Development of Genetically Engineered Vaccine and Post-Exposure Therapy Against Anthrax

Anthrax, caused by the spore forming bacterium Bacillus anthracis, is a severe infectious disease in both animals and humans. Due to its potential to serve as a biological weapon, research and development of effective vaccines and post-exposure therapeutics has been crucial. Currently available anthrax vaccines such as Anthrax Vaccine Adsorbed (AVA) and Anthrax Vaccine Precipitate (AVP) are tightly regulated and not commercially available. FDA approved prophylactic approaches against the disease, Raxibacumab and Obiltoxaximab, can neutralize protective antigen (PA) which provides protective immunity and are effective against inhalational anthrax only. In an attempt to design an effective vaccine against anthrax, we successfully constructed and expressed recombinant PA in a heterologous host. The vaccine could offer 67–100% protection against anthrax challenge in pre-clinical animal models. We have also elucidated the role of amino acid residues of PA that are crucial for its oligomerization (F552, I562, L566, and I574) and translocation (L352 and W346) into the host cytosol, and the residues I207, P205, L203, F202 which are crucial for binding to lethal factor (LF). Further structural validation of LF and edema factor (EF) disclosed a homologous sequence consisting of the amino acid residues (valine, tyrosine, glutamic acid, isoleucine, glycine, and lysine) which are responsible for binding to PA. To design a post-prophylactic approach against the disease, we successfully created a monoclonal antibody which can successfully bind to the common N-terminal of LF and EF and effectively neutralize the toxin components as well as provide 60% protection against a murine model of anthrax. This antibody in combination with ciprofloxacin provided 100% protection in mouse model. Toxin-antitoxin (TA) components in Bacillus anthracis assists the bacteria to cope up with adverse environmental conditions as well as negatively impact host molecular and cellular machinery. We demonstrated that blocking TA system (PemK–PemI) of B. anthracis results in decreased virulence. Most recently, by implementing computational as well as wet lab approaches, we demonstrated that blocking of the sites in PA crucial for binding to LF by quercetin dihydrate (QDH) and 1,3,6,-Trigalloyl-β-D-Glucose (TGG), results in reduced cytotoxicity.