Identification and biophysical characterization of a novel domain-swapped camelid antibody specific for fentanyl.

Opioid use disorders (OUD) and overdoses are ever-evolving public health threats that continue to grow in incidence and prevalence in the United States and abroad. Current treatments consist of opioid receptor agonists and antagonists, which are safe and effective but still suffer from some limitations. Murine and humanized monoclonal antibodies (mAb) have emerged as an alternative and complementary strategy to reverse and prevent opioid-induced respiratory depression. To explore antibody applications beyond traditional heavy-light chain mAbs, we identified and biophysically characterized a novel single-domain antibody specific for fentanyl from a camelid variable-heavy-heavy (VHH) domain phage display library. Structural data suggested that VHH binding to fentanyl was facilitated by a unique domain-swapped dimerization mechanism, which accompanied a rearrangement of complementarity-determining region loops leading to the formation of a fentanyl-binding pocket. Structure-guided mutagenesis further identified an amino acid substitution that improved the affinity and relaxed the requirement for dimerization of the VHH in fentanyl binding. Our studies demonstrate VHH engagement of an opioid and inform on how to further engineer a VHH for enhanced stability and efficacy, laying the groundwork for exploring the in vivo applications of VHH-based biologics against OUD and overdose.

Developing Translational Vaccines against Heroin and Fentanyl through Investigation of Adjuvants and Stability.

The nearly insurmountable adversity that accompanies opioid use disorder (OUD) creates life-altering complications for opioid users. To worsen matters, existing small-molecule drugs continue to inadequately address OUD due to their engagement of the opioid receptor, which can leave the user to deal with side effects and financial hardships from their repeated use. An alternative therapeutic approach utilizes endogenously generated antibodies through active vaccination to reduce the effect of opioids without modulating the opioid receptor. Here, we explore different adjuvants and storage conditions to improve opioid vaccine efficacy and shelf life. Our results revealed that inulin-based formulations (Advax) containing a CpG oligodeoxynucleotide (ODN) acted as effective adjuvants when combined with a heroin conjugate: immunized mice showed excellent recovery from heroin-induced antinociception accompanied by high titer, high opioid affinity serum antibodies similar to the immunopotentiating properties of traditional alum-based adjuvants. Moreover, nonhuman primates vaccinated with a heroin/fentanyl combination vaccine demonstrated potent antibody responses against opioids when formulated with both inulin and alum adjuvants. Finally, storing a freeze-dried opioid vaccine formulation maintained efficacy for up 1 year at room temperature. The results from our studies represent an advance toward a clinically feasible opioid vaccine.

Monoclonal Antibodies Counteract Opioid-Induced Behavioral and Toxic Effects in Mice and Rats.

Monoclonal antibodies (mAbs) and vaccines have been proposed as medical countermeasures to treat opioid use disorder (OUD) and prevent opioid overdose. In contrast to current pharmacotherapies (e.g., methadone, buprenorphine, naltrexone, and naloxone) for OUD and overdose, which target brain opioid receptors, mAbs and vaccine-generated polyclonal antibodies sequester the target opioid in the serum and reduce drug distribution to the brain. Furthermore, mAbs offer several potential clinical benefits over approved medications, such as longer serum half-life, higher selectivity, reduced side effects, and no abuse liability. Using magnetic enrichment to isolate opioid-specific B cell lymphocytes prior to fusion with myeloma partners, this study identified a series of murine hybridoma cell lines expressing mAbs with high affinity for opioids of clinical interest, including oxycodone, heroin and its active metabolites, and fentanyl. In mice, passive immunization with lead mAbs against oxycodone, heroin, and fentanyl reduced drug-induced antinociception and the distribution of the target opioid to the brain. In mice and rats, mAb pretreatment reduced fentanyl-induced respiratory depression and bradycardia, two risk factors for opioid-related overdose fatality. Overall, these results support use of mAbs to counteract toxic effects of opioids and other chemical threats. SIGNIFICANCE STATEMENT: The incidence of fatal overdoses due to the widespread access to heroin, prescription opioids, and fentanyl suggests that current Food and Drug Administration-approved countermeasures are not sufficient to mitigate the opioid epidemic. Monoclonal antibodies (mAbs) may provide acute protection from overdose by binding to circulating opioids in serum. Use of mAbs prophylactically, or after exposure in combination with naloxone, may reduce hospitalization and increase survival.

Heat shock proteins: A dual carrier-adjuvant for an anti-drug vaccine against heroin.

Heroin is a highly abused opioid that has reached epidemic status within the United States. Yet, existing therapies to treat addiction are inadequate and frequently result into rates of high recidivism. Vaccination against heroin offers a promising alternative therapeutic option but requires further development to enhance the vaccine's performance. Hsp70 is a conserved protein with known immunomodulatory properties and is considered an excellent immunodominant antigen. Within an antidrug vaccine context, we envisioned Hsp70 as a potential dual carrier-adjuvant, wherein immunogenicity would be increased by co-localization of adjuvant and antigenic drug hapten. Recombinant Mycobacterium tuberculosis Hsp70 was appended with heroin haptens and the resulting immunoconjugate granted anti-heroin antibody production and blunted heroin-induced antinociception. Moreover, Hsp70 as a carrier protein surpassed our benchmark Her-KLH cocktail through antibody-mediated blockade of 6-acetylmorphine, the main mediator of heroin's psychoactivity. The work presents a new avenue for exploration in the use of hapten-Hsp70 conjugates to elicit anti-drug immune responses.

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 Strategy for the determination of hapten-induced antibody affinities using Microscale thermophoresis.

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.

Chronic Pain and Decreased Opioid Efficacy: An Inflammatory Link.

Chronic pain is a devastating amalgam of symptoms that affects millions of Americans at tremendous cost to our healthcare system and, more importantly, to patients' quality of life. Literature and research demonstrate that neuroimmune cells called glia are not only responsible for initiating and maintaining part of the chronic pain disease process, but also release inflammatory molecules responsible for decreasing the efficacy of one of the most prominent treatments for pain, opioid analgesia. This article describes chronic pain as a disease process that has ineffective treatment modalities, explores the mechanisms of glial cell activation and inflammatory responses that lead to chronic pain and decreased opioid treatment efficacy, and hypothesizes novel chronic pain treatment modalities based on the glial cell inactivation and anti-inflammatory pathways.

Effects of opioids on immunologic parameters that are relevant to anti-tumour immune potential in patients with cancer: a systematic literature review.

BACKGROUND: The immune system has a central role in controlling cancer, and factors that influence protective antitumour immunity could therefore have a significant impact on the course of malignant disease. Opioids are essential for the management of cancer pain, and preclinical studies indicate that opioids have the potential to influence these tumour immune surveillance mechanisms. The aim of this systematic literature review is to evaluate the clinical effects of opioids on the immune system of patients with cancer. METHODS: A systematic search of Ovid MEDLINE (PubMed) and Embase, Cochrane database and Web of Knowledge for clinical studies, which evaluated the effects of opioids on the immune system in patients with cancer, was performed. RESULTS: Five human studies, which have assessed the effects of opioids on the immune system in patients with cancer, were identified. Although all of these evaluated the effect of morphine on immunologic end points in patients with cancer, none measured the clinical effects. CONCLUSIONS: Evidence from preclinical, healthy volunteer and surgical models suggests that different opioids variably influence protective anti-tumour immunity; however, actual data derived from cancer populations are inconclusive and definitive recommendations cannot be made. Appropriately designed and powered studies assessing clinical outcomes of opioid use in people with cancer are therefore required to inform oncologists and others involved in cancer care about the rational use of opioids in this patient group.

Utility of opium seed extract tests in preventing hypersensitivity reactions during surgery.

BACKGROUND: Anaphylaxis during anaesthesia is fatal in 3-9% of patients and analgesics, including opioids, and is the second most common medicament-related cause, although the prevalence is underestimated. We recently found that patients may generate IgE antibodies to opium seeds. OBJECTIVES: To determine the diagnostic accuracy of specific antibodies to morphine, codeine, rocuronium and oil body and aqueous fractions of Papaver somniferum seeds in the diagnosis and prevention of allergy to opioids. METHODS: Patients with hypersensitivity reactions during surgery, and severe clinical allergy (pollen, tobacco), and illicit heroin users were selected. The sensitivity, specificity and predictive values of in vivo and in vitro diagnostic techniques including oil body and aqueous fractions of P. somniferum seeds were measured. RESULTS: We studied 203 patients, with mean age 35.1±17.1 and 200 healthy controls. Patients sensitised to heroin or with hypersensitivity reactions during surgery responded to P. somniferum seed tests. Of patients not known to be sensitised to opioids, the highest positivity was in patients sensitised to tobacco (p<0.001). Opium seed skin tests and IgE, especially the oil body fraction, were more sensitive (64.2%) and specific (98.4%) than morphine, codeine and rocuronium tests for opioid sensitivity. Pollen allergy was not a risk factor for sensitisation to morphine. CONCLUSIONS: Sensitivity to opioids and intraoperative anaphylaxis can be diagnosed by routine tests. IgE and skin tests for the oil body fraction of P. somniferum had the highest sensitivity for sensitisation to opioids.

Opioids and immune modulation: more questions than answers.

Opioid addicts are more likely to present with infections suggesting opioids are immune modulators. The potential sites/mechanism(s) for this modulation are controversial and on close inspection not well supported by the current literature. It has long been assumed that opioid-induced immune modulation occurs via a combination of direct actions on the immune cell itself, via the hypothalamic-pituitary-adrenal (HPA) axis, or both. Opioid receptors are classified as MOP (µ, mu), DOP (δ, delta), and KOP (κ, kappa)--classical naloxone sensitive receptors--or NOP (the receptor for nociceptin/orphanin FQ), which is naloxone insensitive. Opioids currently used in clinical practice predominantly target the MOP receptor. There do not appear to be classical opioid receptors present on immune cells. The evidence for HPA activation is also poor and shows some species dependence. Most opioids used clinically or as drugs of abuse do not target the NOP receptor. Other possible target sites for immune modulation include the sympathetic nervous system and central sites. We are currently unable to accurately define the cellular target for immune modulation and suggest further investigation is required. Based on the differences observed when comparing studies in laboratory animals and those performed in humans we suggest that further studies in the clinical setting are needed.

A Vaccine against Benzimidazole-Derived New Psychoactive Substances That Are More Potent Than Fentanyl.

New psychoactive substance (NPS) opioids have proliferated within the international drug market. While synthetic opioids are traditionally composed of fentanyl analogues, benzimidazole-derived isotonitazene and its derivatives are the current NPS opioids of concern. Hence, in this study, we implement immunopharmacotherapy wherein antibodies are produced with high titers and nanomolar affinity to multiple benzimidazole-derived NPS opioids (BNO). Notably, these antibodies blunt psychoactive and physiological repercussions from BNO exposure, which was observed through antinociception, whole-body plethysmography, and blood-brain biodistribution studies. Moreover, we detail previously unreported pharmacokinetics of these drugs, which explains the struggle of traditional pharmaceutical opioid antagonists against BNO substances. These findings provide further insight into the in vivo effects of BNO drugs and the development of effective broad-spectrum therapeutics against NPS opioids.

The immunomodulatory effects of opioids and implications for intensive care unit populations.

Analgesia within the intensive care unit (ICU) is often achieved via the utilization of opioids in alignment with current guidelines. Recent evidence has not only demonstrated the potential impact of opioids in suppression of immune function, but also the potential harm of immunosuppression of patients within the ICU. Despite the potential immunosuppression seen with opioids in this at-risk population, their use remains frequent. In this review, we highlight the potential immunomodulatory impact of opioids within the critically ill and considerations for their use.

Modulatory Potential of Cannabidiol on the Opioid-Induced Inflammatory Response.

Opioids are effective analgesics; however, there are many negative consequences of chronic use. One important side effect of chronic opioid use is the continuous engagement of the immune response that can exacerbate chronic pain. The opioid, morphine, initiates a Toll-like receptor 4 (TLR4) signaling cascade that drives the activation of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome proteins, resulting in cytokine production and effectively creating a positive feedback loop for continuous TLR4 activation. In addition to driving cytokine production, morphine drives changes in proinflammatory lipid signaling. The alteration of both cytokine and lipid signaling systems by morphine suggests that its chronic use leads to a pathological immune response that would benefit from targeted therapy. Engaging the endogenous cannabinoid system has shown therapeutic benefit, particularly regarding its anti-inflammatory and immunosuppressive effects. Promising preclinical and clinical investigations suggest that cannabidiol (CBD) is an effective adjuvant for treatment of symptoms of opioid use disorders; however, the mechanism through which CBD drives this outcome is unclear. One potential source of insight into this mechanism is in how CBD regulates immune regulators such as cytokines and lipid signaling systems, including endocannabinoids and related immune-responsive lipids. In this review, we outline the immune response to chronic opioid use as well as CBD in the context of a lipopolysaccharide-induced immune response and speculate on the mechanism of CBD as a modulator of chronic opioid-induced immune system dysregulation.

Effect of the morphine/heroin vaccine on opioid and non-opioid drug-induced antinociception in mice.

Pain is a common symptom in patients with opioid use disorder (OUD), which increases synthetic and illicit synthetic opioid abuse and even fatalities due to opioid overdose. Many FDA-approved drugs are available for the treatment of OUD, however, the use of these medications is limited, mainly due to the development of various side effects. Active vaccination is a new therapeutic approach but the resulting antibodies may compromise the use and efficiency of opioid and non-opioid drugs. In this study, we evaluated whether the antibodies produced by the morphine/heroin vaccine (M-TT) would alter the antinociceptive effects of opioid and non-opioid drugs. Female Balb-c mice were immunized with the M-TT vaccine. A solid-phase antibody-capture ELISA was used for monitoring antibody titer responses after each booster dose in vaccinated animals, followed by tail-flick testing. This study found that the M-TT vaccine did not affect the antinociception induced by different doses of morphine or the ability of non-opioid and synthetic opioid drugs to decrease thermal pain. Moreover, the combination of vaccination and naloxone increased the time-course of morphine antagonism relative to either vaccination or naloxone alone. These results suggest that the antibody titers generated by the M-TT vaccine 1) are capable of reducing morphine-induced antinociception and 2) are selective enough not to alter antinociception induced by non-opioid or synthetic drugs. These characteristics support its potential as a treatment agent for patients with symptoms of pain comorbid to OUD.

Evaluation of Murine Macrophage Cytokine Production After In Vivo Morphine Treatment.

The discovery of opioid receptor expression on immune cells has originated a large research activity on the possible modulation by opioid drugs of immune system responses. In this chapter we describe an easy methodology useful to obtain information about the potential immunomodulatory activity of opioid drugs. An in vivo treatment schedule is used, and macrophages are studied for their ability to release different cytokines.

Measurement of Macrophage Toll-Like Receptor 4 Expression After Morphine Treatment.

The immune system is a complex and finely orchestrated system, and many soluble molecules and receptors contribute to its regulation.Recent studies have suggested that many of the modulatory effects induced by morphine on innate immunity, and in particular the effects on macrophage activation and function, can be due to the modulation of an important macrophage surface receptor, the toll-like receptor (TLR), that is primarily involved in early regulatory steps. In this chapter we describe a RT-real-time PCR method for assessing TLR expression in macrophage after in vivo morphine treatment.

Immune cell-mediated opioid analgesia.

Pathological pain is regulated by a balance between pro-algesic and analgesic mechanisms. Interactions between opioid peptide-producing immune cells and peripheral sensory neurons expressing opioid receptors represent a powerful intrinsic pain control in animal models and in humans. Therefore, treatments based on general suppression of immune responses have been mostly unsuccessful. It is highly desirable to develop strategies that specifically promote neuro-immune communication mediated by opioids. Promising examples include vaccination-based recruitment of opioid-containing leukocytes to painful tissue and the local reprogramming of pro-algesic immune cells into analgesic cells producing and secreting high amounts of opioid peptides. Such approaches have the potential to inhibit pain at its origin and be devoid of central and systemic side effects of classical analgesics. In support of these concepts, in this article, we describe the functioning of peripheral opioid receptors, migration of opioid-producing immune cells to inflamed tissue, opioid peptide release, and the consequent pain relief. Conclusively, we provide clinical evidence and discuss therapeutic opportunities and challenges associated with immune cell-mediated peripheral opioid analgesia.

Validation and Cross-Reactivity Data for Fentanyl Analogs With the Immunalysis Fentanyl ELISA.

Every year new fentanyl analog compounds, or fentanyls, appear on the drug scene. Development of immunoassays dedicated for screening individual molecules is challenging due to the short-lived presence of these compounds on the recreational drug market. Therefore, we investigated the detecting capabilities of the immunalysis fentanyl direct enzyme-linked immunosorbent assay (ELISA) kit against fentanyl in whole blood, and determined the cross-reactivity of nine fentanyl analogs (2-fluorofentanyl, acetylfentanyl, acrylfentanyl, carfentanil, cyclopropylfentanyl, tetrahydrofuranylfentanyl, furanylfentanyl, ocfentanil, valerylfentanyl) to confirm its validity for the general screening of fentanyls. Immunalysis ELISA assay was used to test whole blood samples fortified with fentanyl on a TECAN Freedom EVOlyzer platform, according to manufacturer specifications. The kit successfully was validated for fentanyl screening with a cutoff set at 0.5 ng/mL, and all tested analogs, with the exclusion of carfentanil, were detected. The lowest cross-reactivity with the kit was obtained with furanylfentanyl (20% ± 1, 95% confidence intervals (CI)) and 4-fluoroisobutyrfentanyl (25% ± 1, 95% CI), while the highest was recorded using acetylfentanyl (99% ± 11, 95% CI) and acrylfentanyl (94% ± 10, 95% CI). Post-mortem samples containing fentanyl, acrylfentanyl, cyclopropylfentanyl, THF-fentanyl and 4-fluoroisobutyrfentanyl were screened, and sensitivity and specificity of each analog were calculated. Positive screening results were generated by all post-mortem cases containing fentanyl (n = 14), acrylfentanyl (n = 11), cyclopropylfentanyl (n = 14), tetrahydrofuranylfentanyl (n = 13) and 4-fluoroisobutyrfentanyl (n = 10). Concentration of post-mortem fentanyl samples ranged from 0.5 ng/mL (cutoff) to 230 ng/mL, while the range for analogs was 3.4-36 ng/mL (cyclopentylfentanyl), 0.76-370 ng/mL (4-fluoroisobutyrfentanyl), 0.02-12 ng/mL (acrylfentanyl) and 2-26 ng/mL (tetrahydrofuranylfentanyl). The immunalysis fentanyl direct ELISA kit was successfully validated and showed significant cross-reactivity for all tested fentanyls, except carfentanil, making it a suitable technique for fentanyl and fentanyl analogs screening.

Vaccine blunts fentanyl potency in male rhesus monkeys.

One proposed factor contributing to the increased frequency of opioid overdose deaths is the emergence of novel synthetic opioids, including illicit fentanyl and fentanyl analogues. A treatment strategy currently under development to address the ongoing opioid crisis is immunopharmacotherapies or opioid-targeted vaccines. The present study determined the effectiveness and selectivity of a fentanyl-tetanus toxoid conjugate vaccine to alter the behavioral effects of fentanyl and a structurally dissimilar mu-opioid agonist oxycodone in male rhesus monkeys (n = 3-4). Fentanyl and oxycodone produced dose-dependent suppression of behavior in an assay of schedule-controlled responding and antinociception in an assay of thermal nociception (50 °C). Acute naltrexone (0.032 mg/kg) produced an approximate 10-fold potency shift for fentanyl to decrease operant responding. The fentanyl vaccine was administered at weeks 0, 2, 4, 9, 19, and 44 and fentanyl or oxycodone potencies in both behavioral assays were redetermined over the course of 49 weeks. The vaccine significantly and selectively shifted fentanyl potency at least 10-fold in both assays at several time points over the entire experimental period. Mid-point titer levels correlated with fentanyl antinociceptive potency shifts. Antibody affinity for fentanyl as measured by a competitive binding assay improved over time to approximately 3-4 nM. The fentanyl vaccine also increased fentanyl plasma levels approximately 6-fold consistent with the hypothesis that the vaccine sequesters fentanyl in the blood. Overall, these results support the continued development and evaluation of this fentanyl vaccine in humans to address the ongoing opioid crisis.