Using a Syrian (Golden) Hamster Biological Model for the Evaluation of Recombinant Anthrax Vaccines

In this paper, we demonstrate that a Syrian hamster biological model can be applied to the study of recombinant anthrax vaccines. We show that double vaccination with recombinant proteins, such as protective antigen (PA) and fusion protein LF1PA4, consisting of lethal factor I domain (LF) and PA domain IV, leads to the production of high titers of specific antibodies and to protection from infection with the toxicogenic encapsulated attenuated strain B. anthracis 71/12. In terms of antibody production and protection, Syrian hamsters were much more comparable to guinea pigs than mice. We believe that Syrian hamsters are still underestimated as a biological model for anthrax research, and, in some cases, they can be used as a replacement or at least as a complement to the traditionally used mouse model.

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.

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.

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

Genetic Construction of Bacillus subtilis Recombinant Strain, Producing Anthrax Protective Antigen

Anthrax is a serious infectious disease with high mortality. The epidemiological security depends on the vaccination of susceptible animals and population at risk. But many of the existing anthrax vaccine strains possess low levels of protective antigen production and high reactogenicity. One of the most promising trends in production of new generation of vaccines is the cloning of particular determinants of immunogenicity of anthrax microbe for the creation of highly effective producers of Bacillus anthracis protective antigen. The aim of the article is to present the results of the study on the construction of recombinant Bacillus subtilis strain, producing B.anthracis protective antigen, promising for use in chemical anthrax vaccines technology. The pHT43PA plasmid containing the gene pag, providing the synthesis of protective antigen of the anthrax microbe and functioning stably in the cells of the recombinant strain Amy21(pHT43РА) of B. subtilis, was constructed on the basis of the shuttle vector pHT43. It is found out during the research, that the microbial cells of the recombinant strain Amy21(pHT43РА) of B. subtilis provide the production of immunologically active protective antigen in quantities, not inferior than anthrax vaccine strains. These data, as well as safety and simplicity of В. subtilis make it possible to continue the research of this recombinant strain as a producer of anthrax protective antigen, promising for use in vaccines production