Structural requirements for recognition of vasopressin by antibody; thermodynamic and kinetic characteristics of the interaction

Vaccines for cocaine abuse

Treatments for cocaine abuse have been disappointingly ineffective, especially in comparison with those for some other abused substances. A new approach, using vaccination to elicit specific antibodies to block the access of cocaine to the brain, has shown considerable promise in animal models, and more recently in human trials. The mechanism of action for the antibody effect on cocaine is very likely to be the straightforward and intuitive result of the binding of the drug in circulation by antibodies, thereby reducing its entry into the central nervous system and thus its pharmacological effects. The effectiveness of such antibodies on drug pharmacodynamics is a function of both the quantitative and the qualitative properties of the antibodies, and this combination will determine the success of the clinical applications of anti-cocaine vaccines in helping addicts discontinue cocaine abuse. This review will discuss these issues and present the current developmental status of cocaine conjugate vaccines.

Anti-drug vaccines to treat substance abuse

Substance abuse is a growing world-wide problem. The big four drugs of abuse that might lend themselves to immunotherapy are nicotine, cocaine, morphine/heroin and methamphetamine. Tobacco abuse has a well-known enormous impact on major chronic cardiovascular and pulmonary diseases, while the last three, aside from their neuropsychological effects, are illegal, leading to crime and incarceration as well as the transmission of viral diseases. Having an efficient vaccine that would generate antibodies to sequester the drug and prevent its access to the brain could go a long way toward helping a motivated addict quit the addiction. This review will discuss what has been done to bring such vaccines to human use, and what the challenges are for the future of this promising intervention.

Substance abuse vaccines

Conventional substance-abuse treatments have only had limited success for drugs such as cocaine, nicotine, methamphetamine, and phencyclidine. New approaches, including vaccination to block the effects of these drugs on the brain, are in advanced stages of development. Although several potential mechanisms for the effects of antidrug vaccines have been suggested, the most straightforward and intuitive mechanism involves binding of the drug by antibodies in the bloodstream, thereby blocking entry and/or reducing the rate of entry of the drug into the central nervous system. The benefits of such antibodies on drug pharmacodynamics will be influenced by both the quantitative and the qualitative properties of the antibodies. The sum of these effects will determine the success of the clinical applications of antidrug vaccines in addiction medicine. This review will discuss these issues and present the current status of vaccine development for nicotine, cocaine, methamphetamine, phencyclidine, and morphine.

The future of vaccines in the management of addictive disorders

Conventional substance abuse treatments have had only limited success. As a result, new approaches, including vaccination to block the effects of drugs such as cocaine, nicotine, methamphetamine, and phencyclidine, are in development. Although a number of possible rationales for the effects of antidrug vaccines have been suggested, the most straightforward and intuitive mechanism would involve binding of the drug by antibodies in the bloodstream, thereby blocking entry or reducing the rate of entry of the drug into the central nervous system. The theoretical parameters that would influence vaccine-induced drug pharmacodynamics are presented in this review, along with the current status on vaccine development for nicotine, cocaine, methamphetamine, and phencyclidine.

Enzyme linked immunosorbent assay for the neurohypophyseal hormones arginine vasotocin and isotocin

A competitive enzyme linked immunosorbent assay (ELISA) using new polyclonal antibodies was developed for the first time for each of two neurohypophyseal hormones: arginine vasotocin (AVT, ubiquitous in vertebrates) and isotocin (IT, restricted to teleost fish). The antibodies obtained were highly specific, showed no cross-reaction between the two peptides and were able to suppress the activity of the peptides in in vitro bioassays. An original feature of the assays was the covalent binding of the peptidic antigen to Covalink microplates. Competition was thereafter made between this bound antigen and the antigen in samples, for a fixed amount of the relevant antibody. Revelation used peroxidase-labeled antibodies. These ELISAs were sensitive enough to detect 1 ng/ml and 0.1 ng/ml for AVT and IT respectively. Moreover, for the first time, the two hormones were measured separately, each in the presence of the other, and shown to exist as circulating hormones in fish.

Monoclonal antibodies to oxytocin: production and characterization

To induce a good immune response to oxytocin (OT) we developed a two-step technique to conjugate OT to thyroglobulin (TG) using glutaraldehyde. We obtained 30 hybridomas recognizing OT-ovalbumin conjugates and 16 stable lines. Three monoclonal antibodies were selected for further characterization. One of them (O13) was found very specific for OT using three different techniques (enzyme-linked immunosorbent assay, radioimmunoassay and immunohistochemistry); it is directed to the C-terminal tripeptide. The other two probably recognize tyrosine containing epitope(s) also shared by vasopressin and other related nonapeptides.

Hypophysiotrophic function of vasopressin and oxytocin

We have investigated the effects of lesioning the hypothalamic paraventricular nucleus (PVN) on the secretion of two corticotropin-releasing neurohormones, vasopressin (VP) and oxytocin (OT), at the median eminence. The experimental model was the median eminence incubated in vitro, the secretion of neurohormones was stimulated by adding 48 mM KCl to the incubation medium. In addition, immunohistochemical staining was performed to correlate the changes in neuropeptide secretion with the distribution of VP and OT immunoreactive elements in the median eminence. Lesioning of the PVN abolished the KCl-induced release of VP 1 week after hypothalamic surgery. After a longer period of postoperative survival (6 weeks), VP release was restored towards normal. The secretion of OT was reduced by 50% at 1 week after lesioning and rose to 400% of control at six weeks. The changes in VP and OT release at the median eminence largely correlated with the immunohistochemical distribution of VP and OT immunopositive nerve fibers in the external zone of the median eminence. Most importantly, 6 weeks after the PVN lesion a dense network of OT immunoreactive varicosities was observed around primary portal capillaries, where normally OT fiber density is very low. These results demonstrate the functional and structural plasticity of VP- and OT-ergic neuronal systems that project to the median eminence. Furthermore, when taken together with earlier studies on the regulation of corticotropin secretion in long-term PVN-lesioned rats, the data indicate an important role for OT in the regulation of pituitary-adrenocortical function in PVN-lesioned rats.

Vasopressin and oxytocin mRNAs in adrenalectomized and Brattleboro rats: analysis by quantitative in situ hybridization histochemistry

35S-labeled synthetic oligodeoxyribonucleotide probes were used to measure levels of vasopressin (VP) and oxytocin (OT) mRNAs in rat hypothalamus by quantitative in situ hybridization histochemistry (ISHH). VP and OT mRNA-containing cells were seen in the paraventricular (PVN) and supraoptic (SON) nuclei. VP mRNA was found to increase five-fold in the parvocellular region of the PVN after adrenalectomy while no changes occurred in magnocellular VP or OT mRNA levels. In the Brattleboro rat, VP mRNA levels were decreased and OT mRNA levels increased in the magnocellular regions. RNA species containing the VP introns were present at one fortieth of the level of processed VP mRNA in control rats. We also performed ISHH followed by immunohistochemistry on the same sections. We found that VP and its encoding mRNA were always located together as were OT-neurophysin and its encoding mRNA. In this study, we extend previous work by showing the characteristic distributions in the PVN and SON of VP and OT mRNA-containing cells and by measuring neuropeptide mRNA changes.

Comparison of three immunoassays in the screening and characterization of monoclonal antibodies against arginine-vasopressin

A method for screening monoclonal antibodies (McAbs) to neuropeptides was evaluated using 8-arginine-vasopressin (AVP) as a model. Mice were immunized with AVP-thyroglobulin conjugate and their spleen cells were fused with X 63-Ag8.653 mouse myeloma cells. The resulting hybridoma supernatants were screened for specific antibody production using 3 different assays: solid phase enzyme radioimmunoassay in Terasaki plates (Ter-ELISA), liquid phase radioimmunoassay (LPRIA) and an immunohistochemical technique. From 2 independent fusions, 7 McAbs specific for AVP were obtained. They belonged to the IgG1 subclass and reacted more strongly to the ring part of the nonapeptide. The screening strategy proposed relies upon a crude selection of conjugate-reacting hybridomas, followed by neuropeptide-specific hybridoma identification using both LPRIA (with radioiodinated synthetic peptide) and an immunohistochemical technique (to detect natural neuropeptide). During subcloning steps Ter-ELISA is then chosen, to select for specific clones and to eliminate those reacting with the carrier thyroglobulin.

Monoclonal antibodies to antitumor Vinca alkaloids: thermodynamics and kinetics

Spleen cells from a mouse and a rat immunized with vinblastine coupled to bovine serum albumin were fused in two independent experiments with P3 X 63-Ag8 (non-secreting variant) mouse myeloma cells. Three mouse X mouse (Vinca 1-3) and two rat X mouse (Vinca 4 and 5) hybrids were selected for production of Vinca alkaloid binding monoclonal antibodies. Each antibody had characteristic cross-reactivities with alkaloids structurally related to vinblastine: Vinca 1 reacted preferentially with deacetylated alkaloids (deacetyl vinblastine and vindesine) and Vinca 2 had a higher affinity for vinblastine and vincristine. Vinca 3-5 recognized equally vinblastine, vincristine and vindesine but differed with respect to their affinities for other analogues. No significant cross-reactivity of the monomeric alkaloids vindoline or catharanthine was observed with any antibody, and dimeric alkaloids modified in the catharanthine moiety had reduced immunoreactivity. Mouse monoclonal antibodies (Vinca 1 and 3) showed moderate affinity (2.2 X 10(-7) and 5.8 X 10(-9) M) for their respective best ligands and fast kinetics (dissociation rate constants greater than 3 X 10(-3) sec-1). Vinca 4 and 5, derived from the rat X mouse hybrids, had much higher affinities (1.5 X 10(-11) and 1.1 X 10(-11) M) and slower kinetics (dissociation rate constants: 2.4 X 10(-5) and 7.2 X 10(-6) sec-1). The major difference between these two antibodies was that Vinca 4 binds and releases the antigen more rapidly than Vinca 5 does. Somatic hybridization techniques thus generated monoclonal antibodies recognizing a given class of low mol. wt antigens with variable specificity, affinity and kinetic behavior, allowing the selection of reagents most appropriate for particular immunochemical applications.

Biochemical characterization of a vasopressin-like neuropeptide in Locusta migratoria. Evidence of high molecular weight protein encoding vasopressin sequence

The biochemical characterization of a diuretic neurohormone, immunologically related to the mammalian vasopressin (AVP) and present in Locusta migratoria has been performed. The results have been obtained using an AVP radioimmunoassay as method of detection and quantification. The "AVP like" molecule exhibits the same C terminal moiety: the tetrapeptide 1/2 Cys-PrO-Arg-Gly NH2. 125I-radiolabelling allows us to demonstrate the presence of a tyrosyl residue. The molecular weight of this molecule is estimated by gel filtration to 2500 +/- 400 Daltons. The isoelectric point is 7.5 and the electrophoretic migration lead to conclude to the presence of amino acid residues lacking in the vasopressin hormone. We have demonstrated the presence of a vasopressin sequence included in high molecular weight protein which have been quantified in suboesophageal ganglion (biosynthetic site) and in the nervous ventral cord (release site).