Prophylaxis with human serum butyrylcholinesterase protects Göttingen minipigs exposed to a lethal high-dose of sarin vapor

Abstract

Serum-derived human butyrylcholinesterase (Hu BChE) is a stoichiometric bioscavenger that is being developed as a potential prophylactic nerve agent countermeasure. Previously, we reported the prophylactic efficacy of Hu BChE in Göttingen minipigs against a whole-body exposure to 4.1mg/m(3) of sarin (GB) vapor, which produced lethality over 60min. Since the toxicity of nerve agent is concentration-dependent, in the present study, we investigated the toxic effects of an almost 3-fold higher rate of GB vapor exposure and the ability of Hu BChE to protect minipigs against this exposure. Male minipigs were subjected to: (1) air exposure; (2) GB vapor exposure; or (3) pretreatment with 7.5mg/kg of Hu BChE by i.m. injection, 24h prior to whole-body exposure to 11.4mg/m(3) of GB vapor for 10min. Electrocardiogram, electroencephalogram, and pupil size were monitored throughout exposure. Blood drawn before and throughout exposure was analyzed for blood gases, electrolytes, metabolites, acetylcholinesterase and BChE activities, and amount of GB bound to red blood cells and plasma. A novel finding was that saline-treated animals exposed to GB vapor did not develop any seizures, but manifested a variety of cardiac and whole blood toxic signs and rapidly died due to respiratory failure. Strikingly, pre-treatment with 7.5mg/kg of Hu BChE not only prevented lethality, but also avoided all cardiac toxic signs manifested in the non-treated cohort. Thus, Hu BChE alone can serve as an effective prophylactic countermeasure versus a lethal high-dose exposure to GB vapor.

Plant-expressed cocaine hydrolase variants of butyrylcholinesterase exhibit altered allosteric effects of cholinesterase activity and increased inhibitor sensitivity

“…BChE is capable of detoxifying organophosphorous (OP) nerve agents like paraoxon, as well as acetylcholine receptor antagonists, and psychoactive plant alkaloids such as cocaine 2 – 5 . Exogenously-supplied BChE can augment the bioscavenging capacity of the endogenous enzyme and provide broad protection by sequestering the anticholinesterase agents 6 – 9 . Moreover, recombinantly-produced BChE variants with improved binding affinities and catalytic prowess can be created to improve on the parameters of the wild type (WT) enzyme.…”

Creation of a protective pulmonary bioshield against inhaled organophosphates using an aerosolized bioscavenger

“…Structurally, BChE (also known as EC3.1.1.8, pseudocholinesterase, nonspecific cholinesterase) is a serine esterase (MW = 345 kDa) comprising four identical subunits containing 574 amino acids, held together by noncovalent bonds, and 36 carbohydrate chains (23.9% by weight) . The efficacy of BChE prophylaxis, in terms of survivability and prevention of cognitive impairment, has been clearly demonstrated in many animal models against multiple LD 50 s of nerve agents and pesticides, and more recently, the ability of HuBChE delivered by intramuscular (IM) injection has been shown to protect against lethal inhaled sarin in minipigs . In Turkey, frozen plasma (containing 3000–5700 units of BChE), given as an alternative or adjunctive treatment with atropine and oximes, has been shown to prevent mortality and intermediate syndrome in acutely insecticide‐exposed and hospitalized individuals …”

“…9 The efficacy of BChE prophylaxis, in terms of survivability and prevention of cognitive impairment, has been clearly demonstrated in many animal models against multiple LD 50 s of nerve agents and pesticides, [10][11][12] and more recently, the ability of HuBChE delivered by intramuscular (IM) injection has been shown to protect against lethal inhaled sarin in minipigs. 13 In Turkey, frozen plasma (containing 3000-5700 units of BChE), given as an alternative or adjunctive treatment with atropine and oximes, has been shown to prevent mortality and intermediate syndrome in acutely insecticideexposed and hospitalized individuals. 14 However, because of the limited availability and cost of producing sufficient quantities of plasmaderived HuBChE, focus has switched to the development of a recombinant (r) BChE countermeasure.…”

Characterization of butyrylcholinesterase from porcine milk

“…12–15 Pigs have also been used to evaluate protection against OP nerve agent toxicity afforded by pretreatment with bioscavengers such as HuBChE. 16–18 Pharmacokinetic studies showed that the mean residence time of plasma-derived, tetrameric HuBChE in minipigs was 267 h (data not shown), indicating that HuBChE was not rapidly cleared from the circulation of pigs, but remained in the circulation with a half-life similar to that in humans. 19 This suggests a high degree of similarity between human (Hu) and porcine (Po) BChE.…”