Anthrax Edema and Lethal Toxins Differentially Target Human Lung and Blood Phagocytes

Bacillus anthracis, the causative agent of inhalation anthrax, is a serious concern as a bioterrorism weapon. The vegetative form produces two exotoxins: Lethal toxin (LT) and edema toxin (ET). We recently characterized and compared six human airway and alveolar-resident phagocyte (AARP) subsets at the transcriptional and functional levels. In this study, we examined the effects of LT and ET on these subsets and human leukocytes. AARPs and leukocytes do not express high levels of the toxin receptors, tumor endothelium marker-8 (TEM8) and capillary morphogenesis protein-2 (CMG2). Less than 20% expressed surface TEM8, while less than 15% expressed CMG2. All cell types bound or internalized protective antigen, the common component of the two toxins, in a dose-dependent manner. Most protective antigen was likely internalized via macropinocytosis. Cells were not sensitive to LT-induced apoptosis or necrosis at concentrations up to 1000 ng/mL. However, toxin exposure inhibited B. anthracis spore internalization. This inhibition was driven primarily by ET in AARPs and LT in leukocytes. These results support a model of inhalation anthrax in which spores germinate and produce toxins. ET inhibits pathogen phagocytosis by AARPs, allowing alveolar escape. In late-stage disease, LT inhibits phagocytosis by leukocytes, allowing bacterial replication in the bloodstream.

C3 Opsonization of Anthrax Bacterium and Peptidoglycan Supports Recognition and Activation of Neutrophils

Neutrophils are the most abundant innate cell population and a key immune player against invading pathogens. Neutrophils can kill both bacterium and spores of Bacillus anthracis, the causative anthrax pathogen. Unlike interactions with professional phagocytes, the molecular recognition of anthrax by neutrophils is largely unknown. In this study, we investigated the role of complement C3 deposition on anthrax particles for neutrophil recognition of bacterium and/or its cell wall peptidoglycan, an abundant pathogen-associated molecular pattern that supports anthrax sepsis. C3 opsonization and recognition by complement receptors accounted for 70-80% of the affinity interactions between neutrophils and anthrax particles at subphysiologic temperatures. In contrast, C3 supported up to 50% of the anthrax particle ingestion under thermophysiologic conditions. Opsonin-dependent low affinity interactions and, to a lower extent, opsonin-independent mechanisms, provide alternative entry routes. Similarly, C3 supported 58% of peptidoglycan-induced degranulation and, to a lower extent, 23% of bacterium-induced degranulation. Interestingly, an opsonin independent mechanism mediated by complement C5, likely through C5a anaphylatoxin, primes azurophilic granules in response to anthrax particles. Overall, we show that C3 deposition supports anthrax recognition by neutrophils but is dispensable for pathogen ingestion and neutrophil degranulation, highlighting immune recognition redundancies that minimize the risk of pathogen evasion.

Ndumnego O, Ellis C, Buys A, Beyer W, van Heerden H. Immunogenicity of Non-Living Anthrax Vaccine Candidates in Cattle and Protective Efficacy of Immune Sera in A/J Mouse Model Compared to the Sterne Live Spore Vaccine

The Sterne live spore vaccine (SLSV, Bacillus anthracis strain 34F2) is the veterinary vaccine of choice against anthrax though contra-indicated for use with antimicrobials. However, the use of non-living anthrax vaccine (NLAV) candidates can overcome the SLSV limitation. In this study, cattle were vaccinated with either of the NLAV (purified recombinant PA (PrPA) or crude rPA (CrPA) and formaldehyde-inactivated spores (FIS of B. anthracis strain 34F2) and emulsigen-D^®/alhydrogel^® adjuvants) or SLSV. The immunogenicity of the NLAV and SLSV was assessed and the protective efficacies evaluated using a passive immunization mouse model. Polyclonal IgG (including the IgG1 subset) and IgM responses increased significantly across all vaccination groups after the first vaccination. Individual IgG subsets titres peaked significantly with all vaccines used after the second vaccination at week 5 and remained significant at week 12 when compared to week 0. The toxin neutralization (TNA) titres of the NLAV vaccinated cattle groups showed similar trends to those observed with the ELISA titres, except that the former were lower, but still significant, when compared to week 0. The opsonophagocytic assay indicated good antibody opsonizing responses with 75% (PrPA+FIS), 66% (CrPA+FIS) and 80% (SLSV) phagocytosis following spores opsonization. In the passive protection test, A/J mice transfused with purified IgG from cattle vaccinated with PrPA+FIS+Emulsigen-D^®/Alhydrogel^® and SLSV had 73% and 75% protection from challenge with B. anthracis strain 34F2 spores, respectively, whereas IgG from cattle vaccinated with CrPA+FIS+Emulsigen-D^®/Alhydrogel^® offered insignificant protection of 20%. There was no difference in protective immune response in cattle vaccinated twice with either the PrPA+FIS or SLSV. Moreover, PrPA+FIS did not show any residual side effects in vaccinated cattle. These results suggest that the immunogenicity and protective efficacy induced by the NLAV (PrPA+FIS) in the cattle and passive mouse protection test, respectively, are comparable to that induced by the standard SLSV.

Characterization of Bacillus anthracis Spore Proteins Using a Nanoscaffold Vaccine Platform

Subunit vaccines are theoretically safe and easy to manufacture but require effective adjuvants and delivery systems to yield protective immunity, particularly at critical mucosal sites such as the lung. We investigated nanolipoprotein particles (NLPs) containing the Toll-like receptor 4 agonist monophosphoryl lipid A (MPLA) as a platform for intranasal vaccination against Bacillus anthracis. Modified lipids enabled attachment of disparate spore and toxin protein antigens. Intranasal vaccination of mice with B. anthracis antigen-MPLA-NLP constructs induced robust IgG and IgA responses in serum and in bronchoalveolar and nasal lavage. Typically, a single dose sufficed to induce sustained antibody titers over time. When multiple immunizations were required for sustained titers, specific antibodies were detected earlier in the boost schedule with MPLA-NLP-mediated delivery than with free MPLA. Administering combinations of constructs induced responses to multiple antigens, indicating potential for a multivalent vaccine preparation. No off-target responses to the NLP scaffold protein were detected. In summary, the NLP platform enhances humoral and mucosal responses to intranasal immunization, indicating promise for NLPs as a flexible, robust vaccine platform against B. anthracis and potentially other inhalational pathogens.

Rapid Microscopic Detection of Bacillus anthracis by Fluorescent Receptor Binding Proteins of Bacteriophages

Bacillus anthracis, the etiological agent of anthrax disease, is typically diagnosed by immunological and molecular methods such as polymerase chain reaction (PCR). Alternatively, mass spectrometry techniques may aid in confirming the presence of the pathogen or its toxins. However, because of the close genetic relationship between B. anthracis and other members of the Bacillus cereus sensu lato group (such as Bacillus cereus or Bacillus thuringiensis) mis- or questionable identification occurs frequently. Also, bacteriophages such as phage gamma (which is highly specific for B. anthracis) have been in use for anthrax diagnostics for many decades. Here we employed host cell-specific receptor binding proteins (RBP) of (pro)-phages, also known as tail or head fibers, to develop a microscopy-based approach for the facile, rapid and unambiguous detection of B. anthracis cells. For this, the genes of (putative) RBP from Bacillus phages gamma, Wip1, AP50c and from lambdoid prophage 03 located on the chromosome of B. anthracis were selected. Respective phage genes were heterologously expressed in Escherichia coli and purified as fusions with fluorescent proteins. B. anthracis cells incubated with either of the reporter fusion proteins were successfully surface-labeled. Binding specificity was confirmed as RBP fusion proteins did not bind to most isolates of a panel of other B. cereus s.l. species or to more distantly related bacteria. Remarkably, RBP fusions detected encapsulated B. anthracis cells, thus RBP were able to penetrate the poly-γ-d-glutamate capsule of B. anthracis. From these results we anticipate this RBP-reporter assay may be useful for rapid confirmative identification of B. anthracis.

A Unique Isolation of a Lytic Bacteriophage Infected Bacillus anthracis Isolate from Pafuri, South Africa

Bacillus anthracis is a soil-borne, Gram-positive endospore-forming bacterium and the causative agent of anthrax. It is enzootic in Pafuri, Kruger National Park in South Africa. The bacterium is amplified in a wild ungulate host, which then becomes a source of infection to the next host upon its death. The exact mechanisms involving the onset (index case) and termination of an outbreak are poorly understood, in part due to a paucity of information about the soil-based component of the bacterium’s lifecycle. In this study, we present the unique isolation of a dsDNA bacteriophage from a wildebeest carcass site suspected of having succumbed to anthrax. The aggressively lytic bacteriophage hampered the initial isolation of B. anthracis from samples collected at the carcass site. Classic bacteriologic methods were used to test the isolated phage on B. anthracis under different conditions to simulate deteriorating carcass conditions. Whole genome sequencing was employed to determine the relationship between the bacterium isolated on site and the bacteriophage-dubbed Bacillus phage Crookii. The 154,012 bp phage belongs to Myoviridae and groups closely with another African anthrax carcass-associated Bacillus phage WPh. Bacillus phage Crookii was lytic against B. cereus sensu lato group members but demonstrated a greater affinity for encapsulated B. anthracis at lower concentrations (<1 × 10⁸ pfu) of bacteriophage. The unusual isolation of this bacteriophage demonstrates the phage’s role in decreasing the inoculum in the environment and impact on the life cycle of B. anthracis at a carcass site.

Genetic Diversity of Australian Bacillus anthracis Isolates Revealed by Multiple-Locus Variable-Number Tandem Repeat Analysis

Outbreaks of anthrax occur sporadically in Australia and most commonly in the "anthrax belt", a region which extends from southern Queensland through the centre of New South Wales and into northern Victoria. Little is known about the epidemiological links between Bacillus anthracis isolates taken from different outbreaks and the diversity of strains within Australia. We used multiple-locus variable-number tandem repeat analysis employing 25 markers (MLVA25) to genotype 99 B. anthracis isolates from an archival collection of Australian isolates. MLVA25 genotyping revealed eight unique genotypes which clustered within the previously defined A3 genotype of B. anthracis. Genotyping of B. anthracis strains from outbreaks of disease in Victoria identified the presence of multiple genotypes associated with these outbreaks. The geographical distribution of genotypes within Australia suggests that a single genotype was introduced into the eastern states of Australia, followed by the spread and localised differentiation of the pathogen (MLVA25 genotypes MG1-MG6) throughout the anthrax belt. In contrast, unexplained occurrences of disease in areas outside of this anthrax belt which are associated with different genotypes, (MLVA25 genotypes MG7 and MG8) indicate separate introductions of B. anthracis into Australia.

Review: The risk of contracting anthrax from spore-contaminated soil - A military medical perspective

Anthrax is an infectious disease of relevance for military forces. Although spores of Bacillus anthracis obiquitously occur in soil, reports on soil-borne transmission to humans are scarce. In this narrative review, the potential of soil-borne transmission of anthrax to humans is discussed based on pathogen-specific characteristics and reports on anthrax in the course of several centuries of warfare. In theory, anthrax foci can pose a potential risk of infection to animals and humans if sufficient amounts of virulent spores are present in the soil even after an extended period of time. In praxis, however, transmissions are usually due to contacts with animal products and reported events of soil-based transmissions are scarce. In the history of warfare, even in the trenches of World War I, reported anthrax cases due to soil-contaminated wounds are virtually absent. Both the perspectives and the experience of the Western hemisphere and of former Soviet Republics are presented. Based on the accessible data as provided in the review, the transmission risk of anthrax by infections of wounds due to spore-contaminated soil is considered as very low under the most circumstance. Active historic anthrax foci may, however, still pose a risk to the health of deployed soldiers.

Systematic Review and Evaluation of Mathematical Attack Models of Human Inhalational Anthrax for Supporting Public Health Decision Making and Response

BACKGROUND

Anthrax is a potential biological weapon and can be used in an air-borne or mail attack, such as in the attack in the United States in 2001. Planning for such an event requires the best available science. Since large-scale experiments are not feasible, mathematical modelling is a crucial tool to inform planning. The aim of this study is to systematically review and evaluate the approaches to mathematical modelling of inhalational anthrax attack to support public health decision making and response.

METHODS

A systematic review of inhalational anthrax attack models was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The models were reviewed based on a set of defined criteria, including the inclusion of atmospheric dispersion component and capacity for real-time decision support.

RESULTS

Of 13 mathematical modelling studies of human inhalational anthrax attacks, there were six studies that took atmospheric dispersion of anthrax spores into account. Further, only two modelling studies had potential utility for real-time decision support, and only one model was validated using real data.

CONCLUSION

The limited modelling studies available use widely varying methods, assumptions, and data. Estimation of attack size using different models may be quite different, and is likely to be under-estimated by models which do not consider weather conditions. Validation with available data is crucial and may improve models. Further, there is a need for both complex models that can provide accurate atmospheric dispersion modelling, as well as for simpler modelling tools that provide real-time decision support for epidemic response.

A Review of Arguments for the Existence of Latent Infections of Bacillus anthracis, and Research Needed to Understand their Role in the Outbreaks of Anthrax

Hugh-Jones and Blackburn and Turnbull’s collective World Health Organization (WHO) report did literature reviews of the theories and the bases for causes of anthrax outbreaks. Both comment on an often-mentioned suspicion that, even though unproven, latent infections are likely involved. Hugh-Jones suggested Gainer do an updated review of our present-day knowledge of latent infections, which was the basis for Gainer’s talk at the Biology of Anthrax Conference in Bari, Italy 2019. At the Conference Gainer met Vergnaud who presented anthrax genome studies that implied that the disease might have spread throughout Asia and from Europe to North America in a short time span of three or four centuries. Vergnaud wondered if latent infections might have played a role in the process. Several other presenters at the Conference also mentioned results that might suggest the existence of latent infections. Vergnaud subsequently looked into some of the old French literature about related observations, results, and discussions of early Pasteur vaccine usage (late 1800′s) and found mentions of suspected latent infections. The first part of the paper is a focused summary and interpretation of Hugh-Jones and Blackburn’s and Turnbull’s reviews specifically looking for suggestions of latent infections, a few additional studies with slightly different approaches, and several mentions made of presentations and posters at the Conference in Italy. In general, many different investigators in different areas and aspects of the anthrax study at the Conference found reasons to suspect the existence of latent infections. The authors conclude that the affected species most studied, including Homo sapiens, provide circumstantial evidence of latent infections and modified host resistance. The last part of the review explores the research needed to prove or disprove the existence of latent infections.

Animal industry and veterinary science in eastern New Guinea: World War II to Independence, 1975

We have described the efforts of the Australian administration of the Territory of Papua and New Guinea (TPNG) to establish a veterinary service and viable animal industries. These efforts began with planning before the end of World War II in 1945 and continued until independence in 1975. Whereas pre-war cattle had mostly been used to control grass on plantations, post-war, the objective was to use the country's extensive, unoccupied grasslands for cattle production. During this period, the cattle population increased from 4000 to more than 150,000. The greatest success was achieved in herds with crosses of Bos indicus and Bos taurus owned by expatriates. The only serious disease constraint on production was myiasis due to Chrysomya bezziana, a parasite throughout New Guinea and South-east Asia. Attempts were made to increase the productivity of the indigenous pig population. Success was limited by a failure to manage inadequate nutrition and internal parasites and to fully understand the cultural aspects of pig ownership. Similar problems inhibited chicken production in villages. The serious viral infections of pigs and birds were absent from TPNG, but a border with Indonesian Papua represents a potential route for the incursion of animal diseases exotic to both Papua New Guinea and to Australia.

Current Status and Trends in Prophylaxis and Management of Anthrax Disease

Bacillus anthracis has been identified as a potential military and bioterror agent as it is relatively simple to produce, with spores that are highly resilient to degradation in the environment and easily dispersed. These characteristics are important in describing how anthrax could be used as a weapon, but they are also important in understanding and determining appropriate prevention and treatment of anthrax disease. Today, anthrax disease is primarily enzootic and found mostly in the developing world, where it is still associated with considerable mortality and morbidity in humans and livestock. This review article describes the spectrum of disease caused by anthrax and the various prevention and treatment options. Specifically we discuss the following; (1) clinical manifestations of anthrax disease (cutaneous, gastrointestinal, inhalational and intravenous-associated); (2) immunology of the disease; (3) an overview of animal models used in research; (4) the current World Health Organization and U.S. Government guidelines for investigation, management, and prophylaxis; (5) unique regulatory approaches to licensure and approval of anthrax medical countermeasures; (6) the history of vaccination and pre-exposure prophylaxis; (7) post-exposure prophylaxis and disease management; (8) treatment of symptomatic disease through the use of antibiotics and hyperimmune or monoclonal antibody-based antitoxin therapies; and (9) the current landscape of next-generation product candidates under development.

The Landscape of Anthrax Prevention and Control: Stakeholders' Perceptive in Odisha, India

The prevalence and outbreaks of anthrax are interlinked with the animal-environment-human context, which signifies the need for collaborative, trans-disciplinary and multi-sectoral approaches for the prevention and control of anthrax. In India, there are hardly any shreds of evidence on the role of various stakeholders' on anthrax prevention and control. Therefore, this study addressed the experiences of various stakeholders on anthrax prevention and control strategies in Odisha, India. A qualitative explorative study was carried out using 42 in-depth-interviews among the stakeholders from health, veterinary and general administrative departments from the block, district, and state level. Two major themes emerged: (1) Epidemiological investigation of anthrax in Odisha, India, and (2) Biological and social prevention strategies for anthrax in Odisha, India. The study emphasizes setting up the surveillance system as per standard guideline, and strengthening the diagnostic facility at a regional medical college laboratory to avoid delay. Moreover, it emphasizes step-up inter-sectoral co-ordination, collaboration and sensitization among health, veterinary, forestry, education, nutrition and tribal welfare departments at all levels in order to reduce the prevalence and control the outbreaks of anthrax in Odisha state. It also recommends raising community literacy, in particular on safe carcass disposal, changing behavior on dead-livestock consumption, and compliance with livestock vaccinations.

Current State of Anthrax Vaccines and Key R&D Gaps Moving Forward

A licensed anthrax vaccine has been available for pre-exposure prophylaxis in the United States since 1970, and it was approved for use as a post-exposure prophylaxis, in combination with antibiotic treatment, in 2015. A variety of other vaccines are available in other nations, approved under various regulatory frameworks. However, investments in anthrax vaccines continue due to the severity of the threat posed by this bacterium, as both a naturally occurring pathogen and the potential for use as a bioweapon. In this review, we will capture the current landscape of anthrax vaccine development, focusing on those lead candidates in clinical development. Although approved products are available, a robust pipeline of candidate vaccines are still in development to try to address some of the key research gaps in the anthrax vaccine field. We will then highlight some of the most pressing needs in terms of anthrax vaccine research.

Epidemiological Investigation and Etiological Analysis of a Cutaneous Anthrax Epidemic Caused by Butchering Sick Cattle in Guizhou, China

A suspected human cutaneous anthrax epidemic caused by butchering sick cattle occurred in Zhijin County of Guizhou Province, Southwest of China, in 2016. Epidemiological investigation and etiological analysis were performed to provide a scientific basis for the source tracking of the epidemic. The epidemic was epidemiologically investigated, and skin blister samples collected from patients and soil samples collected from the butchering spots were used for Bacillus anthracis isolation. The suspicious B. anthracis isolates were identified using conventional methods and PCR, followed by genotyping using multiple-locus variable-number tandem repeats (VNTRs) analysis (MLVA-15) and canonical single-nucleotide polymorphism (canSNP). The genetic relationship of epidemic strains and isolates collected from other regions was analyzed. Epidemiological investigation results showed that the patients may be infected by B. anthracis during butchering sick cattle. Two suspected B. anthracis strains were isolated from blood samples and blister fluids, respectively. Conventional methods identified the two suspected isolates as B. anthracis, while PCR results showed that anti-protective antigen (PA) and capsule (CAP) gene were positive in the two isolates. MLVA-15 showed that the MLVA profiles of the two isolates were 9-20-12-53-16-2-8-8-8-4-4-4-4-10-4, which is different from the MLVA profiles of representative strains from other regions. CanSNP analysis showed that the two strains belonged to cluster A.Br.001/002. Clustering analysis and minimum spanning tree (MST) demonstrated that the two isolates were clustered with strains previously isolated from Guizhou Province. The results indicated that B. anthracis was the pathogen for this epidemic, and the patients were infected during butchering the sick. The genetic characteristics and the relationship of the B. anthracis isolates to strains from other regions indicated that the epidemic was a local occurrence.

Bacillus anthracis as a biological warfare agent: infection, diagnosis and countermeasures

AIM

Bacillus anthracis is a causative agent of zoonotic anthrax disease. In the last years, significant progress in therapy and diagnosis of anthrax was made. Concurrently, knowledge about anthrax progression, molecular pathology and release of anthrax toxin during the disease has improved. This review covers the recent progress in this field.

METHODS

In this review, specifications of B. anthracis, anthrax disease, medical and biomedical countermeasures and diagnostic tools were surveyed. The actual literature was summarized and relevance of the microorganism as a biological warfare agent and the ways how to reduce its impact including therapeutic protocols were written and discussed.

RESULTS

Currently, the microorganism is considered one of the top biological warfare agents due to lethality, long term stability of spores, easy dissemination and production. The recent research is focused on countermeasures suitable for reduction of consequences by a misuse of the microorganism in form of biological weapon (Tab. 3, Fig. 1, Ref. 101). Text in PDF www.elis.sk.

The elephant-livestock interface modulates anthrax suitability in India

Anthrax is a potentially life-threatening bacterial disease that can spread between wild and livestock animals and humans. Transmission typically occurs indirectly via environmental exposure, with devastating consequences for human and animal health, as well as pastoralist economies. India has a high annual occurrence of anthrax in some regions, but a country-wide delineation of risk has not yet been undertaken. The current study modelled the geographical suitability of anthrax across India and its associated environmental features using a biogeographic application of machine learning. Both biotic and abiotic features contributed to risk across multiple scales of influence. The elephant-livestock interface was the dominant feature in delineating anthrax suitability. In addition, water-soil balance, soil chemistry and historical forest loss were also influential. These findings suggest that the elephant-livestock interface plays an important role in the cycling of anthrax in India. Livestock prevention efforts targeting this interface, particularly within anthropogenic ecotones, may yield successes in reducing ongoing transmission between animal hosts and subsequent zoonotic transmission to humans.

Inhibitory Effects of a Reengineered Anthrax Toxin on Canine Oral Mucosal Melanomas

Canine oral mucosal melanomas (OMM) are the most common oral malignancy in dogs and few treatments are available. Thus, new treatment modalities are needed for this disease. Bacillus anthracis (anthrax) toxin has been reengineered to target tumor cells that express urokinase plasminogen activator (uPA) and metalloproteinases (MMP-2), and has shown antineoplastic effects both, in vitro and in vivo. This study aimed to evaluate the effects of a reengineered anthrax toxin on canine OMM. Five dogs bearing OMM without lung metastasis were included in the clinical study. Tumor tissue was analyzed by immunohistochemistry for expression of uPA, uPA receptor, MMP-2, MT1-MMP and TIMP-2. Animals received either three or six intratumoral injections of the reengineered anthrax toxin prior to surgical tumor excision. OMM samples from the five dogs were positive for all antibodies. After intratumoral treatment, all dogs showed stable disease according to the canine Response Evaluation Criteria in Solid Tumors (cRECIST), and tumors had decreased bleeding. Histopathology has shown necrosis of tumor cells and blood vessel walls after treatment. No significant systemic side effects were noted. In conclusion, the reengineered anthrax toxin exerted inhibitory effects when administered intratumorally, and systemic administration of this toxin is a promising therapy for canine OMM.

Rapid and Sensitive Multiplex Assay for the Detection of B. anthracis Spores from Environmental Samples

Prompt and accurate detection of Bacillus anthracis spores is crucial in the event of intentional spore dissemination in order to reduce the number of expected casualties. Specific identification of these spores from environmental samples is both challenging and time-consuming. This is due to the high homology with other Bacillus species as well as the complex composition of environmental samples, which further impedes assay sensitivity. Previously, we showed that a short incubation of B.anthracis spores in a defined growth medium results in rapid germination, bacterial growth, and secretion of toxins, including protective antigen. In this work, we tested whether coupling the incubation process to a newly developed immune-assay will enable the detection of secreted toxins as markers for the presence of spores in environmental samples. The new immune assay is a flow cytometry-based multiplex that simultaneously detects a protective antigen, lethal factor, and edema factor. Our combined assay detects 1 × 10³–1 × 10⁴/mL spores after a 2 h incubation followed by the ~80 min immune-multiplex detection. Extending the incubation step to 5 h increased assay sensitivity to 1 × 10²/mL spore. The protocol was validated in various environmental samples using attenuated or fully virulent B. anthracis spores. There was no substantial influence of contaminants derived from real environmental samples on the performance of the assay compared to clean samples, which allow the unequivocal detection of 3 × 10³/mL and 3 × 10²/mL spores following 2 and 5 hour’s incubation, respectively. Overall, we propose this method as a rapid, sensitive, and specific procedure for the identification of B. anthracis spores in environmental samples.

A Rare Glimpse into the Past of the Anthrax Pathogen Bacillus anthracis

The bacterium Bacillus anthracis is the causative agent of the zoonotic disease anthrax. While genomics of extant B. anthracis isolates established in-depth phylogenomic relationships, there is scarce information on the historic genomics of the pathogen. Here, we characterized the oldest documented B. anthracis specimen. The inactive 142-year-old material originated from a bovine diseased in Chemnitz (Germany) in 1878 and is contemporary with the seminal studies of Robert Koch on B. anthracis. A specifically developed isolation method yielded high-quality DNA from this specimen for genomic sequencing. The bacterial chromosome featuring 242 unique base-characters placed it into a major phylogenetic clade of B. anthracis (B.Branch CNEVA), which is typical for central Europe today. Our results support the notion that the CNEVA-clade represents part of the indigenous genetic lineage of B. anthracis in this part of Europe. This work emphasizes the value of historic specimens as precious resources for reconstructing the past phylogeny of the anthrax pathogen.

Rapid Nanopore Whole-Genome Sequencing for Anthrax Emergency Preparedness

Human anthrax cases necessitate rapid response. We completed Bacillus anthracis nanopore whole-genome sequencing in our high-containment laboratory from a human anthrax isolate hours after receipt. The de novo assembled genome showed no evidence of known antimicrobial resistance genes or introduced plasmid(s). Same-day genomic characterization enhances public health emergency response.

Repeat-Dose Toxicity Study of a Lyophilized Recombinant Protective Antigen-Based Anthrax Vaccine Adjuvanted With CpG 7909

A recombinant protective antigen (rPA) anthrax vaccine candidate (rPA7909) was developed as a next-generation vaccine indicated for postexposure prophylaxis of disease resulting from suspected or confirmed Bacillus anthracis exposure. The lyophilized form of rPA7909-vaccinated candidate contains 75 µg purified rPA, 750 µg aluminum (as Alhydrogel adjuvant), and 250 µg of an immunostimulatory Toll-like receptor 9 agonist oligodeoxynucleotide CpG 7909 in a 0.5 mL phosphate-buffered suspension. General toxicity and local reactogenicity were evaluated in Sprague Dawley rats vaccinated with the full human dose of rPA7909 by intramuscular injection. Animals were immunized on study days 1, 15, and 29. Control groups were administered diluent only or adjuvant control (excipients, CpG 7909, and Alhydrogel adjuvant in diluent) intramuscularly at the same dose volume and according to the same schedule used for rPA7909. Toxicity was assessed based on the results of clinical observations, physical examinations, body weights, injection site reactogenicity, ophthalmology, clinical pathology (hematology, coagulation, and serum chemistry), organ weights, and macroscopic and microscopic pathology evaluation. The immune response to rPA7909 vaccination was confirmed by measuring serum anti-PA immunoglobulin G levels. The rPA7909 vaccine produced no apparent systemic toxicity and only transient reactogenicity at the injection site. The injection site reaction from animals receiving the adjuvant control was very similar to those receiving rPA7909 with respect to the inflammation. The inflammatory response observed in the injection site and the draining lymph nodes was consistent with expected immune stimulation. The overall results indicated a favorable safety profile for rPA7909.

Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice

Protective antigen (PA) is a component of anthrax toxin that can elicit toxin-neutralizing antibody responses. PA is also the major antigen in the current vaccine to prevent anthrax, but stability problems with recombinant proteins have complicated the development of new vaccines containing recombinant PA. The relationship between antigen physical stability and immunogenicity is poorly understood, but there are theoretical reasons to think that this parameter can affect immune responses. We investigated the immunogenicity of anthrax PA, in the presence and absence of the soluble von Willebrand factor A domain of the human form of receptor capillary morphogenesis protein 2 (sCMG2), to elicit antibodies to PA in BALB/c mice. Prior studies showed that sCMG2 stabilizes the 83-kDa PA structure to pH, chemical denaturants, temperature, and proteolysis and slows the hydrogen-deuterium exchange rate of histidine residues far from the binding interface. In contrast to a vaccine containing PA without adjuvant, we found that mice immunized with PA in stable complex with sCMG2 showed markedly reduced antibody responses to PA, including toxin-neutralizing antibodies and antibodies to domain 4, which correlated with fewer toxin-neutralizing antibodies. In contrast, mice immunized with PA in concert with a nonbinding mutant of sCMG2 (D50A) showed anti-PA antibody responses similar to those observed with PA alone. Our results suggest that addition of sCMG2 to a PA vaccine formulation is likely to result in a significantly diminished immune response, but we discuss the multitude of factors that could contribute to reduced immunogenicity.IMPORTANCE The anthrax toxin PA is the major immunogen in the current anthrax vaccine (anthrax vaccine adsorbed). Improving the anthrax vaccine for avoidance of a cold chain necessitates improvements in the thermodynamic stability of PA. We address how stabilizing PA using sCMG2 affects PA immunogenicity in BALB/c mice. Although the stability of PA is increased by binding to sCMG2, PA immunogenicity is decreased. This study emphasizes that, while binding of a ligand retains or improves conformational stability without affecting the native sequence, epitope recognition or processing may be affected, abrogating an effective immune response.

Optimizing the Design of Diatom Biosilica-Targeted Fusion Proteins in Biosensor Construction for Bacillus anthracis Detection

In vivo functionalization of diatom biosilica frustules by genetic manipulation requires careful consideration of the overall structure and function of complex fusion proteins. Although we previously had transformed Thalassiosira pseudonana with constructs containing a single domain antibody (sdAb) raised against the Bacillus anthracis Sterne strain, which detected an epitope of the surface layer protein EA1 accessible in lysed spores, we initially were unsuccessful with constructs encoding a similar sdAb that detected an epitope of EA1 accessible in intact spores and vegetative cells. This discrepancy limited the usefulness of the system as an environmental biosensor for B. anthracis. We surmised that to create functional biosilica-localized biosensors with certain constructs, the biosilica targeting and protein trafficking functions of the biosilica-targeting peptide Sil3_T8 had to be uncoupled. We found that retaining the ER trafficking sequence at the N-terminus and relocating the Sil3_T8 targeting peptide to the C-terminus of the fusion protein resulted in successful detection of EA1 with both sdAbs. Homology modeling of antigen binding by the two sdAbs supported the hypothesis that the rescue of antigen binding in the previously dysfunctional sdAb was due to removal of steric hindrances between the antigen binding loops and the diatom biosilica for that particular sdAb.

Biological agents of bioterrorism - preparedness is vital

Bioterrorist threats and attacks are still an issue of concern in the world. Biological agents are divided into three categories. The highest priority agents classified in category A pose a massive risk to public health and national security. The society should be prepared for this risk. Health professionals in the Czech Republic should be aware of the diseases caused by category A agents, which are not common in the country. In this context, the project of the Ministry of the Interior of the Czech Republic &#8220;Decontamination of the injured persons&#8221; has been implemented at the Faculty of Health Sciences, Palacký University, Olomouc. The article provides an overview of selected serious infectious risks and information on the project the aim of which is to create certified methodical procedures and guidelines on situations related to bioterrorism.