Use of a monoclonal antibody to estrone-3-glucuronide in an enzyme-linked immunosorbent assay (ELISA)

Concepts for the syntheses of biotinylated steroids. Part I: testosterone derivatives as immunochemical probes

We describe synthetic strategies for the biotinylation of testosterone (T) at positions 3, 7alpha, 17alpha, and 19. These T probes are able to mimic ligand binding and may provide for a better understanding of the biospecific interaction with steroid-binding proteins such as the androgen receptor, anti-steroid antibodies, or steroid-binding serum globulins. For the 7alpha- and 17alpha-derivatives, biotinyl-N-hydroxy-succinimide esters with different types of spacer chains were used. The 3-biotin hydrazone derivative was produced using N-(epsilon-biotinyl)-caproyl hydrazide, whereas for the 19-biotinylation, a biotinyl-1-N-diamino-3, 6-dioxaoctane-amide was applied. Key reaction for the biotinylation at position 3 is the oximation of the 3-oxo function. The 17alpha-position is accessible by the reaction of the 3-protected 4-androsten-17-epoxide with oxygen in the beta-position, followed by nucleophilic ring opening with cyanide which provides the 17alpha-cyanomethyl derivative. The key step is the regioselective ketal protection of the 3-oxo function of androst-4-ene-3,17-dione using a stannoxane catalyst. An alternative pathway for the insertion of biotin at the 19-position was established by the synthesis of 17beta-hydroxy-androst-4-en-3-one-19-yl carboxymethyl ether. After activation by the carbodiimide method, the compound reacts with aminoterminal biotin derivatives. The copper(I)-catalyzed 1,6 Michael addition of 17-acetoxy-6,7-dehydro-T leads to 7alpha-derivatives by use of omega-silyl protected hydroxylalkyl-modified Grignard reagents. A functional group interconversion using the Staudinger reaction transforms the azide function into a primary omega-amino group. The absolute configurations of the different biotinylated derivatives were investigated by (1)H NMR studies. For the 7alpha-biotinylated T series, additionally, an X-ray analysis proved the axial position of the spacer group. This results in a vertical orientation of the biotin moiety toward the alpha-face of the planar tetracyclic backbone. Thus, a negligible alteration of the original structure of the upper beta-face offers the feasibility of applying the 7alpha-derivatives as optimal immunochemical tracers in competitive immunoassays. Biotinylated T derivatives should be also suitable for ligand-binding studies to the androgen receptor or to sex hormone-binding globulin.

Synthesis of 17 beta-hydroxyandrost-4-en-3-one-7 alpha-(biotinyl-6-N-hexylamide), a conjugate useful for affinity chromatography and for testosterone immunoassays

We describe the synthesis of 17 beta-hydroxyandrost-4-en-3-one-7 alpha-(biotinyl-6-N-hexylamide) from 17 beta-hydroxyandrost-4-en-3-one (testosterone) via copper-catalyzed 1,6 Michael addition of a 6-(tertbutyldimethylsilyloxyhexyl) chain to 6-dehydrotestosterone 17 beta-acetate. After chromatographic separation of the 7 alpha-isomer from the alpha / beta mixture and cleavage of the silyl ether, the alcohol was oxidized to the 6-hexanal side chain and then subjected to reductive amination. The resulting primary amine is easily biotinylated using biotinyl-N-hydroxysuccinimide ester. The overall yield for the epimeric 7 alpha-end product was 30%. The absolute configurations of the epimers were investigated by 1H NMR studies by the nuclear Overhauser effect. We introduced a biotin label to the testosterone molecule at ring position 7 in compliance with Landsteiner's principle, which states that antibody specificity is directed primarily at that portion of the hapten furthest from the functional group linking it to the carrier protein. Thus, this negligible alteration in comparison to the structure of the respective testosterone hapten used to elicit antibodies offers the feasibility of applying the testosterone derivative as an optimal immunoadsorbent in affinity chromatography. The 7 alpha-biotinylated testosterone was used to obtain active antitestosterone antibodies from a specific antiserum by affinity chromatography. This was achieved by attaching the biotinylated testosterone to agarose-coupled streptavidin beads. Accordingly, a 3H-testosterone-binding test demonstrated a 20-fold increase in affinity of the purified antibody to the steroid compared to the original antiserum, and a recovery of > 80% could be obtained. The antitestosterone antibody, obtained by that method, is an effective component for use in a competitive immunoassay for testosterone in human sera. An assay configuration is conceivable with the same 7 alpha-biotinylated testosterone employed as tracer in combination with a streptavidin-linked reporter enzyme.

Evaluation of antibody- and antigen-coated enzymeimmunoassays for measuring oestrone-3-glucuronide concentrations in urine

A monoclonal antibody to oestrone-3-glucuronide (OG) was generated and incorporated into antigen- and antibody-coated competitive enzymeimmunoassays (EIAs) using OG-, 6-ketoestrone-6-O-carboxymethyl-oxime (OCMO) and oestrone-3-hemisuccinate (OHS) as the steroid coating antigens or 'tracers' in each format respectively. In the coated-antigen format, standard curves with the lowest mean values (pg/well) for sensitivity (1.1 +/- 0.1), mid-point (ED50; 8.2 +/- 0.7) and high-point (ED20; 31 +/- 2) were obtained using OCMO coupled to bovine serum albumin (BSA) as the coating antigen, and horseradish peroxidase (HRP) as the enzyme label coupled directly to the monoclonal antibody. Standard curves generated using enzyme-labelled OG, OCMO and OHS as 'tracers' in the antibody-coated EIA format were all similar, but had higher mean sensitivity, ED50 and ED20 values than those obtained in the optimal coated-antigen format. In both EIA formats alkaline phosphatase (AP) was found to be inferior to HRP as an enzyme label. Measurement of OG concentrations in early morning urine samples from women with natural, regular menstrual cycles, using the antigen-coated EIA, demonstrated the characteristic elevation in OG concentrations associated with the onset of the urinary LH surge. This technically straightforward and robust antigen-coated EIA may be of interest to laboratories with a requirement to measure OG concentrations in urine, or other biological samples.

Re-examining steroid hormone metabolites as ovulation markers using monoclonal antibodies

Plasma progesterone and plasma estradiol levels are commonly used to monitor ovulation in women although for the adequate documentation of ovulation the expense and discomfort of multiple venipuncture sampling may be required. Accurate and definitive information on ovulation in women can be obtained by the simple measurement of metabolites of progesterone and estradiol in early morning urine samples. These analyses have been made possible by the use of our own highly specific monoclonal antibodies to both pregnanediol-3-glucuronide (P-3-G) and estrone-3-glucuronide (E-3-G) and the development of simple, direct, automated enzyme-linked immunosorbent assays. Sequential sampling and the generation of ovulation profiles allows detection of ovulation and identification of the infertile/fertile phases of the cycle for either planned pregnancies or natural family planning. Aberrations in ovulation are easily detected as is documentation of the transition to menopause. The use of sequential, spaced, early morning urine samples for P-3-G and E-3-G allows accurate assessment of ovulatory function rather than relying on the usual single plasma sampling. The data presented also show that the direct determination of plasma pregnanediol-3-glucuronide in plasma is as informative as plasma progesterone measurement.

Assessment of the effect of ovarian suppressants on women with the premenstrual syndrome: iterative spectral analysis

The daily mood symptoms of four women with the premenstrual syndrome (PMS) were recorded before, and after spontaneous or induced ovarian failure. Response was assessed by iterative spectral analysis and the results compared with techniques based on changes in the mean or median mood score, or the measurement of premenstrual tension in arbitrary 'menstrual' cycles. Only iterative spectral analysis had the capacity to establish the significance of a change in symptom cyclicity, an important attribute for a condition such as the PMS.

The premenstrual syndrome: amelioration of symptoms after hysterectomy

What is the role of the uterus in the aetiology of the premenstrual syndrome (PMS)? Twelve women kept a daily symptom record before and after hysterectomy. Psychological and physical symptom patterns were analysed by Fourier analysis and the response to hysterectomy by maximum likelihood ANOVA. Hysterectomy was associated with a 66% reduction in mean premenstrual tension (PMT) severity for both psychological and physical symptoms (p less than 0.005). The milder symptoms appeared unrelated to post-operative changes in health or ovarian function. Seven women experienced mood-related PMT in every pre-hysterectomy cycle; the persistence of unfailing mood-related PMT in one of these women after hysterectomy suggests that her symptoms were hormonally controlled and the loss of regular PMT in the other six women suggests that a uterine factor, or psychological factors associated with the menstrual cycle were implicated. We conclude that a uterus is not essential for the expression of PMT, but that its removal often results in the amelioration of symptoms.

An indirect ELISA for urinary gonadotropins using immobilized human menopausal gonadotropin

An indirect ELISA for the estimation of urinary gonadotropins is described. Human menopausal gonadotropin is adsorbed on a microtitre plate, where it serves as an immunosorbent. The residual antigonadotropin antibody is captured by the immunosorbent after reaction with the sample or standard and detected with enzyme-labelled antispecies antibody (antirabbit gamma-globulin-horse radish peroxidase). The assay developed here is rapid and satisfies usual validatory criteria expected from an immunoassay. Moreover, it obviates the need for extraction of samples with acetone, as shown by the close agreement between the respective lutropin or follitropin concentrations in extracted and unextracted urine samples.

A direct dot-enzyme immunoassay to detect human ovulation

This paper describes an original dot-enzyme-linked immunosorbent assay (ELISA) for predicting ovulation in women, based on the detection of the pre-ovulatory estrogen peak in urine. A monoclonal anti-estrogen antibody is used which recognizes not only free estrogens but also some of their urinary metabolites (17-glucuro- and sulfo-conjugates) allowing a direct assay on early morning urines. Antigen is immobilized as a spot on a nitrocellulose membrane which is immersed in urine in the presence of this antibody. A peroxidase-labeled second antibody allows the detection of the first antibody bound to the membrane. Antigen and anti-estrogen antibody concentrations are chosen to obtain a maximal enzymatic coloration of spots corresponding to basal urinary estrogen levels and no coloration corresponding to the pre-ovulatory surge. Six menstrual cycles were studied, comparing dot-ELISA results with patterns of: (1) urinary estrogens measured by RIA either directly or after hydrolysis and extraction, and (2) basal body temperatures. The validity of the pre-ovulatory signal obtained and the requirements for an adaptation of this methodology to a reliable home kit are discussed.

Production of a monoclonal antibody to cortisol: application to a direct enzyme-linked immunosorbent assay of plasma

Cortisol mouse monoclonal antibodies were produced and characterized. Of the four clones studied, supernatant from one clone (A2), compared with other cortisol monoclonal antibodies, showed minimal cross-reactivity to other C21 steroids and was suitable for the direct determination of cortisol in plasma by enzyme-linked immunosorbent assay using a standard 96-well microtiter plate. The enzyme-linked immunosorbent assay uses the immobilized antigen approach, in which cortisol in plasma samples or standards competes with immobilized steroid for antibody-binding sites. After washing, the cortisol antibody bound to the wells of the microtiter plate is detected with antimouse immunoglobulin conjugated to horseradish peroxidase. Following further washing, o-phenylenediamine substrate is added. The enzyme-linked immunosorbent assay is robust and semiautomated. The mean +/- SD recovery from plasma was 97% +/- 6%. Precision studies on three different plasma pools showed mean coefficients of variation of 7.6% and 8.6% for within- and between-assay variation, respectively. The satisfactory performance criteria allow its use in the routine laboratory.