The optimization of ELISA for methamphetamine determination: the effect of immunogen, tracer and antibody purification method on the sensitivity

Vaccine development against methamphetamine drug addiction

INTRODUCTION

There are currently no effective treatments for Methamphetamine (METH) addiction and psychotherapy remains the sole treatment option. The development of immunopharmacotherapies for the treatment of drug addiction, overdose, and relapse management appears to be promising alternative and a significant body of information has been generated using various vaccine development strategies. Herein, we present an update on the developments toward anti-METH vaccines and their study outcomes in preclinical and clinical studies.

AREAS COVERED

The scope of this article is to present an update on METH vaccine development strategies such as active vaccination through hapten design and the passive immunization through monoclonal antibodies along with preclinical and clinical studies. The relevant literatures and clinical trial outcomes were searched in databases including Google, Google Scholar, PubMed, Science Direct, ClinicalTrials.gov, and www.anzctr.org.au using specific keywords.

EXPERT OPINION

Significant improvements have been developed for immunopharmacotherapies for METH addiction over the last two decades. However, only one monoclonal antibody candidate has been evaluated in a phase I clinical trial. At this moment, it is essential to evaluate the safety and efficacy of potential candidates in clinical trials to validate the importance of this platform drug-vaccine conjugation in order to manage or overcome METH addiction.

Synthesis of Quenchbodies for One-Pot Detection of Stimulant Drug Methamphetamine

The problem of illicit drug use and addiction is an escalating issue worldwide. As such, fast and precise detection methods are needed to help combat the problem. Herein, the synthesis method for an anti-methamphetamine Quenchbody (Q-body), a promising sensor for use in simple and convenient assays, has been described. The fluorescence intensity of the Q-body generated by two-site labeling of Escherichia coli produced anti-methamphetamine antigen-binding fragment (Fab) with TAMRA-C2-maleimide dyes increased 5.1-fold over background in the presence of a hydroxyl methamphetamine derivative, 3-[(2S)-2-(methylamino)propyl]phenol. This derivative has the closest structure to methamphetamine of the chemicals available for use in a laboratory. Our results indicate the potential use of this Q-body as a novel sensor for the on-site detection of methamphetamine, in such occasions as drug screening at workplace, suspicious substance identification, and monitoring patients during drug rehabilitation.

Ethical Implications in Vaccine Pharmacotherapy for Treatment and Prevention of Drug of Abuse Dependence

Different immunotherapeutic approaches are in the pipeline for the treatment of drug dependence. "Drug vaccines" aim to induce the immune system to produce antibodies that bind to drugs and prevent them from inducing rewarding effects in the brain. Drugs of abuse currently being tested using these new approaches are opioids, nicotine, cocaine, and methamphetamine. In human clinical trials, "cocaine and nicotine vaccines" have been shown to induce sufficient antibody levels while producing few side effects. Studies in humans, determining how these vaccines interact in combination with their target drug, are underway. However, although vaccines can become a reasonable treatment option for drugs of abuse, there are several disadvantages that must be considered. These include i) great individual variability in the formation of antibodies, ii) the lack of protection against a structurally dissimilar drug that produces the same effects as the drug of choice, and iii) the lack of an effect on the drug desire that may predispose an addict to relapse. In addition, a comprehensive overview of several crucial ethical issues has not yet been widely discussed in order to have not only a biological approach to immunotherapy of addiction. Overall, immunotherapy offers a range of possible treatment options: the pharmacological treatment of addiction, the treatment of overdoses, the prevention of toxicity to the brain or the heart, and the protection of the fetus during pregnancy. So far, the results obtained from a small-scale experiment using vaccines against cocaine and nicotine suggest that a number of important technical challenges still need to be overcome before such vaccines can be approved for clinical use.

Antibody purification using affinity chromatography: a case study with a monoclonal antibody to ractopamine

The application of antibodies to small molecules in the field of bioanalytics requires antibodies with stable biological activity and high purity; thus, there is a growing interest in developing rapid, inexpensive and effective procedures to obtain such antibodies. In this work, a ractopamine (RAC) derivative, N-4-aminobutyl ractopamine (ABR), was synthesized for preparing new specific affinity chromatography to purify a murine monoclonal antibody (mAb) against RAC from ascites. The performance of the new specific chromatography was compared with four other purification methods in terms of recovery, purity and biological activity of mAb. These four purification methods were prepared by using specific ligands (RAC and RAC-ovalbumin) and commercial ligands (protein G and protein A), respectively. The results showed that the highest recovery (88.1%) was achieved using the new chromatography; in comparison, the recoveries from the other methods were all below 70%. The purity of the mAbs from the new chromatography was 88.3%, while, the highest purity of 97.6% was from protein G chromatography and the lowest purity of 84.7% was from protein A chromatography. The biological activity of the purified mAb from all of the chromatography methods was comparable in enzyme-linked immunosorbent immunoassay (ELISA).

Vaccines against drugs of abuse: where are we now?

Drug addiction is a serious problem worldwide. One therapy being investigated is vaccines against drugs of abuse. The antibodies elicited against the drug can take up the drug and prevent it from reaching the reward centers in the brain. Few such vaccines have entered clinical trials, but research is going on apace. Many studies are very promising and more clinical trials should be coming out in the near future.

Defunct brain stem cardiovascular regulation underlies cardiovascular collapse associated with methamphetamine intoxication

BACKGROUND

Intoxication from the psychostimulant methamphetamine (METH) because of cardiovascular collapse is a common cause of death within the abuse population. For obvious reasons, the heart has been taken as the primary target for this METH-induced toxicity. The demonstration that failure of brain stem cardiovascular regulation, rather than the heart, holds the key to cardiovascular collapse induced by the pesticide mevinphos implicates another potential underlying mechanism. The present study evaluated the hypothesis that METH effects acute cardiovascular depression by dampening the functional integrity of baroreflex via an action on brain stem nuclei that are associated with this homeostatic mechanism.

METHODS

The distribution of METH in brain and heart on intravenous administration in male Sprague-Dawley rats, and the resultant changes in arterial pressure (AP), heart rate (HR) and indices for baroreflex-mediated sympathetic vasomotor tone and cardiac responses were evaluated, alongside survival rate and time.

RESULTS

Intravenous administration of METH (12 or 24 mg/kg) resulted in a time-dependent and dose-dependent distribution of the psychostimulant in brain and heart. The distribution of METH to neural substrates associated with brain stem cardiovascular regulation was significantly larger than brain targets for its neurological and psychological effects; the concentration of METH in cardiac tissues was the lowest among all tissues studied. In animals that succumbed to METH, the baroreflex-mediated sympathetic vasomotor tone and cardiac response were defunct, concomitant with cessation of AP and HR. On the other hand, although depressed, those two indices in animals that survived were maintained, alongside sustainable AP and HR. Linear regression analysis further revealed that the degree of dampening of brain stem cardiovascular regulation was positively and significantly correlated with the concentration of METH in key neural substrate involved in this homeostatic mechanism.

CONCLUSIONS

We conclude that on intravenous administration, METH exhibits a preferential distribution to brain stem nuclei that are associated with cardiovascular regulation. We further found that the concentration of METH in those brain stem sites dictates the extent that baroreflex-mediated sympathetic vasomotor tone and cardiac responses are compromised, which in turn determines survival or fatality because of cardiovascular collapse.

Bioenergetics failure and oxidative stress in brain stem mediates cardiovascular collapse associated with fatal methamphetamine intoxication

BACKGROUND

Whereas sudden death, most often associated with cardiovascular collapse, occurs in abusers of the psychostimulant methamphetamine (METH), the underlying mechanism is much less understood. The demonstration that successful resuscitation of an arrested heart depends on maintained functionality of the rostral ventrolateral medulla (RVLM), which is responsible for the maintenance of stable blood pressure, suggests that failure of brain stem cardiovascular regulation, rather than the heart, holds the key to cardiovascular collapse. We tested the hypothesis that cessation of brain stem cardiovascular regulation because of a loss of functionality in RVLM mediated by bioenergetics failure and oxidative stress underlies the cardiovascular collapse elicited by lethal doses of METH.

METHODOLOGY/PRINCIPAL FINDINGS

Survival rate, cardiovascular responses and biochemical or morphological changes in RVLM induced by intravenous administration of METH in Sprague-Dawley rats were investigated. High doses of METH induced significant mortality within 20 min that paralleled concomitant the collapse of arterial pressure or heart rate and loss of functionality in RVLM. There were concurrent increases in the concentration of METH in serum and ventrolateral medulla, along with tissue anoxia, cessation of microvascular perfusion and necrotic cell death in RVLM. Furthermore, mitochondrial respiratory chain enzyme activity or electron transport capacity and ATP production in RVLM were reduced, and mitochondria-derived superoxide anion level was augmented. All those detrimental physiological and biochemical events were reversed on microinjection into RVLM of a mobile electron carrier in the mitochondrial respiratory chain, coenzyme Q10; a mitochondria-targeted antioxidant and superoxide anion scavenger, Mito-TEMPO; or an oxidative stress-induced necrotic cell death inhibitor, IM-54.

CONCLUSION

We conclude that sustained anoxia and cessation of local blood flow that leads to bioenergetics failure and oxidative stress because of mitochondrial dysfunction, leading to acute necrotic cell death in RVLM underpins cardiovascular collapse elicited by lethal doses of METH.

Effects of the competitor on antibody-hapten binding in immunoassays

The effects of competitors on antibody (Ab)-hapten binding in an immunoassay were investigated using a goat antimethamphetamine (MA) antibody (Ab). An N-4-aminobutyl derivative of methamphetamine (4-ABMA) was conjugated with keyhole limpet hemocyanine (KLH) and used as an immunogen. The antiserum was purified by affinity chromatography with various ligands, including 4-ABMA-protein conjugates, free haptens, and protein G. Direct and indirect competitive enzyme-linked immunosorbent assays (ELISA) were conducted with a competitor of 4-ABMA-fluorescein isothiocyanate (4-ABMA-FITC). The results were compared to those of ELISA with a different competing antigen, 4-ABMA-ovalbumin (4-ABMA-OVA), in terms of sensitivity and specificity. In both direct and indirect assay formats, the sensitivity was much improved with 4-ABMA-FITC, compared to that with 4-ABMA-OVA, suggesting that different labels on the same haptenic moiety for competitors considerably influence the assay performance. All the purified Abs also showed a distinct feature of strong affinity for benzphetamine with 4-ABMA-FITC, whereas they had their respective binding specificities with 4-ABMA-OVA. Comparing the results to those from other assay systems, we determined that the assay sensitivity was dependent on both the system and the competitor employed, and that the specificity was primarily dependent on the competitor used.

Influence of the antibody purification method on immunoassay performance: hapten-antibody binding in accordance with the structure of the affinity column ligand

The effects of ligands for immunoaffinity chromatography on the immunoassay were investigated with three goat anti-methamphetamine (anti-MA) antibodies (Abs). An N-4-aminobutyl derivative of methamphetamine (4-ABMA) was conjugated with proteins and used as immunogens. All the antisera produced were purified by affinity chromatography with various ligands of 4-ABMA-proteins and of haptens as well as protein G: 4-ABMA-bovine serum albumin (4-ABMA-BSA), 4-ABMA-keyhole limpet hemocyanine (4-ABMA-KLH), 4-ABMA-ovalbumin (4-ABMA-OVA), MA, 4-ABMA, and amphetamine were used as ligands. Enzyme-linked immunosorbent assay (ELISA) was conducted to examine characteristics of the purified Abs with the 4-ABMA-OVA competitor coated. The results obtained revealed that characters of the purified Abs were closely related with chemical structures of ligands used. The Abs from the MA and the amphetamine columns showed better sensitivities than those from the others in each antiserum. Particularly, the Ab from the amphetamine column gave the best results in terms of sensitivity and specificity. The recognition or the affinity of the Ab selected was considered to be affected by the structure of the ligand concerned. These results suggest that the Ab purification method should be considered as an important parameter which has great influence on the performance of immunoassays with polyclonal Abs.

Production and characterization of monoclonal antibodies specific to atrazine group compounds: effects of coating ligand structure on the variation of sensitivity and specificity

Hybridoma cells were prepared by immunizing mice with carboxylic derivatives of atrazine conjugate to bovine serum albumin. After the screening of culture supernatant of hybridomas, five cell lines producing monoclonal antibodies were established and 1.8-5.3 ml of ascitic fluid per mouse was obtained from each cell line. The protein A affinity purification yielded 0.35-0.65 mg per ml of ascitic fluid from each cell line. The characterization studies in terms of sensitivity and specificity indicate that MAb 2F9 and MAb 4B9 showed the best responses with atrazine and its group of ametryne and cyanazine, using microtiter plate coated with simazine derivative of 6-amino hexanoic acid; no cross-reactivity was shown with simazine and cyanuric chloride.

Comparison of capillary electrophoresis-based immunoassay with fluorescence polarization immunoassay for the immunodetermination of methamphetamine using various methamphetamine antibodies

An accurate and simple immunoassay using capillary electrophoresis (CE) with laser-induced fluorescence (LIF) was performed for the detection of methamphetamine (MA) in urine. The CE-LIF was conducted with an untreated fused-silica column using antiserum and a tracer of fluorescein isothiocyanate (FITC)-labeled MA. This CE-LIF system was compared with fluorescence polarization immunoassay (FPIA) in a TDx analyzer in the photo-check mode using the same FITC-labeled tracer and the same antiserum. Various antibodies, not only those prepared by our own immunogens but also those from commercial sources, were screened and characterized in both assay systems with regard to sensitivity, precision, and cross-reactivity. Both systems satisfied analytical precision and gave similar cross-reactivity patterns. However, the CE-LIF-based immunoassay was approximately one order superior to FPIA in sensitivity, requiring less volume of sample, antiserum, and tracer for the assay. Considering that the FPIA system is well known to be a useful tool for screening antibodies and detecting drugs, the CE-LIF-based immunoassay system, which is seemingly more advantageous than the FPIA system, appears to have great power for the characterization of antibodies and for the detection of MA in urine.

Immunological analysis of methamphetamine antibody and its use for the detection of methamphetamine by capillary electrophoresis with laser-induced fluorescence

An accurate, simple and rapid immunoassay is demonstrated for the detection of methamphetamine in urine by capillary electrophoresis (CE) with laser-induced fluorescence (LIF). An aminobutyl derivative of methamphetamine was conjugated with proteins, and used as an immunogen to produce antibodies for the assay. The methamphetamine derivative was also labeled with fluorescein isothiocyanate (FITC) to compete with free methamphetamine in the sample for the antibody binding site. Levels of free and antibody-bound FITC-labeled methamphetamine were monitored by performing CE-LIF using an untreated fused-silica column. This competitive immunoassay used antiserum instead of purified antibody or antibody fragment, yet was found to have good precision with a sensitivity of lower than 20 ng/ml. Various antibodies were also screened, and cross-reactivity of anti-MA antibody with methamphetamine analogues were also investigated. The results indicate that CE-LIF-based immunoassay is a powerful tool for the screening and characterization of antibody and may have possible applications in the detection of abused drugs in urine.