, 1968 ), and is a primary glomerular nephritis having features with clinically poor symptoms except for continuous proteinuria and hematuria, and histological features with precipitants consisting of mainly IgA in the mesangium. The incidence of IgA nephropathy in Japan is high and accounts for 30% of the chronic nephritis. The long term prognosis is not so favorable, and 10-15% of patients with 10 years progress and about 30% of patients with 20 years progress suffer from terminal renal failure. Consequently, IgA nephropathy is especially noticed as a causal disease for terminal renal failure.
At present, the only known test method for IgA nephropathy is the renal biopsy. This test method, however, causes emotional distress for the patients, and further may cause peripheral hemorrhage in the kidney after the biopsy. In addition, the patients must have absolute rest for more than 24 hours after the renal biopsy, and this requires the patients to stay in hospital for several days, and this causes a heavy financial burden for them. Furthermore, the test method has disadvantages including requiring many kinds of test facilities together with long term testing time.
Consequently, a test method for IgA nephropathy is desired, which is simple and operable within a short time as well as giving less emotional distress, without risk of peripheral hemorrhage of kidney and with less financial burden.
PROBLEMS TO BE SOLVED BY THE INVENTION
An object of the present invention is to provide a rapid and simple test method for IgA nephropathy. Such a test method requires no renal biopsy, which has been essential in the conventional test method for IgA nephropathy. The test method is comprised of detecting antibody, which recognizes the core peptide of the hinge region in IgA1, in specimens. As a result, the patients' emotional distress, risk of peripheral hemorrhage of the kidney and the financial burden can be reduced.
MEANS FOR SOLVING THE PROBLEMS
We have made various trials for solving the above problems and have found a rapid and simple test method for IgA nephropathy and a determination method for antibody, which recognizes the core peptide of hinge region in IgA1, and completed the present invention. Such a test method is comprised of detecting antibody, which recognizes the core peptide of the hinge region in IgA1, in specimens. As a result, the patients' emotional distress, risk of peripheral hemorrhage of the kidney and the financial burden can be reduced.
The present invention relates to a test method for IgA nephropathy by detecting antibody recognizing the core peptide of the hinge region in IgA1 in specimens. According to preferred embodiments of the present invention, a test method comprising detecting antibody recognizing the core peptide of the hinge acid sequence consisting of region having at least a part of amino acid sequence consisting of
Pro Val Pro Ser Thr Pro Pro Thr Pro
Ser Pro Ser Thr Pro Pro Thr Pro Ser
Pro Ser Cys (SEQ ID NO: 1)
or at least three amino acids thereof. According to a further preferred embodiment of the present invention, the test method comprises using an immobilized solid phase core peptide of the hinge region, said immobilized solid phase of which is microtiter plate or latex particles.
Examples of detection methods for the antibody of the present invention are test method for IgA nephropathy which includes enzyme immunoassay, latex agglutination photometric immunoassay, nephelometric immunoassay, latex slide agglutination test, turbidimetric immunoassay, luminescent immunoassay, fluorescence polarization immunoassay, fluorescence immunoassay and radioimmunoassay.
The present invention is explained in detail with reference to the drawings as follows.
FIG. 1
illustrates a schematic drawing showing the outline of a molecular structure of IgA1.
IgA, which may be involved in a cause for IgA nephropathy, is a type of immunoglobulin. The IgA molecule consists of two heavy chains and two light chains, and is classified into subtypes of IgA1 and IgA2 depending on the difference in heavy chain structures.
In IgA nephropathy, since the deposited IgA in the glomeruli is mainly IgA1 subtype (Conley et al., J. Clin. Invest. 66, pp. 1432-1436, 1980), the properties of IgA1 between those of patients with IgA nephropathy and those of healthy subjects or patients with non-IgA nephropathy may differ from one another.
The largest structural difference between IgA1 and IgA2 exists in the hinge region of the heavy chain. The hinge region of IgA2 is deficient in 13 amino acids (Frangione et al., Proc. Natl. Acad. Sci. USA, 69, pp. 3673-3676, 1972) as compared with the hinge region of IgA1 (SEQ ID NO: 13) [Basic immunology, Upper Vol., pp. 158-162, (1986), The University Tokyo Press].
Baenziger et al. reported that an O-linked sugar chain is bonded to five serine residues of the hinge region in IgA1 molecule (J. Biol. Chem. 249, pp. 7270-7281, 1974).
We have demonstrated that the binding ability between the antibody obtained from rabbit immunized with synthetic peptide of the hinge region in IgA1 and the serum IgA1 of patients with IgA nephropathy was higher than the binding ability between the above antibody and the serum IgA1 of healthy subjects or patients with non-IgA nephropathy. As a result, we have reported that IgA1 of the patients with IgA nephropathy was abnormal in the O-linked sugar chain bound to the hinge region, and in conclusion, the core peptide of the hinge region (core peptide of hinge region means the peptide constructing the hinge region) was in an exposed state (J. Am. Renal. Soc. 8, pp. 538 A, 1997).
The core peptide of the hinge region has structural similarity with mucin insofar as containing large amounts of proline, serine and threonine.
The immunologically activating ability of human mucin core peptide has been known. For example, Kotera et al. reported that the mucin which is frequently expressed in some types of cancer cells has less sugar chain, and, as a result, immune reaction against the exposed core peptide occurs in the host (Cancer Res., 54, pp. 2856-2860, 1994).
We have made extensive studies based on the above findings. As a result, we have found that, in patients with IgA nephropathy, O-linked sugar chain bonded with the hinge region of IgA1 is decreased, and this results in exposing the core peptide of the hinge region, such that an immune reaction against the core peptide of the hinge region in IgA1 is generated and the antibody titer recognizing the core peptide of the hinge region in IgA1 is increased; and that these findings can be applied for testing IgA nephropathy, and completed the present invention.
A rapid test for IgA nephropathy can be performed by determining antibody, which recognizes the core peptide of the hinge region of IgA1, in specimens such as body fluid of the patients. Namely, the present invention relates to a test method for IgA nephropathy based on determining antibody, which recognizes the core peptide of the hinge region in IgA1, in specimens.
In the present invention, the hinge region of IgA1 indicates the region between CH1 domain and CH2 domain in the heavy chains, which construct IgA1 molecule, and may optionally include a structure having added thereto a sequence of Pro-Val—in the N-terminal region.
This region contains disulfide bond between heavy chains, and is rich in proline, serine and threonine.
In the present invention, the core peptide of the hinge region in IgA1 as an an
Arai Kenji
Kokubo Tohru
Toma Kazunori
Asahi Kasei Kabushiki Kaisha
Chin Christopher L.
Grun James L.
Young & Thompson
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