Novel protein-based solutions for organophosphorus nerve agent detection and elimination

Organophosphorus (OP) nerve agents are some of the deadliest chemicals ever synthesized by man. These toxins, which include sarin, soman, cyclosarin, tabun, and VX, inhibit the neurotransmitter-regulating enzyme, acetylcholinesterase (AChE). This leads to continual acetylcholine muscarinic and nicotinic receptor stimulus and may eventually result in death due to prolonged muscles contraction and diaphragm incapacitation. Current treatments for OP poisoning include injections of atropine, to dampen acetylcholine stimulation, a strong-nucleophile oxime, such a 2-pralidoxime, to reactivate inhibited AChE, and diazepam for seizures. These treatments are limited, however, because they do not protect against poisoning, cannot be administered prior to exposure, and don't address the long-term side effects associated with nerve agent poisoning. Additionally, there is no broad-spectrum oxime effective against all nerve agents. A better therapeutic would be a prophylactic molecule capable of catalytically degrading the OP prior to AChE inhibition. Protein-based therapeutics are an emerging remedy for OP toxicity. It has been shown that pre-administration of excess AChE in mice can protein against 8-10 normally lethal doses of soman. Current enzyme therapeutics can be categorized as either stoichiometric or catalytic. Stoichiometric OP binders, such as AChE or the homologous butyrylcholinesterase (BChE), benefit from nanomolar (nM) dissociation constants, but suffer in their ability to recover after OP exposure, thereby requiring large enzyme doses for effective treatment. Catalytic protein therapeutics, including serum paraoxonase (PON1) or the bacterial organophosphate hydrolase (OPH) exhibit rapid rates of in vitro nerve agent hydrolysis, but are limited by high dissociation constants, making them ineffective in vivo. Human carboxylesterase 1 (hCE1) is a liver serine hydrolase in the same [alpha]/[beta] super family as AChE and BChE, which may have more favorable attributes as an OP bioscavenger. Indeed rodents express a serum carboxylesterase that affords them high levels of protection against OPs. Using structural and biochemical studies, we determined the stereopreference, rates of spontaneous reactivation, and availability of rapid oxime-assisted reactivation of hCE1 with nerve agents. Next, using structurally guided protein design, we engineered a form of the hCE1 that combines the benefits of both bioscavenger classes, exhibiting nM dissociation constants and enhanced rates of hydrolysis, up to 48,700-fold, against the nerve agents sarin, soman, and cyclosarin. Finally, novel mutants of hCE1 were developed that exhibit-increased rates of reactivation against specific agents, and can be utilized to detect and identify chemical agents

Nerve Agent Hydrolysis Activity Designed into a Human Drug Metabolism Enzyme

Organophosphorus (OP) nerve agents are potent suicide inhibitors of the essential neurotransmitter-regulating enzyme acetylcholinesterase. Due to their acute toxicity, there is significant interest in developing effective countermeasures to OP poisoning. Here we impart nerve agent hydrolysis activity into the human drug metabolism enzyme carboxylesterase 1. Using crystal structures of the target enzyme in complex with nerve agent as a guide, a pair of histidine and glutamic acid residues were designed proximal to the enzyme's native catalytic triad. The resultant variant protein demonstrated significantly increased rates of reactivation following exposure to sarin, soman, and cyclosarin. Importantly, the addition of these residues did not alter the high affinity binding of nerve agents to this protein. Thus, using two amino acid substitutions, a novel enzyme was created that efficiently converted a group of hemisubstrates, compounds that can start but not complete a reaction cycle, into bona fide substrates. Such approaches may lead to novel countermeasures for nerve agent poisoning

Human Carboxylesterase 1 Stereoselectively Binds the Nerve Agent Cyclosarin and Spontaneously Hydrolyzes the Nerve Agent Sarin

Organophosphorus (OP) nerve agents are potent toxins that inhibit cholinesterases and produce a rapid and lethal cholinergic crisis. Development of protein-based therapeutics is being pursued with the goal of preventing nerve agent toxicity and protecting against the long-term side effects of these agents. The drug-metabolizing enzyme human carboxylesterase 1 (hCE1) is a candidate protein-based therapeutic because of its similarity in structure and function to the cholinesterase targets of nerve agent poisoning. However, the ability of wild-type hCE1 to process the G-type nerve agents sarin and cyclosarin has not been determined. We report the crystal structure of hCE1 in complex with the nerve agent cyclosarin. We further use stereoselective nerve agent analogs to establish that hCE1 exhibits a 1700- and 2900-fold preference for the PR enantiomers of analogs of soman and cyclosarin, respectively, and a 5-fold preference for the PS isomer of a sarin analog. Finally, we show that for enzyme inhibited by racemic mixtures of bona fide nerve agents, hCE1 spontaneously reactivates in the presence of sarin but not soman or cyclosarin. The addition of the neutral oxime 2,3-butanedione monoxime increases the rate of reactivation of hCE1 from sarin inhibition by more than 60-fold but has no effect on reactivation with the other agents examined. Taken together, these data demonstrate that hCE1 is only reactivated after inhibition with the more toxic PS isomer of sarin. These results provide important insights toward the long-term goal of designing novel forms of hCE1 to act as protein-based therapeutics for nerve agent detoxification

Implementation of consensus-based perioperative care pathways to reduce clinical variation for elective surgery in an Australian private hospital: a mixed-methods pre–post study protocol

Introduction Addressing clinical variation in elective surgery is challenging. A key issue is how to gain consensus between largely autonomous clinicians. Understanding how the consensus process works to develop and implement perioperative pathways and the impact of these pathways on reducing clinical variation can provide important insights into the effectiveness of the consensus process. The primary objective of this study is to understand the implementation of an organisationally supported, consensus approach to implement perioperative care pathways in a private healthcare facility and to determine its impact.Methods A mixed-methods Effectiveness-Implementation Hybrid (type III) pre–post study will be conducted in one Australian private hospital. Five new consensus-based perioperative care pathways will be developed and implemented for specific patient cohorts: spinal surgery, radical prostatectomy, cardiac surgery, bariatric surgery and total hip and knee replacement. The individual components of these pathways will be confirmed as part of a consensus-building approach and will follow a four-stage implementation process using the Exploration, Preparation, Implementation and Sustainment framework. The process of implementation, as well as barriers and facilitators, will be evaluated through semistructured interviews and focus groups with key clinical and non-clinical staff, and participant observation. We anticipate completing 30 interviews and 15–20 meeting observations. Administrative and clinical end-points for at least 152 participants will be analysed to assess the effectiveness of the pathways.Ethics and dissemination This study received ethical approval from Macquarie University Human Research Ethics Medical Sciences Committee (Reference No: 520221219542374). The findings of this study will be disseminated through peer-reviewed publications, conference presentations and reports for key stakeholders

Multicenter Evaluation of BioFire FilmArray Meningitis/Encephalitis Panel for Detection of Bacteria, Viruses, and Yeast in Cerebrospinal Fluid Specimens.

Rapid diagnosis and treatment of infectious meningitis and encephalitis are critical to minimize morbidity and mortality. Comprehensive testing of cerebrospinal fluid (CSF) often includes Gram stain, culture, antigen detection, and molecular methods, paired with chemical and cellular analyses. These methods may lack sensitivity or specificity, can take several days, and require significant volume for complete analysis. The FilmArray Meningitis/Encephalitis (ME) Panel is a multiplexed in vitro diagnostic test for the simultaneous, rapid (∼1-h) detection of 14 pathogens directly from CSF specimens: Escherichia coli K1, Haemophilus influenzae, Listeria monocytogenes, Neisseria meningitidis, Streptococcus pneumoniae, Streptococcus agalactiae, cytomegalovirus, enterovirus, herpes simplex virus 1 and 2, human herpesvirus 6, human parechovirus, varicella-zoster virus, and Cryptococcus neoformans/Cryptococcus gattii We describe a multicenter evaluation of 1,560 prospectively collected CSF specimens with performance compared to culture (bacterial analytes) and PCR (all other analytes). The FilmArray ME Panel demonstrated a sensitivity or positive percentage of agreement of 100% for 9 of 14 analytes. Enterovirus and human herpesvirus type 6 had agreements of 95.7% and 85.7%, and L. monocytogenes and N. meningitidis were not observed in the study. For S. agalactiae, there was a single false-positive and false-negative result each, for a sensitivity and specificity of 0 and 99.9%, respectively. The specificity or negative percentage of agreement was 99.2% or greater for all other analytes. The FilmArray ME Panel is a sensitive and specific test to aid in diagnosis of ME. With use of this comprehensive and rapid test, improved patient outcomes and antimicrobial stewardship are anticipated

Multicenter Evaluation of BioFire FilmArray Meningitis/Encephalitis Panel for Detection of Bacteria, Viruses, and Yeast in Cerebrospinal Fluid Specimens.

Rapid diagnosis and treatment of infectious meningitis and encephalitis are critical to minimize morbidity and mortality. Comprehensive testing of cerebrospinal fluid (CSF) often includes Gram stain, culture, antigen detection, and molecular methods, paired with chemical and cellular analyses. These methods may lack sensitivity or specificity, can take several days, and require significant volume for complete analysis. The FilmArray Meningitis/Encephalitis (ME) Panel is a multiplexed in vitro diagnostic test for the simultaneous, rapid (∼1-h) detection of 14 pathogens directly from CSF specimens: Escherichia coli K1, Haemophilus influenzae, Listeria monocytogenes, Neisseria meningitidis, Streptococcus pneumoniae, Streptococcus agalactiae, cytomegalovirus, enterovirus, herpes simplex virus 1 and 2, human herpesvirus 6, human parechovirus, varicella-zoster virus, and Cryptococcus neoformans/Cryptococcus gattii We describe a multicenter evaluation of 1,560 prospectively collected CSF specimens with performance compared to culture (bacterial analytes) and PCR (all other analytes). The FilmArray ME Panel demonstrated a sensitivity or positive percentage of agreement of 100% for 9 of 14 analytes. Enterovirus and human herpesvirus type 6 had agreements of 95.7% and 85.7%, and L. monocytogenes and N. meningitidis were not observed in the study. For S. agalactiae, there was a single false-positive and false-negative result each, for a sensitivity and specificity of 0 and 99.9%, respectively. The specificity or negative percentage of agreement was 99.2% or greater for all other analytes. The FilmArray ME Panel is a sensitive and specific test to aid in diagnosis of ME. With use of this comprehensive and rapid test, improved patient outcomes and antimicrobial stewardship are anticipated

Bimolecular rates of inhibition, Michaelis-Menten constants, and rates of reactivation for wild-type and V146H/L363E hCE1 against racemic cyclosarin and stereoisomers of cyclosarin model compounds.

<p>N = 3, s.d., N.D. is not determined, N.R. is no reactivation, pH 7.4, 25°C.</p>a<p>Racemic <i>bona fide</i> cyclosarin,</p>b<p>stereoisomers of cyclosarin model compounds,</p>c<p>(8).</p

Catalytic efficiencies (<i>k</i>_cat/<i>K</i>_m) of engineered enzymes towards hemisubstrates.

a<p>(16).</p>b<p>(32).</p>c<p>(32).</p