A plant-produced protective antigen vaccine confers protection in rabbits against a lethal aerosolized challenge withBacillus anthracisAmes spores

Abstract

The potential use of Bacillus anthracis as a bioterrorism weapon threatens the security of populations globally, requiring the immediate availability of safe, efficient and easily delivered anthrax vaccine for mass vaccination. Extensive research efforts have been directed toward the development of recombinant subunit vaccines based on protective antigen (PA), the principal virulence factor of B. anthracis. Among the emerging technologies for the production of these vaccine antigens is our launch vector-based plant transient expression system. Using this system, we have successfully engineered, expressed, purified and characterized full-length PA (pp-PA83) in Nicotiana benthamiana plants using agroinfiltration. This plant-produced antigen elicited high toxin neutralizing antibody titers in mice and rabbits after two vaccine administrations with Alhydrogel. In addition, immunization with this vaccine candidate protected 100% of rabbits from a lethal aerosolized B. anthracis challenge. The vaccine effects were dose-dependent and required the presence of Alhydrogel adjuvant. In addition, the vaccine antigen formulated with Alhydrogel was stable and retained immunogenicity after two-week storage at 4°C, the conditions intended for clinical use. These results support the testing of this vaccine candidate in human volunteers and the utility of our plant expression system for the production of a recombinant anthrax vaccine.

Influence of Protein Formulation and Carrier Solution on Asymmetrical Flow Field-Flow Fractionation: A Case Study of the Plant-Produced Recombinant Anthrax Protective Antigen pp-PA83

“…Peaks 3 and 4 correspond to the main populations of pp‐PA83 having similar molar masses, 125 ± 10 kDa for Peak 3 and 142 ± 10 kDa for Peak 4. The afFFF–MALS data in Figure c are similar with the SEC–MALS results . The molecular mass of 125 kDa for pp‐PA83 (Peak 3) measured by afFFF–MALS is higher than the value of 85 kDa measured by SEC–MALS, Figure in Ref.…”

“…A case study showing that this assumption is not always correct is presented in this paper: for the same formulation, different afFFF fractograms were obtained with different carrier solutions using the same afFFF method. The investigated protein was a plant‐produced anthrax toxin protective antigen, pp‐PA83, recently described in the literature to be efficacious in vaccination against anthrax infection . pp‐PA83 monomer has four flexible domains and can change conformation from a packed to a more extended structure .…”

Advax-Adjuvanted Recombinant Protective Antigen Provides Protection against Inhalational Anthrax That Is Further Enhanced by Addition of Murabutide Adjuvant

“…PA complexes with the toxin subunits EF and LF and interacts with host cell receptors to translocate the toxins into the cytosol (14). Due to its essential role in anthrax pathogenesis, recombinant PA is the lead candidate in development of next-generation anthrax vaccines (20,21).…”

Controlled release of an anthrax toxin‐neutralizing antibody from hydrolytically degradable polyethylene glycol hydrogels

“…During the past 10 years, several human antibodies against anthrax PA have been demonstrated to provide passive protection in variety of animal models including rats, rabbits, guinea pigs and non‐human primates . One such mAb was developed by Fraunhofer USA Center for Molecular Biotechnology (FhCMB) and shown to provide full protection against an inhalation anthrax spore challenge in non‐human primates . FhCMB engineered this mAb in their plant‐based production platform to be a non‐glycosylated (NG) version of a mAb against PA, termed PANG.…”