Anthrax antigens and methods of use

#Anthrax is a lethal infectious disease caused by Bacillus anthracis, a spore-forming, gram-positive bacterium. In its most contagious and lethal form, pulmonary or inhalation anthrax, anthrax spores (endospores) are inhaled and germinate in alveolar macrophages. The macrophages transport the bacterium from the lungs to the host circulatory system. Once released from the macrophages, B. anthracis replicates extracellularly, causing flu-like symptoms followed by massive hypotension and pulmonary edema. (Demicheli et al. Vaccine 16:880-884 (1998); Friedlander. J. Appl. Microbiol. 87:303 (1999); Hambleton et al. 1984. Vaccine 2:125-132 (1984); Jernigan et al. Emerg. Infect. Dis. 7:933-944 (2001))

#Two major B. anthracis virulence factors are plasmids, pXO1 and pXO2. (Okinaka et al. Sequence and organization of pXO1, the large Bacillus anthracis plasmid harboring the anthrax toxin genes J. Bacteriol. 181(20):6509-6515 (1999); Okinaka et al. Sequence, assembly and analysis of pX01 and pX02. J. Appl. Microbiol. 87(2):261-262 (1999)) pXO2 encodes poly-γ-D-glutamic acid (PGA), which is a major component of the bacterium's capsule. PGA is weakly immunogenic and possesses antiphagocytic properties, i.e., unencapsulated strains are readily phagocytized and virtually avirulent. pXO1 encodes the protein subunits of the secreted exotoxins, lethal toxin (LeTx) and Edema Toxin (EdTx). Each exotoxin contains A and B subunits. The A subunit of EdTx is edema factor (EFa), an adenyl cyclase. The A subunit of LeTx is lethal factor (LFa), a metalloproteinase. The B subunit of both exotoxins is protective antigen (PA), which is a binding partner of the toxins' cellular receptor. In the presence of furin-like proteases, a 20 kDa piece is removed from the full length PA molecule (83 kDa), forming PA63 (63 kDa). PA63 interacts with other PA63 molecules to form heptamer(s) (PA7) and also interacts with LFa and/or EFa to form LeTx and EdTx, respectively.

#The current human anthrax vaccine is an aluminum hydroxide-adsorbed supernatant from fermentor cultures of a toxigenic, non-encapsulated strain of B. anthracis V770-NPI-R (Anthrax Vaccine Adsorbed (AVA)). The vaccine is expensive to produce, requires repeated immunizations, and causes local pain with edema and erythema. The course of immunization consists of three subcutaneous injections 2 weeks apart, three injections 6 months apart, and an annual injection as long as the subject remains at risk. Recent events have demonstrated the potential of anthrax as a bioweapon and the susceptibility of large segments of the civilian population. (Friedlander et al. J. Infect. Dis. 167:1239-1243 (1993)). The disadvantages of the current vaccine make it unfeasible for widespread administration before or after a bioterrorist attack. (Institute of Medicine. 2002. The Anthrax Vaccine. Is It safe? Does It Work? National Academy Press, Washington, D.C.)

#The skilled artisan will appreciate that the drawings and accompanying descriptions, below, are for illustration purposes only and therefore are not intended to limit the scope of the present disclosure in any way.

#FIG. 1 shows ELISA results for sera collected at 4 weeks (Left) and 8 weeks (Right) following initial vaccination (Example 1). The value of each individual mouse is indicated by a circle. Mean values for each treatment ±standard error of the mean are indicated by bars. The PA content of immunizations is indicated in the horizontal axis labels.

#FIG. 2 shows survival of a lethal intravenous LeTx challenge by immunized mice (Example 1). The change in survivorship over time is indicated in hours post-challenge.

#In this application, the use of the singular includes the plural unless specifically stated otherwise. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in any way. While the present teachings are described in conjunction with various embodiments, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art.

#The present invention is directed to the discovery that certain anthrax antigens administered to a mucosal surface of a subject induce an immune response to anthrax and do not substantially induce, cause, and/or exacerbate anthrax disease. Thus, anthrax antigens disclosed herein find use as therapeutics and preventative treatments of anthrax disease.

#In addition to compositions, the present invention provides methods of inducing an immune response to anthrax by inducing an immune response to anthrax antigens. The immune response induced by the anthrax antigens reacts with the etiologic agent of anthrax disease and/or an anthrax virulence factor, thereby treating or preventing one or more disease symptoms.