Routes of Spread of Anthrax in Natural Ecosystems

Anthrax is a particularly dangerous zooanthroponosis caused by the Gram-positive spore-forming bacterium Bacillus anthracis. This disease mainly affects hoofed herbivores, including those used in agriculture, but can occur in other animals and in humans. That is why the majority of studies of this infection are focused on anthrax in humans and farm animals, as the most important issues from a practical point of view. At the same time, the issues of anthrax epidemiology in natural ecosystems are described in the literature in insufficient detail and often very fragmentary. This paper provides a review of the literature describing the main pathways, patterns and risks of the spread of various clinical forms of anthrax infection in nature, primarily among wild animals. Among other things, we cover some non-notable aspects of intestinal infection with anthrax which, for instance, explain the difference in sensitivity to infection in herbivorous and carnivorous mammals and even different sex and age groups within the same species.

Neutralization of the anthrax toxin by antibody-mediated stapling of its membrane-penetrating loop

Anthrax infection is associated with severe illness and high mortality. Protective antigen (PA) is the central component of the anthrax toxin, which is one of two major virulence factors of Bacillus anthracis, the causative agent of anthrax disease. Upon endocytosis, PA opens a pore in the membranes of endosomes, through which the cytotoxic enzymes of the toxin are extruded. The PA pore is formed by a cooperative conformational change in which the membrane-penetrating loops of PA associate, forming a hydrophobic rim that pierces the membrane. Due to its crucial role in anthrax progression, PA is an important target for monoclonal antibody-based therapy. cAb29 is a highly effective neutralizing antibody against PA. Here, the cryo-EM structure of PA in complex with the Fab portion of cAb29 was determined. It was found that cAb29 neutralizes the toxin by clamping the membrane-penetrating loop of PA to the static surface-exposed loop of the D3 domain of the same subunit, thereby preventing pore formation. These results provide the structural basis for the antibody-based neutralization of PA and bring into focus the membrane-penetrating loop of PA as a target for the development of better anti-anthrax vaccines.

Neutralization of the anthrax toxin by antibody-mediated stapling of its membrane penetrating loop

Anthrax infection is associated with severe illness and high mortality. Protective antigen (PA) is the central component of the anthrax toxin, which is the main virulent factor of anthrax. Upon endocytosis, PA opens a pore in the membranes of endosomes, through which the toxin's cytotoxic enzymes are extruded. The PA pore is formed by a cooperative conformational change where PA's membrane-penetrating loops associate, forming a hydrophobic rim that pierces the membrane. Due to its crucial role in anthrax progression, PA is an important target of monoclonal antibodies-based therapy. cAb29 is a highly effective neutralizing antibody against PA. We determined the cryo-EM structure of PA in complex with the Fab portion of cAb29. We found that cAb29 neutralizes the toxin by clamping the membrane-penetrating loop of PA to a static region on PA's surface, thereby preventing pore formation. Therefore, our results provide the structural basis for the antibody-based neutralization of PA and bring to focus the membrane-penetrating loop of PA as a target for the development of better anti-anthrax vaccines.

Bacillus anthracis edema toxin inhibits hypoxic pulmonary vasoconstriction via edema factor and cAMP-mediated mechanisms in isolated perfused rat lungs

The most important findings here are edema toxin’s potent adenyl cyclase activity can interfere with hypoxic pulmonary vasoconstriction, an action that could worsen hypoxemia during invasive anthrax infection with lung involvement. These findings, coupled with other studies showing that lethal toxin can disrupt pulmonary vascular integrity, indicate that both toxins can contribute to pulmonary pathophysiology during infection. In combination, these investigations provide a further basis for the use of antitoxin therapies in patients with worsening invasive anthrax disease.

Teixobactin Provides Protection against Inhalation Anthrax in the Rabbit Model

The use of antibiotics is a vital means of treating infections caused by the bacteria Bacillus (B.) anthracis. Importantly, with the potential future use of multidrug-resistant strains of B. anthracis as bioweapons, new antibiotics are needed as alternative therapeutics. In this blinded study, we assessed the protective efficacy of teixobactin, a recently discovered antibiotic, against inhalation anthrax infection in the adult rabbit model. New Zealand White rabbits were infected with a lethal dose of B. anthracis Ames spores via the inhalation route, and blood samples were collected at various times to assess antigenemia, bacteremia, tissue bacterial load, and antibody production. Treatments were administered upon detection of B. anthracis protective antigen in the animals’ sera. For comparison, a fully protective dose of levofloxacin was used as a positive control. Rabbits treated with teixobactin showed 100% survival following infection, and the bacteremia was completely resolved by 24–48 h post-treatment. In addition, the bacterial/spore loads in tissues of the animals treated with teixobactin were either zero or dramatically less relative to that of the negative control animals. Moreover, microscopic evaluation of the tissues revealed decreased pathology following treatment with teixobactin. Overall, these results show that teixobactin was protective against inhalation anthrax infection in the rabbit model, and they indicate the potential of teixobactin as a therapeutic for the disease.

Modeling the Environmental Suitability for Bacillus Anthracis Spores Survival in the Qinghai Lake Basin, China

Introduction: Bacillus anthracis spores may remain viable for many years in soil. Previous studies have identified East Qinghai and neighbouring Gansu in northwest China as a potential source of anthrax infection. This study was carried out to identify conditions and areas in the Qinghai lake basin that are environmentally suitable for Bacillus anthracis spore survival. Materials and Methods: Anthrax occurrence data from 2005 – 2016 and environmental variables were spatially modeled by a maximum entropy algorithm to evaluate the contribution of the variables to the distribution of the spore. A Principal Component and Variance Inflation Analysis were adopted to limit the number of environmental variables and minimize multicollinearity. Results: The three variables that contributed most to the suitability model for B. anthracis spores are a relatively high annual mean temperature (53%), soil type (35%), and a high human population density (12%). The most significant soil types were cambisols and kastanozems. The resulting distribution map identifies the permanently inhabited rim of the Qinghai Lake as highly suitable for the survival and persistence of the spores. Conclusion: The highly suitable areas for spores could be considered as a risk zone for Anthrax infection by spores of the livestock and the human population. Our environmental suitability map and the identified variables provides the nature reserve managers and animal health authorities readily available information to devise a surveillance strategy in B. anthracis suitable regions to abate future epidemics.

Pathoanatomical Pattern of Brain Damage of White Mice Infected with Experimental Anthrax

Background. Bacillus anthracis is a microorganism that causes anthrax. Because of irrational therapy, this particularly dangerous infectious disease leads to a systemic spread of bacteria in the body through histohematological barriers. Bacilli entering the brain subsequently lead to hemorrhagic meningitis. Despite intensive antibiotic therapy, that kind of meningitis is difficult to cure and therefore highly lethal. Studying characteristics of anthrax’s isolates of different origin and genotype is an actual area of research.The aim of the study is searching for pathomorphological and histological changes in the brain regions of experimental animals with anthrax infection, caused by B. anthracis with different plasmid spectrum.Materials and methods: The study was conducted on 200 certified white mice, three B. anthracis strains were used as research objects: B. anthracis I-323 (рХО1– /рХО2– ), B. anthracis I-275 (рХО1- /рХО2- ), and B. anthracis I-217 (рХО1+ / рХО2– ). The material for histological examination was the brain of mice, embedded in paraffin, and then sections were prepared using a microtome and stained with hematoxylin-eosin and Nissl toluidine blue. The degree of neuronal damage was assessed by calculating the semi-quantitative factor and determining the average size of the neuron nuclei, and the numerical density of cells in 1mm2 was studied. Microphotography and quantitative analysis was performed using the Motic Images Plus 2.0 application package. Statistical processing of the results was performed using the program “Statistica 6.0”.The results of the study showed that the brain of infected mice shows signs of hemorrhagic leptomeningitis, the manifestations of which are more pronounced in mice infected with weakly virulent plasmid strains of B. anthracis and fallen mice.Conclusion. Multicomponent exotoxin and specialized proteins, encoded in the pathogenicity plasmid of microorganisms, allow B. anthracis to easily overcome histohematological barriers and cause severe septic anthrax. The results obtained during the study supplement the available information on the pathogenesis of anthrax and indicate the need for further research in this direction.

Vaccinal Preventon of Anthrax in the Russian Federation and Its Immediate Prospects

Th e purpose of the work is to show the possibilities of vaccine prophylaxis of anthrax in the Russian Federation and its immediate prospects. Th e article is dedicated to the vaccine preparations, available in Russia and abroad in the arsenal of medical remedies at present, to the history of their creation, to the eff ectiveness of their use and to the main directions of the improving of the vaccine prevention. Th e eff orts to develop a new generation of vaccines are aimed mainly at the increasing of the safety of vaccines, reducing the frequency of their administration and improving their production technologies. Th e combined anthrax vaccine developed in the USSR can be used in the emergency prophylaxis of anthrax along with antibiotics. The development of vaccines based on immunogenic antigens synthesized by recombinant producers solves the problem of residual virulence and reactogenicity, as well as the problem of increasing stability and reduction of doses of modern anthrax vaccines. In the nearest future it is necessary: to develop an industrial technology of the production of anthrax vaccines based on recombinant strains – hyperproducers of protective antigen and include them in the prophylaxis and treatment regimens of anthrax infection; to develop scientifi c and methodological approaches and vaccines for mass immunization against anthrax; to evaluate the possibility of using new adjuvants for the construction of anthrax vaccines, more eff ective and safer than the existing ones

Enhanced Production of Protective Antigen, a Potent Diagnostic Protein of Bacillus anthracis, the Causative Agent of Anthrax

Protective antigen (PA) produced by Bacillus anthracis is a highly immunogenic protein. Therefore, it has significant importance in serodiagnosis as well as a vaccine candidate for anthrax. In the present study, codons for PA gene were optimised and synthesised for its expression in Escherichia coli. Various expression conditions were optimised for scaled up production of rPA. The final yield of affinity chromatography purified protein was 40.8 mg/l during batch fermentation. For further purification, affinity purified protein was diafiltered and subjected to anion exchange chromatography. SDS-PAGE and Western blot was used to characterise the purified rPA protein. The diagnostic potential of purified rPA was evaluated in Western blot using standards reference serum AVR 801 and cutaneous anthrax clinical sera. The results of the present study established the optimum production of rPA in E. coli after codon optimisation for its subsequent use in diagnosis of anthrax infection.