Monoclonal Antibody-based Method Research Articles

Diagnosis of hepatocellular carcinoma using a novel anti-glycocholic acid monoclonal antibody-based method.

Glycocholic acid (GCA) is a novel identified biomarker for hepatocellular carcinoma (HCC). However, clinical pathological study of GCA has not been extensive due to the limited availability of anti-GCA monoclonal antibodies (mAbs) and restricted detection methods. In the present study, using human GCA conjugated with bovine serum albumin as the immunogen to immunize BALB/c mice, a novel anti-GCA mAb was generated and characterized. The isotypes of heavy chain and light chain of anti-GCA mAb were examined to be IgG2a and κ, respectively, with a high affinity constant (2.6×108 mol/l). The anti-GCA mAb binds GCA with high specificity and sensitivity, and the 50% inhibitory rate was 77.09 ng/ml. The present study also established a rapid, sensitive and efficient indirect competitive ELISA analysis using this anti-GCA mAb to detect the level of GCA produced by different HCC cell lines. Therefore, the present study may successfully develop a novel method for early HCC diagnosis, and also provide insights for further research and treatment of HCC.

Interleukin-6 Levels in Cerebrospinal Fluid and Plasma in Patients with Severe Spontaneous Subarachnoid Hemorrhage

Inflammatory processes play a key role in the pathophysiology of subarachnoid hemorrhage (SAH). This study evaluated whether different temporal patterns of intrathecal and systemic inflammation could be identified in the acute phase after SAH. The intensity of the inflammation was also assessed in clinical subgroups. Cerebrospinal fluid (CSF) and blood samples were collected at days 1, 4, and 10 after ictus in 44 patients with severe SAH. Interleukin-6 (IL-6) was analyzed by a routine monoclonal antibody-based method. Median IL-6 values for each day were calculated. Day 4 IL-6 values were compared in dichotomized groups (age, sex, World Federation of Neurosurgical Societies [WFNS] grade, Fisher scale grade, outcome, vasospasm, central nervous system infection and systemic infections). CSF IL-6 levels were significantly elevated from day 1 to days 4 and 10, whereas plasma IL-6 showed a different trend at lower levels. Median CSF IL-6 concentrations for days 1, 4, and 10 were 876.5, 3361, and 1567 ng/L, whereas plasma was 26, 27.5, and 15.9 ng/L, respectively. No significant differences in CSF concentrations were observed between the subgroups, with the most prominent one being in day 4 IL-6 in the WFNS subgroups (grades 1-3 vs. 4-5, 1158.5 vs. 5538 ng/L; P= 0.056). Patients with systemic infection had significantly higher plasma IL-6 concentrations than patients without infection (31 vs. 16.05 ng/L, respectively; P= 0.028). Distinctly different inflammatory patterns could be seen intrathecally compared with the systemic circulation. In plasma, a significant difference in the intensity of the inflammation was seen in cases with systemic infection. No other subgroup showed statistically significant differences.

Lipoprotein (a): structure, pathophysiology and clinical implications.

The chemical structure of lipoprotein (a) is similar to that of LDL, from which it differs due to the presence of apolipoprotein (a) bound to apo B100 via one disulfide bridge. Lipoprotein (a) is synthesized in the liver and its plasma concentration, which can be determined by use of monoclonal antibody-based methods, ranges from < 1 mg to > 1,000 mg/dL. Lipoprotein (a) levels over 20-30 mg/dL are associated with a two-fold risk of developing coronary artery disease. Usually, black subjects have higher lipoprotein (a) levels that, differently from Caucasians and Orientals, are not related to coronary artery disease. However, the risk of black subjects must be considered. Sex and age have little influence on lipoprotein (a) levels. Lipoprotein (a) homology with plasminogen might lead to interference with the fibrinolytic cascade, accounting for an atherogenic mechanism of that lipoprotein. Nevertheless, direct deposition of lipoprotein (a) on arterial wall is also a possible mechanism, lipoprotein (a) being more prone to oxidation than LDL. Most prospective studies have confirmed lipoprotein (a) as a predisposing factor to atherosclerosis. Statin treatment does not lower lipoprotein (a) levels, differently from niacin and ezetimibe, which tend to reduce lipoprotein (a), although confirmation of ezetimibe effects is pending. The reduction in lipoprotein (a) concentrations has not been demonstrated to reduce the risk for coronary artery disease. Whenever higher lipoprotein (a) concentrations are found, and in the absence of more effective and well-tolerated drugs, a more strict and vigorous control of the other coronary artery disease risk factors should be sought.

Detection of Ricin Contamination in Ground Beef by Electrochemiluminescence Immunosorbent Assay

Ricin is a highly toxic protein present in the seeds of Ricinus communis (castor), grown principally as a source of high quality industrial lubricant and as an ornamental. Because ricin has been used for intentional poisoning in the past and could be used to contaminate food, there is a need for analytical methodology to detect ricin in food matrices. A monoclonal antibody-based method was developed for detecting and quantifying ricin in ground beef, a complex, fatty matrix. The limit of detection was 0.5 ng/g for the electrochemiluminescence (ECL) method and 1.5 ng/g for enzyme-linked immunosorbent assay (ELISA). The detection of nanogram per gram quantities of ricin spiked into retail samples of ground beef provides approximately 10,000-fold greater sensitivity than required to detect a toxic dose of ricin (>1 mg) in a 100 g sample.

Monoclonal antibody-based method for measuring olive pollen major allergen Ole e 1

Olive tree pollen is an important cause of inhalant allergy in Mediterranean countries. The major allergen of this pollen, Ole e 1, has caused reactions in the sera of >80% of olive-sensitive patients. Accurate standardization of allergenic products for diagnosis and immunotherapy is essential to guarantee their quality, and measurement of the major allergen content is becoming an important aspect of standardization procedures. To develop a two-site enzyme-linked immunoadsorbent assay (ELISA) for the quantification of Ole e 1. BALB/c mice were immunized with purified natural Ole e 1. After fusion and screening by direct ELISA, one of the monoclonal antibodies (5A3) was selected as the capture antibody in an ELISA for Ole e 1 quantification. Bound allergens were detected by a combination of biotinylated Ole e 1-specific polyclonal rabbit antibody and peroxidase-conjugated streptavidin. This ELISA was subsequently evaluated and compared with other techniques. The developed ELISA was highly reproducible and sensitive, with a detection limit of 0.5 ng/mL and a practical range of 1 to 10 ng/mL. The Ole e 1 content ranged from 3 to 50% of the total protein among the nine Olea europaea pollen extracts studied. The assay also detected Ole e 1-like proteins in pollen from other Oleaceae. Correlation was good between the Ole e 1 content determined by ELISA and scanning densitometry and the immunoglobulin E-binding activity of the extracts. The described Ole e 1 ELISA is sensitive, reproducible, specific, and reliable, and therefore, can be helpful for standardization of olive pollen extracts intended for clinical use.

Production of ultrasensitive antibodies against aflatoxin B1.

To produce specific antibodies against the haptenic fungal toxin aflatoxin B1 (AFB1) and apply these antibodies in immunochemical assays for aflatoxins. Rabbits were immunized using an AFB1-bovine serum albumin conjugate and serum titres determined by double-antibody enzyme immunoassay. High titres of antibodies with very high affinity for AFB1 were obtained 15 and 4 weeks after the initial immunization and the first booster immunization respectively. The antibodies were employed in enzyme immunoassay (EIA) and immunoaffinity chromatography (IAC) methods for aflatoxins. With a detection limit of 15.8 pg ml(-1) for AFB1, the EIA employing these antibodies is the most sensitive test for AFB1 described so far. In IAC columns, these antibodies provided high binding capacity for all major aflatoxins, including AFB1, AFB2, AFG1 and AFG2. The antibodies described here are useful for the analysis of trace levels of aflatoxins. Polyclonal antibody-based EIA and IAC methods for aflatoxin analysis offer a suitable alternative to the more expensive monoclonal antibody-based methods.

Production of ultrasensitive antibodies against aflatoxin B 1

Aims: To produce specific antibodies against the haptenic fungal toxin aflatoxin B 1 (AFB 1 ) and apply these antibodies in immunochemical assays for aflatoxins. Methods and Results: Rabbits were immunized using an AFB 1 -bovine serum albumin conjugate and serum titres determined by double-antibody enzyme immunoassay. High titres of antibodies with very high affinity for AFB 1 were obtained 15 and 4 weeks after the initial immunization and the first booster immunization respectively. The antibodies were employed in enzyme immunoassay (EIA) and immunoaffinity chromatography (IAC) methods for aflatoxins. With a detection limit of 15.8 pg ml -1 for AFB 1 , the EIA employing these antibodies is the most sensitive test for AFB 1 described so far. In IAC columns, these antibodies provided high binding capacity for all major aflatoxins, including AFB 1 , AFB 2 , AFG 1 and AFG 2 . Conclusions: The antibodies described here are useful for the analysis of trace levels of aflatoxins. Significance and Impact of the Study: Polyclonal antibody-based EIA and IAC methods for aflatoxin analysis offer a suitable alternative to the more expensive monoclonal antibody-based methods.

Monoclonal antibody-based method to quantify Gly m 1. Its application to assess environmental exposure to soybean dust.

The demonstration that some asthma epidemics have been caused by allergens of soybean-hull dust prompted us to develop a two-site ELISA, suitable for the quantification of the major allergen (Gly m 1), to be used for the prevention of new episodes. BALB/c mice were injected with Gly m 1 purified from soybean hulls. After fusion and screening, 10 monoclonal antibodies (mAbs) were obtained that were shown to be specific for Gly m 1 Two of them (6G1 as the capture antibody; 1G10 as the tracer) were selected to develop a quantitative two-site ELISA for the indoor and outdoor determination of Gly m 1. The two-site ELISA developed is very sensitive, with a detection limit of less than 0.2 ng/ml and a practical working range of 0.4-10 ng/ml. The assay is also highly reproducible with an intra-assay coefficient of variation of 3.5% and an interassay coefficient of variation of 12.5%. The method was applied to measure the concentration of Gly m 1 in air-sampler filters and in house-dust samples. Our results illustrate that there is a good correlation between the content of Gly m 1 in a number of samples and the allergenic activity as measured by ELISA inhibition. A specific and sensitive method is presented that can be used for the quantification of Gly m 1. The application of this method may allow the establishment of risk limits for soybean dust, and thus may contribute to the control of environmental contamination and to the prevention of new asthma epidemics.

CD34+ selected cells in clinical transplantation.

The CD34 antigen is expressed by early hematopoietic stem cells and progenitors and is detected on the surface of approximately 1% of bone marrow mononuclear cells [1-3]. Several monoclonal antibody-based methods have been developed to isolate these cells from clinical samples of bone marrow or peripheral blood based on their expression of this antigen, utilizing either biotin-avidin affinity, panning or immunomagnetic beads. Roughly 50% of CD34+ cells, with 20-90% purity, are recovered from clinical samples using these methods. Several clinical trials have demonstrated hematopoietic recovery using CD34+ selected cells to support high dose therapy. CD34+ cells may be useful in several areas of clinical stem cell transplantation, including purging of tumor cells, T cell depletion, stem cell expansion and gene therapy. This paper reviews the current methods for purification of CD34+ cells from clinical samples and discusses potential uses of these cells in transplantation.

Monitoring Cyclosporine in Liver-Transplant Recipients: Effects of Clinical Status on the Performance of Two Monoclonal Antibody-Based Methods

The characteristics of the Abbott selective fluorescence polarization immunoassay for cyclosporine in whole blood (TDXSP) were compared with the Incstar radioimmunoassay by using kit standards (INCSP) or TDXSP standards (INCTDX) with samples from adult (48) and pediatric (24) liver-transplant recipients and a further 32 control specimens. The TDXSP assay was faster, less labor intensive, and more precise at higher concentrations; it gave results a median of 5 micrograms/L lower than INCSP values, irrespective of biliary T-tube status, patient's age, or severity of cholestasis in nine patients, comparisons being made for serum bilirubin more than eight times normal or less than 50 mumol/L. However, both assays overestimated INCTDX values by approximately 10%. There was a progressive increase in the ratio of TDXSP to both INCSP and INCTDX results in 57 samples stratified in relation to serum bilirubin concentrations. Cross-reactivity of TDXSP with cyclosporine metabolites M1 (23%) or M17 (12%) was greater than for INCSP (15% and 5%, respectively) or INCTDX (22% and 4%, respectively), but the converse was true with M21 (2% for TDXSP vs 4% and 8%, respectively). Some overestimation of cyclosporine whole-blood concentrations (relative to INCTDX results) may be detected with either the TDXSP (because of cross-reactivity with metabolites) or the INCSP assays (probably because of matrix effects). The similar magnitude of these overestimations suggests that alternative factors such as speed, precision, and cost may influence which method one selects for use in routine monitoring.

Comparison of sex steroid receptor determinations in human breast cancer by enzyme immunoassay and radioligand binding

Most investigators comparing ligand-binding procedures for quantifying estrogen and progestin receptors in human breast cancer with procedures employing monoclonal antibody-based methods have utilized an inappropriate variety of reaction conditions, including the elimination of sodium molybdate in the steroid-binding assays. We studied 197 biopsies of human breast cancer, comparing the results of simultaneous measurements of both estrogen and progestin receptors in identical cytosols by enzyme immunoassay and by radioligand binding using the commercially available kits developed by Abbott Laboratories and by DuPont/NEN Products, respectively. Regression analyses comparing the results from the two procedures indicated a linear relationship, with correlation coefficients ranging from 0.79 to 0.93 for both types of receptors over a wide range of data. Using the widely established cutoff value of 10 fmol/mg of cytosol protein for the ligand-binding method, and calculating sensitivity and specificity limits according to McNeil et al. (1975), an equivalent cutoff value of 15 fmol/mg of cytosol protein was determined for the enzyme immunoassay of these receptors. Endocrine status of the patient did not appear to alter the cutoff values of either estrogen or progestin receptors when determined by enzyme immunoassay. We recommend that these cutoff values be considered until the results of clinical correlations are completed.

Comparison of conventional staining methods and monoclonal antibody-based methods for Cryptosporidium oocyst detection

The sensitivity and specificity of seven microscopy-based Cryptosporidium oocyst detection methods were compared after application to unconcentrated fecal smears. The seven methods were as follows: (i) a commercial acid-fast (AF) stain (VOLU-SOL) method, (ii) Truant auramine-rhodamine (AR) stain method, (iii) fluorescein-conjugated C1B3 monoclonal antibody (MAb) direct fluorescence method, (iv) OW3 MAb indirect fluorescence method, (v) biotinylated OW3 indirect fluorescence method, (vi) biotinylated OW3-indirect diaminobenzidine (DAB) method, and (vii) biotinylated OW3-aminoethylcarbazole (AEC) method. A total of 281 randomly collected Formalin-fixed fecal samples (submitted to the Maricopa County Health Department, Phoenix, Ariz.) and 30 known positives (Formalin-fixed and K2Cr2O7-preserved stools from our laboratory) were examined in a blind test; 32 of 311 samples (10.3%) were confirmed positive. Of the confirmed positives, 40.6% were identified by the AF method, 93.8% were identified by the AR method, 93.8% were identified by the C1B3 method, 81.3% were identified by the OW3-DAB method, 71.9% were identified by the OW3-AEC method, 100% were identified by the OW3 indirect fluorescence method, and 100% were identified by the biotinylated OW3 indirect fluorescence method. False-positives were encountered by the AF and AR methods (52.0 and 85.7% specificity, respectively), while no false-positives encountered by the MAb-based methods. Oocysts in infected tissue sections were easily detected by the MAb-based methods.

Laboratory and clinical experience with a monoclonal antibody-based radioimmunoassay for serum total thyroxine.

The performance characteristics and diagnostic value of a monoclonal antibody-based radioimmunoassay for serum total thyroxine (Mallinckrodt) are described. Between-batch precision (coefficient of variation) was 10.4% at 87 nmol/l and 3.3% at 185 nmol/l. Scatchard analysis revealed a linear plot with a Ka of 5.4 X 10(8) l/mol. Sensitivity was 4.5 nmol/l of thyroxine. An association study showed that the assay reached equilibrium well within the specified incubation time. Cross-reaction of triiodothyronine and reverse triiodothyronine in the assay was 0.6% and 25.0% respectively. Analytical recovery was 91-110%. Linearity was well demonstrated but dilutions of a high concentration of thyroxine in serum did not parallel the standard curve. The correlation coefficient for comparison with a polyclonal antibody assay was 0.95 for 83 patients. The diagnostic accuracy of the monoclonal antibody assay was adequate for most patients with thyroid disease, pregnant women, oral contraceptive users and subjects on thyroxine-replacement therapy. Measurement of total thyroxine by a monoclonal antibody-based method shows no definite advantage over the conventional polyclonal antibody assay.