Microbiological, biological, and chemical weapons of warfare and terrorism

Plant-derived human butyrylcholinesterase, but not an organophosphorous-compound hydrolyzing variant thereof, protects rodents against nerve agents

The concept of using cholinesterase bioscavengers for prophylaxis against organophosphorous nerve agents and pesticides has progressed from the bench to clinical trial. However, the supply of the native human proteins is either limited (e.g., plasma-derived butyrylcholinesterase and erythrocytic acetylcholinesterase) or nonexisting (synaptic acetylcholinesterase). Here we identify a unique form of recombinant human butyrylcholinesterase that mimics the native enzyme assembly into tetramers; this form provides extended effective pharmacokinetics that is significantly enhanced by polyethylene glycol conjugation. We further demonstrate that this enzyme (but not a G117H/E197Q organophosphorus acid anhydride hydrolase catalytic variant) can prevent morbidity and mortality associated with organophosphorous nerve agent and pesticide exposure of animal subjects of two model species.

Transgenic plants as a source for the bioscavenging enzyme, human butyrylcholinesterase

Organophosphorous pesticides and nerve agents inhibit the enzyme acetylcholinesterase at neuronal synapses and in neuromuscular junctions. The resulting accumulation of acetylcholine overwhelms regulatory mechanisms, potentially leading to seizures and death from respiratory collapse. While current therapies are only capable of reducing mortality, elevation of the serum levels of the related enzyme butyrylcholinesterase (BChE) by application of the purified protein as a bioscavenger of organophosphorous compounds is effective in preventing all symptoms associated with poisoning by these toxins. However, BChE therapy requires large quantities of enzyme that can easily overwhelm current sources. Here, we report genetic optimization, cloning and high-level expression of human BChE in plants. Plant-derived BChE is shown to be biochemically similar to human plasma-derived BChE in terms of catalytic activity and inhibitor binding. We further demonstrate the ability of the plant-derived bioscavenger to protect animals against an organophosphorous pesticide challenge.

Clostridium perfringens epsilon toxin targets granule cells in the mouse cerebellum and stimulates glutamate release

Epsilon toxin (ET) produced by C. perfringens types B and D is a highly potent pore-forming toxin. ET-intoxicated animals express severe neurological disorders that are thought to result from the formation of vasogenic brain edemas and indirect neuronal excitotoxicity. The cerebellum is a predilection site for ET damage. ET has been proposed to bind to glial cells such as astrocytes and oligodendrocytes. However, the possibility that ET binds and attacks the neurons remains an open question. Using specific anti-ET mouse polyclonal antibodies and mouse brain slices preincubated with ET, we found that several brain structures were labeled, the cerebellum being a prominent one. In cerebellar slices, we analyzed the co-staining of ET with specific cell markers, and found that ET binds to the cell body of granule cells, oligodendrocytes, but not astrocytes or nerve endings. Identification of granule cells as neuronal ET targets was confirmed by the observation that ET induced intracellular Ca(2+) rises and glutamate release in primary cultures of granule cells. In cultured cerebellar slices, whole cell patch-clamp recordings of synaptic currents in Purkinje cells revealed that ET greatly stimulates both spontaneous excitatory and inhibitory activities. However, pharmacological dissection of these effects indicated that they were only a result of an increased granule cell firing activity and did not involve a direct action of the toxin on glutamatergic nerve terminals or inhibitory interneurons. Patch-clamp recordings of granule cell somata showed that ET causes a decrease in neuronal membrane resistance associated with pore-opening and depolarization of the neuronal membrane, which subsequently lead to the firing of the neuronal network and stimulation of glutamate release. This work demonstrates that a subset of neurons can be directly targeted by ET, suggesting that part of ET-induced neuronal damage observed in neuronal tissue is due to a direct effect of ET on neurons.

Ricin toxicokinetics and its sensitive detection in mouse sera or feces using immuno-PCR

BACKGROUND

Ricin (also called RCA-II or RCA(60)), one of the most potent toxins and documented bioweapons, is derived from castor beans of Ricinus communis. Several in vitro methods have been designed for ricin detection in complex food matrices in the event of intentional contamination. Recently, a novel Immuno-PCR (IPCR) assay was developed with a limit of detection of 10 fg/ml in a buffer matrix and about 10-1000-fold greater sensitivity than other methods in various food matrices.

METHODS AND FINDINGS

In order to devise a better diagnostic test for ricin, the IPCR assay was adapted for the detection of ricin in biological samples collected from mice after intoxication. The limit of detection in both mouse sera and feces was as low as 1 pg/ml. Using the mouse intravenous (iv) model for ricin intoxication, a biphasic half-life of ricin, with a rapid t(1/2)α of 4 min and a slower t(1/2)β of 86 min were observed. The molecular biodistribution time for ricin following oral ingestion was estimated using an antibody neutralization assay. Ricin was detected in the blood stream starting at approximately 6-7 h post- oral intoxication. Whole animal histopathological analysis was performed on mice treated orally or systemically with ricin. Severe lesions were observed in the pancreas, spleen and intestinal mesenteric lymph nodes, but no severe pathology in other major organs was observed.

CONCLUSIONS

The determination of in vivo toxicokinetics and pathological effects of ricin following systemic and oral intoxication provide a better understanding of the etiology of intoxication and will help in the future design of more effective diagnostic and therapeutic methods.

Ricin Toxin Activates the NALP3 Inflammasome

Ricin exhibits well characterized ribotoxic actions that lead to the inhibition of protein synthesis and the phosphorylation of stress activated protein kinases (SAPKs). Proinflammatory effects of ricin are thought to be caused by upregulation of genes encoding proinflammatory transcripts as a result of the activation of c-Jun N-terminal kinase (JNK) and p38 MAPK. We reported previously that macrophages and interleukin-1β (IL-1β) signaling are required for murine host immune responses to ricin delivered to the lungs. Here we report that ricin-mediated IL-1β release from bone-marrow derived macrophages is dependent on the NALP3 inflammasome, a scaffolding complex that mediates pro-IL-1β cleavage to active IL-1β by caspase-1. Release of IL-1β from macrophages was suppressed by the reactive oxygen species (ROS) scavenger N-acetyl cysteine (NAC) and high extracellular K(+), which are two agents known to inhibit NALP3/cryopyrin/CIAS1 inflammasome formation. By employing inhibitors of p38 MAPK and JNK, we demonstrated that ricin-mediated release of IL-1β was enhanced, rather than suppressed, by inhibition of SAPK phosphorylation. In contrast, proteasomal inhibitors bortezomib and MG-132 completely suppressed ricin-induced IL-1β release from macrophages. These data suggest that ricin-mediated translational inhibition itself, by fostering the disappearance of labile protein(s) that normally suppress inflammasome formation, may constitute the mechanism underlying IL-1-dependent inflammatory signaling by ricin.

Analysis of Botulinum Neurotoxin Serotype A Metalloprotease Inhibitors: Analogs of a Chemotype for Therapeutic Development in the Context of a Three-Zone Pharmacophore

Botulinum neurotoxins (BoNTs), and in particular serotype A, are the most poisonous of known biological substances, and are responsible for the flaccid paralysis of the disease state botulism. Because of the extreme toxicity of these enzymes, BoNTs are considered highest priority biothreat agents. To counter BoNT serotype A (BoNT/A) poisoning, the discovery and development of small molecule, drug-like inhibitors as post-intoxication therapeutic agents has been/is being pursued. Specifically, we are focusing on inhibitors of the BoNT/A light chain (LC) (ie, a metalloprotease) subunit, since such compounds can enter neurons and provide post-intoxication protection of the enzyme target substrate. To aid/facilitate this drug development effort, a pharmacophore for inhibition of the BoNT/A LC subunit was previously developed, and is continually being refined via the incorporation of novel and diverse inhibitor chemotypes. Here, we describe several analogs of a promising therapeutic chemotype in the context of the pharmacophore for BoNT/A LC inhibition. Specifically, we describe: 1) the pharmacophoric 'fits' of the analogs and how these 'fits' rationalize the in vitro inhibitory potencies of the analogs and 2) pharmacophore refinement via the inclusion of new components from the most potent of the presented analogs.

Bioterrorism and biologic warfare

Biologic agents have been used throughout history to influence battles. Recently, biologic agents have been used as terrorist weapons. A review of the history of biologic weapons and a medical overview of the Centers for Disease Control and Prevention Category A and B agents is provided, including history, pathogenesis, clinical presentation, microbiology/virology, diagnosis, treatment, and each agent's use or potential use as a weapon. Background information on public health issues surrounding bioterrorism and the role of oral and maxillofacial surgeons in a bioterrorist event also is provided.

The identification and biochemical characterization of drug-like compounds that inhibit botulinum neurotoxin serotype A endopeptidase activity

A robust, high-throughput, two-tiered assay for screening small molecule inhibitors against botulinum neurotoxin serotype A was developed and employed to screen 16,544 compounds. Thirty-four compounds were identified as potent hits employing the first-tier assay. Subsequently, nine were confirmed as actives by our second-tier confirmatory assay. Of these, one displayed potent inhibitory efficacy, possessing an IC(50)=16 microM (+/-1.6 microM) in our in vitro assay. This inhibitor (0831-1035) is highly water-soluble, and possesses an IC(50)=47 microM (+/-7.0 microM) in our primary cell culture assay (with virtually no cytotoxicity up to 500 microM), suggesting that this inhibitor is a good candidate for further development as a therapeutic countermeasure to treat botulism resulting from botulinum neurotoxin serotype A intoxication. An enzyme kinetics study indicated that this inhibitor exhibits mixed non-competitive inhibition, with a K(I)=9 microM.

An efficient drug delivery vehicle for botulism countermeasure

Background

Botulinum neurotoxin (BoNT) is the most potent poison known to mankind. Currently no antidote is available to rescue poisoned synapses. An effective medical countermeasure strategy would require developing a drug that could rescue poisoned neuromuscular synapses and include its efficient delivery specifically to poisoned presynaptic nerve terminals. Here we report a drug delivery strategy that could directly deliver toxin inhibitors into the intoxicated nerve terminal cytosol.

Results

A targeted delivery vehicle was developed for intracellular transport of emerging botulinum neurotoxin antagonists. The drug delivery vehicle consisted of the non-toxic recombinant heavy chain of botulinum neurotoxin-A coupled to a 10-kDa amino dextran via the heterobifunctional linker 3-(2-pyridylthio)-propionyl hydrazide. The heavy chain served to target botulinum neurotoxin-sensitive cells and promote internalization of the complex, while the dextran served as a platform to deliver model therapeutic molecules to the targeted neurons. Our results indicated that the drug delivery vehicle entry into neurons was via BoNT-A receptor mediated endocytosis. Once internalized into neurons, the drug carrier component separated from the drug delivery vehicle in a fashion similar to the separation of the BoNT-A light chain from the holotoxin. This drug delivery vehicle could be used to deliver BoNT-A antidotes into BoNT-A intoxicated cultured mouse spinal cord cells.

Conclusion

An effective BoNT-based drug delivery vehicle can be used to directly deliver toxin inhibitors into intoxicated nerve terminal cytosol. This approach can potentially be utilized for targeted drug delivery to treat other neuronal and neuromuscular disorders. This report also provides new knowledge of endocytosis and exocytosis as well as of BoNT trafficking.

Pulmonary inflammation triggered by ricin toxin requires macrophages and IL-1 signaling

Ricin is a potent ribotoxin considered to be a potentially dangerous bioterrorist agent due to its wide availability and the possibility of aerosol delivery to human populations. Studies in rodents and nonhuman primates have demonstrated that ricin delivered to the pulmonary system leads to acute lung injury and symptoms resembling acute respiratory distress syndrome. Increasing evidence suggests that the inflammatory effects triggered by ricin are responsible for its lethality. We demonstrated previously that ricin administered to the lungs of mice causes death of pulmonary macrophages and the release of proinflammatory cytokines, suggesting macrophages may be a primary target of ricin. Here we examined the requirement for macrophages in the development of ricin-mediated pulmonary inflammation by employing transgenic (MAFIA) mice that express an inducible gene driven by the c-fms promoter for Fas-mediated apoptosis of macrophages upon injection of a synthetic dimerizer, AP20187. Administration of aerosolized ricin to macrophage-depleted mice led to reduced inflammatory responses, including recruitment of neutrophils, expression of proinflammatory transcripts, and microvascular permeability. When compared with control mice treated with ricin, macrophage-depleted mice treated with ricin displayed a reduction in pulmonary IL-1beta. Employing mice deficient in IL-1, we found that ricin-induced inflammatory responses were suppressed, including neutrophilia. Neutrophilia could be restored by co-administering ricin and exogenous IL-1beta to IL-1alpha/beta(-/-) mice. Furthermore, IL1Ra/anakinra cotreatment inhibited ricin-mediated inflammatory responses, including recruitment of neutrophils, expression of proinflammatory genes, and histopathology. These data suggest a central role for macrophages and IL-1 signaling in the inflammatory process triggered by ricin.

Real-time contaminant detection and classification in a drinking water pipe using conventional water quality sensors: techniques and experimental results

Accurate detection and identification of natural or intentional contamination events in a drinking water pipe is critical to drinking water supply security and health risk management. To use conventional water quality sensors for the purpose, we have explored a real-time event adaptive detection, identification and warning (READiw) methodology and examined it using pilot-scale pipe flow experiments of 11 chemical and biological contaminants each at three concentration levels. The tested contaminants include pesticide and herbicides (aldicarb, glyphosate and dicamba), alkaloids (nicotine and colchicine), E. coli in terrific broth, biological growth media (nutrient broth, terrific broth, tryptic soy broth), and inorganic chemical compounds (mercuric chloride and potassium ferricyanide). First, through adaptive transformation of the sensor outputs, contaminant signals were enhanced and background noise was reduced in time-series plots leading to detection and identification of all simulated contamination events. The improved sensor detection threshold was 0.1% of the background for pH and oxidation-reduction potential (ORP), 0.9% for free chlorine, 1.6% for total chlorine, and 0.9% for chloride. Second, the relative changes calculated from adaptively transformed residual chlorine measurements were quantitatively related to contaminant-chlorine reactivity in drinking water. We have shown that based on these kinetic and chemical differences, the tested contaminants were distinguishable in forensic discrimination diagrams made of adaptively transformed sensor measurements.

Hepatic injuries of hexachloroethane smoke inhalation: the first analytical epidemiological study

There has been no human epidemiological data regarding the hepatic injuries of hexachloroethane-zinc oxide (HC/ZnO) inhalation. This is the first epidemiological study to investigate whether HC/ZnO inhalation exposure can induce hepatic dysfunction in exposed soldiers. Twenty soldiers, exposed to high concentration of HC/ZnO smoke for 3-10 min in a narrow tunnel (0.6 m in width) during military training, were recruited as exposed group and they were divided into high-exposed group (n=10) and low-exposed group (n=10) by the distance from the explosion locale as a surrogate of exposure condition. Another 64 soldiers, not visiting the explosion areas, were recruited as referents. Venous blood was collected for liver function analyses. After log transformation of alanine aminotransferase (ALT) and adjustment for potential confounders, serum ALT in high-exposed soldiers was statistically significantly higher than those of referents for the 3 weeks following exposure. The serum ALT in low exposed soldiers was statistically significantly higher than those of referents at the 3rd week following exposure. The mean ALT levels also showed decreasing gradients by the distance from exposure locale. In addition, the proportions of abnormality on ALT (>40U/L) were also significantly different among three exposure conditions. Follow-up study showed that the hepatic dysfunction started from 1 to 2 weeks and peaked from 3rd to 5th week after exposure. ALT level was then returned to normal within 6-8 weeks after removing from HC/ZnO smoke exposure. No sequelas in hepatic dysfunction were found until 72 weeks follow-up.

CONCLUSION

We concluded that inhalation of HC/Zn smoke can induce acute, dose-dependent and definite temporal relationship hepatic dysfunction.

Evaluation of an in vitro bioassay for the detection of purified ricin and castor bean in beverages and liquid food matrices

The potential use of ricin as a biological weapon in food highlights the necessity for the development of food-specific detection methods. Current methods for the detection of ricin consist of various immunoassays, which detect only one subunit of the ricin toxin and therefore may not be indicative of a biologically active molecule. An in vivo assay, such as a mouse bioassay, can indicate the biological activity of the toxin; however, this method is not feasible for laboratories that do not have animal testing facilities. The purpose of this study was to develop an in vitro assay for the detection of biologically active ricin in beverages and liquid foods. Acidic and high-protein beverages were spiked with either purified ricin or ground castor beans and added to cultured human Jurkat cells. After an overnight incubation, the supernatant was tested for lactate dehydrogenase (LDH) activity with a colorimetric assay. LDH was released from the cytosol upon cell damage and was positively correlated with cell death. Ricin was detectable in all the matrices tested, with a sensitivity of 10 to 100 pg/ml. Biologically active ricin was detectable in all the matrices incubated with ground castor bean material. This method provides a confirmatory way to detect biologically active ricin that can be utilized by laboratories lacking animal facilities.

Botulism diagnostics: from clinical symptoms to in vitro assays

Botulinum neurotoxin (BoNT), which cause the deadly neuroparalytic disease, botulism, is the most toxic substance known to man. BoNT can be used as potential bioterrorism agents, and therefore, pose great threat to national security and public health. Rapid and sensitive detection of BoNTs using molecular and biochemical techniques is an essential component in the diagnosis of botulism, and is yet to be achieved. The most sensitive and widely accepted assay method for BoNTs is mouse bioassay, which takes 4 days to complete. This clearly can not meet the need for clinical diagnosis of botulism, botulinum detection in field conditions, and screening of large scale samples. Consequently, the clinical diagnosis of botulism relies on the clinical symptom development, thus limiting the effectiveness of antitoxin treatment. In response to this critical need, many in vitro methods for BoNT detection are under development. This review is focused on recently developed in vitro detection methods for BoNTs, and emerging new technologies with potential for sensitive and rapid in vitro diagnostics for botulism.

Plant-derived human acetylcholinesterase-R provides protection from lethal organophosphate poisoning and its chronic aftermath

Therapeutically valuable proteins are often rare and/or unstable in their natural context, calling for production solutions in heterologous systems. A relevant example is that of the stress-induced, normally rare, and naturally unstable "read-through" human acetylcholinesterase variant, AChE-R. AChE-R shares its active site with the synaptic AChE-S variant, which is the target of poisonous organophosphate anticholinesterase insecticides such as the parathion metabolite paraoxon. Inherent AChE-R overproduction under organophosphate intoxication confers both short-term protection (as a bioscavenger) and long-term neuromuscular damages (as a regulator). Here we report the purification, characterization, and testing of human, endoplasmic reticulum-retained AChE-R(ER) produced from plant-optimized cDNA in Nicotiana benthamiana plants. AChE-R(ER) purified to homogeneity showed indistinguishable biochemical properties, with IC50 = 10(-7) M for the organophosphate paraoxon, similar to mammalian cell culture-derived AChE. In vivo titration showed dose-dependent protection by intravenously injected AChE-R(ER) of FVB/N male mice challenged with a lethal dose of paraoxon, with complete elimination of short-term clinical symptoms at near molar equivalence. By 10 days postexposure, AChE-R prophylaxis markedly limited postexposure increases in plasma murine AChE-R levels while minimizing the organophosphate-induced neuromuscular junction dismorphology. Our findings present plant-produced AChE-R(ER) as a bimodal agent, conferring both short- and long-term protection from organophosphate intoxication.

Enhancing public health preparedness for a terrorist attack involving cyanide

The US government considers cyanide to be among the most likely agents of chemical terrorism. Cyanide differs from many other biological or chemical agents for which little or no defense is available because its individual and public health effects are largely remediable through appropriate preparedness and response. Because the toxicity of the cyanide antidote currently available in the United States renders it ill-suited for use in terrorist incidents and other situations requiring rapid out-of-hospital treatment, hydroxocobalamin--an effective and safe cyanide antidote being used in other countries--has been introduced in the United States. Unlike the other available cyanide antidote, hydroxocobalamin can be administered at the scene of a cyanide disaster, and it need not be reserved for cases of confirmed cyanide poisoning but can be administered in cases of suspected poisoning. Both of these attributes facilitate the rapid intervention necessary for saving lives. To realize the potential benefits of hydroxocobalamin, progress also needs to be realized in other aspects of readiness, including but not limited to developing plans for ensuring local and regional availability of antidote, educating emergency responders and health care professionals in the recognition and management of cyanide poisoning, and raising public awareness of the potential for a chemical weapons attack and of how to respond.

Characterization of highly toxic type 2 ribosome-inactivating proteins from Adenia lanceolata and Adenia stenodactyla (Passifloraceae)

From the caudices of the Passifloraceae Adenia lanceolata and A. stenodactyla, two lectins called lanceolin and stenodactylin, respectively, were purified by affinity chromatography on CL Sepharose 6B. The lectins are glycoproteins with M(r) 61,243 (lanceolin) and 63,131 (stenodactylin), consisting of an enzymatic A chain linked to a larger B chain with lectin properties, with N-terminal amino acid sequences similar to that of volkensin, the toxic lectin from A. volkensii. The lectins agglutinate red blood cells, inhibit protein synthesis both by a cell-free system and by whole cells, and depurinate ribosomes and DNA, but not tRNA or poly(A). They are highly toxic to cells, in which they induce apoptosis, and to mice, with LD(50)s 8.16 microg/kg (lanceolin) and 2.76 microg/kg (stenodactylin) at 48 h. Thus, lanceolin and stenodactylin have all the properties of the toxic type 2 ribosome-inactivating proteins and are amongst the most potent toxins of plant origin.

Public health investigation after the discovery of ricin in a South Carolina postal facility

OBJECTIVES

In October 2003, a package containing ricin and a note threatening to poison water supplies was discovered in a South Carolina postal facility, becoming the first potential chemical terrorism event involving ricin in the United States. We examined the comprehensive public health investigation that followed and discuss the lessons learned from it.

METHODS

An investigation consisting primarily of environmental sampling for ricin contamination, performance of health assessments on affected personnel, and local, regional, and national surveillance for ricin-associated illness.

RESULTS

Laboratory analysis of 75 environmental sampling specimens revealed no ricin contamination. Health assessments of 36 affected employees were completed. Local surveillance initially identified 3 suspected cases, and national surveillance identified 399 outliers during the 2-week period after the incident. No confirmed cases of ricin-associated illness were identified.

CONCLUSIONS

A multifaceted and multidisciplinary approach is required for an effective public health response to a chemical threat such as ricin. The results of all of the described activities were used to determine that the facility was safe to reopen and that no public health threat existed.

Human paraoxonase: A promising approach for pre-treatment and therapy of organophosphorus poisoning

The limited efficiency of medical countermeasures against poisoning by nerve agent justifies efforts to find new prophylactic means and new antidotes. The concept of bioscavengers has emerged as an alternative approach to pharmacological pre- and post-exposure treatments. Catalytic scavengers are enzymes displaying a turnover with OPs as substrates, allowing rapid and efficient protection using administration of small doses. Several reasons have endorsed human paraoxonase (PON1) to be a pertinent candidate as catalytic bioscavenger. The physiological function of PON1 has not yet been unambiguously identified. Considered as a promiscuous enzyme, PON1 appears to be primarily a lactonase and also displays an anti-atherogenic activity closely linked to its localization on HDL particles. A HDL-associated phosphate transporter termed human phosphate binding protein (HPBP) was found to be a partner of natural human PON. In the absence of its natural environment (or mimicry by detergents), human PON1 is unstable and tends to aggregate. Converging data indicate that both the activity and the stability of PON1 are dramatically dependent on the HDL component molecular environment, including HPBP. Therefore, biochemical and physiological characterization of PON1-HPBP complexes, the environment allowing retaining functional enzyme state(s), and the thermal and storage stability of PON1 are mandatory. Synergistic efforts on characterization of recombinant hybrid PON1 expressed in E. coli and natural human PON1 provide information for the future rational design of stable mutants of PON1-based catalytic scavengers to be used as safe and effective countermeasures to OP intoxication.

[Biodefense: a new challenge for microbiology and public health]

Bioterrorism and the potential use of biological weapons has become an important concern of governments and responsible authorities. An example of this threat occurred in 2001 in the USA, when letters were sent containing spores of the agent that produces anthrax; this resulted in some deaths, and caused panic and negative effects on the world economy. If this small-scale event was able to cause such a huge impact, the repercussions of a massive attack could be catastrophic. In many countries, these events have resulted in the implementation of measures directed toward preventing and responding to bioterrorist threats and acts. As a whole, these measures are known as biodefense. This article briefly analyzes several aspects related to detecting and identifying acts of bioterrorism, and considers the biological agents that are implicated. The microbiological diagnosis that allows identification of the causal agent, a key point for taking suitable control measures, is also included.

Role of apoptotic signaling pathways in regulation of inflammatory responses to ricin in primary murine macrophages

Because of its lethal effects, ease of preparation, and ability to be delivered by aerosolization, ricin has been developed as a lethal weapon by various terrorist groups. When introduced into the pulmonary system of rodents, ricin causes pathological changes in the lung that are known to occur in acute respiratory distress syndrome (ARDS). Early response cytokines such as TNF-alpha and IL-1 are known to play a critical role in the pathogenesis of ARDS. Ricin induces the release of these pro-inflammatory cytokines and the transcriptional activation of the genes that encode them in vitro and in vivo. Macrophages, considered to act as upstream regulators of inflammatory cascades, may play a central role in the pathogenesis and the development of ricin-induced ARDS because of their ability to make and secrete pro-inflammatory cytokines. Exposure of primary macrophages to ricin in vitro led to activation of stress-activated protein kinases, increased expression of pro-inflammatory mRNA transcripts, subsequent increase in the synthesis and secretion of TNF-alpha, and apoptotic cell death. Interestingly, macrophages required the engagement of the apoptotic cascade for the maximal synthesis and release of some pro-inflammatory mediators. This work identifies a cross talk between the apoptotic and inflammatory signaling pathways induced by ricin in primary macrophages.

Disruption of lipid rafts enhances activity of botulinum neurotoxin serotype A

Botulinum neurotoxin serotype A (BoNT/A), one of seven serotypes of botulinum neurotoxin, is taken up by neurons of the peripheral nervous system. Within the neurons it catalyzes cleavage of the synaptosomal-associated protein having a mass of 25kDa, SNAP-25, thereby blocking neurotransmission. BoNT/A has been shown to interact with SV2, as well as gangliosides that are often found in lipid rafts. Lipid rafts are microdomains that can be found on the outer leaflet of the plasma membrane and are enriched in cholesterol and glycosphingolipids. To determine whether lipid rafts are needed for BoNT/A activity, those associated with the plasma membranes of murine N2a neuroblastoma cells were disrupted using either methyl-beta-cyclodextrin or filipin. Disruption of cholesterol-containing lipid rafts by either reagent did not prevent the action of BoNT/A on N2a cells, in fact activity was enhanced. While our results indicate that disruption of lipid rafts enhances BoNT/A activity, disruption of clathrin-dependent endocytosis appeared to be inhibitory.

Acute lung injury following inhalation exposure to nerve agent VX in guinea pigs

A microinstillation technique of inhalation exposure was utilized to assess lung injury following chemical warfare nerve agent VX [methylphosphonothioic acid S-(2-[bis(1-methylethyl)amino]ethyl) O-ethyl ester] exposure in guinea pigs. Animals were anesthetized using Telazol-meditomidine, gently intubated, and VX was aerosolized using a microcatheter placed 2 cm above the bifurcation of the trachea. Different doses (50.4 microg/m3, 70.4 micro g/m(m3), 90.4 microg/m(m3)) of VX were administered at 40 pulses/min for 5 min. Dosing of VX was calculated by the volume of aerosol produced per 200 pulses and diluting the agent accordingly. Although the survival rate of animals exposed to different doses of VX was similar to the controls, nearly a 20% weight reduction was observed in exposed animals. After 24 h of recovery, the animals were euthanized and bronchoalveolar lavage (BAL) was performed with oxygen free saline. BAL was centrifuged and separated into BAL fluid (BALF) and BAL cells (BALC) and analyzed for indication of lung injury. The edema by dry/wet weight ratio of the accessory lobe increased 11% in VX-treated animals. BAL cell number was increased in VX-treated animals compared to controls, independent of dosage. Trypan blue viability assay indicated an increase in BAL cell death in 70.4 microg/m(m3) and 90.4 microg/m(m3) VX-exposed animals. Differential cell counting of BALC indicated a decrease in macrophage/monocytes in VX-exposed animals. The total amount of BAL protein increased gradually with the exposed dose of VX and was highest in animals exposed to 90.4 microg/m(m3), indicating that this dose of VX caused lung injury that persisted at 24 h. In addition, histopathology results also suggest that inhalation exposure to VX induces acute lung injury.

Ricin: current understanding and prospects for an antiricin vaccine

Ricin is a potent cytotoxin that can be rapidly internalized into mammalian cells leading to cell death. The ease in obtaining the toxin and its deadly nature combine to implicate ricin as a convenient agent for bioterrorism. Research into the mechanism of toxicity, as well as strategies for treatment and protection from the toxin has been widely undertaken for a number of years. This article reviews the current understanding of the mechanism of action of the toxin, the clinical effects of ricin intoxication and how these relate to current and continuing prospects for vaccine development.

Case report: hexachloroethane smoke inhalation: a rare cause of severe hepatic injuries

CONTEXT

We report on two patients, a 23-year-old man and a 24-year-old man, who had chemical pneumonitis and respiratory distress after inhaling hexachloroethane/zinc oxide (HC/ZnO) smoke during military training.

CASE PRESENTATION

The patients had been healthy previously and denied any history of alcohol or drug abuse. Hematologic tests revealed leukocytosis with neutrophils predominant. The respiratory conditions of both patients improved after steroid therapy and oxygen support, but deterioration of liver function was found. The laboratory results showed that alanine aminotransferase (ALT) and gamma-glutamyl transpeptidase levels were elevated about 1.5-fold the normal limits and that aspartate aminotransferase (AST) levels were marginally elevated. The elevation of liver aminotransferase started from day 1 and day 2 and peaked from day 18 to day 22. ALT/AST levels then returned to normal in 6 weeks. Common viral hepatitis was ruled out after serologic tests. Abdominal sonography and physical examination failed to show any specific findings.

DISCUSSION

The hepatotoxic effect was attributed to inhalation of high-concentration HC/ZnO smoke in an enclosed area, where several hepatotoxicants, including ZnCl2, HC, and chlorinated vapors, could have been generated and mixed in the smoke.

RELEVANCE TO CLINICAL PRACTICE

These case reports elaborate the hepatic effects that may occur in addition to pulmonary effects of HC/ZnO smoke.

Intranasal exposure to bacterial superantigens induces airway inflammation in HLA class II transgenic mice

Staphylococcus aureus is widely prevalent in the nasopharynges of healthy individuals (carriers) but can also cause serious infections. S. aureus can elaborate a variety of superantigen exotoxins in "carrier" or "pathogenic" states. Streptococcus pyogenes can also colonize the nasopharynx and elaborate superantigens. Unlike the acute effects of superantigen exotoxins absorbed through the gut or vaginal mucosa, little is known regarding the pathogenesis of superantigens entering through the intranasal route. In the current study, we evaluated the local and systemic effects of staphylococcal enterotoxin B (SEB) and streptococcal pyrogenic exotoxin A (SPEA) delivered through the intranasal route. Superantigens were administered intranasally on multiple occasions, and experimental animals were sacrificed on day 8 for experimental analyses. SEB-induced airway inflammation was more pronounced for HLA-DR3 transgenic mice than for BALB/c mice, consistent with bacterial superantigens binding more efficiently to human than murine major histocompatibility complex class II. The nature of the airway inflammation in HLA-DR3 mice was determined by the concentration of SEB applied intranasally. Low concentrations (20 ng) induced eosinophilic airway inflammation as well as eosinophil degranulation, whereas intranasal exposure to higher concentrations (2,000 ng) resulted in neutrophilic airway inflammation, permanent airway destruction, toxic shock, and mortality. SEB-induced eosinophilic inflammatory response was enhanced in signal transducer and activator of transcription (STAT)-4-deficient HLA-DQ8 transgenic mice with defective interleukin-12 signaling. Intranasal administration of SPEA induced airway inflammation and systemic immune activation in HLA-DQ8 transgenic mice. In conclusion, repeated chronic intranasal exposure to bacterial superantigens causes airway inflammation and systemic immune activation.

Mustard: a potential agent of chemical warfare and terrorism

As one of the most important vesicant agents, the destructive properties of mustards on the skin, eyes and respiratory system, combined with a lack of antidote, makes them effective weapons. Such weapons are inexpensive, easily obtainable and frequently stockpiled. Sulphur mustard (mustard gas) has been used as a chemical warfare agent in at least 10 conflicts. In this article, the use of mustard as a potential agent of chemical warfare and terrorism is outlined. The dose-dependent effects of acute sulphur mustard exposure on the skin, eyes, and respiratory system are described, as well as the possible extents of injuries, the mechanisms of action and the long-term complications. Prevention and management of mustard exposure are briefly discussed. The need for awareness and preparedness in the dermatological community regarding mustard exposure is emphasized.

Investigation of acute toxicity of chlorpyrifos-methyl on guppy Poecilia reticulata

Static bioassays were made to determine acute toxicity of chlorpyrifos-methyl, a wide spectrum organophosphorus insecticide and potential toxic pollutant of aquatic ecosystem, Guppy fish (Poecilia reticulata). Bioassays were made at a regulated temperature of 22+/-1 degrees C and were repeated three times. Lethal doses of the insecticides were determined using LC50 software programme of U.S. EPA based on Finney's Probit Analysis statistical method. The 96 h LC50 value and 95% confidence limit of chlorpyrifos-methyl for Guppy was estimated as 1.79 (1.47-2.10) mg/l. The fish exposed to chlorpyrifos-methyl exhibited behavioral changes in the form of neurotoxin toxicity: less general activity than control group, loss of equilibrium, erratic swimming and staying motionless at a certain location generally at mid-water level for prolonged periods. The 1 mg/l (lowest) concentration had similar behavior (NOEC) with the control group.

Neurobiological Weapons

Biological warfare is a potential threat on the battlefield and in daily life. It is vital for neurologists and other health care practitioners to be familiar with biological and toxic agents that target the nervous system. most illnesses caused by biological warfare agents are not commonly considered neurologic disease, however. Many of these agents (such as anthrax) may present with headache, meningitis, or mental status changes in addition to fever and other symptoms and signs (Tables 2 and 3). Thus, a neurologist may be consulted acutely to aid in diagnosis. Because of the incubation time of many biological agents and their protean manifestations, it is likely that health care workers will be on the front lines in the event of a bioterrorist attack. We must be prepared.

Investigation of acute toxicity of chlorpyrifos-methyl on Nile tilapia (Oreochromis niloticus L.) larvae

Chlorpyrifos-methyl, a wide-spectrum organophosphorus insecticide and potential toxic pollutant contaminating aquatic ecosystems, was investigated for acute toxicity. Larvae of the freshwater fish Nile tilapia (Oreochromis niloticus L.) were selected for the bioassay experiments. The experiments were repeated three times and the 96 h LC50 was determined for the larvae. The static test method for assessing acute toxicity was used. Water temperature was maintained at 25+/-1 degrees C. In addition, behavioral changes at each chlorpyrifos-methyl concentration were observed for the individual fish. Data obtained from the chlorpyrifos-methyl acute toxicity tests were evaluated using Finney's probit analysis statistical method. The 96 h LC50 value for Nile tilapia larvae was calculated to be 1.57 mg/l.

Ricin: Mechanism of Toxicity, Clinical Manifestations, and Vaccine Development. A Review

Ricin is one of the most potent plant toxins known, and the castor plant from which it is derived, Ricinus communis, is ubiquitous. The harvesting of castor beans exceeds one million tons annually, and ricin is easier to produce than either anthrax or botulinum. As a result, ricin is a convenient, potent, and available toxin for terrorist acts. This paper will review the mechanism of toxicity, major clinical manifestations, treatment, current methods of detection, and vaccine development.

Medical aspects of biologic toxins

Biologic toxins are molecules produced by living organisms that are poisonous to other species, such as humans. Some biologic toxins are so potent and relatively easy to produce that they have been classified as biothreat agents. These include the botulinum neurotoxins, ricin, staphylococcal enterotoxin B, and Clostridium perfringens epsilon toxin. This article focuses on these four biothreat toxins and their medical aspects. The majority of the article is spent on the botulinum neurotoxins, because these are the most poisonous substances known and are the only toxins classified as Category A threat agents-the highest level of threat agent. The remainder of the article is devoted to sections on the other three biothreat toxins: ricin, staphylococcal enterotoxin B, and C perfringens epsilon toxin.

Probiotics for mother and child

For the survival of humankind, nothing can be as important as the health of a mother and a child. As the world's population grows to more than 6 billion, it might seem ridiculous to suggest that any real threat exists to the human species. Diseases have long ravaged populations, as have wars, poverty, and malnutrition. Life today is no different with new and emerging diseases such as SARS and Mad Cow Disease leaving a trail of concern around the planet. All that being said, the AIDS crisis is threatening humans like no other. In countries such as Botswana, close to half the population of pregnant women is infected. Of great concern, the disease is now prevalent among women and teenage girls, threatening not only their lives but those of their offspring. Efforts to control this spread are quite abysmal, albeit well intentioned. Likewise, the death of a child every 15 seconds from diarrheal disease is not being addressed with the same vigor as SARS, even though the risk of dying from the latter for most people is similar to being struck by lightning. In the end, it is the economy and politics that dictate health spending. Image and perception are everything. While deaths mount among women and children from AIDS and other infections, the potential to intervene with a low-risk natural concept of probiotics seemed all too distant. As evidence mounts of the attributes of certain probiotic strains to treat diarrhea and reduce the risk of urogenital and other diseases, the developing world has failed to embrace it, support its evaluation and implementation, and take it to where it is needed the most. In this review, the case for and against probiotics for urogenital and intestinal infections is presented based on current literature. The story is far from complete, but the potential for improving the health of the mother and child is significant. United Nations and World Health Organization guidelines have now been developed to vanquish the unproved marketing hype products that have given probiotics a bad name. It is now up to science to deliver the remedies, and to society to make sure that only proven products reach the marketplace and the people in most need.

Future applications of phosphotriesterases in the prophylaxis and treatment of organophosporus insecticide and nerve agent poisonings

Organophosphorus compounds (OPs) are being used as insecticides and warfare agents. OP insecticides represent an important problem of public health, causing around 200,000 deaths annually. The World Health Organization has pointed to the necessity to introduce new medical practices that improve the results of classical treatments. Many studies have shown that the administration of phosphotriesterases (enzymes that detoxify OPs through hydrolysis) is a promising treatment of persons poisoned with OPs. Such an enzyme-based treatment might introduce important improvements in the treatment of patients having ingested large amounts of OPs. Phosphotriesterases might also be suitable for prophylactic treatment of persons at risk to be severely exposed. The new experimental treatments do not exhibit the intrinsic neurotoxicity of the classical prophylaxis based on carbamates and antimuscarinic drugs. Experimental data suggest that might be time to initiate clinical trials in order to study the efficacy of phosphotriesterases in the therapy and prophylaxis of OP intoxication.

Sulphur and skin: from Satan to Saddam!

Since the dawn of time, Beelzebub has been showering fire and brimstone (sulphur) on tortured souls, but the cutaneous effects of this have been poorly described. Sulphur has also been used for centuries as a treatment for many skin conditions, such as fungal infections, scabies, psoriasis, eczema and acne. It has also been used extensively in cosmetic preparations and by cosmetic dermatologists treating conditions such as seborrhoeic eczema. Many natural bathing spas have high levels of sulphur; such balneology has been advocated by medical and cosmetic dermatologists as an effective treatment for cutaneous disorders for more than 500 years. Sulphur was often the active agent in many of the so-called 'patent medicines' that became popular in the mid-nineteenth century. Time has not withered medical practitioners' enthusiasm for sulphur. There are various reports in the medical literature of its current use. However sulphur treatment is not without its risks; a sulphur spring dermatitis has been described from a spa bath in Taiwan. With the satanic threat of bio-terrorism, some dermatologists may be treating the effects of contact with sulphur mustard all too soon.

Toxicology in the critically ill patient

Intoxications present in many forms including: known drug overdose or toxic exposure, illicit drug use, suicide attempt, accidental exposure, and chemical or biological terrorism. A high index of suspicion and familiarity with toxidromes can lead to early diagnosis and intervention in critically ill, poisoned patients. Despite a paucity of evidence-based information on the management of intoxicated patients, a rational and systematic approach can be life saving.