title: Adenoviral Expression of a Bispecific VHH-Based Neutralizing Agent That Targets Protective Antigen Provides Prophylactic Protection from Anthrax in Mice.
abstract: Bacillus anthracis, the causative agent of anthrax, secretes three polypeptides, which form the bipartite lethal and edema toxins (LT and ET, respectively). The common component in these toxins, protective antigen (PA), is responsible for binding to cellular receptors and translocating the lethal factor (LF) and edema factor (EF) enzymatic moieties to the cytosol. Antibodies against PA protect against anthrax. We previously isolated toxin-neutralizing variable domains of camelid heavy-chain-only antibodies (VHHs) and demonstrated their in vivo efficacy. In this work, gene therapy with an adenoviral (Ad) vector (Ad/VNA2-PA) (VNA, VHH-based neutralizing agents) promoting the expression of a bispecific VHH-based neutralizing agent (VNA2-PA), consisting of two linked VHHs targeting different PA-neutralizing epitopes, was tested in two inbred mouse strains, BALB/cJ and C57BL/6J, and found to protect mice against anthrax toxin challenge and anthrax spore infection. Two weeks after a single treatment with Ad/VNA2-PA, serum VNA2-PA levels remained above 1 μg/ml, with some as high as 10 mg/ml. The levels were 10- to 100-fold higher and persisted longer in C57BL/6J than in BALB/cJ mice. Mice were challenged with a lethal dose of LT or spores at various times after Ad/VNA2-PA administration. The majority of BALB/cJ mice having serum VNA2-PA levels of >0.1 μg/ml survived LT challenge, and 9 of 10 C57BL/6J mice with serum levels of >1 μg/ml survived spore challenge. Our findings demonstrate the potential for genetic delivery of VNAs as an effective method for providing prophylactic protection from anthrax. We also extend prior findings of mouse strain-based differences in transgene expression and persistence by adenoviral vectors.
authors.affiliation: Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Mahtab
authors.initials: M
authors.lastname: Moayeri
authors.affiliation: Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts, USA.
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Tremblay
authors.affiliation: Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Debatis
authors.affiliation: Department of Radiation Oncology, Washington University, St. Louis, Missouri, USA.
authors.forename: Igor P
authors.initials: IP
authors.lastname: Dmitriev
authors.affiliation: Department of Radiation Oncology, Washington University, St. Louis, Missouri, USA.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Kashentseva
authors.affiliation: Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Yeh
authors.affiliation: Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Gordon Y C
authors.initials: GY
authors.lastname: Cheung
authors.affiliation: Department of Radiation Oncology, Washington University, St. Louis, Missouri, USA.
authors.forename: David T
authors.initials: DT
authors.lastname: Curiel
authors.affiliation: Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Leppla
authors.affiliation: Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, Massachusetts, USA charles.shoemaker@tufts.edu.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Shoemaker
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D000881:Anthrax / Q000276:immunology / Q000517:prevention & control*; D000907:Antibodies, Bacterial / Q000235:genetics / Q000276:immunology; D000942:Antigens, Bacterial / Q000276:immunology*; D001408:Bacillus anthracis / Q000276:immunology / Q000472:pathogenicity; D001427:Bacterial Toxins / Q000276:immunology*; D005260:Female; D007106:Immune Sera / Q000276:immunology; D007116:Immunization, Passive / Q000379:methods*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D057127:Single-Chain Antibodies / Q000235:genetics* / Q000276:immunology*; D013171:Spores, Bacterial / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D007106:Immune Sera; D007143:Immunoglobulin Heavy Chains; D057127:Single-Chain Antibodies; C030325:anthrax toxin