Characterization and optimization of heroin hapten-BSA conjugates: method development for the synthesis of reproducible hapten-based vaccines

On-line screening and verification of haptens in Xiangdan injection combining chemical analysis with activity detection

Xiangdan injection (XDI), as a well-known traditional Chinese medicine injection, is of great significance to treat cardiovascular and cerebrovascular diseases. The haptens causing allergic reactions are urged to be detected due to the adverse reaction. In this study, an efficient approach was established to rapidly identify and screen potential haptens in XDI for the first time by combining high performance liquid chromatography-diode array detector-electrospray ionization-ion trap-time of flight-mass spectrometry with human serum albumin-fluorescence detector (HPLC-DAD-ESI-IT-TOF-MS-HSA-FLD). 21 compounds were identified according to their mass spectrum or comparison with reference substances and 8 salvianolic acids in XDI showed interactions with HSA in varying degrees. After that, surface plasmon resonance (SPR) was applied to screen the compounds showing specific affinity with human serum albumin (HSA). Subsequently, active systemic anaphylaxis (ASA) in guinea pigs was carried out to verify the sensitization of active compounds, In the meantime the serum IgE level before and after challenge was measured by the enzyme-linked immunosorbent assay (ELISA). Ultimately, it was tested that salvianolic acid C had a strong sensitization, in addition, lithospermic acid, rosmarinic acid and salvianolic acid B had potential sensitization. This study suggest that the on-line method provides rapid preliminary searching for haptens in XDI, combined with SPR and ASA, offering an efficient, rapid and comprehensive approach to screen haptens.

Modular Set of Reagents in Lateral Flow Immunoassay: Application for Antibiotic Neomycin Detection in Honey

A scheme of modular competitive immunochromatography with an analyte-independent test strip and changeable specific immunoreactants has been proposed. Native (detected) and biotinylated antigens interact with specific antibodies during their preincubation in solution, that is, without the immobilization of reagents. After this, the detectable complexes on the test strip are formed by the use of streptavidin (which binds biotin with high affinity), anti-species antibodies, and immunoglobulin-binding streptococcal protein G. The technique was successfully applied for the detection of neomycin in honey. The visual and instrumental detection limits were 0.3 and 0.014 mg/kg, respectively, and the degree of neomycin revealed in honey samples varied from 85% to 113%. The efficiency of the modular technique with the use of the same test strip for different analytes was confirmed for streptomycin detection. The proposed approach excludes the necessity of finding the condition of immobilization for each new specific immunoreactant and transferring the assay to other analytes by a simple choice of concentrations for preincubated specific antibodies and the hapten-biotin conjugate.

Design, Synthesis, and In Vivo Evaluation of C1-Linked 4,5-Epoxymorphinan Haptens for Heroin Vaccines

In our continuing effort to develop effective anti-heroin vaccines as potential medications for the treatment of opioid use disorder, herein we present the design and synthesis of the haptens: 1-AmidoMorHap (1), 1-AmidoMorHap epimer (2), 1 Amido-DihydroMorHap (3), and 1 Amido-DihydroMorHap epimer (4). This is the first report of hydrolytically stable haptenic surrogates of heroin with the attachment site at the C1 position in the 4,5-epoxymorophinan nucleus. We prepared respective tetanus toxoid (TT)–hapten conjugates as heroin vaccine immunogens and evaluated their efficacy in vivo. We showed that all TT–hapten conjugates induced high antibody endpoint titers against the targets but only haptens 2 and 3 can induce protective effects against heroin in vivo. The epimeric analogues of these haptens, 1 and 4, failed to protect mice from the effects of heroin. We also showed that the in vivo efficacy is consistent with the results of the in vitro drug sequestration assay. Attachment of the linker at the C1 position induced antibodies with weak binding to the target drugs. Only TT-2 and TT-3 yielded antibodies that bound heroin and 6-acetyl morphine. None of the TT–hapten conjugates induced antibodies that cross-reacted with morphine, methadone, naloxone, or naltrexone, and only TT-3 interacted weakly with buprenorphine, and that subtle structural difference, especially at the C6 position, can vastly alter the specificity of the induced antibodies. This study is an important contribution in the field of vaccine development against small-molecule targets, providing proof that the chirality at C6 in these epoxymorphinans is a vital key to their effectiveness.

Progress in Immunoassays of Toxic Alkaloids in Plant-Derived Medicines: A Review

Plants are the cradle of the traditional medicine system, assuaging human or animal diseases, and promoting health for thousands of years. However, many plant-derived medicines contain toxic alkaloids of varying degrees of toxicity that pose a direct or indirect threat to human and animal health through accidental ingestion, misuse of plant materials, or through the food chain. Thus, rapid, easy, and sensitive methods are needed to effectively screen these toxic alkaloids to guarantee the safety of plant-derived medicines. Antibodies, due to their inherent specificity and high affinity, have been used as a variety of analytical tools and techniques. This review describes the antigen synthesis and antibody preparation of the common toxic alkaloids in plant-derived medicines and discusses the advances of antibody-based immunoassays in the screening and detection of toxic alkaloids in plants or other related matrices. Finally, the limitations and prospects of immunoassays for toxic alkaloids are discussed.

Bivalent Conjugate Vaccine Induces Dual Immunogenic Response That Attenuates Heroin and Fentanyl Effects in Mice

Opioid use disorders and fatal overdose due to consumption of fentanyl-laced heroin remain a major public health menace in the United States. Vaccination may serve as a promising potential remedy to combat accidental overdose and to mitigate the abuse potential of opioids. We previously reported the heroin and fentanyl monovalent vaccines carrying, respectively, a heroin hapten, 6-AmHap, and a fentanyl hapten, para-AmFenHap, conjugated to tetanus toxoid (TT). Herein, we describe the mixing of these antigens to formulate a bivalent vaccine adjuvanted with liposomes containing monophosphoryl lipid A (MPLA) adsorbed on aluminum hydroxide. Immunization of mice with the bivalent vaccine resulted in IgG titers of >10⁵ against both haptens. The polyclonal sera bound heroin, 6-acetylmorphine, morphine, and fentanyl with dissociation constants (K_d) of 0.25 to 0.50 nM. Mice were protected from the anti-nociceptive effects of heroin, fentanyl, and heroin +9% (w/w) fentanyl. No cross-reactivity to methadone and buprenorphine was observed in vivo. Naloxone remained efficacious in immunized mice. These results highlighted the potential of combining TT-6-AmHap and TT-para-AmFenHap to yield an efficacious bivalent vaccine that could ablate heroin and fentanyl effects. This vaccine warrants further testing to establish its potential translatability to humans.

Effect of Preexisting Immunity to Tetanus Toxoid on the Efficacy of Tetanus Toxoid-Conjugated Heroin Vaccine in Mice

Opioid use disorder (OUD) is a serious health problem that has dramatically increased over the last decade. Although current therapies for the management of OUD can be effective, they have limitations. The complementary strategy to combat the opioid crisis is the development of a conjugate vaccine to generate high affinity antibodies in order to neutralize opioids in circulation before reaching the brain. The components of an opioid vaccine include an opioid hapten (6-AmHap) that is conjugated to a carrier protein (tetanus toxoid) with the addition of adjuvants (Army Liposome Formulation adsorbed to aluminum hydroxide-ALFA). There is no consensus in the literature as to whether preexisting immunity to the carrier protein may impact the immunogenicity of the conjugate vaccine by inducing an enhanced or suppressed immune response to the hapten. Here, we investigated whether pre-exposure to tetanus toxoid would affect the immunogenicity and efficacy of the heroin vaccine, TT-6-AmHap. Mice were primed with diphtheria, tetanus, and acellular pertussis (DTaP) vaccine at weeks -4 and -2, then immunized with TT-6-AmHap vaccine at weeks 0, 3, and 6. Using ELISA and behavioral assays, we found that preexisting immunity to tetanus toxoid had no influence on the immunogenicity and efficacy of the TT-6-AmHap vaccine.

Synthesis of a deuterated 6-AmHap internal standard for the determination of hapten density in a heroin vaccine drug product

A deuterated hapten was designed and synthesized that will be essential for a future study of residual hapten and stability of a hapten-protein conjugate. This hapten, 6-AmHap, was chosen for a heroin vaccine that is now slated for a Phase 1 clinical trial. A maleimide-thiol bioconjugation strategy was successfully applied to our heroin vaccine to connect the hapten 6-AmHap with an immunogenic carrier protein (tetanus toxoid, TT) through a trityl-protected 3-mercaptopropanamide linker. The antibodies induced by the vaccine have been found to have activity against several opioids, including heroin and its metabolites, and, importantly, leave alternate pain treatment medications such as methadone untouched. To the best of our knowledge, no other hapten for a heroin vaccine has been deuterated, yet this tool may prove to be of great importance in the study of residual hapten during product release and the long-term stability program of a hapten-protein conjugate as part of FDA regulatory requirements. Hydrocodone was the starting material for the synthesis of the deuterated 6-AmHap, with a stable amide at C6 and a 3-mercaptopropanamide linker attached at C3. The desired deuterated product was prepared as the disulfide, 3,3'-disulfanediylbis(N-((7S,7aR,12bS)-7-acetamido-3-[² H₃ ]methyl)-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9-yl)propanamide), that could be easily reduced to form the needed hapten, N-((4aR,7S,7aR,12bS)-7-acetamido-3-[² H₃ ]methyl]-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9-yl)-3-mercaptopropanamide.

Novel Vaccine That Blunts Fentanyl Effects and Sequesters Ultrapotent Fentanyl Analogues

Active immunization is an emerging potential modality to combat fatal overdose amid the opioid epidemic. In this study, we described the design, synthesis, formulation, and animal testing of an efficacious vaccine against fentanyl. The vaccine formulation is composed of a novel fentanyl hapten conjugated to tetanus toxoid (TT) and adjuvanted with liposomes containing monophosphoryl lipid A adsorbed on aluminum hydroxide. The linker and hapten N-phenyl-N-(1-(4-(3-(tritylthio)propanamido)phenethyl)piperidin-4-yl)propionamide were conjugated sequentially to TT using amine-N-hydroxysuccinimide-ester and thiol–maleimide reaction chemistries, respectively. Conjugation was facile, efficient, and reproducible with a protein recovery of >98% and a hapten density of 30–35 per carrier protein molecule. In mice, immunization induced high and robust antibody endpoint titers in the order of >10⁶ against the hapten. The antisera bound fentanyl, carfentanil, cyclopropyl fentanyl, para-fluorofentanyl, and furanyl fentanyl in vitro with antibody-drug dissociation constants in the range of 0.36–4.66 nM. No cross-reactivity to naloxone, naltrexone, methadone, or buprenorphine was observed. In vivo, immunization shifted the antinociceptive dose–response curve of fentanyl to higher doses. Collectively, these preclinical results showcased the desired traits of a potential vaccine against fentanyl and demonstrated the feasibility of immunization to combat fentanyl-induced effects.

Polymer-mediated delivery of vaccines to treat opioid use disorders and to reduce opioid-induced toxicity

Vaccines offer a potential strategy to treat opioid use disorders (OUD) and to reduce the incidence of opioid-related overdoses. Vaccines induce opioid-specific polyclonal antibodies that selectively and effectively bind the target opioid and prevent its distribution across the blood-brain barrier. Because antibody-mediated reduction of drug distribution to the brain reduces drug-induced behavior and toxicity, vaccine efficacy depends on the quantity and quality of the antibody response. This study tested whether polymer-mediated delivery could improve vaccine efficacy against opioids as well as eliminate the need for booster injections normally required for a successful immunization. A series of novel biodegradable biocompatible thermogelling pentablock co-polymers were used to formulate a candidate vaccine against oxycodone in mice and rats. Polymer-based delivery of the anti-oxycodone vaccine was equally or more effective than administration in aluminum adjuvant in generating oxycodone-specific antibodies and in reducing oxycodone-induced effects and oxycodone distribution to the brain in mice and rats. The composition and release kinetics of the polymer formulations determined vaccine efficacy. Specifically, a formulation consisting of three simultaneous injections of the anti-oxycodone vaccine formulated in three different polymers with slow, intermediate, and fast release kinetics was more effective than an immunization regimen consisting of three sequential injections with the vaccine adsorbed on aluminum. The novel three-phased polymer vaccine formulation was effective in blocking oxycodone-induced antinociception, respiratory depression and bradycardia in rats.

A unique algorithm for the determination of peptide-carrier protein conjugation ratio by amino acid analysis using intrinsic internal standard

An N-terminal peptide of the HIV-1 fusion peptide (FP) with eight amino acid residues (FP8) was conjugated to a recombinant Tetanus Toxoid Heavy Chain Fragment C (rTTHc) as a carrier protein to help boosting immunogenicity against HIV-1. In this rapid communication, a unique algorithm to determine FP-rTTHc conjugation ratio was developed based off the amino acid analysis. Five well recovered amino acids (present in both FP and rTTHc) were used to calculate the conjugation ratio, while proline (present only in rTTHc) was identified and utilized as the intrinsic internal standard for normalization. With this calculation, the assay variability was minimized (<20%), especially for conjugates with moderate to low conjugation ratios as being compared to previously reported methods. The approach offers a reliable tool to determine the efficiency of the conjugation reactions for in-process monitoring and for final conjugate product characterization.

Raising antibodies against epoxyscillirosidine, the toxic principle contained in Moraea pallida Bak. (Iridaceae), in rabbits

Moraea pallida Bak. (yellow tulp) poisoning is the most important plant cardiac glycoside toxicosis in South Africa. The toxic principle, a bufadienolide, is 1α, 2α-epoxyscillirosidine. The aim was to investigate the potential to develop a vaccine against epoxyscillirosidine. Epoxyscillirosidine, proscillaridin and bufalin, were successfully conjugated to hen ovalbumin (OVA), bovine serum albumin (BSA) and keyhole limpet haemocyanin (KLH). There was a low immune response following vaccination of adult male New Zealand White rabbits with epoxyscillirosidine-OVA (n = 3) and OVA (n = 3) using Freund's adjuvant in Trial (T) 1. The immune response improved significantly in T2 following doubling of the dose to 0.8 mg/rabbit and changing the adjuvant to Montanide. In T3, the rabbits (n = 15), allocated into 5 equal groups, vaccinated with proscillaridin-BSA, bufalin-BSA, epoxyscillirosidine-KLH, epoxyscillirosidine-BSA and BSA respectively, using Montanide adjuvant, developed antibodies against the administered immunogens, with epoxyscillirosidine-KLH inducing the highest immune response. Proscillaridin and bufalin antibodies cross-reacted with epoxyscillirosidine in an enzyme linked immunosorbent assay. The conjugation methodology will be adjusted in the future to target optimal conjugation efficiency. Additional vaccination will be conducted in search of neutralizing antibodies against the yellow tulp toxin. The cross-reactivity of proscillaridin and bufalin antibodies with epoxyscillirosidine could be studied in future to explore the potential to prevent yellow tulp poisoning.

PCSK9 Hapten Multicopy Displayed onto Carrier Protein Nanoparticle: An Antiatherosclerosis Vaccine

In recent years, various vaccination strategies have shed new light on the treatment of atherosclerosis. Proprotein convertase subtilisin/Kexin type 9 (PCSK9) is a hot target in the development of antiatherosclerosis vaccine. However, the efficacy of conventional PCSK9 is largely limited by poor immunogenicity and low hapten density. Therefore, we hypothesized whether a nanostructure synthesized by self-assembled carrier protein accompanied by multicopy hapten display could improve the efficacy of vaccine. In this study, bovine serum albumin (BSA) was self-assembled into sub-100 nm nanoparticles via an intermolecular disulfide network as the inner core. Then, sequences of PCSK9 were conjugated onto the surface of nanoparticles by "click" chemistry to consequently form an orderly structured of nanovaccine with repetitive hapten display. Compared with conventional PCSK9 peptide vaccine, our immunization study demonstrated that the PCSK9 multicopy display nanovaccine (PMCDN) was able to induce higher titers of PCSK9 antibody and more efficient lymph node drainage and improve endocytosis by antigen presenting cells.

Formulation and Characterization of Conjugate Vaccines to Reduce Opioid Use Disorders Suitable for Pharmaceutical Manufacturing and Clinical Evaluation

This study focused on formulating conjugate vaccines targeting oxycodone and heroin for technology transfer, good manufacturing practice (GMP), and clinical evaluation. Lead vaccines used the highly immunogenic carrier protein keyhole limpet hemocyanin (KLH), which poses formulation problems because of its size. To address this barrier to translation, an oxycodone-based hapten conjugated to GMP-grade subunit KLH (OXY-sKLH) and adsorbed on alum adjuvant was studied with regard to carbodiimide coupling reaction time, buffer composition, purification methods for conjugates, conjugate size, state of aggregation, and protein/alum ratio. Vaccine formulations were screened for post-immunization antibody levels and efficacy in reducing oxycodone distribution to the brain in rats. While larger conjugates were more immunogenic, their size prevented characterization of the haptenation ratio by standard analytical methods and sterilization by filtration. To address this issue, conjugation chemistry and vaccine formulation were optimized for maximal efficacy, and conjugate size was measured by dynamic light scattering prior to adsorption to alum. An analogous heroin vaccine (M-sKLH) was also optimized for conjugation chemistry, formulated in alum, and characterized for potency against heroin in rats. Finally, this study found that the efficacy of OXY-sKLH was preserved when co-administered with M-sKLH, supporting the proof of concept for a bivalent vaccine formulation targeting both heroin and oxycodone. This study suggests methods for addressing the unique formulation and characterization challenges posed by conjugating small molecules to sKLH while preserving vaccine efficacy.

Evaluation of in vitro neutralization of epoxyscillirosidine by antibodies raised in sheep

Intoxication by Moraea pallida Bak. (yellow tulp) in livestock is of great importance in South Africa, ranking top among all plant-induced cardiac glycoside toxicosis. The toxic principle, a bufadienolide, is 1α, 2α-epoxyscillirosidine. Treatment of poisoning is challenging and affected livestock often succumbs due to the stress of handling. Manipulating animals to resist poisoning is a potential management strategy. The goal of this study was to explore the potential to develop a vaccine against epoxyscillirosidine by raising antibodies against epoxyscillirosidine in sheep and to assess the neutralization ability of the antibodies in vitro. Epoxyscillirosidine was successfully conjugated to keyhole limpet haemocyanin (KLH) and bovine serum albumin (BSA) rendering them immunogenic. The sheep, vaccinated with epoxyscillirosidine-KLH conjugate (n = 4) and KLH (n = 2) with Montanide, developed antibodies as determined with an indirect enzyme linked immunosorbent assay (ELISA). Total immunoglobulins from sera of vaccinated and control sheep that were purified and concentrated using ammonium sulphate precipitation were 11,940 and 7850 μg, respectively. The in vitro neutralization assay using the methyl blue tetrazolium bromide (MTT) cell viability assay indicated no significant difference (p > 0.05) between anti-epoxyscillirosidine-KLH and KLH antibodies. Rather, the antibodies seemed to enhance the cytotoxicity of epoxyscillirosidine in H9c2 cells. Thus, it is necessary to develop improved vaccination methods to generate antibodies capable of neutralizing the functional group responsible for epoxyscillirosidine toxicity.

Preclinical Efficacy and Characterization of Candidate Vaccines for Treatment of Opioid Use Disorders Using Clinically Viable Carrier Proteins

Vaccines may offer a new treatment strategy for opioid use disorders and opioid-related overdoses. To speed translation, this study evaluates opioid conjugate vaccines containing components suitable for pharmaceutical manufacturing and compares analytical assays for conjugate characterization. Three oxycodone-based haptens (OXY) containing either PEGylated or tetraglycine [(Gly)₄] linkers were conjugated to a keyhole limpet hemocyanin (KLH) carrier protein via carbodiimide (EDAC) or maleimide chemistry. The EDAC-conjugated OXY(Gly)₄-KLH was most effective in reducing oxycodone distribution to the brain in mice. Vaccine efficacy was T cell-dependent. The lead OXY hapten was conjugated to the KLH, tetanus toxoid, diphtheria cross-reactive material (CRM), as well as the E. coli-expressed CRM (EcoCRM) and nontoxic tetanus toxin heavy chain fragment C (rTTHc) carrier proteins. All vaccines induced early hapten-specific B cell expansion and showed equivalent efficacy against oxycodone in mice. However, some hapten-protein conjugates were easier to characterize for molecular weight and size. Finally, heroin vaccines formulated with either EcoCRM or KLH were equally effective in reducing heroin-induced antinociception and distribution to the brain of heroin and its metabolites in mice. This study identifies vaccine candidates and vaccine components for further development.

A rapid solution-based method for determining the affinity of heroin hapten-induced antibodies to heroin, its metabolites, and other opioids

We describe for the first time a method that utilizes microscale thermophoresis (MST) technology to determine polyclonal antibody affinities to small molecules. Using a novel type of heterologous MST, we have accurately measured a solution-based binding affinity of serum antibodies to heroin which was previously impossible with other currently available methods. Moreover, this mismatch approach (i.e., using a cross-reactive hapten tracer) has never been reported in the literature. When compared with equilibrium dialysis combined with ultra-performance liquid chromatography/tandem mass spectrometry (ED-UPLC/MS/MS), this novel MST method yields similar binding affinity values for polyclonal antibodies to the major heroin metabolites 6-AM and morphine. Additionally, we herein report the method of synthesis of this novel cross-reactive hapten, MorHap-acetamide—a useful analog for the study of heroin hapten–antibody interactions. Using heterologous MST, we were able to determine the affinities, down to nanomolar accuracies, of polyclonal antibodies to various abused opioids. While optimizing this method, we further discovered that heroin is protected from serum esterase degradation by the presence of these antibodies in a concentration-dependent manner. Lastly, using affinity data for a number of structurally different opioids, we were able to dissect the moieties that are crucial to antibody binding. The novel MST method that is presented herein can be extended to the analysis of any ligand that is prone to degradation and can be applied not only to the development of vaccines to substances of abuse but also to the analysis of small molecule/protein interactions in the presence of serum.

Graphical abstract

A Stable Heroin Analogue That Can Serve as a Vaccine Hapten to Induce Antibodies That Block the Effects of Heroin and Its Metabolites in Rodents and That Cross-React Immunologically with Related Drugs of Abuse

An improved synthesis of a haptenic heroin surrogate 1 (6-AmHap) is reported. The intermediate needed for the preparation of 1 was described in the route in the synthesis of 2 (DiAmHap). A scalable procedure was developed to install the C-3 amido group. Using the Boc protectng group in 18 allowed preparation of 1 in an overall yield of 53% from 4 and eliminated the necessity of preparing the diamide 13. Hapten 1 was conjugated to tetanus toxoid and mixed with liposomes containing monophosphoryl lipid A as an adjuvant. The 1 vaccine induced high anti-1 IgG levels that reduced heroin-induced antinociception and locomotive behavioral changes following repeated subcutaneous and intravenous heroin challenges in mice and rats. Vaccinated mice had reduced heroin-induced hyperlocomotion following a 50 mg/kg heroin challenge. The 1 vaccine-induced antibodies bound to heroin and other abused opioids, including hydrocodone, oxycodone, hydromorphone, oxymorphone, and codeine.

Predictable Peptide Conjugation Ratios by Activation of Proteins with Succinimidyl Iodoacetate (SIA)

The small heterobifunctional linker succinimidyl iodoacetate (SIA) was examined for the preparation of peptide–protein bioconjugates with predicable conjugation ratios. For many conjugation protocols, the protein is either treated with a reductant to cleave disulfide bonds or is reacted with thiolation chemicals, such as Traut’s reagent. Both approaches are difficult to control, need individual optimization and often lead to unsatisfactory results. In another popular approach, a heterobifunctional linker with a N-hydroxysuccinimide (NHS) and a maleimide functionality is applied to the protein. After the activation of some lysine ε-amino groups with the NHS ester functionality, a cysteine-containing peptide is attached to the activated carrier protein via maleimide. Particularly, the maleimide reaction leads to some unwanted byproducts or even cleavage of the linker. Many protocols end up with conjugates with unpredictable and irreproducible conjugation ratios. In addition, the maleimide-thiol addition product should be assumed immunogenic in vivo. To avoid these and other disadvantages of the maleimide approach, we examined the known linker succinimidyl iodoacetate (SIA) in more detail and developed two protocols, which lead to peptide–protein conjugates with predefined average conjugation ratios. This holds potential to eliminate tedious and expensive optimization steps for the synthesis of a bioconjugate of optimal composition.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.

Physical characterization of nanoparticle size and surface modification using particle scattering diffusometry

As the field of colloidal science continues to expand, tools for rapid and accurate physiochemical characterization of colloidal particles will become increasingly important. Here, we present Particle Scattering Diffusometry (PSD), a method that utilizes dark field microscopy and the principles of particle image velocimetry to measure the diffusivity of particles undergoing Brownian motion. PSD measures the diffusion coefficient of particles as small as 30 nm in diameter and is used to characterize changes in particle size and distribution as a function of small, label-free, surface modifications of particles. We demonstrate the rapid sizing of particles using three orders-of-magnitude less sample volume than current standard techniques and use PSD to quantify particle uniformity. Furthermore, PSD is sensitive enough to detect biomolecular surface modifications of nanometer thickness. With these capabilities, PSD can reliably aid in a wide variety of applications, including colloid sizing, particle corona characterization, protein footprinting, and quantifying biomolecule activity.

Fragmentation of Injectable Bioadhesive Hydrogels Affords Chemotherapeutic Macromolecules

Implantation of drug delivery depots into or proximal to targeted tissue is an effective method to deliver anticancer drugs in a sustained localized manner. Herein, syringe-injectable polydextran aldehyde (PDA)-based bioadhesive gels are prepared that can locally deliver cytotoxins upon their hydrolytic fragmentation. Adhesive gels are formed by mixing doxorubicin (DOX)-functionalized PDA (DOX-PDA) and bovine serum albumin (BSA) using a dual-barrel syringe. Upon mixing and delivery, the DOX-PDA reacts with the cross-linker BSA as well as the extracellular matrix via imine bond formation to define the cohesive and adhesive properties of the gel, respectively. Resulting gels are mechanically rigid (∼10 kPa) and adherent (adhesive stress ∼ 4 kPa). Once formed, the DOX-PDA-BSA gels undergo slow hydrolytic degradation (>2 months) locally releasing free DOX and DOX-PDA as expected. Surprisingly, we found that macromolecules composed of DOX, PDA, and BSA are also released from the bulk material. These DOX-PDA-BSA macromolecules, along with free DOX and DOX-PDA conjugate, are internalized by A549 lung carcinoma cells, resulting in potent cell death.

Synthesis of Hapten-Protein Conjugate Vaccines with Reproducible Hapten Densities

The ability to prepare hapten-carrier conjugates reproducibly with consistent lot-to-lot hapten densities and protein yields is a critical component of hapten vaccine development. This entails the development of appropriate coupling chemistries that do not cause protein precipitation and the development of methods to quantify hapten density. Recently, extensive efforts have been devoted to design vaccines against drugs of abuse. We describe, herein, a method for conjugation of a morphine-like hapten (MorHap) to tetanus toxoid (TT), which involves conjugation of MorHap to the surface lysines of TT through the N-hydroxysuccinimide portion of a heterobifunctional linker and the subsequent attachment of the thiol on MorHap to the maleimide portion of the cross-linker. Methods are described for the analytical quantification of the hapten density of the conjugates using modified Ellman's test, trinitrobenzenesulfonic acid (TNBS) assay, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS).

A simple nonradioactive method for the determination of the binding affinities of antibodies induced by hapten bioconjugates for drugs of abuse

The accurate analytical measurement of binding affinities of polyclonal antibody in sera to heroin, 6-acetylmorphine (6-AM), and morphine has been a challenging task. A simple nonradioactive method that uses deuterium-labeled drug tracers and equilibrium dialysis (ED) combined with ultra performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) to measure the apparent dissociation constant (K d) of antibodies to 6-AM and morphine is described. The method can readily detect antibodies with K d in the low nanomolar range. Since heroin is rapidly degraded in sera, esterase inhibitors were included in the assay, greatly reducing heroin hydrolysis. MS/MS detection directly measured the heroin in the assay after overnight ED, thereby allowing the quantitation of % bound heroin in lieu of K d as an alternative measurement to assess heroin binding to polyclonal antibody sera. This is the first report that utilizes a solution-based assay to quantify heroin-antibody binding without being confounded by the presence of 6-AM and morphine and to measure K d of polyclonal antibody to 6-AM. Hapten surrogates 6-AcMorHap, 6-PrOxyHap, MorHap, DiAmHap, and DiPrOxyHap coupled to tetanus toxoid (TT) were used to generate high affinity antibodies to heroin, 6-AM, and morphine. In comparison to competition ED-UPLC/MS/MS which gave K d values in the nanomolar range, the commonly used competition enzyme-linked immunosorbent assay (ELISA) measured the 50% inhibition concentration (IC50) values in the micromolar range. Despite the differences in K d and IC50 values, similar trends in affinities of hapten antibodies to heroin, 6-AM, and morphine were observed by both methods. Competition ED-UPLC/MS/MS revealed that among the five TT-hapten bioconjugates, TT-6-AcMorHap and TT-6-PrOxyHap induced antibodies that bound heroin, 6-AM, and morphine. In contrast, TT-MorHap induced antibodies that poorly bound heroin, while TT-DiAmHap and TT-DiPrOxyHap induced antibodies either did not bind or poorly bound to heroin, 6-AM, and morphine. This simple and nonradioactive method can be extended to other platforms, such as oxycodone, cocaine, nicotine, and methamphetamine for the selection of the lead hapten design during substance abuse vaccine development.

The Rapid Screening of Triazophos Residues in Agricultural Products by Chemiluminescent Enzyme Immunoassay

A highly sensitive chemiluminescent enzyme immunoassay (CLEIA) method was developed in this study for efficient screening of triazophos residues in a large number of samples. Based on the maximum residue limits (MRLs) set by China and CAC for triazophos in different agro-products, the representative apple, orange, cabbage, zucchini, and rice samples were selected as spiked samples, and the triazophos at the concentrations of the MRL values were spiked to blank samples. Subsequently, the five samples with the spiked triazophos standard were measured by CLEIA 100 times, and the detection results indicated that the correction factors of the apple, orange, cabbage, zucchini, and rice were determined as 0.79, 0.66, 0.85, 0.76, and 0.91, respectively. In this experiment, 1500 real samples were detected by both the CLEIA and the GC-MS methods. With the GC-MS method, 1462 samples were identified as negative samples and 38 samples as positive samples. Based on the correction factors, the false positive rate of the CLEIA method was 0.13%, and false negative rate was 0. The results showed that the established CLEIA method could be used to screen a large number of real samples.

Efficacy, but not antibody titer or affinity, of a heroin hapten conjugate vaccine correlates with increasing hapten densities on tetanus toxoid, but not on CRM197 carriers

Vaccines against drugs of abuse have induced antibodies in animals that blocked the biological effects of the drug by sequestering the drug in the blood and preventing it from crossing the blood-brain barrier. Drugs of abuse are too small to induce antibodies and, therefore, require conjugation of drug hapten analogs to a carrier protein. The efficacy of these conjugate vaccines depends on several factors including hapten design, coupling strategy, hapten density, carrier protein selection, and vaccine adjuvant. Previously, we have shown that 1 (MorHap), a heroin/morphine hapten, conjugated to tetanus toxoid (TT) and mixed with liposomes containing monophosphoryl lipid A [L(MPLA)] as adjuvant, partially blocked the antinociceptive effects of heroin in mice. Herein, we extended those findings, demonstrating greatly improved vaccine induced antinociceptive effects up to 3% mean maximal potential effect (%MPE). This was obtained by evaluating the effects of vaccine efficacy of hapten 1 vaccine conjugates with varying hapten densities using two different commonly used carrier proteins, TT and cross-reactive material 197 (CRM197). Immunization of mice with these conjugates mixed with L(MPLA) induced very high anti-1 IgG peak levels of 400-1500 μg/mL that bound to both heroin and its metabolites, 6-acetylmorphine and morphine. Except for the lowest hapten density for each carrier, the antibody titers and affinity were independent of hapten density. The TT carrier based vaccines induced long-lived inhibition of heroin-induced antinociception that correlated with increasing hapten density. The best formulation contained TT with the highest hapten density of ≥30 haptens/TT molecule and induced %MPE of approximately 3% after heroin challenge. In contrast, the best formulation using CRM197 was with intermediate 1 densities (10-15 haptens/CRM197 molecule), but the %MPE was approximately 13%. In addition, the chemical synthesis of 1, the optimization of the conjugation method, and the methods for the accurate quantification of hapten density are described.