Inflammation is the body's first line of defense against infection or injury, responding to challenges by activating innate and adaptive responses. Microbes have evolved a diverse range of strategies to avoid triggering inflammatory responses. However, some pathogens, such as the influenza virus and the Gram-negative bacterium Francisella tularensis, do trigger life-threatening "cytokine storms" in the host which can result in significant pathology and ultimately death. For these diseases, it has been proposed that downregulating inflammatory immune responses may improve outcome. We review some of the current candidates for treatment of cytokine storms which may prove useful in the clinic in the future and compare them to more traditional therapeutic candidates that target the pathogen rather than the host response.

Microbiology, Dstl Porton Down, Salisbury, Wiltshire SP4 0JQ, UK As antibiotic resistance increases worldwide, there is an increasing pressure to develop novel classes of antimicrobial compounds to fight infectious disease. Peptide therapeutics represent a novel class of therapeutic agents. Some, such as cationic antimicrobial peptides and peptidoglycan recognition proteins, have been identified from studies of innate immune effector mechanisms, while others are completely novel compounds generated in biological systems. Currently, only selected cationic antimicrobial peptides have been licensed, and only for topical applications. However, research using new approaches to identify novel antimicrobial peptide therapeutics, and new approaches to delivery and improving stability, will result in an increased range of peptide therapeutics available in the clinic for broader applications.

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Yersinia pestis, the causative agent of plague, and the enteropathogen Yersinia pseudotuberculosis have nearly identical nucleotide similarity yet cause markedly different diseases. To investigate this conundrum and to study Yersinia pathogenicity, we developed a high-density oligonucleotide array-based modification of signature-tagged mutagenesis (STM). Y. pseudotuberculosis YPIII mutants constructed with the tagged transposons were evaluated in the murine yersiniosis infection model. The DNA tags were amplified using biotinylated primers and hybridized to high-density oligonucleotide arrays containing DNA complementary to the tags. Comparison of the hybridization signals from input pools and output pools identified a mutant whose relative abundance was significantly reduced in the output pool. Sequence data from 31 transposon insertion regions was compared to the complete Y. pestis CO92 genome sequence. The 26 genes present in both species were found to be almost identical, but five Y. pseudotuberculosis genes identified through STM did not have counterparts in the Y. pestis genome and may contribute to the different tropisms in these closely related pathogens. Potential virulence genes identified include those involved in lipopolysaccharide biosynthesis, adhesion, phospholipase activity, iron assimilation, and gene regulation. The phospholipase A (PldA) mutant exhibited reduced phospholipase activity compared to the wild-type strain and in vivo attenuation of the mutant was confirmed. The combination of optimized double tag sequences and high-density array hybridization technology offers improved performance, efficiency, and reliability over classical STM and permits quantitative analysis of data.Yersinia pseudotuberculosis, a cause of gastroenteritis and mesenteric lymphadenitis in humans (18) has many virulence factors as well as sequences in common with the two other pathogenic representatives of Yersinia, Yersinia pestis and Yersinia enterocolitica (6). In fact, comparison of the available sequences of Y. pseudotuberculosis genes with those from the complete Y. pestis genome (http://www.sanger.ac.uk/Projects /Y_pestis/) reveals that the two species are almost identical at the nucleotide level. Moreover, it has been suggested that Y. pestis is a recently emerged clone of Y. pseudotuberculosis (1). Despite this nucleotide similarity, the mechanisms of pathogenicity of the two species are different: Y. pseudotuberculosis and Y. enterocolitica cause gastrointestinal disease, whereas Y. pestis is the causative agent of plague.To understand this enigma and to gain further insight into Yersinia pathogenesis, we initiated a signature-tagged mutagenesis (STM) study of Y. pseudotuberculosis and tested tagged mutants in the murine yersiniosis model of infection. STM (20) allows the simultaneous analysis of large numbers of mutants in a complex environment, such as an animal model (reviewed in reference 28). It has been used successfully in the identification of virulence-associated factors in many pathogenic bacter...

Emerging pathogenic viruses such as Ebola and Middle Eastern Respiratory Syndrome coronavirus (MERS-CoV) can cause acute infections through the evasion of the host's antiviral immune responses and by inducing the upregulation of inflammatory cytokines. This immune dysregulation, termed a cytokine storm or hypercytokinemia, is potentially fatal and is a significant underlying factor in increased mortality of infected patients. The prevalence of global outbreaks in recent years has offered opportunities to study the progression of various viral infections and have provided an improved understanding of hypercytokinemia associated with these diseases. However, despite this increased knowledge and the study of the infections caused by a range of emerging viruses, the therapeutic options still remain limited. This review aims to explore alternative experimental strategies for treating hypercytokinemia induced by the Ebola, avian influenza and Dengue viruses; outlining their modes of action, summarizing their preclinical assessments and potential clinical applications.

Clostridium perfringens phospholipase C (Cp-PLC), also called ␣-toxin, is the major virulence factor in the pathogenesis of gas gangrene. Previously, a cellular UDP-Glc deficiency was related with a hypersensitivity to the cytotoxic effect of Cp-PLC. Because UDP-Glc is required in the synthesis of proteoglycans, N-linked glycoproteins, and glycosphingolipids, the role of these glycoconjugates in the cellular sensitivity to Cp-PLC was studied. The cellular sensitivity to Cp-PLC was significantly enhanced by glycosphingolipid synthesis inhibitors, and a mutant cell line deficient in gangliosides was found to be hypersensitive to Cp-PLC. Gangliosides protected hypersensitive cells from the cytotoxic effect of Cp-PLC and prevented its membrane-disrupting effect on artificial membranes. Removal of sialic acids by C. perfringens sialidase increases the sensitivity of cultured cells to Cp-PLC and intramuscular co-injection of C. perfringens sialidase, and Cp-PLC in mice potentiates the myotoxic effect of the latter. This work demonstrated that a reduction in gangliosides renders cells more susceptible to the membrane damage caused by Cp-PLC and revealed a previously unrecognized synergism between Cp-PLC and C. perfringens sialidase, providing new insights toward understanding the pathogenesis of clostridial myonecrosis.

Recombinant Bacillus subtilis endospores have been used to vaccinate against tetanus and anthrax. In this work, we have developed spores that could be used to vaccinate against Clostridium perfringens alpha toxin and that could be used to protect against gas gangrene in humans and necrotic enteritis in poultry. The primary active agent in both cases is alpha toxin. A carboxy-terminal segment of the alpha toxin gene (

Toxins are substances produced from biological sources (e.g., animal, plants, microorganisms) that have deleterious effects on a living organism. Despite the obvious health concerns of being exposed to toxins, they are having substantial positive impacts in a number of industrial sectors. Several toxin-derived products are approved for clinical, veterinary, or agrochemical uses. This review sets out the case for toxins as 'friends' that are providing the basis of novel medicines, insecticides, and even nucleic acid sequencing technologies. We also discuss emerging toxins ('foes') that are becoming increasingly prevalent in a range of contexts through climate change and the globalisation of food supply chains and that ultimately pose a risk to health. Toxins and Toxinology In the natural world, toxins are employed for diverse purposes, from the prey-incapacitating molecules found in snake, spider, and cone snail venom, to the defensive compounds harboured by numerous poisonous plant and animal species. While the consequences of human intoxication can be severe (Box 1), the functional diversity of biological toxins has led to their frequent use as experimental tools for studying physiological and pharmacological mechanisms (e.g., synaptic transmission, ion channel subtypes) (Figure 1). Toxinology involves the identification, characterisation, production, and engineering of biological toxins along with their application or repurposing as research tools and clinical products. As such, toxinology encompasses the study of the evolution, chemistry, biology, and clinical effects of toxins and includes potential biotechnological and/or therapeutic applications. Experimental applications of toxins as tools for physiologists go back a long time, including Claude Bernard's experiments in the 1800s with curare to demonstrate the existence of chemical signalling between nerves and muscles [2], and Henry Dale's use of muscarine and nicotine to show different subtypes of receptors for acetylcholine [3]. Snake toxins were critical for the first isolation of a receptor for a neurotransmitter [a-bungarotoxin and nicotinic acetylcholine receptors (nAChRs)] [4]. Recently, peptide toxins have been very useful in teasing out the functional importance of different subtypes of ion channels that are critical for neuronal function and cellular signalling [5-7]. An increasing number of toxins are now transitioning from the laboratory to the clinic and the balance of research in this aspect of toxinology is shifting from the classical development of anti-toxins and anti-venoms towards drug discovery [8,9]. The attraction of toxins for drug discovery lies in their often unique selectivity of their biological effects coupled with high potency. Toxic plant alkaloids were the first source of toxin-derived therapeutics, notably