Development of Rapid and Sensitive One‐Step Direct Enzyme Linked Immunosorbent Assay for 17‐α‐OH‐Progesterone in Serum

Impact of bridge heterology on functional parameters of ELISA for 17α-methyltestosterone

In this study, we have developed bridge heterologous ELISA for the detection of 17α- Methyltestosterone by incorporating aromatic spacers between 17α-Methyltestosterone-3-Carboxymethyloxime and Horseradish peroxidase label through N-hydroxysuccinimide mediated carbodiimide reaction method. The immunogen 17α-Methyltestosterone-3-Carboxymethyloxime-Bovine serum albumin used to generate the antibody was also prepared by the N-hydroxysuccinimide mediated carbodiimide reaction without using any spacer. We have studied the impact of bridge/aromatic spacers on functional parameters i.e. sensitivity, affinity and ED50 of the bridge heterologous assay and compared it with homologous assay. The five combinations of bridge heterologous assay using 17α-Methyl testosterone-3-CMO-BSA antiserum and 17α-MT-3-CMO-4,4'-Diaminodiphenyl sulphide-HRP, 17α MT-3-CMO-4,4'-Oxydianiline-HRP, 17α-MT-3-CMO-Benzidine-HRP, 17α- MT-3-CMO-p-Phenylenediamine-HRP and 17α-MT-3-CMO-Dapson-HRP enzyme conjugates were evaluated. Out of these five combinations, the combination 17α-MT-3-CMO-BSA with 17α-MT-3-CMO-Benzidine-HRP showed the best results. Sensitivity, affinity and ED50 were improved and found to be 0.02 ng/mL, 0.086 × 10-8 L/mol and 2.95 ng/mL than homologous assay where Sensitivity, affinity and ED50 were 0.11 ng/mL, 0.02 × 10-8 L/mol and 5.78 ng/mL respectively. The cross-reactivity for this bridge heterologous assay combination was seen with only 4 steroids (6-hydrotestosterone- 6%, Testosterone-5.14%, Danazol-0.9% and Nandrolone-0.85%) instead of eight steroids (6-hydrotestosterone-43.75%, Testosterone-38.3%, Danazol-25.14%, Androstenediol-19.16%, Nandrolone-19%, Metandienone-5%, Androstenedione-3.52%, and 17α dimethyltestosterone-2%) as in homologous assay out of 59 structurally related steroids. Thus, the results of this study conclude that the incorporation of aromatic spacer (bridge) in enzyme conjugate has a crucial role in improving sensitivity, specificity, ED50 and affinity of the developed assay. The assay was then studied for parameters such as recovery (97.4%-108.6%), precision (Inter and Intra-assay coefficient of variation <10%), correlation coefficient (R2 = 0.96) by comparing with the commercial kit and validated by measuring levels of 17α- methyltestosterone in rat serum after administering them.

Development and optimization of an in-house heterologous ELISA for detection of prednisolone drug in enzyme conjugates using spacers

The introduction of spacers in coating steroid protein complexes and/or enzyme conjugates or immunogens is known to exert an influence on the sensitivity of steroid enzyme immunoassays. We investigated the impact of different homobifunctional spacers, ranging in atomic length from 3 to 10, on the sensitivity and specificity of prednisolone (PSL) enzyme immunoassays. In this study, four homo-bifunctional spacers, namely, carbohydrazide (CH), adipic acid dihydrazide (ADH), ethylene diamine (EDA), and urea (U), were incorporated between PSL and horseradish peroxidase (HRP) for preparing the enzyme conjugate with an aim to improve the sensitivity of the assay without compromising assay specificity. The assays were developed using these enzymes conjugated with antibodies raised against the PSL-21-HS-BSA immunogen. The sensitivity of the PSL assays after insertion of a bridge in the enzyme conjugate was 1.22 ng/mL, 0.59 ng/mL, 0.48 ng/mL, and 0.018 ng/mL with ADH, CH, EDA, and urea as a spacer, respectively. Among the four combinations, the PSL-21-HS-BSA-antibody with PSL-21-HS-U-HRP-enzyme conjugate gave better sensitivity and less cross-reaction. The percent recovery of PSL from the exogenously spiked human serum pools was in the range of 88.32%-102.50%. The intra and inter-assay CV% was< 8.46%. The PSL concentration was estimated in the serum samples of patients on PSL treatment. The serum PSL values obtained by this method correlated well with the commercially available kit (r2 = 0.98). The present study suggests that the nature of the spacer is related to assay sensitivity and not the spacer length.

17-Hydroxyprogesterone in children, adolescents and adults

17-Hydroxyprogesterone (17-OHP) is an intermediate steroid in the adrenal biosynthetic pathway from cholesterol to cortisol and is the substrate for steroid 21-hydroxylase. An inherited deficiency of 21-hydroxylase leads to greatly increased serum concentrations of 17-OHP, while the absence of cortisol synthesis causes an increase in adrenocorticotrophic hormone. The classical congenital adrenal hyperplasia (CAH) presents usually with virilisation of a girl at birth. Affected boys and girls can have renal salt loss within a few days if aldosterone production is also compromised. Diagnosis can be delayed in boys. A non-classical form of congenital adrenal hyperplasia (NC-CAH) presents later in life usually with androgen excess. Moderately raised or normal 17-OHP concentrations can be seen basally but, if normal and clinical suspicion is high, an ACTH stimulation test will show 17-OHP concentrations (typically >30 nmol/L) above the normal response. NC-CAH is more likely to be detected clinically in females and may be asymptomatic particularly in males until families are investigated. The prevalence of NC-CAH in women with androgen excess can be up to 9% according to ethnic background and genotype. Mutations in the 21-hydroxylase genes in NC-CAH can be found that have less deleterious effects on enzyme activity. Other less-common defects in enzymes of cortisol synthesis can be associated with moderately elevated 17-OHP. Precocious puberty, acne, hirsutism and subfertility are the commonest features of hyperandrogenism. 17-OHP is a diagnostic marker for CAH but opinions differ on the role of 17OHP or androstenedione in monitoring treatment with renin in the salt losing form. This review considers the utility of 17-OHP measurements in children, adolescents and adults.

Influence of different homologous and heterologous combinations of antibodies and enzyme conjugates of dehydroepiandrostosterone on the sensitivity and specificity of DHEA ELISA

Anti-sera were raised against three immunogen: dehydroepiandrostosterone-17-carboxymethyl-oxime-bovine serum albumin (DHEA-17-CMO-BSA), DHEA-7-CMO-BSA, and dehydroepiandrostosterone-3-hemisuccinate-bovine serum albumin (DHEA-3-HS-BSA). They were evaluated with horseradish peroxidase (HRP)-labeled DHEA-17-CMO, DHEA-7-CMO, DHEA-3-HS enzyme conjugates for their influence on the sensitivity and specificity of ELISA. Of the various combinations, DHEA-3-HS-BSA antiserum along with DHEA-7-CMO-horseradish peroxidase (DHEA-7-CMO-HRP) enzyme conjugate showed no cross-reaction with any of the closely related steroids. All the homologous combinations appeared to be less sensitive due to their low affinity for dehydroepiandrostosterone. Out of six heterologous systems tested, only three combinations, (1) anti-DHEA-17-CMO antiserum and DHEA-7-CMO-horseradish peroxidase, (2) anti-DHEA-7-CMO-antiserum and DHEA-3-HS-horseradish peroxidase, and (2) anti-DHEA-3-HS-antiserum and DHEA-7-CMO-horseradish peroxidase, showed displacement. The former two assays were less specific; the first one showed 15.38% and 16.66% cross-reaction with androstenediol and testosterone, respectively, whereas the second assay showed 30.3%, 22.72%, 111.1%, 62.5%, and 31.25% cross-reaction with DHEA-glucuronide, 16-dihydroxyprogesterone, androstenediol, etiocholon-3-β-ol-17-one, and aldosterone, respectively. The ability of DHEA to displace the DHEA-enzyme conjugate and the specificity of the assay appear to depend on the position of the enzyme label on the DHEA molecule as well as on the availability of antigenic sites in particular combinations of antibody and DHEA-enzyme conjugates.

Realizing individualized medicine: the road to translating proteomics from the laboratory to the clinic

The sequencing of the human genome has brought great promise and potential for the future of medicine, as well as providing a strong momentum for the burgeoning field of individualized medicine. Tests based on genetic information can be used to allow physicians to target therapies for those patients most likely to benefit from specific therapies and identify potential risk before the onset of disease. While advances in genomics-based molecular diagnostics are progressing, producing some useful US FDA-approved/-cleared diagnostic tests, protein-based molecular diagnostics have not met its promised potential. This article will provide an overview of protein-based analysis technologies, identify their strengths and limitations, discuss barriers to protein-based biomarker development and identify issues which must be addressed in order to successfully transfer the field of proteomics from the laboratory to the clinic.