Preparation and characterization of antisera and monoclonal antibodies to serotonergic and dopaminergic ligands

Direct Ring Conjugation of Catecholamines and Their Immunological Interactions

Catecholamine derivatives were synthesized with potential applications as coating antigens in biosensors or in the raising of specific antibodies. Thioether-bridged derivatives of the catecholamines dopamine, norepinephrine, and epinephrine that attach carboxylic acid functionalities directly to the aromatic ring via an easily incremented linker chain were synthesized by an electrochemical method. These derivatives were purified by convenient ion-exchange chromatography, exact positions of conjugation determined by NMR, and a dopamine derivative immobilized in situ in a BIAcore surface plasmon resonance (SPR) biosensor and its antibody binding studied in comparison with immobilization via the catecholamine primary amine. Binding of an antibody raised to an amine-conjugated protein conjugate showed clear distinction between conjugations at different positions on the catecholamine, illustrating the importance of rational conjugate design in immunosensing of the catecholamines.

Monoclonal-based ELISA for the identification of herbicidal cyclohexanedione analogues that inhibit graminaceous acetyl coenzyme-A carboxylase

Cyclohexanediones are one of four known structural classes of herbicides that inhibit graminaceous acetyl coenzyme-A carboxylase (ACCase; EC 6.4.1.2). Five monoclonal antibodies were raised against cyclohexanediones conjugated to bovine serum albumin. Cross-reactivity studies using a homologous competitive indirect enzyme-linked immunosorbent assay (ciELISA) against 24 cyclohexanedione analogues revealed that two monoclonal antibodies (mAb A and mAb B) could segregate the analogues into active and inactive ACCase inhibitors on the basis of the analogue concentration required to inhibit 50% of antibody binding to the coating conjugate (IC(50)). Both mAb A and mAb B were also found to cross-react with various members of the indolizidinedione structural class of ACCase inhibitors in ciELISA, suggesting that both cyclohexanediones and indolizidinediones possess features recognized by monoclonal antibodies important for the inhibition of ACCase activity. In conclusion, pharmacophore-specific antibodies may be potentially valuable screening tools for the identification of new lead chemistries in a pesticide discovery program.

Analysis of hapten-carrier protein conjugates by nondenaturing gel electrophoresis

Hapten-carrier protein conjugates were made using five different small haptens (MW < 1000), two carrier proteins and two methods of conjugation. Nondenaturing agarose gel electrophoresis was used to demonstrate that when as few as two molecules of a small hapten are attached to the carrier, the conjugate band migrates differently from that of the carrier alone or of the coupling reagent-treated carrier. Furthermore, the direction of the change in migration of each conjugate correlates with the change in charge which occurs upon attachment of the hapten to the carrier.

Kinetics of haloperidol binding to monoclonal antibodies as measured by direct fluorescence quenching

Monoclonal antibodies which bind small neurogenic ligands may mimic certain aspects of the stereospecific binding present in the natural biological receptor, and may prove useful in designing engineered protein receptors, provided their interactions are correctly understood. We report here the kinetic and equilibrium characteristics of ligand-antibody complexes of haloperidol, a dopaminergic antagonist, with three of its monoclonal antibodies as studied by fluorescence quenching techniques. These antibodies possessed moderate to high affinity constants, ranging from 10(5) to 10(9) M-1, and caused fluorescence quenching of a fluorescein-labeled haloperidol as well as quenching (40-60%) of the internal tryptophan fluorescence. The dissociation rates of the ligand from the complexes were measured at different conditions of temperature, pH and ionic strength. The results provide important information regarding the kinetic and thermodynamic parameters of the binding pockets of these antibodies.

Production and characterization of monoclonal idiotypes and anti-idiotypes for small ligands

The procedures described in this chapter have enabled us to identify and characterize monoclonal antibodies and their respective anti-idiotypes. We have developed several different types of immunoassays which afford greater flexibility to the investigator, depending on the type of antibodies desired and the availability of labeled antigens. Use of the intrasplenic injection technique for the final booster immunization prior to the fusion protocol has enabled us to achieve more consistent results than the usual intravenous or intraperitoneal injection routes. Isoelectric focusing of tissue culture supernatant from monoclonal antibody-secreting clones can easily identify possible duplicate clones, and thereby reduces the amount of labor required for extensive characterization of a large number of clones. We have found that these techniques have enabled us to identify "sister clones" or redundancies in our collection of antiligand and anti-idiotype antibodies rapidly and accurately. These various techniques have allowed us to save much time, labor, and money in the search for specific antibodies with desired characteristics.

Monoclonal antibodies against glutaraldehyde-conjugated dopamine

Four mice were immunized with dopamine (DA)-glutaraldehyde (G)--protein conjugates over a period of 8-10 weeks. Polyclonal antisera, obtained at various intervals, were tested using an enzyme-linked immunosorbent assay (ELISA). All had anti-conjugated DA antibodies. As soon as good antibody affinity was detected between 10(-10) and 10(-6) M, the mouse yielding the highest apparent affinity was killed, and the spleen was dissected out. Hybridomas were obtained from spleen cells fused with SP2/O/Ag myeloma cells. Supernatant culture media of hybridomas were tested for the presence of anti-conjugated DA antibodies with the ELISA method. Selected hybridomas giving good antibody affinity and specificity were then cloned by the limiting dilution technique. The resulting supernatant culture media were again tested by ELISA. Clones that gave a high antibody affinity (10(-10)-10(-8)M) for G-conjugated DA were used for histochemical localization of DA in rat brain. G-fixed rat brains were sectioned from the telencephalon to the mesencephalon, reduced with sodium borohydride, and prepared for peroxidase-antiperoxidase immunocytochemistry using supernatant (diluted 1:100) or ascites fluid (diluted 1:50,000). Dense networks of very fine fibers were observed in the striatum, septum, and cortex. Numerous immunoreactive cell bodies were found in the ventral tegmental area, the substantia nigra, the hypothalamus, and the dorsal raphe. The ELISA tests and adsorption controls suggested that the monoclonal antibody allowed highly specific detection of DA in tissues.

A simple 'free 3H-ligand' assay for rapid screening of hybridoma monoclonal antibodies against neurotransmitter analogs and anti-idiotype antibodies

Effective, rapid screening of hybridoma supernatants for monoclonal antibodies against the dopaminergic antagonists pimozide and haloperidol, and the serotonergic antagonist ketanserin was performed using a 'free 3H-ligand' assay. Anti-mouse Ig-coated microtiter plates were incubated with hybridoma supernatants prior to incubation with excess 3H-ligand. After removal of free 3H-ligand, bound 3H-ligand was eluted with acid for liquid scintillation counting. With minor modification, the assay can be used to screen hybridomas for anti-anti-ligand (anti-idiotypic) antibodies.

Preparation and characterization of antisera and monoclonal antibodies to haloperidol

For the first time a library, of monoclonal antibodies (MoAbs) to the butyrophenone haloperidol (D-2 antagonist) has been prepared. Synthesis of a haloperidol derivative suitable for chemical coupling to a protein carrier via oxobutyric acid produced an immunogen which was used to develop two polyclonal antisera and twelve MoAbs specific for the hapten. Our library of MoAbs can be grouped into three classes; 1) high affinity and specificity for free 3H-haloperidol, 2) moderate affinity with significant cross-reactivity to other butyrophenone ligands, and 3) a group which binds poorly to free 3H-haloperidol but instead recognizes the ligand only when it is coupled to carrier protein. Clone (189(2)-6) was found to have the highest equilibrium binding affinity (Kd = 4 nM) and is far more specific than the currently available antisera to haloperidol. This MoAb has significantly lower affinity for all of the common metabolites of haloperidol. This capability makes 189(2)-6 a candidate for further development with regard to use in clinical radioimmuno-assays of therapeutic drug levels. In addition, one of the anti-haloperidol Moabs (190(2)-6) binds more tightly to spiperone than to haloperidol and displays a qualitative correlation in the rank order of neuroleptic binding affinity for a limited series of analogs when compared to membrane bound D-2 receptor binding.