Abstracts Toxins 2012 / Toxicon 60 (2012) 95–248 99

4. Biohazards of Botulinum Neurotoxins

Ornella RossettoDepartment of Biomedical Sciences, University of Padova, ItalyE-mail address: ornella.rossetto@unipd.it.

Review: Botulinum neurotoxins (BoNTs) are produced bytoxigenic strains of C. botulinum in seven serotypes (namedAthrough G). They are responsible for the clinical syndrome ofbotulism blocking the acetylcholine release from peripheralnerves and thus causing a flaccid paralysis. Respiratoryfailure secondary to paralysis of the respiratory muscles canlead to death unless appropriate therapy is promptly initi-ated. Structurally, BoNTs are composed of three domains:a Light Chain (LC), which acts in the cytosol as a metal-loprotease and cleaves protein components (SNAREs) of theneuroexocytosis apparatus; a translocation domain (HN) anda receptor binding domain (HC). The high affinity binding,due to a double receptor interaction and the extremelyspecific enzymatic activity, make botulinum toxin the mostlethal substance known, with a LD50 of 1 nanogram of toxinper kilogram body mass. Nevertheless, it also serves asa remarkably effective treatment for hypercholinergicdisorders such as blepharospasm, strabismus, hemifacialspasm, certain types of spasticity and other ailments and forcosmetic anti-aging treatments. Due to the severity andpotency of this neurotoxin, its importance as a biologicalweapon is of major concern to public health officials and, infact, it belongs to “category A” of agents which representserious risk when misused for military and/or criminalactivities. Despite its widespread accessibility and highlethality, however, BoNThas never been used successfully forpurposes of warfare or bioterrorrism. Several countriesinvestigated botulinum toxin as a biologic agent sinceWorldWar II. Botulism's sole link to a presumed successful planneduse as a weapon is provided by Paul Fildes, a high-rankingBritish specialist in bacterial weapons development duringWorldWar II, who has alluded to the fact that he contributedto the assassination of Reinhard Heydrick, head of theGestapo.More recently, in the early 1990s, before their attackwith Sarin on the Tokyo subway system, the Japanese cultAum Shinrikyo, had released an ineffectively produced C.botulinum preparation in Japan. During the United Nations’inspections of Iraq's capabilities for biologic warfare in 1991,botulinum toxin was clearly an area in which research hadbeen directed.More botulinum toxinwas produced than anyother weaponizable agent in Iraq. Botulinum toxin can beabsorbed by either gastrointestinal or respiratory epitheliumbut does not penetrate intact skin. The clinical forms ofbotulismdependon themodeof contamination but botulismthrough inhalation can only be the result of a deliberate actusing an aerosol.

Keywords: botulinum toxins, botulism, bioterrorism10.1016/j.toxicon.2012.04.005

5. Bioterrorism and Biological Toxins

Cesare MontecuccoDepartment of Biomedical Sciences, University of Padova, ItalyE-mail address: cesare.montecucco@unipd.it.

Review: The use of biological agents as a warfare goesback to ancient time, but it is only in modern times thatseveral countries have developed programs of research anddevelopment of biological warfare. More recently, initia-tives to control the possible use of these weapons haveemerged and three lists (A, B and C) of biological agents ofdifferent potential danger have been drawn. In thispresentation I will discuss one toxin producing bacteriumincluded in list A: Bacillus anthracis and two plant proteintoxins included in list B. The mechanisms of action of thetwo anthrax toxins and their immunosuppressive proper-ties will be illustrated together with the mechanism ofaction and pathogenetic consequences of the poisoningwith ricin or abrin will be illustrated. Finally, possiblemethods of preventing their action will be considered.

Keywords: anthrax toxin, ricin, abrin, bioterrorism10.1016/j.toxicon.2012.04.006

6. The Diverse Roles of Botulinum Toxins

Jeffrey BrentToxicology Associates, University of Colorado School of Medicine, Denver,Colorado, USAE-mail address: jeffrey.brent@ucdenver.edu.

Review: Botulinumneurotoxin is a cause of the naturallyoccurring disease botulism, a pharmaceutical, and a poten-tial biowarfare/terrorism agent. The bacterium Clostridiumbotulinum is the primary source of this toxin in humandisease. Clostridium botulinum exists as serotypes A-G,although human disease is almost entirely restricted totypes A, B, and E. Up to now there has been no systematicassessment of the differences in disease presentation bydifferent strains. Because botulinum neurotoxins are themost potent substances known, the CDC has listed it asa type A biothreat. The neurotoxin consists of a 150 KDamolecule comprised of a 100 kDA heavy chain (HC) and a 50kDA light chain (LC). Its toxicity results from its interactionwith cholinergic nerve terminals at the neuromuscularjunction (NMJ). TheHC is responsible for facilitating the pH-dependent endocytotic translocation of the toxin intomotor nerve terminals at the NMJ. Once internalized the LCcleaves the SNARE proteins that are responsible for facili-tating the release of acetylcholine into the NMJ. Theresulting failure of acetylcholine release is responsible forthe subsequent loss of skeletal muscle function and theensuing paralytic syndrome. However, the various strains ofbotulinum toxin do not all cleave the same SNARE proteins.The degree to which these differences influence the clinicalpresentation has not been well characterized. There arethree potential preventive and therapeutic approaches tobotulism syndromes: vaccines, pharmacologic interven-tions and therapeutic antibodies. The immunologicmeasures almost certainly are only effective before inter-nalization of the neurotoxin. Vaccines, therefore, areunlikely to be effective therapeutically. Vaccines, however,have been used for many years to protect researchers ormilitary personnel who are to be at risk for encounteringbotulinum toxin. Such vaccinations are effective in inducingneutralizing antibodies. Therapeutic antibodies directed

Abstracts Toxins 2012 / Toxicon 60 (2012) 95–248100

against botulinum toxin represent the most promising ofthe post-exposure therapeutic approaches on the short-term horizon. They must be given before a clinicallysignificant amount of neurotoxin is internalized into theNMJ. In the US there is currently one approved therapeuticantibody preparation. A number of pharmacologic agentsare currently being studied, however none have yet showngreat promise. Theoretically these might be effective in thepost-NMJ internalization phase. Currently we are assessingthe diversity in the presentations of botulinum syndromescaused by various strains. It is anticipated that elucidationof these difference might provide information on potentialtherapeutic approaches to botulism syndromes. Results ofthese studies will be presented.

Keywords: Botulism, neurotoxin, biothreat10.1016/j.toxicon.2012.04.007

7. Biological Weapons and Toxins: A Short History andLook at the Future

Barbara B. PriceASA, Inc. and International Institute of NonProliferation Studies, IINPS,Kaneohe, HI, USAE-mail address: info@asanltr.com.

Review: This review is a look back at the past and intothe future; of the history of toxins used as weapons, and thepossible dangers facing us in the future. Before 2001, therewas recognition that biological weapons, including toxins,were weapons that required state sponsorship. But that isno longer true. As the asymmetries of weapons and politicshave changed, so has the probable use of toxins asweapons. Our understanding and expectation of likely useof toxins in weapons has changed. Even the word “toxin” iscommonly used inappropriately to mean toxic chemicalrather than a chemical produced by organisms. Prior to2001, toxins were evaluated on their ability to be manu-factured or purified from natural resources. Many infec-tious disease specialists regard bacterial toxins as theeventual cause of cell damage and cell death. Where are wein the spectrum of toxins as weapons, from a clear use ofbiological weapons to a purified chemical? Do we needpurified chemicals? Are toxins the ultimate dual useagents? Do toxinologists need to examine their publica-tions for possible illicit use?

Keywords: toxin, biological weapon, bioterrorism10.1016/j.toxicon.2012.04.008

8. Biotoxins and Bioterrorism: Ricin and Saxitoxin

Peter G. BlainMedical Toxicology Centre, Faculty of Medical Sciences, Newcastle University,Newcastle upon Tyne, UKE-mail address: peter.blain@newcastle.ac.uk.

Introduction:Natural biotoxins have been considered bynation states for use as chemobiological weapons, andseveral specifically developed for weaponisation. Ricingained notoriety when it was allegedly used as an agent of

assassination, and saxitoxin was the key component ina weapon system designed to target individuals and beunattributable. Terrorist and extremist groups have includedbiotoxins in their planning, and documents describing theextraction and preparation of ricin have been found in thepossession of terrorist cells.

Toxicology: Ricin is a glycoprotein found in the seedsof the castor oil plant (Ricinus communis). The nativemolecule consists of two polypeptide chains, A and B,which are linked by a disulphide bond that is easilyreduced. On systemic absorption, the B chain (a lectin)binds to cell surface receptors present on eukaryote cellsbut not in prokaryotes. There is endocytic uptake of thetoxin into the cytosol where the chains dissociate and theA chain binds to the 28s ribosomal subunit, blockingprotein synthesis and resulting in the death of the cell.Clinical features develop over several hours and, in onenotorious case, death occurred 3 days after injection ofa pellet containing ricin. Saxitoxins are a group ofcompounds produced by a variety of marine dinoflagel-lates and freshwater cyanophytes (blue-green algae).Ingestion of shellfish that have extracted and concen-trated these toxins may result in paralytic shellfishpoisoning in humans. This toxic effect results from highaffinity binding of saxitoxin to voltage dependent sodiumchannels in the membranes of excitable cells that theninhibits depolarization. Peripheral nerves appear to beparticularly susceptible.

Medical Countermeasures: Symptomatic and supportivetreatments are the primary approach to the medicalmanagement of patients poisoned with either of these bio-toxins. A ricin anti-toxin is under development and assess-ment, but currently there is no antidote to saxitoxinpoisoning.

Conclusion: The biotoxins ricin and saxitoxin are rela-tively easily weaponised and highly toxic to humans. Assuch they are bioterrorist threat agents, especially sincestate programmes have demonstrated their potential use inassassination.

Key words: biotoxins, bioterrorism, ricin, saxitoxin10.1016/j.toxicon.2012.04.009

B. Drug Discovery & Development

9. Genotoxic Potential of Micrurus corallinus Venom onthe DNA of Human Lymphocytes

Silvana Marcussi, C. Trento Marcus Vinicius,Mateus W. EleutérioDepartment of Chemistry, Federal University of Lavras - UFLA, Lavras, MG,BrazilE-mail address: marcusvinicius_ct@hotmail.com (C.T. Marcus Vinicius).

Background: The articles that report the effects ofvenoms and their toxins, isolated from Brazilianwildlife, onhuman DNA are restricted to Apis mellifera and Crotalus d.terrificus. There is little information on the genotoxic and/ormutagenic potential of venoms and isolated toxins of broadmedical and scientific interest, but due to the toxic and