Scorpionism and serotherapy in Mexico

Production of recombinant scorpion antivenoms in E. coli: current state and perspectives

Scorpion envenomation is a serious health problem in tropical and subtropical zones. The access to scorpion antivenom is sometimes limited in availability and specificity. The classical production process is cumbersome, from the hyper-immunization of the horses to the IgG digestion and purification of the F(ab)'₂ antibody fragments. The production of recombinant antibody fragments in Escherichia coli is a popular trend due to the ability of this microbial host to produce correctly folded proteins. Small recombinant antibody fragments, such as single-chain variable fragments (scFv) and nanobodies (V_HH), have been constructed to recognize and neutralize the neurotoxins responsible for the envenomation symptoms in humans. They are the focus of interest of the most recent studies and are proposed as potentially new generation of pharmaceuticals for their use in immunotherapy against scorpion stings of the Buthidae family. This literature review comprises the current status on the scorpion antivenom market and the analyses of cross-reactivity of commercial scorpion anti-serum against non-specific scorpion venoms. Recent studies on the production of new recombinant scFv and nanobodies will be presented, with a focus on the Androctonus and Centruroides scorpion species. Protein engineering-based technology could be the key to obtaining the next generation of therapeutics capable of neutralizing and cross-reacting against several types of scorpion venoms. KEY POINTS: • Commercial antivenoms consist of predominantly purified equine F(ab)'₂fragments. • Nanobody-based antivenom can neutralize Androctonus venoms and have a low immunogenicity. • Affinity maturation and directed evolution are used to obtain potent scFv families against Centruroides scorpions.

Comparative Proteomic Analysis of the Venoms from the Most Dangerous Scorpions in Morocco: Androctonus mauritanicus and Buthus occitanus

Morocco is known to harbor two of the world's most dangerous scorpion species: the black Androctonus mauritanicus (Am) and the yellow Buthus occitanus (Bo), responsible for 83% and 14% of severe envenomation cases, respectively. Scorpion venom is a mixture of biological molecules of variable structures and activities, most of which are proteins of low molecular weights referred to as toxins. In addition to toxins, scorpion venoms also contain biogenic amines, polyamines, and enzymes. With the aim of investigating the composition of the Am and Bo venoms, we conducted an analysis of the venoms by mass spectrometry (ESI-MS) after separation by reversed-phase HPLC chromatography. Results from a total of 19 fractions obtained for the Am venom versus 22 fractions for the Bo venom allowed the identification of approximately 410 and 252 molecular masses, respectively. In both venoms, the most abundant toxins were found to range between 2-5 kDa and 6-8 kDa. This proteomic analysis not only allowed the drawing of an extensive mass fingerprint of the Androctonus mauritanicus and Buthus occitanus venoms but also provided a better insight into the nature of their toxins.

Comparison of the Scorpionism Caused by Centruroidesmargaritatus, Tityuspachyurus and Tityus n. sp. aff. metuendus Scorpion Venoms in Colombia

Among other scorpion species, Colombia has two genera of the Buthidae family Centruroides and Tityus, considered to be dangerous to humans. This research shares scientific knowledge aiming to a better understanding about the pathophysiological effects of such venoms. The venom of the three species: Centruroides margaritarus, Tityus pachyurus, and T. n. sp. aff. metuendus with biomedical interest were studied. An initial pre-glycemic sample was taken from ICR mice. They were later intraperitoneally inoculated with doses of 35% and 70% of LD₅₀ of total venom. Poisoning signs were observed during a 6-h period to determine the level of scorpionism. After observation, a second glycemic sample was taken, and a histopathological evaluation of different organs was performed. This work revealed that all three venoms showed considerably notorious histopathological alterations in main organs such as heart and lungs; and inducing multiple organ failure, in relation to the glycemia values, only C. margaritatus and T. n. sp. aff. metuendus showed significant changes through manifestation of hyperglycemia. According to the Colombian scorpionism level; signs were mild to severe affecting the autonomous nervous system.

Biochemical and Proteomic Characterization, and Pharmacological Insights of Indian Red Scorpion Venom Toxins

The Indian red scorpion (Mesobuthus tamulus) is one of the world's deadliest scorpions, with stings representing a life-threatening medical emergency. This species is distributed throughout the Indian sub-continent, including eastern Pakistan, eastern Nepal, and Sri Lanka. In India, Indian red scorpions are broadly distributed in western Maharashtra, Saurashtra, Kerala, Andhra Pradesh, Tamil Nadu, and Karnataka; however, fatal envenomations have been recorded primarily in the Konkan region of Maharashtra. The Indian red scorpion venom proteome comprises 110 proteins belonging to 13 venom protein families. The significant pharmacological activity is predominantly caused by the low molecular mass non-enzymatic Na+ and K+ ion channel toxins. Other minor toxins comprise 15.6% of the total venom proteome. Indian red scorpion stings induce the release of catecholamine, which leads to pathophysiological abnormalities in the victim. A strong correlation has been observed between venom proteome composition and local (swelling, redness, heat, and regional lymph node involvement) and systemic (tachycardia, mydriasis, hyperglycemia, hypertension, toxic myocarditis, cardiac failure, and pulmonary edema) manifestations. Immediate administration of antivenom is the preferred treatment for Indian red scorpion stings. However, scorpion-specific antivenoms have exhibited poor immunorecognition and neutralization of the low molecular mass toxins. The proteomic analysis also suggests that Indian red scorpion venom is a rich source of pharmacologically active molecules that may be envisaged as drug prototypes. The following review summarizes the progress made towards understanding the venom proteome of the Indian red scorpion and addresses the current understanding of the pathophysiology associated with its sting.

The venom of the scorpion Centruroides limpidus, which causes the highest number of stings in Mexico, is neutralized by two recombinant antibody fragments

Phage display and directed evolution have made it possible to generate recombinant antibodies in the format of single chain variable fragments (scFvs) capable of neutralizing different toxins and venoms of Mexican scorpions. Despite having managed to neutralize a significant number of venoms, some others have not yet been completely neutralized, due to the diversity of the toxic components present in them. An example is the venom of the scorpion Centruroides limpidus, which contains three toxins of medical importance, called Cll1, Cll2 and Cl13. The first two are neutralized by scFv 10FG2, while Cl13, due to its sequence divergence, was not even recognized. For this reason, the aim of the present work was the generation of a new scFv capable of neutralizing Cl13 toxin and thereby helping to neutralize the whole venom of this scorpion. By hybridoma technology, a monoclonal antibody (mAb B7) was generated, which was able to recognize and partially neutralize Cl13 toxin. From mAb B7, its scFv format was obtained, named scFv B7 and subjected to three cycles of directed evolution. At the end of these processes, scFv 11F which neutralized Cl13 toxin was obtained. This scFv, administered in conjunction with scFv 10FG2, allowed to fully neutralize the whole venom of Centruroides limpidus scorpion.

Animal Venoms-Curse or Cure?

An estimated 15% of animals are venomous, with representatives spread across the majority of animal lineages. Animals use venoms for various purposes, such as prey capture and predator deterrence. Humans have always been fascinated by venomous animals in a Janus-faced way. On the one hand, humans have a deeply rooted fear of venomous animals. This is boosted by their largely negative image in public media and the fact that snakes alone cause an annual global death toll in the hundreds of thousands, with even more people being left disabled or disfigured. Consequently, snake envenomation has recently been reclassified by the World Health Organization as a neglected tropical disease. On the other hand, there has been a growth in recent decades in the global scene of enthusiasts keeping venomous snakes, spiders, scorpions, and centipedes in captivity as pets. Recent scientific research has focussed on utilising animal venoms and toxins for the benefit of humanity in the form of molecular research tools, novel diagnostics and therapeutics, biopesticides, or anti-parasitic treatments. Continued research into developing efficient and safe antivenoms and promising discoveries of beneficial effects of animal toxins is further tipping the scales in favour of the “cure” rather than the “curse” prospect of venoms.

Factors involved in the resilience of incidence and decrease of mortality from scorpion stings in Mexico

In Mexico, scorpion sting envenomation (SSE) is a significant public health issue that has engaged the attention of health authorities for more than a century. Rigorously characterized today, scorpion sting incidence is stable around 230 stings per 100,000 population, i.e. 300,000 annual stings treated in Mexican health centers and hospitals. Higher incidence is observed mainly in central and Pacific Mexico. Scorpion populations thrive in populated places, particularly in impoverished areas. Scorpion stings occur in houses. This could explain similar incidence according to gender and age. The number of scorpion stings has remained stable since the mid-2000s. In contrast, mortality, which was over 1500 deaths per year before the 1960s, underwent a dramatic drop after the 1970s, from 500 deaths per year to fewer than 50 annual deaths today. Case fatality rates have shown similar trend. We noted a significantly higher specific mortality in males than in females (0.199 and 0.168 per 100,000 respectively; P < 1.9·10^-6). Three causes explained the drop in mortality and case fatality rate, a) ongoing improvement in hospital care, particularly in terms of supportive standardized treatments, b) the use of highly purified immunoglobulin F(ab')₂ fragments after 1995 and, c) increasing access to health services for most of the Mexican population. The authors retrace the history of the management of SSE, including the development of antivenoms, in Mexico between 1905 and today.

Defensive Venoms: Is Pain Sufficient for Predator Deterrence?

Pain, though unpleasant, is adaptive in calling an animal’s attention to potential tissue damage. A long list of animals representing diverse taxa possess venom-mediated, pain-inducing bites or stings that work by co-opting the pain-sensing pathways of potential enemies. Typically, such venoms include toxins that cause tissue damage or disrupt neuronal activity, rendering painful stings honest indicators of harm. But could pain alone be sufficient for deterring a hungry predator? Some venomologists have argued “no”; predators, in the absence of injury, would “see through” the bluff of a painful but otherwise benign sting or bite. Because most algogenic venoms are also toxic (although not vice versa), it has been difficult to disentangle the relative contributions of each component to predator deterrence. Southern grasshopper mice (Onychomys torridus) are voracious predators of arthropods, feeding on a diversity of scorpion species whose stings vary in painfulness, including painful Arizona bark scorpions (Centruroides sculpturatus) and essentially painless stripe-tailed scorpions (Paravaejovis spinigerus). Moreover, southern grasshopper mice have evolved resistance to the lethal toxins in bark scorpion venom, rendering a sting from these scorpions painful but harmless. Results from a series of laboratory experiments demonstrate that painful stings matter. Grasshopper mice preferred to prey on stripe-tailed scorpions rather than bark scorpions when both species could sting; the preference disappeared when each species had their stingers blocked. A painful sting therefore appears necessary for a scorpion to deter a hungry grasshopper mouse, but it may not always be sufficient: after first attacking and consuming a painless stripe-tailed scorpion, many grasshopper mice went on to attack, kill, and eat a bark scorpion even when the scorpion was capable of stinging. Defensive venoms that result in tissue damage or neurological dysfunction may, thus, be required to condition greater aversion than venoms causing pain alone.

Approach to scorpion stings in pregnancy: A retrospective case series and literature review

OBJECTIVE

Scorpion stings remain a serious health problem in many parts of the world. There is very limited information regarding the effects of therapies delivered for scorpion stings in pregnant women on the mother and fetus. They can cause acute conditions such as fetal loss, preterm delivery, or placental abnormalities and can also result in other conditions that may have an effect on the baby in the long term.

MATERIALS AND METHODS

In this study the medical records of 24 pregnant women who were admitted to the emergency room at Suruç State Hospital due to scorpion stings between January 1, 2013 and January 1, 2014 were retrospectively reviewed. Age, gestational week, monthly distribution of the cases, type of delivery, status of the fetus, affected body sites, and local and systemic findings were evaluated. The clinical severity of each case was assessed using Abroug's classification. A fetal biophysical profile test was administered in pregnant women above 24 weeks of gestation. The newborns underwent follow-up for mental and motor functions in the pediatric department at three-month intervals for 12 months.

RESULTS

24 patients, with a mean age of 26.1 ± 2.4 years, were included in the study. The most common region stung by scorpions was Lower extremity (58.3%). The most common symptom occurred in cases was immediate localized pain (58%). In terms of gestational age, 41.6% of scorpion sting were within the third trimester. Biophysical profile scores were 8 and above. Only symptomatic treatment, without use of anti-venom, was done to all the patients in this study. And neither death nor major sequel happened.

CONCLUSION

Scorpion stings during pregnancy may not have significant adverse effects on the fetus and the mother. Decisions regarding the use of anti-venom in pregnant women should be considered carefully when only limited safety information, especially in those patients with only local symptoms.

A review on Respiratory allergy caused by insects

Hypersensitivity or allergy encompasses a wide range of immunological reactions that generally have adverse consequences involving one or many organ systems of the body. Allergens are usually glycoprotein or chemically complex low molecular weight substances. The common allergens include pollen, fungal spores, house dust mite and house dust, animal danders, drugs, foods, insect emanations, and detritus, etc. Information on the role of insects in respiratory allergy is increasing in the literature. There are about 30 million living species of insects. These insects can broadly be classified as stinging insects, biting insects and non-stinging and non-biting insects. All materials form insets namely wings, scales, saliva; dried feces and venom can cause allergic diseases, such as rhinitis, conjunctivitis, asthma and urticaria. There are wide varieties of insects such as moths, butterflies, bees, wasps, hornets, yellow jackets, flies, beetles, cockroaches, and mosquitoes. Exposure to emanations and detritus of these insects may lead to several allergies in some genetically predisposed individuals. Therefore, it is of interest to review allergies caused by various insect's stings and bites and their adverse effect on the human body.

North American scorpion species of public health importance with a reappraisal of historical epidemiology

Scorpionism is a severe threat to public health in North America. Historically, few species of Centruroides have been considered to be the offending taxa, but we know now that their diversity is greater and our knowledge incomplete. Current distribution maps are inadequate for some species. Epidemiologic studies are sporadic and local, and a complete synthesis for North America is missing. We analyze historical and recent knowledge about the identity, distribution and epidemiology of species of medical importance in North America. PubMed, Google Scholar, the National Collection of Arachnids, and results of recent field work were consulted in the preparation of our analysis. We recognized 21 species and one subspecies of medically important scorpions in need of precise geographical delimitation. All these species are found in Mexico, which is clearly a hotspot for scorpionism. Although mortality has been steadily decreasing, deaths still occur, and morbidity remains high. Mortality is most common at age classes of 0-10 years and >50. Morbidity is highest in age class 15-50 years, including the most economically active segment of the population. The season of the highest incidence of scorpion sting peaks between spring and summer but there appears to be a second, lower peak at the end of the summer. Although the systematics of the genus Centruroides has advanced considerably, our knowledge of its diversity remains fragmentary. There is a disconnection between the actual distribution of the scorpions and the incidence maps constructed from scorpion sting records. Despite a historically robust knowledge of the distribution of well-known species, most recently described species are known from only a few localities. Some of the epidemiological parameters are consistent among studies reported herein.

Ultrasensitive sensing of Androctonus australis hector scorpion venom toxins in biological fluids using an electrochemical graphene quantum dots/nanobody-based platform

Rapid and sensitive detection of low levels of scorpion venom toxins in biological fluids is of tremendous importance for decision-taking in cases of envenomation by scorpions stings. In Tunisia, at least 1200 severe envenomation cases by Androctonus australis hector (Aah) scorpion stings were reported annually. In this work, we report on a novel electrochemical immuno-sandwich to detect the Aah50 toxic fraction within the Aah scorpion venom using the bispecific nanobody format specially designed to highly recognize and neutralize the two most toxic molecules in the AahG50 venom fraction (i.e. AahI and AahII toxins), graphene quantum dots (GQDs) constructed on the surface carbon screen-printed electrodes. Hydroquinone/H₂O₂/peroxidase system was used to amplify the current in order to achieve the detection of low levels of AahG50. Electrochemical studies revealed a high sensitivity toward the AahG50 with a sensitivity of 18.2 nA mL pg^-1 and a picomolar limit of detection as low as 0.55 pg mL^-1. The platform exhibits very good metrological performances such as repeatability, reproducibility, selectivity and long storage stability. Matrix effect was found to be insignificant as demonstrated by assays performed in human blood serum and urine.

Mass fingerprinting and electrophysiological analysis of the venom from the scorpion Centruroides hirsutipalpus (Scorpiones: Buthidae)

Background

Centruroides hirsutipalpus, of the family Buthidae, is a scorpion endemic to the Western Pacific region of Mexico. Although medically important, its venom has not yet been studied. Therefore, this communication aims to identify their venom components and possible functions.

Methods

Fingerprinting mass analysis of the soluble venom from this scorpion was achieved by high-performance liquid chromatography and electrospray mass spectrometry. Furthermore, the soluble venom and its toxic effects were evaluated extensively via electrophysiological assays in HEK cells expressing human voltage-gated Na⁺ channels (hNav 1.1 to Nav1.6), CHO cells expressing hNav 1.7, potassium channel hERG 1 (Ether-à-go-go-related-gene) and the human K⁺-channel hKv1.1.

Results

The separation of soluble venom produced 60 fractions from which 83 distinct components were identified. The molecular mass distribution of these components varies from 340 to 21,120 Da. Most of the peptides have a molecular weight between 7001 and 8000 Da (46% components), a range that usually corresponds to peptides known to affect Na⁺ channels. Peptides with molecular masses from 3000 to 5000 Da (28% of the components) were identified within the range corresponding to K⁺-channel blocking toxins. Two peptides were obtained in pure format and completely sequenced: one with 29 amino acids, showing sequence similarity to an “orphan peptide” of C. limpidus, and the other with 65 amino acid residues shown to be an arthropod toxin (lethal to crustaceans and toxic to crickets). The electrophysiological results of the whole soluble venom show a beta type modification of the currents of channels Nav1.1, Nav1.2 and Nav1.6. The main effect observed in channels hERG and hKv 1.1 was a reduction of the currents.

Conclusion

The venom contains more than 83 distinct components, among which are peptides that affect the function of human Na⁺-channels and K⁺-channels. Two new complete amino acid sequences were determined: one an arthropod toxin, the other a peptide of unknown function.

Dangerous arachnids-Fake news or reality?

The public perception of spiders and scorpions is skewed towards the potential harm they can inflict in humans, despite recent scientific evidence that arachnid venom components might be useful as bioinsecticides or even human therapeutics. Nevertheless, arachnids are becoming more popular as pets in Europe, America and Asia, raising the question for regulatory agencies in these regions as to whether they need to take measurements to protect their citizens. In order to decide upon the necessary regulatory steps, they first need to determine which arachnids are actually dangerous to humans. This review therefore provides an overview of the current literature on verified bites and stings from spiders and scorpions with the aim of assessing their potential danger for human health. As a guideline, we also provide a list of those arachnid genera that we consider as potentially dangerous, which includes 10 spider and 11 scorpion genera. The arachnid genera classified as dangerous comprise less than a quarter of all extant scorpion species and only 0.5% of all spiders species, with the actual number most likely being much lower than that, as not all species in those genera might turn out to pose an actual threat for humans. In conclusion, we found that only a small percentage of scorpions and a minute percentage of all spiders can be considered as potentially dangerous to humans. While in some countries of origin the high incidence of envenomations by dangerous arachnids can result in a serious problem to the health system, we assessed the risk that the same species pose when kept as pets under controlled maintenance conditions as significantly lower.

Clinical and Epidemiological Aspects of Scorpionism in the World: A Systematic Review

OBJECTIVE

Scorpion stings are registered worldwide, but the incidence and the features of the envenomations vary depending on the region. The aim of this review was to summarize the epidemiological, clinical, diagnostic, and therapeutic data worldwide regarding humans stung by scorpions.

METHODS

A systematic review of the literature was conducted through the online databases of the Virtual Health Library (VHL), which hosts Medline and the Latin American and Caribbean Center on Health Sciences Informational (LILACS) database. We selected articles published between January 1, 2002 and July 31, 2014.

RESULTS

Scorpion envenomation reports were found throughout the world, mainly in subtropical and tropical regions. The clinical manifestations were sympathetically and parasympathetically mediated, depending on the species of scorpion. Some of the most common severe complications of scorpionism included respiratory distress syndrome, pulmonary edema, cardiac dysfunction, impaired hemostasis, pancreatitis, and multiple organ failure. Scorpion envenomation could be classified as mild, moderate, and severe, and the therapeutic approach was based on the case severity. The treatment comprised 3 components: symptomatic measures, vital functions support, and injection of antivenom. Moreover, the time that elapsed between the sting and administration of the appropriate medical care was extremely important to the patient's prognosis.

CONCLUSIONS

The large number of scorpion stings worldwide is concerning and reaffirms the need for new prevention measures and policies to reduce the incidence, prevalence, morbidity, and mortality rates from these poisonous arachnids.

Antivenom Evaluation by Electrophysiological Analysis

Scorpion stings on humans are medically relevant because they may contain toxins that specifically target ion channels. During antivenom production, pharmaceutical companies must use a large number of experimental animals to ensure the antivenom's efficacy according to pharmacopeia methods. Here we present an electrophysiological alternative for the evaluation of horse antivenoms produced against two species of Moroccan scorpions: Buthus mardochei and Androctonus mauretanicus. Human sodium and potassium channels and acetylcholine nicotinic receptors were analyzed by standard patch-clamp techniques. The results showed that the antivenom is capable of reversing ion current disruption caused by the venom application. We propose the use of this in vitro technique for antivenom evaluation as an alternative to using a large number of live animals.

Design and expression of recombinant toxins from Mexican scorpions of the genus Centruroides for production of antivenoms

This manuscript describes the design of plasmids containing the genes coding for four main mammalian toxins of scorpions from the genus Centruroides (C.) of Mexico. The genes that code for toxin 2 of C. noxius (Cn2), toxin 2 from C. suffusus (Css2) and toxins 1 and 2 from C. limpidus (Cll1 and Cll2) were included into individual plasmids carrying the genetic construction for expression of fusion proteins containing a leader peptide (pelB) that directs the expressed protein to the bacterial periplasm, a carrier protein (thioredoxin), the cleavage site for enterokinase, the chosen toxin and a poly-histidine tag (6xHis-tag) for purification of the hybrid protein by immobilized metal ion affinity chromatography after expression in Escherichia coli strain BL21 (DE3). The purified hybrid proteins containing the recombinant toxins (abbreviated Thio-EK-Toxin) were used for immunization of three independent groups of ten mice and four rabbits. Challenging the first group of mice, immunized with recombinant Thio-EK-Css2, with three median lethal doses (LD₅₀) of C. suffusus soluble venom resulted in the survival of all the test animals without showing intoxication symptoms. All control mice (none immunized) died. Similar results were obtained with mice previously immunized with Thio-EK-Cn2 and challenged with C. noxius venom. The third group of mice immunized with both Thio-EK-Cll1 and Thio-EK-Cll2 showed an 80% survival ratio when challenged with only one LD₅₀ of C. limpidus venom, all showing symptoms of intoxication. The sera from rabbits immunized with a combination of the four recombinant toxins were collected separately and used to assess their neutralization capacity in vitro (pre-incubating the serum with the respective scorpion venom and injecting the mixture into mice), using six mice for each serum/venom combination tested. The venoms from the six most dangerous scorpion species of Mexico were assayed: C. noxius, C. suffusus, C. limpidus, C. elegans, C. tecomanus and C. sculpturatus. Two hundred and 50 μL of serum from any of the immunized rabbits were enough to neutralize three LD₅₀ of any of the tested venoms, with mice showing no symptoms of intoxication. These results confirm that the recombinant forms of the main toxins from the most dangerous scorpions of Mexico are excellent immunogens for the production of antivenoms to treat scorpion intoxications.

Functional and immuno-reactive characterization of a previously undescribed peptide from the venom of the scorpion Centruroides limpidus

A previously undescribed toxic peptide named Cl13 was purified from the venom of the Mexican scorpion Centruroides limpidus. It contains 66 amino acid residues, including four disulfide bonds. The physiological effects assayed in 7 different subtypes of voltage gated Na⁺-channels, showed that it belongs to the β-scorpion toxin type. The most notorious effects were observed in subtypes Nav1.4, Nav1.5 and Nav1.6. Although having important sequence similarities with two other lethal toxins from this scorpion species (Cll1m and Cll2), the recently developed single chain antibody fragments (scFv) of human origin were not capable of protecting against Cl13. At the amino acid sequence level, in 3 stretches of peptide Cl13 (positions 7-9, 30-38 and 62-66) some differences with respect to other similar toxins are observed. Some of these differences coincide with contact points with the human antibody fragments.

[Passive immunization in dogs and cats]

Antibodies play an important role in the defense against infectious diseases. Passive immunization provides immediate protection through transfer of exogenous antibodies to a recipient. It is mainly used for prophylaxis in dogs and cats that failed to receive maternal antibodies through the colostrum or when there is an acute risk to acquire infectious diseases. Only a small number of placebo-controlled studies have been published regarding the therapeutic use of passive immunization in small animals. While positive effects were reported in cats with acute virus infections of the upper respiratory tract and in dogs with distemper, no statistically significant influence could be demonstrated in the treatment of canine parvovirosis. Prospective, double-blinded, and placebo-controlled studies using adequate numbers of patients are warranted for a definitive statement regarding the therapeutic and prophylactic use of passive immunization in dogs and cats.

Comprehensive analysis of venom from the scorpion Centruroides tecomanus reveals compounds with antimicrobial, cytotoxic, and insecticidal activities

Centruroides tecomanus is a medically important scorpion of the state of Colima (Mexico). This communication reports the identification of venom components of this scorpion with biological activity over insects/crickets (Acheta domestica), crustaceans/fresh water shrimps (Cambarellus montezumae), and mammalians/mice (Mus musculus, strain CD1). It also describes the pharmacological effects on cell lines in culture (L5178Y cells, HeLa cells, HuTu cells and Jurkat E6-1 cells), as well as on several types of bacteria (see below). The soluble venom of this scorpion was fractionated by high-performance liquid chromatography (HPLC) and collected separately in twelve independent fractions collected over 60 min run (5 min time apart each other). The HPLC components of fraction VII were lethal to all three species used for assay. The IVth fraction had a toxic effect on freshwater shrimps. In this species, fractions VI, VII and VIII were all lethal. For crickets, fractions V and VI were toxic and fraction VII was lethal. In mouse, the lethal components were found in fraction VII, whereas fraction VIII was toxic, but not lethal, at the doses assayed. The molecular weight of peptides from the various group of fractions were identified by mass spectrometry determination. Components lethal to mice showed molecular weights from 7013 to 7487 Da. Two peptides were obtained in homogeneous form and shown to be lethal to the three species of animal used for assay. The soluble venom tested on L5178Y cell line survival was shown to be cytotoxic, at 10-100 μg/mL concentration, when compared to control murine splenocytes (p = 0.007). The soluble venom applied to Hela, Hutu and Jurkat cell lines did not show cytotoxic effects at these concentrations. On the contrary, it seems to have a proliferative effect. However the HPLC fractions I, III, VI and XII do have a cytotoxic effect on Jurkat E06-1 cells in culture at 200 μg/mL concentration. The antimicrobial activity of the venom fractions on Staphylococcus aureus (gram-positive), Escherichia coli, Pseudomonas aeruginosa y Salmonella spp (gram-negative) was measured, using the liquid inhibition growth system. The four strains of bacteria used were susceptible to fractions III and IV, affecting all four bacterial strains at concentrations below 5 μg/mL.

Transcriptome analysis of scorpion species belonging to the Vaejovis genus

Scorpions belonging to the Buthidae family have traditionally drawn much of the biochemist's attention due to the strong toxicity of their venoms. Scorpions not toxic to mammals, however, also have complex venoms. They have been shown to be an important source of bioactive peptides, some of them identified as potential drug candidates for the treatment of several emerging diseases and conditions. It is therefore important to characterize the large diversity of components found in the non-Buthidae venoms. As a contribution to this goal, this manuscript reports the construction and characterization of cDNA libraries from four scorpion species belonging to the Vaejovis genus of the Vaejovidae family: Vaejovis mexicanus, V. intrepidus, V. subcristatus and V. punctatus. Some sequences coding for channel-acting toxins were found, as expected, but the main transcribed genes in the glands actively producing venom were those coding for non disulfide-bridged peptides. The ESTs coding for putative channel-acting toxins, corresponded to sodium channel β toxins, to members of the potassium channel-acting α or κ families, and to calcium channel-acting toxins of the calcin family. Transcripts for scorpine-like peptides of two different lengths were found, with some of the species coding for the two kinds. One sequence coding for La1-like peptides, of yet unknown function, was found for each species. Finally, the most abundant transcripts corresponded to peptides belonging to the long chain multifunctional NDBP-2 family and to the short antimicrobials of the NDBP-4 family. This apparent venom composition is in correspondence with the data obtained to date for other non-Buthidae species. Our study constitutes the first approach to the characterization of the venom gland transcriptome for scorpion species belonging to the Vaejovidae family.

Scorpionism in Brazil in the years 2000 to 2012

Background

Scorpionism is a serious public health problem in Brazil. Nationwide epidemiological analyses of scorpion stings are scarce. In this context, the present study aims to provide an epidemiological analysis of accidents involving scorpions in Brazil.

Methods

An analytical epidemiological study of the scorpion accidents reported in the Information System for Notifiable Diseases (SINAN) was conducted from 2000 to 2012 in Brazil.

Results

During this period, 482,616 accidents and 728 deaths were reported. The annual average incidence and mortality rates per 100,000 inhabitants were 19.6 and 0.030, respectively, with annual average lethality rate of 0.16%. The highest accident frequency was recorded in male subjects, aged 20–49 years, from September to December and in urban areas, except in the northern region of the country, where accidents were most frequent in June and July, and in rural areas. Males up to age 9 and rural areas were defined as an age group and area for greatest death risk, respectively.

Conclusions

Scorpionism in Brazil is a predominantly urban health problem that mostly affects people at an economically active age. The Northeast and Southeast hold the majority of cases and deaths, as well as the highest annual incidence and mortality averages, but the Central West and North presented the highest average annual lethality rates. The epidemiological changes described in this study highlight the need for intensifying health surveillance actions to prevent scorpion accidents in Brazil.

Efficacy of scorpion antivenom plus prazosin versus prazosin alone for Mesobuthus tamulus scorpion sting envenomation in children: a randomised controlled trial

OBJECTIVE

To assess the efficacy of combined use of scorpion antivenom (SAV) with prazosin, compared with prazosin alone in children with Mesobuthus tamulus scorpion envenomation.

STUDY DESIGN

Randomised controlled trial.

SETTING

A tertiary care hospital in south India.

PATIENTS

50 children with definite history and/or systemic manifestations of scorpion envenomation were recruited from the paediatric emergency or outpatient department from February 2012 to July 2013.

INTERVENTIONS

The children were randomised into two groups. In 25 children, SAV was administrated as a slow intravenous bolus combined with prazosin (group A). Others received prazosin alone (group B). Results were analysed by Student t test and χ(2) test.

MAIN OUTCOME MEASURES

Time required for resolution of autonomic symptoms, total dose of prazosin, adverse events.

RESULTS

Children in group A recovered earlier than those in group B (mean difference 9.1 h, 95% CI 6.0 to 12.2). 23 children (92%) in group A were clear of autonomic symptoms within 10 h, compared with 10 children (40%) in group B (mean difference 52%, 95% CI 29% to 75%). The proportion of children deteriorating to clinical grade 3 or 4 was 8% in group A as against 44% in group B (p<0.01). The mean dose of prazosin required was 54 µg/kg versus 130.8 µg/kg in group A and B, respectively (p<0.01). SAV was not associated with severe adverse reactions.

CONCLUSIONS

Usage of SAV led to faster recovery and reduced the incidence of myocardial dysfunction. Combined therapy with SAV and prazosin is beneficial for children with M tamulus scorpion envenomation.

TRIAL REGISTRATION NUMBER

CTRI/2013/09/004002 (Clinical Trials Registry of India).

Comments on Environmental and Sanitary Aspects of the Scorpionism by Tityus trivittatus in Buenos Aires City, Argentina

Deaths by venomous animals are medical emergencies that can lead to death and thus constitute sanitary problems in some regions of the world. In the South of America, the accidents by these animals are a common sanitary problem especially in warm, tropical or subtropical regions, related with rural work in several countries. Argentina is located in the extreme South of South America and a minor part of the continental surface is in tropical or subtropical regions, where most of the accidents by venomous animals happen. However, in the big cities in the center and South of the country, with no relation to rural work, scorpionism, mostly due to the synanthropic and facultative parthenogenetic scorpion Tityus trivittatus, has become a sanitary problem in the last few decades. This scorpion is present in the biggest cities of Argentina and in the last decades has killed over 20 children in provinces of the center and north of the country, mostly in big cities. In addition, it seems that this species is growing and spreading in new regions of the cities. In this revision, some characteristics of this scorpion regarding its habitat, spreading in Buenos Aires city, combat measures and available treatments are discussed.

Clinical toxinology specialty training

Clinical toxinology is the medical discipline dealing with the diagnosis, treatment and prevention of toxin diseases caused by exposure to venomous animals and poisonous animals, plants and mushrooms. Currently there is no national or international organisation accrediting or training doctors in this discipline, but the role of the IST in this area is the subject of a recently approved revised Constitution. A few courses covering some aspects of clinical toxinology exist, either with limited curricula, or with only a minor clinical focus, or with a very regional, non-global focus. The only comprehensive clinical toxinology course is the one provided in Adelaide, Australia, running regularly since 1997. This course may form the nucleus from which IST can develop a global accredited training scheme in clinical toxinology. Such a scheme will require input from diverse global regions and will be far more comprehensive and over a much longer time than the current Short Course, though may incorporate the Short Course in some way, or a derivative of it. Accreditation of medical expertise in clinical toxinology will be required at the national level and this might be accomplished by the IST working with existing national medical specialty organisations and governments, with the IST supervising the training and accreditation requirements and the national organisations providing the framework for registration of medical expertise at the local level.

Pediatric scorpion envenomation in the United States: morbidity, mortality, and therapeutic innovations

In the Southwestern United States, the venom of the scorpion Centruroides sculpturatus (common name bark scorpion) can cause serious and potentially fatal neurotoxicity, with young children most vulnerable to its effects. Historically, advances in the quality of supportive care have made significant improvements in morbidity and mortality. In recent years, the development of effective antivenom therapies has changed the landscape of caring for these patients. This article reviews the background, pathophysiology, diagnosis, and treatment options for C. sculpturatus envenomation. Recent advances in immunotherapy and subsequent implications for pediatric emergency care providers are discussed.

Turkish scorpion Buthacus macrocentrus: general characterization of the venom and description of Bu1, a potent mammalian Na⁺-channel α-toxin

The venom of the scorpion Buthacus macrocentrus of Turkey was fractionated by high performance liquid chromatography (HPLC) and its mass finger print analysis was obtained by spectrometry. More than 70 different fractions were obtained, allowing the determination of the molecular masses of at least 60 peptides ranging between 648 and 44,336 Da. The venom is enriched with peptides containing molecular masses between 3200-4500 Da, and 6000-7500 Da. They very likely correspond to K⁺-channel and Na⁺-channel specific peptides, respectively, as expected from venoms of scorpions of the family Buthidae, already determined for other species. The major component obtained from HPLC was shown to be lethal to mice and was further purified and characterized. It contains 65 amino acid residues maintained closely packed by 4 disulfide bridges, and shows a molecular weight of 7263 Da. Additionally, a cDNA from the venomous glands of this scorpion was used in conjunction with sequence data from Edman degradation and mass spectrometry for cloning the gene that codes for Bu1 as we named this toxin. This gene codes for a 67 amino acid residues peptide, where the two last are eliminated post-translationally for production of an amidated C-terminal arginine. Its sequence is closely related to toxins from the species Leiurus quinquestriatus, as revealed by a phylogenetic tree analysis. Electrophysiological results conducted with Bu1 using patch-clamp techniques indicate that it modifies the Na⁺ currents, in a similar way as other well known α-scorpion toxins. These results support the conclusion that this species of scorpions is dangerous to humans, having an epidemiological interest for the country.

Perfis clínico e hematológico de camundongos submetidos ao envenenamento escorpiônico experimental por Tityus fasciolatus

Estudou-se o quadro clínico do veneno decorrente do envenenamento por Tityus fasciolatus e sua ação refletida nos componentes hematológicos no modelo murino. Para o estudo do perfil hematológico, foram utilizados 54 camundongos Swiss CF1, machos, com 30g, distribuídos em três grupos (G) (n=18) inoculados via subcutânea com: 50µL de PBS (G1); 24µg de veneno de T. fasciolatus (G2) e 8µg de veneno de T. serrulatus (G3). Cada grupo foi subdividido em três subgrupos (n=6) de acordo com o momento da coleta de sangue que foi estipulada em uma, oito e 24h após a inoculação do veneno, e foram realizados o hemograma e a dosagem de proteínas totais e fracionadas. O veneno de T. fasciolatus na dose de 24µg causou piloereção, comportamento nociceptivo, secreção nasal e oral acentuada, dispneia, prurido na face e reflexos exacerbados. No exame hematológico, foram observadas policitemia relativa e leucocitose com linfocitose.

Scorpion envenomation and antivenom therapy

Scorpion envenomation is a dangerous and common global event that can result in a variety of toxic clinical effects. These are typically managed with supportive care or antivenom. Antivenom use is controversial because of conflicting evidence of effectiveness for adrenergic toxicity. However, both controlled and uncontrolled studies have shown that antivenom is effective in resolving neuromotor toxicity associated with envenomations by the scorpions of genus Centruroides.

Isolation and characterization of a human antibody fragment specific for Ts1 toxin from Tityus serrulatus scorpion

Scorpion stings are a common event that occurs in tropical and subtropical areas of the world, being a public health problem in certain countries. In most places, medical treatment relays on antivenoms obtained from the sera of hyper-immunized horses, however some efforts are being made to prepare specific antibodies of human origin, using phage display methodology. This communication describes the strategy followed for obtaining a protective human single chain antibody (scFv) capable of partially neutralizing the effect of Ts1, the major toxin isolated from the venom of the Brazilian scorpion Tityus serrulatus. Phage display technique allowed the isolation of scFv 15e from a human library of antibodies, after four rounds of selection against Ts1. This clone codes for 124 amino acids belonging to the family VH6 and 114 amino acids of family VK4. This scFv also recognizes toxins from the scorpions Tityus packyurus and Tityus cambridgei from the Amazonian region. Mice challenged with a LD(50) of Ts1 in the presence of this scFv were substantially resistant to intoxication. ScFv 15e is a leading compound for the development of better anti-scorpion antidotes.

Efficacy and safety of scorpion antivenom plus prazosin compared with prazosin alone for venomous scorpion (Mesobuthus tamulus) sting: randomised open label clinical trial

OBJECTIVE

Envenomation by Mesobuthus tamulus scorpion sting can result in serious cardiovascular effects. Scorpion antivenom is a specific treatment for scorpion sting. Evidence for the benefit of scorpion antivenom and its efficacy compared with that of commonly used vasodilators, such as prazosin, is scarce. We assessed the efficacy of prazosin combined with scorpion antivenom, compared with prazosin alone, in individuals with autonomic storm caused by scorpion sting.

DESIGN

Prospective, open label randomised controlled trial.

SETTING

General hospital inpatients (Bawaskar Hospital and Research Centre Mahad Dist-Raigad Maharashtra, India).

PARTICIPANTS

Seventy patients with grade 2 scorpion envenomation, older than six months, with no cardiorespiratory or central nervous system abnormalities.

INTERVENTION

Scorpion antivenom plus prazosin (n=35) or prazosin alone (n=35) assigned by block randomisation. Treatment was not masked. Analysis was by intention to treat.

MAIN OUTCOME MEASURES

The primary end point was the proportion of patients achieving resolution of the clinical syndrome (sweating, salivation, cool extremities, priapism, hypertension or hypotension, tachycardia) 10 hours after administration of study drugs. Secondary end points were time required for complete resolution of clinical syndrome, prevention of deterioration to higher grade, doses of prazosin required overall and within 10 hours, and adverse events. The study protocol was approved by the independent ethics committee of Mumbai.

RESULTS

Mean (SD) recovery times in hours for the prazosin plus scorpion antivenom group compared with the prazosin alone groups were: sweating 3 (1.1) v 6.6 (2.6); salivation 1.9 (0.9) v 3 (1.9); priapism 4.7 (1.5) v 9.4 (1.5). Mean (SD) doses of prazosin in the groups were 2 (2.3) and 4 (3.5), respectively. 32 patients (91.4%, 95% confidence interval 76.9% to 97.8%) in the prazosin plus antivenom group showed complete resolution of the clinical syndrome within 10 hours of administration of treatment compared with eight patients in the prazosin group (22.9%, 11.8% to 39.3%). Patients from the antivenom plus prazosin group recovered earlier (mean 8 hours, 95% CI 6.5 to 9.5) than those in the control group (17.7 hours, 15.4 to 19.9; mean difference -9.7 hours, -6.9 to -12.4). The number of patients whose condition deteriorated to a higher grade was similar in both groups (antivenom plus prazosin four of 35, prazosin alone five of 35). Hypotension was reported in fewer patients in the antivenom plus prazosin group (12 of 35, 34.3%) than in the prazosin group (19 of 35, 54.3%), but the difference was not statistically significant. No difference was noted in change in blood pressure and pulse rate over time between two groups.

CONCLUSION

Recovery from scorpion sting is hastened by simultaneous administration of scorpion antivenom plus prazosin compared with prazosin alone.

TRIAL REGISTRATION NUMBER

CTRI/2010/091/000584 (Clinical Trials Registry India).

ImKTx88, a novel selective Kv1.3 channel blocker derived from the scorpion Isometrus maculates

Scorpion toxins are useful in the structure-function research of ion channels and valuable resources for drug design. The Kv1.3 channel is an important pharmacological target for the therapy of T cell-mediated autoimmune diseases, and many toxin peptides targeting Kv1.3 have been identified as good drug candidates in recent years. In this study, a novel toxin gene ImKTx88 was isolated from the venom of the scorpion Isometrus maculates through the construction of the cDNA library method, and the recombinant toxin peptide was purified and characterized physiologically. The mature peptide of ImKTx88 contained 39 amino acid residues including six cysteines and was predicted to be a new member of α-KTx scorpion family by sequence analysis. The electrophysiological experiments further indicated that the rImKTx88 peptide had a novel pharmacological profile: it inhibited Kv1.3 channel current with an IC₅₀ of 91 ± 42 pM, and exhibited very good selectivity for Kv1.3 over Kv1.1 (4200-fold) and Kv1.2 (93000-fold) channels, respectively. All these results suggested that, as a new selective Kv1.3 channel blocker, the ImKTx88 peptide may serve as a potential drug candidate in the therapy of autoimmune diseases.

Exploiting cross-reactivity to neutralize two different scorpion venoms with one single chain antibody fragment

We report the optimization of a family of human single chain antibody fragments (scFv) for neutralizing two scorpion venoms. The parental scFv 3F recognizes the main toxins of Centruroides noxius Hoffmann (Cn2) and Centruroides suffusus suffusus (Css2), albeit with low affinity. This scFv was subjected to independent processes of directed evolution to improve its recognition toward Cn2 (Riaño-Umbarila, L., Juárez-González, V. R., Olamendi-Portugal, T., Ortíz-León, M., Possani, L. D., and Becerril, B. (2005) FEBS J. 272, 2591-2601) and Css2 (this work). Each evolved variant showed strong cross-reactivity against several toxins, and was capable of neutralizing Cn2 and Css2. Furthermore, each variant neutralized the whole venoms of the above species. As far as we know, this is the first report of antibodies with such characteristics. Maturation processes revealed key residue changes to attain expression, stability, and affinity improvements as compared with the parental scFv. Combination of these changes resulted in the scFv LR, which is capable of rescuing mice from severe envenomation by 3 LD(50) of freshly prepared whole venom of C. noxius (7.5 μg/20 g of mouse) and C. suffusus (26.25 μg/20 g of mouse), with surviving rates between 90 and 100%. Our research is leading to the formulation of an antivenom consisting of a discrete number of human scFvs endowed with strong cross-reactivity and low immunogenicity.

Scorpion envenomation among children: clinical manifestations and outcome (analysis of 685 cases)

Our objective was to characterize both epidemiologically and clinically manifestations after severe scorpion envenomation and to define simple factors indicative of poor prognosis in children. We performed a retrospective study over 13 years (1990-2002) in the medical intensive care unit (ICU) of a university hospital (Sfax-Tunisia). The diagnosis of scorpion envenomation was based on a history of scorpion sting. The medical records of 685 children aged less than 16 years who were admitted for a scorpion sting were analyzed. There were 558 patients (81.5%) in the grade III group (with cardiogenic shock and/or pulmonary edema or severe neurological manifestation [coma and/or convulsion]) and 127 patients (18.5%) in the grade II group (with systemic manifestations). In this study, 434 patients (63.4%) had a pulmonary edema, and 80 patients had a cardiogenic shock; neurological manifestations were observed in 580 patients (84.7%), 555 patients (81%) developed systemic inflammatory response syndrome (SIRS), and 552 patients (80.6%) developed multi-organ failure. By the end of the stay in the ICU, evolution was marked by the death in 61 patients (8.9%). A multivariate analysis found the following factors to be correlated with a poor outcome: coma with Glasgow coma score ≤ 8/15 (odds ratio [OR] = 1.3), pulmonary edema (OR = 2.3), and cardiogenic shock (OR = 1.7). In addition, a significant association was found between the development of SIRS and heart failure. Moreover, a temperature > 39°C was associated with the presence of pulmonary edema, with a sensitivity at 20.6%, a specificity at 94.4%, and a positive predictive value at 91.7%. Finally, blood sugar levels above 15 mmol/L were significantly associated with a heart failure. In children admitted for severe scorpion envenomation, coma with Glasgow coma score ≤ 8/15, pulmonary edema, and cardiogenic shock were associated with a poor outcome. The presence of SIRS, a temperature > 39°C, and blood sugar levels above 15 mmol/L were associated with heart failure.

Pharmacokinetics of a F(ab')2 scorpion antivenom administered intramuscularly in healthy human volunteers

This paper presents the first study of F(ab')(2) scorpion antivenom pharmacokinetics in humans after intramuscular (im) administration. The specific anti-Centruroides scorpion antivenom was used in 6 human healthy volunteers. The fabotherapeutic was administered as a 47.5mg im bolus. Blood samples were drawn at 0, 5, 15, 30, 45, 60 , 90, 120, and 180 min, 6h and at 1, 2, 3, 4, 10 and 21 days after antivenom administration. We measured antivenom concentrations in serum using a specific high sensitivity ELISA method for F(ab')(2). Antivenom concentration in serum was fit to a 3 compartment model (inoculation site, plasma and extra vascular extracellular space), it was assumed that the venom may also be irreversibly removed from plasma. Calculated time course of antivenom content shows that at any time no more that 16.6 (5.3, 31.9)% (median and 95% confidence interval) of the antivenom bolus is present in plasma. The time to peak plasma [F(ab')(2)] was 45 (33, 74) h. The most significant antivenom pharmacokinetic parameters determined were: AUC(im,∞)=803 (605, 1463) mg·h·L(-1); V(c)=8.8 (2.8, 23.6) L; V(ss,im)=55 (47, 64) L; MRT(im)=776(326, 1335) h; CL(t)=3.7 (0.6, 1.9) mL·min(-1); f(im,)V(ss)=0.300 (0.153, 0.466). Comparing these parameters with the ones obtained intravenously by Vázquez et al., the parameters were more disperse between subjects, determined with more uncertainty in each individual subject, and the peak F(ab')(2) in plasma occurred with considerable delay; all indicating that the IM route should not be used to administer the antivenom, with the possible exception of cases occurring very far from hospitals, as an extreme means to provide some protection before the IV route becomes available.

Scorpion stings in Turkey: epidemiological and clinical aspects between the years 1995 and 2004

The most important health-threatening scorpions found in Turkey are; Androctonus crassicauda, Leiurus quinquestriatus, Mesobuthus gibbosus and M. eupeus species, all of which belong to the Buthidae family. The epidemiological and clinical findings of scorpion stings in Turkey were evaluated between the years 1995 and 2004 based on data recorded in the National Poison Information Center (NPIC). A total of 930 cases were recorded. The cases mostly occurred in the month of July. The gender distribution was 50.22% female and 45.48% male. It was shown that the 20-29 age group presented more scorpion stings. Most of the stings occurred in Central Anatolia and Marmara regions of Turkey. Patients at the hospital showed signs of localized (pain, hyperemia, edema and numbness) and systemic effects (hyperthermia, nausea and vomiting, tachycardia, shivering and lethargy) but no lethality was notified. According to records, 33% of the poisoned patients were treated with antivenin in healthcare facilities.

Identification of potent nanobodies to neutralize the most poisonous polypeptide from scorpion venom

Scorpion venom, containing highly toxic, small polypeptides that diffuse rapidly within the patient, causes serious medical problems. Nanobodies, single-domain antigen-binding fragments derived from dromedary heavy-chain antibodies, have a size that closely matches that of scorpion toxins. Therefore these nanobodies might be developed into potent immunotherapeutics to treat scorpion envenoming. Multiple nanobodies of sub-nanomolar affinity to AahII, the most toxic polypeptide within the Androctonus australis hector venom, were isolated from a dromedary immunized with AahII. These nanobodies neutralize the lethal effect of AahII to various extents without clear correlation with the kinetic rate constants kon or koff, or the equilibrium dissociation constant, KD. One particular nanobody, referred to as NbAahII10, which targets a unique epitope on AahII, neutralizes 7 LD50 of this toxin in mice, corresponding to a neutralizing capacity of approx. 37000 LD50 of AahII/mg of nanobody. Such high neutralizing potency has never been reached before by any other monoclonal antibody fragment.

Molecular cloning and functional identification of a new K(+) channel blocker, LmKTx10, from the scorpion Lychas mucronatus

Scorpions have a venom gland which is an important determinant in contributing to their successful survival for more than 400 million years. Their venoms contain a diversity of neurotoxins, which represent a tremendous hitherto partially unexplored resource not only for understanding ion channels but also for use in drug design and development. In this investigation, LmKTx10, a new toxin gene was identified from the venom of the scorpion Lychas mucronatus by constructing cDNA library method, and its product was expressed and characterized physiologically. The mature peptide has 38 residues including six conserved cysteines. The electrophysiological experiments further indicated that the recombinant LmKTx10 peptide has an interesting pharmacological profile: it blocks Kv1.3 channel with IC(50)=28nM which is moderate Kv1.3 channel blocking activity compared to the other a-KTxs toxins, and exhibits good selectivity on Kv1.3 over Kv1.1 and Kv1.2, about 60 folds and 450 folds, respectively. These data not only enrich the family of K(+) channel toxins from scorpion venoms but also present a potential drug template for selectively targeting the Kv1.3 channel.