Sensitive enzyme immunoassay for human aldolase B

Detection of autoantibody to aldolase B in sera from patients with troglitazone-induced liver dysfunction

Troglitazone is a thiazolidinedione antidiabetic agent with insulin-sensitizing activities that was withdrawn from the market in 2000 due to its association with idiosyncratic hepatotoxicity. To address the suspected autoantibody production associated with troglitazone, we investigated autoantibodies in sera from patients with type II diabetes mellitus with troglitazone-induced liver dysfunction. Two female patients (47- and 70-year-old) ceased taking troglitazone (400 mg/day) after 23.5 and 16 weeks, respectively, due to increased serum ALT. Using two-dimensional electrophoresis and amino acid sequence analyses, aldolase B was identified as an autoantigen that reacted with antibodies in sera from both patients. The titer of anti-aldolase B remained high for several weeks after stopping troglitazone administration. The mean reactivity of autoantibodies to aldolase B determined by ELISA with sera of patients with chronic hepatitis (n = 40) and liver cirrhosis (n = 40) was significantly higher (p < 0.05 and p < 0.001, respectively) than with sera of healthy subjects (n = 80). These findings suggest that liver injury may cause the appearance of autoantibodies to aldolase B which may then aggravate the hepatitis. In addition, the anti-aldolase B titer might indicate the severity of liver dysfunction.

Aldolase C in neuroendocrine tumors: an immunohistochemical study

The expression of cerebral type aldolase C was investigated immunohistochemically in six varieties of neuroendocrine (n = 57) and six types of non-endocrine tumor (n = 76) using the avidin-biotin complex method. Aldolase C expression in the neuroendocrine tumors was also compared with those of chromogranin and gamma enolase. Aldolase C was detected in all the islet cell (7/7) and carcinoid tumors (10/10), thyroid medullary carcinomas (7/7), and pheochromocytomas (10/10), as well as in the majority of neuronal tumors (8/10) and bronchial small cell carcinomas (10/13). Chromogranin immunoreactivity was restricted to the tumors with abundant neuroendocrine granules. Gamma enolase positivity was generally similar to that of aldolase C, but there were some differences. Amongst the bronchial small cell carcinomas, three tumors negative for gamma enolase were positive for aldolase C, while another three tumors were positive for gamma enolase only. However all the small cell carcinomas were positive for at least one of these two enzymes. Aldolase C was detected in 28 (37%) of the 76 non-endocrine tumors and tended to be expressed preferentially in the differentiated portions of these tumors. Although aldolase C was expressed in many bronchial squamous cell carcinomas, the immunoreactivity was localized mainly in keratinizing foci and the less differentiated parts of these tumors expressed the enzyme only occasionally. Thus aldolase C, in conjunction with other neuroendocrine-associated markers, may be of value in identifying tumors of neuroendocrine type.

Rapid enzyme immunoassay of anti-streptokinase antibodies in human plasma

A simple enzyme immunoassay for determination of anti-streptokinase antibodies (aSKa) in plasma is described. Commercially available reagents have been used for the assay, which is calibrated with a reference preparation of aSKa containing 100 AU/ml. The assay is specific and reproducible with a variation coefficient of 4.8%. In healthy individuals a broad range of values between 4 and 291 AU/ml was observed with a large difference between the mean and median value (55 AU/ml and 27 AU/ml, respectively). Data from a study on 21 patients with myocardial infarction treated with the streptokinase derivative antistreplase suggest that a high titre of aSKa before treatment is associated with failure of thrombolytic therapy. The assay procedure can be shortened to 0.5 h to screen patients for a high aSKa level. This assay allows a more routine assessment of aSKa in the clinic.

Elevated levels of serum aldolase A in patients with renal cell carcinoma

To clarify whether serum aldolase A is a useful biomarker for renal cell carcinoma (RCC), we determined serum levels of the aldolase A isozyme by an enzyme immunoassay in patients suffering from RCC, other urological tumors, and benign urological diseases. Forty-six of 126 patients with RCC (37%) had elevated serum aldolase A. The positive rates were 23% in stage I, 40% in stage II, 63% in stage III, and 46% in stage IV. In 10 (83%) of 12 patients whose serum levels had been elevated preoperatively, these were reduced to within the normal range after nephrectomy. Four of 7 patients (57%) with progressive disease had elevated levels of aldolase A. In contrast, the positive rates were only 9.9% in 71 patients with other urological tumors and 5.8% in 52 cases of benign urological diseases. High concentrations of aldolase A isozyme in RCC tissues might be reflected in elevated serum levels. The present findings indicate that serum aldolase A is a useful biomarker for monitoring the clinical course of patients with RCC.

Sensitive enzyme immunoassay for human 28 kDa calbindin-D

A sandwich-type enzyme immunoassay for human 28 kDa vitamin D-dependent calcium binding protein (calbindin-D) was established with a sensitivity of 1 pg/tube. Antisera were generated in rabbits injected with highly purified human kidney calbindin-D, and specific antibodies to calbindin-D were purified by the use of a column of calbindin-D-coupled Sepharose. The purified antibodies showed a single band at the position corresponding to calbindin-D on an immunoblotting test with a crude extract of human kidney. The assay system consisted of polystyrene balls with immobilized F(ab')2 antibodies and the same antibodies labeled with beta-D-galactosidase from Escherichia coli. The assay was specific to 28 kDa calbindin-D, showing no cross-reactivity with other calcium binding proteins such as S-100a0 (alpha alpha), S-100b (beta beta), parvalbumin and calmodulin. The assay was also reproducible (coefficients of variation between assays were less than 10%). With the present method, immunoreactive calbindin-D could be detected in various human tissues, with major concentrations in kidney and brain. The values for immunoreactive calbindin-D in various body fluids of healthy subjects varied from undetectable in serum and semen to 3.8 +/- 2.0 (SD) micrograms/g creatinine in urine and 2.9 +/- 0.8 (SD) micrograms/l in cerebrospinal fluid. Immunohistochemically, the calbindin-D in human kidney was localized in epithelial cells of distal tubules.

Sensitive immunoassay for rat parvalbumin: tissue distribution and developmental changes

A sensitive enzyme immunoassay for measurements of rat parvalbumin was established using antibodies raised in rabbits with parvalbumin purified from skeletal muscles. Antibodies in the antiserum were purified with a parvalbumin-coupled Sepharose column. The sandwich-type immunoassay system for parvalbumin was composed of polystyrene balls with immobilized purified antibodies and the same antibodies labeled with beta-D-galactosidase from Escherichia coli. The assay was highly sensitive and the minimum detection limit was 1 pg parvalbumin/tube. The assay did not cross-react with other calcium binding proteins, including human S-100a0 and S-100b proteins, rat 28-kDa calbindin-D, and bovine calmodulin. High concentrations of parvalbumin were observed in the skeletal muscles, especially in those composed of fast-twitch fibers, and in the diaphragm and tongue, but not in heart muscle. A relatively high concentration was estimated in the central nervous tissue. Parvalbumin was detected in the cerebral cortex and cerebellum of gestational 15-day fetuses. However, the levels of parvalbumin in the muscle tissues and central nervous tissue were very low in rats before 1 week of age. Thereafter, they increased sharply, reaching the adult levels by 5 weeks in most of the tissues. Parvalbumin concentrations in adult rat soleus muscle increased less than 20-fold within 10 days after transection of the ipsilateral sciatic nerve, while the concentrations in the extensor digitorum longus muscle did not change in the same period.

An immunochemical and immunohistochemical study of aldolase isozymes in renal cell carcinoma

To assess changes in aldolase isozyme patterns (A, B, and C) in renal cell carcinoma (RCC) tissues and to evaluate whether serum aldolase A might be a useful marker for RCC, quantitative analysis by enzyme immunoassay and immunohistochemical localization were performed. Concentrations of aldolase A in RCC (7300 +/- 6300 ng./mg. protein n = 26) were significantly higher than those of normal cortex (720 +/- 410 ng./mg. protein, n = 14, p less than 0.01); concentrations of aldolase C in RCC (48.0 +/- 8.0 ng./mg. protein) were also significantly higher than those of normal cortex (8.7 +/- 4.7 ng./mg. protein, p less than 0.01). On the other hand, concentrations of aldolase B in normal cortex were 18,100 +/- 10,100 ng./mg. protein (n = 14), whereas the values in RCC were only 130 +/- 270 ng./mg. protein, a significant lowering (p less than 0.01). Immunohistochemically, aldolases A and C were found localized in all RCC tissues (n = 10); aldolase B was faintly stained in only a few tumor cells of two cases (20%). Levels of serum aldolase A were elevated (greater than 300 ng./ml.) in 30 (75%) of 40 patients with RCC as compared to three (6.3%) of 48 individuals with urogenital benign diseases and in seven (21%) of 34 cases with non-RCC urogenital malignancies. Since it is generally accepted that RCC are derived from renal proximal tubules, these findings indicate that aldolase B, the predominant isozyme in the normal case, changes into aldolases A and C during carcinogenesis and that serum aldolase A could be a new useful biomarker for RCC.

Immunochemical and immunohistochemical studies on three aldolase isozymes in human lung cancer

The aldolase isozymes A, B, and C in tumor tissues (63) and sera (104) of patients with lung cancer were determined with an enzyme immunoassay system, compared with normal lung tissues (13), and the sera of normal healthy subjects (100). Tissue aldolase A and C concentrations were enhanced in 83% (52/63) and 51% (32/63) of patients with lung cancer, respectively, regardless of histologic type or stage (P less than 0.01). But aldolase B was not elevated in tissue levels. In the sera of patients with lung cancer, there were no significant elevations of the isozymes. Immunohistochemically aldolase A and C stained more intensely in the cytoplasm of lung cancer cells than those in normal tissues. These results indicate lung cancer cells contain enhanced tissue levels of aldolase A and C.

Sensitive enzyme immunoassay for human aldolase A

A sensitive sandwich-type enzyme immunoassay for the aldolase isozyme, A4, was developed using purified antibodies specific to the A subunit of aldolase. The antibodies were raised in sheep being immunized with purified aldolase A4 and then purified by immunoaffinity chromatography on a column of aldolase A4-coupled Sepharose. The assay system consisted of polystyrene balls with immobilized antibody F(ab')2 fragments and the same antibody F(ab')2 fragments labeled with beta-D-galactosidase from Escherichia coli. The assay was sensitive enough to detect 10 pg/tube of aldolase A4. The assay was specific to the A subunit of aldolase (aldolase A). It cross-reacted about 40% to aldolase A3C, 7% to A2C2 and 0.3% to AC3, but not cross-reacted with C4 nor B4. Coefficients of variation in intra- and inter-assay were less than 16%. Serum aldolase A levels were determined in healthy adults, which were about 200 ng/ml. The distribution and concentrations of immunoreactive aldolase A in various human tissues were also determined. High concentrations of aldolase A were found in skeletal muscle, heart muscle, cerebrum and lymphatic tissue.