Lethal Toxins Research Articles

The potential benefits of snake venom

Snake venom is one of the most lethal saliva toxins in the world. It consists of more than 20 distinct compounds, mainly of which are proteins， peptides or polypeptides. Proteins are responsible for 90%-95% of snake venom’s dry weight and are capable of some biological uses. The venom facilitates digestion and immobilization of prey and can help the snake to resist threats as well. Snake bites can easily kill a human or any other animal species. There are multiple sorts of snake venom with different toxicity abilities, causing various physiological effects. While snake venom is considered as a highly risky toxin, it still can be used to benefit human beings. For example, in the biomedical area, specific snake venom can treat serval diseases and even has a cosmetic effect. This article will solve the question that how snake venom can be lethal and beneficial at the same time, and how it be used to contribute to biological resources.

Cytokine profile in <i>in vitro</i> mouse macrophage culture infected with <i>Bacillus anthracis</i> spores with varying plasmid composition

Bacillus anthracis, the causative agent of anthrax, is able to exist both in environmental conditions (soil) and in the macroorganism. The manifestation of pathogenic properties of B. anthracis strains is determined by relevant plasmid composition, because the main toxin and the capsule-related virulence factors are located in bacterial plasmid. Modeling anthrax infection in vitro in macrophage culture might reveal an influence of individual B. anthracis strain characteristics on infection and development of infectious process. The aim of this study was to analyze cytokine level during infection of in vitro macrophage cell cultures with spores of anthrax microbe strains bearing varying plasmid composition. The dependence of the macrophage cell cytokine profile on the plasmid composition of B. anthracis strains was revealed while modeling anthrax infection in vitro. The presence of the toxin-producing plasmid pXO1 in anthrax microbe strains has a powerful stimulating effect on the production of macrophages J774A cell line cytokines. B. anthracis strains lacking the pXO1 plasmid virtually stimulated no production of IL-1, caused very low secretion of IL-1, IL-6, MCP-1, MIP-1, MIP-1, IL-12 (p70) and active G-CSF products. The low cytokine response of macrophage cells infected with monoplasmid strains bearing only the capsule-forming plasmid was due not only to the absence of a binary toxin, but also to disturbed regulation of capsule production associated with the absence of the atxA gene. The capsule, along with lethal and edematous toxins, belongs to the main virulence factors of B. anthracis, but strains lacking the pXO1 virulence plasmid, had its production impaired, because the main regulator of capsule synthesis is the atxA gene localized on the pXO1 plasmid being positively regulated by the acpA and acpB genes, so that strains lacking the toxin-forming plasmid, even in the presence of the encapsulation plasmid, elicit a weak cytokine response in infected cells. Diplasmid strains of B. anthracis, due to produced main virulence factors a two-component toxin and a capsule, enforce macrophages (in the experiment) to actively produce IL-1, IL-6, MCP-1, G-CSF, MIP-1; MIP-1, IL-12 (p70). Strains with moderate virulence and capable of capsulation in air virtually did not differ from highly virulent strains in terms of their effect on in vitro macrophage culture.

Immunoinformatic analysis of the whole proteome for vaccine design: An application to Clostridium perfringens.

Clostridium perfringens is a dangerous bacterium and known biological warfare weapon associated with several diseases, whose lethal toxins can produce necrosis in humans. However, there is no safe and fully effective vaccine against C. perfringens for humans yet. To address this problem, we computationally screened its whole proteome, identifying highly immunogenic proteins, domains, and epitopes. First, we identified that the proteins with the highest epitope density are Collagenase A, Exo-alpha-sialidase, alpha n-acetylglucosaminidase and hyaluronoglucosaminidase, representing potential recombinant vaccine candidates. Second, we further explored the toxins, finding that the non-toxic domain of Perfringolysin O is enriched in CTL and HTL epitopes. This domain could be used as a potential sub-unit vaccine to combat gas gangrene. And third, we designed a multi-epitope protein containing 24 HTL-epitopes and 34 CTL-epitopes from extracellular regions of transmembrane proteins. Also, we analyzed the structural properties of this novel protein using molecular dynamics. Altogether, we are presenting a thorough immunoinformatic exploration of the whole proteome of C. perfringens, as well as promising whole-protein, domain-based and multi-epitope vaccine candidates. These can be evaluated in preclinical trials to assess their immunogenicity and protection against C. perfringens infection.

Characterization of Four Medically Important Toxins from Centruroides huichol Scorpion Venom and Its Neutralization by a Single Recombinant Antibody Fragment.

Centruroides huichol scorpion venom is lethal to mammals. Analysis of the venom allowed the characterization of four lethal toxins named Chui2, Chui3, Chui4, and Chui5. scFv 10FG2 recognized well all toxins except Chui5 toxin, therefore a partial neutralization of the venom was observed. Thus, scFv 10FG2 was subjected to three processes of directed evolution and phage display against Chui5 toxin until obtaining scFv HV. Interaction kinetic constants of these scFvs with the toxins were determined by surface plasmon resonance (SPR) as well as thermodynamic parameters of scFv variants bound to Chui5. In silico models allowed to analyze the molecular interactions that favor the increase in affinity. In a rescue trial, scFv HV protected 100% of the mice injected with three lethal doses 50 (LD50) of venom. Moreover, in mix-type neutralization assays, a combination of scFvs HV and 10FG2 protected 100% of mice injected with 5 LD50 of venom with moderate signs of intoxication. The ability of scFv HV to neutralize different toxins is a significant achievement, considering the diversity of the species of Mexican venomous scorpions, so this scFv is a candidate to be part of a recombinant anti-venom against scorpion stings in Mexico.

Clostridium perfringens Types A and D Involved in Peracute Deaths in Goats Kept in Cholistan Ecosystem During Winter Season

Enterotoxemia is a severe and peracute disease caused by Clostridium perfringens (C. perfringens) rendering high mortality leading to huge economic losses, especially in small ruminants. The bacterium induces peracute death in animals based on the rapid production of different lethal toxins. Mortality occurred three private herds of two breeds, i.e., Makhi Cheeni and Beetal, and one non-descriptive (Teddy) herds reared in the desert area of Bahawalpur, Pakistan. At necropsy, tissue samples for histopathology and intestinal contents for bacterial isolation and culture were collected. Following the standard procedure, tissue slides were prepared. Multiplex PCR was used to identify toxinotypes using specific primers. Morbidity, mortality, and case fatality in Makhi Cheeni, Beetal, and Teddy goats caused by enterotoxemia were 87.58, 75.81, and 76.11%, respectively. Based on toxinotypes in the present outbreaks, C. perfringens type A (cpα = 20.7%; cpα + cpβ2 = 11.2%) and C. perfringens type D (cpα + cpβ2 + etx = 47.7%; cpα + etx = 20.7%) were detected. Deaths due to C. perfringens type D (68.10%) were significantly higher (p < 0.001) compared with deaths by C. perfringens type A (34.90%). Petechiation of serosal surfaces, hemorrhage of intestines, lungs, and liver were seen. Kidneys were soft, and under the microscope, tubules were studded with erythrocytes. There was stunting and fusion in the intestinal villi. From this study, we concluded that endotoxemia can occur in any season; thus, a proper vaccination schedule must be followed for the protection of small ruminants' health.

Detection of Epsilon Toxin in Goats Affected with Acute Enterotoxaemia and the Haemato-biochemical Alterations

Background: The principal cause of caprine enterotoxaemia is Clostridium perfringens type D which is normally resident in digestive tract and soil in fairly low numbers. Overeating of carbohydrate rich diet or sudden change in diet leads to proliferation of the bacteria and release of lethal toxins in intestine of the host. It causes sudden death in affected ruminants of different ages, though lambs of 3 to 10 weeks of age are highly susceptible. It causes sever enterocolitis with or without haemorrhagic diarrhoea and encephalitis resulting in acute nervous signs with a fatal outcome. Methods: Thirty goats of different breeds under 1-4 years age and both sex were presented to Veterinary Clinical Complex, Veterinary College and Research Institute, Tirunelveli with the neurological signs and diarrhoea were the subject of study. Faecal samples were collected from all these cases and tested on spot by immunochromatographic test kit to identify the Clostridium perfringens Epsilon toxin (ETX). Blood and serum samples were collected and subjected haemato-biochemical analysis. Peripheral blood smears were also collected to rule out haemoprotozoan infections in all the cases. Result: Epsilon toxin was detected from faecal samples of 36.6 per cent of the goats. Diarrhoea was the most consistent finding which is due to enterocolitis in acute cases. A significant increase (P less than 0.001) in the neutrophils and leukocytes count and a significant increase (P less than 0.05) in the levels of BUN, creatinine, glucose, ALP and chloride levels were observed. All the cases were treated with sulphadimidine at recommended dose with supportive therapy but no response was reported due to the fatal encephalitis.

Non-peptide secondary metabolites from poisonous mushrooms: overview of chemistry, bioactivity, and biosynthesis.

Covering: up to June 2021A wide variety of mushrooms have traditionally been recognized as edible fungi with high nutritional value and low calories, and abundantly produce structurally diverse and bioactive secondary metabolites. However, accidental ingestion of poisonous mushrooms can result in serious illnesses and even death. Chemically, mushroom poisoning is associated with secondary metabolites produced in poisonous mushrooms, causing specific toxicity. However, many poisonous mushrooms have not been fully investigated for their secondary metabolites, and the secondary metabolites of poisonous mushrooms have not been systematically summarized for details such as chemical composition and biosynthetic mechanisms. The isolation and identification of secondary metabolites from poisonous mushrooms have great research value since these compounds could be lethal toxins that contribute to the toxicity of mushrooms or could provide lead compounds with remarkable biological activities that can promote advances in other related disciplines, such as biochemistry and pharmacology. In this review, we summarize the structures and biological activities of secondary metabolites identified from poisonous mushrooms and provide an overview of the current information on these metabolites, focusing on their chemistry, bioactivity, and biosynthesis.

Solution Structures of Bacillus anthracis Protective Antigen Proteins Using Small Angle Neutron Scattering and Protective Antigen 63 Ion Channel Formation Kinetics.

We are studying the structures of bacterial toxins that form ion channels and enable macromolecule transport across membranes. For example, the crystal structure of the Staphylococcus aureus α-hemolysin (α-HL) channel in its functional state was confirmed using neutron reflectometry (NR) with the protein reconstituted in membranes tethered to a solid support. This method, which provides sub-nanometer structural information, could also test putative structures of the Bacillus anthracis protective antigen 63 (PA63) channel, locate where B. anthracis lethal factor and edema factor toxins (LF and EF, respectively) bind to it, and determine how certain small molecules can inhibit the interaction of LF and EF with the channel. We report here the solution structures of channel-forming PA63 and its precursor PA83 (which does not form channels) obtained with small angle neutron scattering. At near neutral pH, PA83 is a monomer and PA63 a heptamer. The latter is compared to two cryo-electron microscopy structures. We also show that although the α-HL and PA63 channels have similar structural features, unlike α-HL, PA63 channel formation in lipid bilayer membranes ceases within minutes of protein addition, which currently precludes the use of NR for elucidating the interactions between PA63, LF, EF, and potential therapeutic agents.

Isolation and Characterization of Photorhabdus Spp. (Enterobacteriaceae) Isolated From Heterorhabditis Bacteriophora in Kashere, Nigeria

Photorhabdus bacteria are symbiotically associated with the infective juveniles of entomopathogenic nematodes of the genus Heterorhabditis. These bacteria after infecting a susceptible host, produces a host of lethal toxins that killthe insect hosts within 24 to 72 hours. Consequently they have emerged and are trending as excellent biological control agents against insect pests of agricultural crops. Therefore, this study aim to isolate, identify and test the pathogenicity of Photorhabdus bacteria isolated from Heterorhabditis bacteriophora, entomopathogenic nematode from Kashere, Gombe State, Nigeria. To this end phenotypic and biochemical tests were conducted. The tests conducted showed that the isolate exhibited characteristics similar to those of Photorhabdus bacteria that have been identified. Last instar larvae of G. mellonella exposed to different concentrations of the bacterial isolate showed some level of susceptibility of the larvae to the bacterial isolate confirming its biological control potential.

Tetrodotoxins in French Bivalve Mollusks-Analytical Methodology, Environmental Dynamics and Screening of Bacterial Strain Collections.

Tetrodotoxins (TTXs) are potentially lethal paralytic toxins that have been identified in European shellfish over recent years. Risk assessment has suggested comparatively low levels (44 µg TTX-equivalent/kg) but stresses the lack of data on occurrence. Both bacteria and dinoflagellates were suggested as possible biogenic sources, either from an endogenous or exogenous origin. We thus investigated TTXs in (i) 98 shellfish samples and (ii) 122 bacterial strains, isolated from French environments. We optimized a method based on mass spectrometry, using a single extraction step followed by ultrafiltration without Solid Phase Extraction and matrix-matched calibration for both shellfish and bacterial matrix. Limits of detection and quantification were 6.3 and 12.5 µg/kg for shellfish and 5.0 and 10 µg/kg for bacterial matrix, respectively. Even though bacterial matrix resulted in signal enhancement, no TTX analog was detected in any strain. Bivalves (either Crassostrea gigas or Ruditapes philippinarum) were surveyed in six French production areas over 2.5–3 month periods (2018–2019). Concentrations of TTX ranged from ‘not detected’ to a maximum of 32 µg/kg (Bay of Brest, 17 June 2019), with events lasting 2 weeks at maximum. While these results are in line with previous studies, they provide new data of TTX occurrence and confirm that the link between bacteria, bivalves and TTX is complex.

A Review on Neurotoxins from Clostridium botulinum against Neuro-muscular Disorders

Neuro-muscular disorders cause a series of serious complications in the human body, where some lead to considerable morbidity and mortality ocassionally. Neurological diseases result in dystrophy, inhibited growth, etc. This present review aimed to emphasize the employment of neurotoxins against neuro degenerative disorders. The source of neurotoxins includes botulinum (Clostridium botulinum), snakes like Vespa orientalis and some medically important arthropods like hornets and spiders. The review not only describes the potential of the neurotoxins in the treatment but also elucidates the mechanism of action of lethal toxins like botulinum. Safety and dosage regimens of various toxins with the help of proven study data would aid in endorsing researchers for further research on toxins making them more superior targeted drugs.

Pathophysiological profile of awake and anesthetized pigs following systemic exposure to the highly lethal ricin toxin

Ricin, a plant-derived toxin originating from the seeds of Ricinus communis (castor bean plant), is one of the most lethal toxins known. To date, no in-depth study of systemic exposure to ricin in a standardized large animal model has been reported. This study details for the first time the pathophysiological hemodynamic profile following systemic/intramuscular exposure to the ricin toxin in a porcine model by comprehensive cardiorespiratory monitoring of awake and anesthetized pigs. Unlike respiratory exposure to ricin, which is characterized by the development of acute respiratory distress syndrome, following intramuscular exposure to ricin respiratory parameters were grossly unaffected, however the hemodynamics of both awake and anesthetize pigs were unsustainably compromised. We show that in the early phase until approximately 24 h post-exposure, cardiac output is not impaired although one of its components, stroke volume, is relatively low. This is due to compensatory increase in heart rate, which eventually becomes insufficient. Later, distributive shock develops, characterized by severe vasodilatation (decreased systemic vascular resistance), low central venous oxygen saturation and elevation of venous-to-arterial carbon dioxide difference indicating increase in tissue oxygen demand not met by cardiac supply. These findings serve as a basis for further studies to evaluate the ability of supportive treatments such as vasoactive and inotropic drugs, to postpone the hemodynamic deterioration and thus expand the therapeutic window for the anti-ricin treatment. Such studies are of crucial importance for judicious treatment of victims of acts of bioterrorism or of intentional self-poisoning.

Evolution of Interbacterial Antagonism in Bee Gut Microbiota Reflects Host and Symbiont Diversification.

Gram-negative bacteria frequently possess type VI secretion systems (T6SSs), protein complexes that are able to inject toxic proteins into nearby cells. Many aspects of T6SS structure and function have been characterized for model species, but less is known about the evolutionary processes that shape T6SS and effector (toxin) diversity in host-associated microbial communities. The bee gut microbiota is a simple community that has codiversified with bees for >80 million years. This study investigated how complements of T6SSs and effectors within the bee microbiota changed as bacteria and their hosts diversified into isolated species. We used protein homology to survey 198 isolate genomes of 9 Gram-negative species for genes encoding T6SS structural components; Rhs toxins, which are common T6SS effectors; and VgrG proteins, which are structural components associated with specific toxins. T6SS loci were present in 5 species clusters found only in bees, namely Apibacter spp., Gilliamella spp., Frischella perrara, "Candidatus Schmidhempelia bombi," and Snodgrassella alvi The distribution of T6SS loci suggests that at least 3 were present in the microbiota of the common ancestor of social bees and that loss of these genes in some bacterial lineages was linked to both host and bacterial speciation. Isolates differed enormously in repertoires of Rhs and VgrG proteins. We found that bacterial species employ different mechanisms for toxin acquisition and diversification and that species and strains sometimes lose the T6SS entirely, likely causing shifts in competitive dynamics within these communities.IMPORTANCE Antagonistic interactions between bacteria affect diversity and dynamics of host-associated communities, including gut communities that are linked to host health. In many bacterial communities, including human and honey bee gut microbiotas, antagonism is mediated by type VI secretion systems (T6SSs) that deliver lethal toxins to competing strains. In this study, we explored how T6SSs and associated toxins have evolved in the simple, host-specific gut microbiota of honey bees and bumble bees. Using comparative genomics, we explored the conservation, recombination, horizontal transfer, and loss of T6SSs and effectors during 80 million years of evolution of this bee-associated community. We find that that patterns of T6SS loss and retention are linked to differences in biology across host species, while trends in effector diversification are mostly specific to bacterial lineages.

Acute Hepatopancreases Necrosis Diseases (AHPND) as Challenging Threat in Shrimp

White feces syndrome (WFS) is an emerging problem for penaeid shrimp farming industries in South East Asia countries. Outbreaks began in cultivated shrimp Penaeus (Penaeus) monodon, and Penaeus (Litopenaeus) vannamei and spread progressively worldwide, although the disease's cause was unknown. In 2011 a case definition for AHPND (as acute hepatopancreatic necrosis diseases) and white fecal syndrome (WFS) were reported. The presence of white feces floating on water and clinical symptoms include pale empty gut region, reduced growth, movable shell, and black discoloration. The pacific white shrimp, Litopenaeus vannamei, with the major shrimp cultivable species globally, is currently in danger by a severe disease- WFS, which causes serious losses worldwide. It has been confirmed that the causative agent of WFS/AHPND is a bacterium that is a pathogen - probably Vibrio parahaemolyticus. This bacterium currently reported has acquired plasmids that encode lethal binary toxins PirA/PirB causing rapid death of infected shrimp. Additionally, this plasmid acquired some virulence factor which is directly related to pathogenicity. Further rapid diagnostic tests for early detection of WFS/AHPND pathogens will promote the production of hatchery and pond maintenance and contribute to the long-term explication of the disease's various aspects.

A Quest for a Universal Plasma-Derived Antivenom Against All Elapid Neurotoxic Snake Venoms.

This review describes the research aimed at the development of universal antivenom against elapid neurotoxic snake venoms. The antivenoms produced in Thailand in the 1980s were of low potency, especially against the elapid venoms. This was thought to be due to the low immunogenicity of the α-neurotoxins, which are the most lethal toxins in these venoms. Comparisons of various α-neurotoxin conjugates and polymers, and also different immunological adjuvants, showed that the adjuvant used is the major determinant in the antibody response in horses. The potent Freund’s adjuvant was not used due to its severe local side-effect in horses. Therefore, a novel immunization protocol termed ‘low dose, low volume multi-site’ was developed for use in horses. This immunization protocol has led to the production of highly potent monospecific antivenoms against several elapid and viperid venoms, and two potent polyspecific antivenoms, one against 4 neurotoxic and another against 3 hematotoxic venoms. The immunization protocol has also led to other improvements in antivenom production including: several fold increases in antiserum potency, a reduction in the time required to reach therapeutically useful antibody titers, a 90% reduction in the amount of venom used, and 100% of the horses responding to the immunization program. This development is partly responsible for significant decrease in the Thailand’s annual snakebite death toll from a few dozens to mostly nil in recent years. Finally, a simple and novel immunization strategy, using a ‘diverse toxin repertoire’ composed of numerous elapid toxin fractions as immunogen, was proposed and tested. This immunization procedure has resulted in the successful production of a widely paraspecific antiserum against at least 36 neurotoxic venoms of 28 species encompassing 10 genera and from 20 countries on four continents, and possibly against all elapid venoms with α-neurotoxins as the lethal toxins. These results indicate that, with optimizations of the composition of the ‘diverse toxin repertoire’, the immunization scheme and antibody fractionation to increase the antivenom neutralizing potency, an effective universal antivenom against the neurotoxic elapid snakes of the world can be produced.

Analysis of the microRNA and mRNA expression profile of ricin toxin-treated RAW264.7 cells reveals that miR-155-3p suppresses cell inflammation by targeting GAB2

Ricin toxin (RT) is one of the most lethal toxins derived from the seed of castor beans. In addition to its main toxic mechanism of inhibiting the synthesis of cellular proteins, RT can induce the production of inflammatory cytokines. MicroRNAs (miRNAs) play a key role in regulating both innate and adaptive immunity. To elucidate the regulation of miRNAs in RT-induced inflammation injury, the RNA high-throughput sequencing (RNA-Seq) technology was used to analyze the expression profile of miRNAs and mRNAs in RT-treated RAW264.7 cells. Results showed that a total of 323 mRNAs and 19 miRNAs differentially expressed after RT treated. Meanwhile, 713 miRNA-mRNA interaction pairs were identified by bioinformatics analysis. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis showed that those interaction pairs were mainly involved in JAK-STAT, T cell receptor, and MAPK signaling pathways. Moreover, we further predicted and determined the targeting relationship between miR-155-3p and GAB2 through TargetScan and dual-luciferase reporter assay. Mechanically, overexpression of miR-155-3p can reduce the secretion of TNF-α in RAW264.7 cells, revealing a possible mechanism of miR-155-3p regulating RT-induced inflammatory injury. This study provides a new perspective for clarifying the mechanism of RT-induced inflammatory injury and reveals the potential role of miRNAs in innate immune regulation.

Evaluation and Comparison of Clostridium Epsilon-Alpha Fusion Gene Expression Using Different Commercial Expression Vector.

Clostridium perfringens and Clostridium septicum are gram-positive, anaerobic, spore-forming rods and pathogens for humans and livestock, which are widespread in nature as well as human and animal digestive systems. C. perfringens produces numerous different exoproteins, which are various systems of action. The major C. perfringens toxins include alpha, beta, epsilon, and iota. C. perfringens are classified into five groups (A-E) on the basis of the production of these lethal toxins. Furthermore, toxins secreted from C. septicum include alpha, beta, delta, and gamma. Epsilon and alpha toxins of C. perfringens and C. septicum are the major causes of enterotoxemia and braxy in sheep and goats, respectively. The production of recombinant immunogenic proteins of these bacteria using suitable expression vectors and expression prokaryotic hosts can be a convenient method for the reduction of the costs and production time of clostridial anaerobic vaccines. In the present study, recombinant Escherichia coli strain TOP10 containing pJET&amp;epsilon;&amp;alpha; was used for the evaluation of C. perfringens type D and C. septicum epsilon-alpha fusion protein using different commercial vectors. After the extraction of pJET&amp;epsilon;&amp;alpha; from the recombinant cell, it was digested by NdeI and XhoI restriction enzymes and subcloned into pET22b (+), pET26b (+), and pGEM-B1 expression vectors in E. coli/Rosetta and E. coli/BL21 (DE3). The expression of recombinant fusion toxin was evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting in three different temperatures, various isopropyl &amp;beta;-D-1-thiogalactopyranoside (IPTG) gradients, and different times using pGEM&amp;epsilon;&amp;alpha;, pET22&amp;epsilon;&amp;alpha;, and pET26&amp;epsilon;&amp;alpha; vectors in E. coli/Rosetta and E. coli/BL21 (DE3). According to the obtained results, recombinant E. coli/Rosetta/pET22&amp;epsilon;&amp;alpha; showed better expression at a temperature of 37&amp;deg;C after 6 h of induction by IPTG.

Coral Keratitis: Case Report and Review of Mechanisms of Action, Clinical Management and Prognosis of Ocular Exposure to Palytoxin.

Palytoxin is one of the most lethal natural toxins ever discovered. This molecule has been isolated from various marine animals, including zoanthid corals. This popular organism is commonly found in many home saltwater aquariums due to its beauty and survivability. As a result of an increase in popularity, an increased number of individuals are at risk for exposure to this potentially deadly toxin. Affected patients may experience various symptoms based on the route of exposure (ie, cutaneous contact, inhalation of aerosolized toxin, ocular exposure, or ingestion). Ocular exposure can occur in various ways (eg, contact with contaminated water, rubbing the eye with a dirtied hand, or direct spraying into the eye), and incidence rates have dramatically risen in recent years. In this review, we discuss a case of systemic toxicity from inhalation and ocular exposure to presumed palytoxin on a zoanthid coral which resulted in an intensive care unit (ICU) stay, and corneal perforation which required a corneal transplant. Additionally, we review what is known about the mechanism of action of this toxin, propose a comprehensive hypothesis of its effects on corneal cells, and discuss the prognosis and clinical management of patients with systemic symptoms secondary to other routes of exposure.

The MBAssociates M1 Silent Pistol & Javette Projectiles: Chemical & Biological Warfare at the Individual Level

Small arms delivering chemical or biological payloads have been developed by a number of states in the modern era. As the war in Vietnam was intensifying in the mid-1960s, the U. S. Army became aware of one such weapon system being developed by MBAssociates of San Ramon, California. This could silently and covertly deliver non-lethal tranquilisers to military guard dogs or lethal toxins to enemy personnel by projecting a tiny, dartlike ‘Javette’—capable of striking a target unnoticed. The Army’s Special Operations Division, Army Biological Warfare Laboratories, and the CIA subsequently acquired the new weapon, operationalising it by treating Javettes with deadly toxins such as saxitoxin. When, in 1969–1970, President Richard Nixon renounced the United States’ use of toxins and ordered stockpiles destroyed, the MBAssociates weapon was catapulted into the limelight through the actions of an unscrupulous CIA employee. This article traces the full arc of Javette development, from the predecessor experiments conducted by Robert Mainhardt and his colleagues beginning in 1960, through the Senate hearings conducted by the Church Committee in 1975, to Mainhardt’s final attempts to generate government sales in the 1990s. The author focuses on the little-known Javette projectiles themselves, but also addresses delivery devices (handguns), toxins, and the broader historical context.

Complex Physiological Phenotypes: Structural Variation in the Muscle Voltage-Gated Sodium Channel Imparts Resistance to Lethal Scorpion Toxins

SUMMARYExtreme environments drive the evolution of adaptations that underlie tolerance to painful stimuli. However, painful stimuli provide valuable warnings to animals about conditions that could damage tissues or cause death. Thus, reduced pain sensitivity should evolve as part of a phenotype that includes physiological resistance to lethal stimuli. Interactions between Arizona (AZ) bark scorpions and southern grasshopper mice provide an ideal system to investigate complex physiological phenotypes across multiple levels of biological organization. Grasshopper mice prey on AZ bark scorpions, despite the painful and deadly toxins associated with their sting. Adaptation of the pain receptor Nav1.8 imparts grasshopper mice with resistance to painful toxins, but mechanisms underlying resistance to lethal toxins, necessary for survival, remain unknown. The pathophysiological effects of bark scorpion venom include respiratory failure from impaired muscle contraction. Two classes of venom proteins, alpha and beta toxins, enhance activation and delay inactivation in the voltage-gated sodium channel (Nav1.4) that regulates muscle contraction. We show that grasshopper mice soleus muscle is resistant to bark scorpion venom, and that Nav1.4 is resistant to alpha- and beta-toxin effects on channel activation and inactivation. Reduced sensitivity to b-toxin effects on activation is due, in part, to molecular variation at two distinct locations within the channel. Computational models of Nav1.4 revealed that amino acid substitutions alter the biochemical properties of the channel near toxin binding sites. Elucidating the structure-activity relationships in physiologically critical proteins will advance efforts to determine the rules that govern how genotypes interact with the environment to yield complex physiological phenotypes.