Anthrax prevention through vaccine and post-exposure therapy

Early expression of capsule during Bacillus anthracis germination

Bacillus anthracis is a spore-forming bacterium that produces two major virulence factors, a tripartite toxin with two enzymatic toxic activities and a pseudo-proteic capsule. One of the main described functions of the poly-gamma-d-glutamate capsule is to enable B. anthracis bacilli to escape phagocytosis. Thus, kinetics of expression of the capsule filaments at the surface of the emerging bacillus during germination is an important step for the protection of the nascent bacilli. In this study, through immunofluorescence and electron microscopic approaches, we show the emergence of the capsule through a significant surface of the exosporium in the vast majority of the germinating spores, with co-detection of BclA and capsular material. This suggests that, due to an early capsule expression, the extracellular life of B. anthracis might occur earlier than previously thought, once germination is triggered. This raises the prospect that an anti-capsular vaccine may play a protective role at the initial stage of infection by opsonisation of the nascent encapsulated bacilli before their emergence from the exosporium.

Antibody engineering and its therapeutic applications

As a natural function, antibodies defend the host from infected cells and pathogens by recognizing their pathogenic determinants. Antibodies (Abs) gained wide acceptance with an enormous impact on human health and have predominantly captured the arena of bio-therapeutics and bio-diagnostics. The scope of Ab-based biologics is vast, and it is likely to solve many unmet clinical needs in future. The majority of attention is now devoted to developing innovative technologies for manufacturing and engineering Abs, better suited to satisfy human needs. The advent of Ab engineering technologies (AET) led to phenomenal developments leading to the generation of Abs-/Ab-derived molecules with desirable functional properties proportional to their expanding requirements. Evolution brought by AET, from the naturally occurring Ab forms to several advanced Ab formats and derivatives, was much needed as it is of great interest to the pharmaceutical industry. Thus, numerous advancements in AET have propelled success in therapeutic Ab development, along with the potential for ever-increasing improvements. Unique characteristics of Abs, such as its diversity, specificity, structural integrity and an array of possible applications, together inspire continuous innovation in the field. Overall, the AET could assist in conquer of several limitations of Abs in terms of their applicability in the field of therapeutics, diagnostics and research; AET has so far led to the production of next-generation Abs, which have revolutionized these arenas. Here in this review, we discuss the various distinguished engineering platforms for Ab development and the progress in modern therapeutics by the so-called "next-generation Abs."

Single Low-Dose Nanovaccine for Long-Term Protection against Anthrax Toxins

Anthrax infections caused by Bacillus anthracis are an ongoing bioterrorism and livestock threat worldwide. Current approaches for management, including extended passive antibody transfusion, antibiotics, and prophylactic vaccination, are often cumbersome and associated with low patient compliance. Here, we report on the development of an adjuvanted nanotoxoid vaccine based on macrophage membrane-coated nanoparticles bound with anthrax toxins. This design leverages the natural binding interaction of protective antigen, a key anthrax toxin, with macrophages. In a murine model, a single low-dose vaccination with the nanotoxoids generates long-lasting immunity that protects against subsequent challenge with anthrax toxins. Overall, this work provides a new approach to address the ongoing threat of anthrax outbreaks and bioterrorism by taking advantage of an emerging biomimetic nanotechnology.

Epizootological and epidemiological situation of anthrax in Ukraine in the context of mandatory specific prevention in susceptible animals

The problem of zoonoses remains relevant in the context of reliable prevention of human disease and effective ways to achieve this result, in particular through the impact on susceptible animals by the efforts of veterinary medicine. Anthrax is an acute, particularly dangerous infectious disease of all species of farm, domestic and wild animals, as well as humans, which is caused by Bacillus anthracis microbes. The causative agent of anthrax belongs to the group of aerobic spore-forming bacteria and exists in two main forms: vegetative and spore. The vegetative form in the body of an infected animal can form a "capsule". In Ukraine, according to the provisions of the current "Instruction for the prevention and control of animal anthrax" (2000), the main method of preventing anthrax among animals is regular vaccination of animals susceptible to this disease. The authors conducted a retrospective analysis of the epizootic and epidemiological situation of anthrax in Ukraine for the period 1994–2021 and made a critical assessment of the performance of mandatory measures for specific prevention of susceptible animals. In order to find out the ecological and geographical features of the spread of anthrax, data on outbreaks of the disease in cattle, swine, small ruminants and humans on the territory of Ukraine were analyzed by regions for the time period under investigation. Over the past 28 years in Ukraine, animal anthrax was registered in in all areas except Zhytomyr region. In total, during the analyzed period, 177 affected points and 637 infected animals (cattle, small ruminants, pigs, horses, wild and fur-bearing animals, dogs) were registered (estimated at 3.59 animals per outbreak). Cattle were most often involved in the epizootic process, followed by pigs and small ruminants, while horses and other animal species were least infected. Ecological and geographical analysis showed that the largest number of affected points among animals during the analyzed period was found in Kyiv, Volyn, Kharkiv, Luhansk, Khmelnytskyi, Cherkasy, Odesa, and Vinnytsia regions. A small number of affected points during the analyzed period were found in Zakarpattia, Ternopil, Kherson, Autonomous Republic of Crimea, Poltava, Dnipropetrovsk and Ivano-Frankivsk regions. During the analyzed period, 68 people in 11 regions of Ukraine were infected with anthrax, 15 outbreaks were registered (4.46 people per outbreak). Most cases were reported in Donetsk, Kyiv and Odesa regions. The association between outbreaks of anthrax in animals and cases of anthrax among humans has been established, this dependency was 86.6% (the index of contiguity, which takes into account the number of years with simultaneous registration of animal and human cases, was 0.5). The authors thoroughly proved that it is vaccination among susceptible animals that will finally prevent the incidence of anthrax among people.

Common garlic (Allium sativum L.) has potent Anti-Bacillus anthracis activity

ETHNOPHARMACOLOGICAL RELEVANCE

Gastrointestinal anthrax, a disease caused by Bacillus anthracis, remains an important but relatively neglected endemic disease of animals and humans in remote areas of the Indian subcontinent and some parts of Africa. Its initial symptoms include diarrhea and stomachache. In the current study, several common plants indicated for diarrhea, dysentery, stomachache or as stomachic as per traditional knowledge in the Indian subcontinent, i.e., Aegle marmelos (L.) Correa (Bael), Allium cepa L. (Onion), Allium sativum L. (Garlic), Azadirachta indica A. Juss. (Neem), Berberis asiatica Roxb. ex DC. (Daruharidra), Coriandrum sativum L. (Coriander), Curcuma longa L. (Turmeric), Cynodon dactylon (L.) Pers. (Bermuda grass), Mangifera indica L. (Mango), Morus indica L. (Black mulberry), Ocimum tenuiflorum L. (Ocimum sanctum L., Holy Basil), Ocimum gratissimum L. (Ram Tulsi), Psidium guajava L. (Guava), Zingiber officinale Roscoe (Ginger), were evaluated for their anti-Bacillus anthracis property. The usage of Azadirachta indica A. Juss. and Curcuma longa L. by Santals (India), and Allium sp. by biblical people to alleviate anthrax-like symptoms is well documented, but the usage of other plants is traditionally only indicated for different gastrointestinal disturbances/conditions.

AIM OF THE STUDY

Evaluate the above listed commonly available edible plants from the Indian subcontinent that are used in the traditional medicine to treat gastrointestinal diseases including those also indicated for anthrax-like symptoms for the presence of potent anti-B. anthracis activity in a form amenable to use by the general population in the endemic areas.

MATERIALS AND METHODS

Aqueous extracts made from fourteen plants indicated above were screened for their anti-B. anthracis activity using agar-well diffusion assay (AWDA) and broth microdilution methods. The Aqueous Garlic Extract (AGE) that displayed most potent anti-B. anthracis activity was assessed for its thermostability, stability under pH extremes encountered in the gastrointestinal tract, and potential antagonistic interaction with bile salts as well as the FDA-approved antibiotics used for anthrax control. The bioactive fractions from the AGE were isolated by TLC coupled bioautography followed by their characterization using GC-MS.

RESULTS

Garlic (Allium sativum L.) extract was identified as the most promising candidate with bactericidal activity against B. anthracis. It consistently inhibited the growth of B. anthracis in AWDA and decreased the viable colony-forming unit counts in liquid-broth cultures by 6-logs within 6-12 h. The AGE displayed acceptable thermostability (>80% anti-B. anthracis activity retained on incubation at 50 °C for 12 h) and stability in gastric pH range (2-8). It did not antagonize the activity of FDA-approved antibiotics used for anthrax control. GC-MS analysis of the TLC separated bioactive fractions of AGE indicated the presence of previously unreported constituents such as phthalic acid derivatives, acid esters, phenyl group-containing compounds, steroids etc. CONCLUSION: The Aqueous Garlic Extract (AGE) displayed potent anti-B. anthracis activity. It was better than that displayed by Azadirachta indica A. Juss. (Neem) and Mangifera indica L., while Curcuma longa L. (Turmeric) did not show any activity under the assay conditions used. Further work should be undertaken to explore the possible application of AGE in preventing anthrax incidences in endemic areas.