Anthrax

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Bacillus anthracis is a Gram-positive, spore-forming, Category A organism that has already been used as a weapon of bioterrorism in the US. Its principal virulence factors are two toxins, Lethal Toxin (LT) and Edema Toxin (ET) and an anti-phagocytic capsule. Although an efficacious vaccine (Biothrax), consisting primarily of Protective Antigen (PA), is licensed in the US, the need to immunize a large segment of the population on short notice in case of attack requires a new vaccine that is less reactogenic and able to elicit a rapid protective response. The objectives of this project are to identify new antigens from B. anthracis spores (Sub-Project I.1) and vegetative cells (Sub-Project 1.2) that can be included in a new anthrax vaccine. The genes for these antigens will be cloned, expressed as recombinant proteins and tested for protective activity. To understand better and visualize the process and location of germination, a new mouse model will be developed, using conditional expression of a lux gene in B. anthracis (Sub-Project I. 1). The host immune response to B. anthracis antigens, including the role of T cells and the importance of HLA type, will be characterized using blood/cells from subjects who have had anthrax or have been immunized with the vaccine (Sub-Project 1.2). Despite availability of new structural information on ET and LT, little is known about their cellular actions or roles in anthrax. These issues will be addressed in Sub-Project 1.3, by exploration of the intracellular consequences of ET and LT enzymatic activities, alone and together, and evaluation of reagents to block their effects. Finally, a novel strategy for anthrax immunity, the mucosal-prime/parenteral-boost paradigm using a Salmonella-based live vector vaccine, will be tested (Sub-Project 1.4). With this approach, the host system is primed with mucosally administered, attenuated S. Typhi expressing PA and/or other antigens from Sub-Projects I.1 and 1.2, so that the host response will be more vigorous to subsequent parenteral boosting with PA (Biothrax), recombinant PA, or PA conjugated to the other newly identified antigens from spores or vegetative cells [Sub- Projects 1.1 and 1.2]. This research will be carried out by a team of investigators who have extensive experience in microbial pathogenesis, antigen identification, animal models, toxin mechanisms, and vaccine development and testing. The deliverables include new antigens from B. anthracis, tested in murine and NHP systems, compounds with potential to impede or block the molecular mechanisms by which individuals die of anthrax, and a new mouse model for imaging germination and bacterial distribution.