A cationic lipid-formulated plasmid DNA vaccine confers sustained antibody-mediated protection against aerosolized anthrax spores

Abstract

DNA vaccines provide an attractive technology platform against bioterrorism agents due to their safety record in humans and ease of construction, testing, and manufacture. We have designed monovalent and bivalent anthrax plasmid DNA (pDNA) vaccines encoding genetically detoxified protective antigen (PA) and lethal factor (LF) proteins and tested their immunogenicity and ability to protect rabbits from an aerosolized inhalation spore challenge. Immune responses after two or three injections of cationic lipidformulated PA, PA plus LF, or LF pDNAs were at least equivalent to two doses of anthrax vaccine adsorbed (AVA). High titers of anti-PA, anti-LF, and neutralizing antibody to lethal toxin (Letx) were achieved in all rabbits. Eight or nine animals in each group were challenged with 100؋ LD50 of aerosolized anthrax spores 5 or 9 weeks after vaccination. An additional 10 animals vaccinated with PA pDNA were challenged >7 months postvaccination. All animals receiving PA or PA plus LF pDNA vaccines were protected. In addition, 5 of 9 animals receiving LF pDNA survived, and the time to death was significantly delayed in the others. Groups receiving three immunizations with PA or PA plus LF pDNA showed no increase in anti-PA, anti-LF, or Letx neutralizing antibody titers postchallenge, suggesting little or no spore germination. In contrast, titer increases were seen in AVA animals, and in surviving animals vaccinated with LF pDNA alone. Preclinical evaluation of this cationic lipid-formulated bivalent PA and LF vaccine is complete, and the vaccine has received U.S. Food and Drug Administration Investigational New Drug allowance.

Protective immunity against botulism provided by a single dose vaccination with an adenovirus-vectored vaccine

“…This resulted in high-level expression of H C 50. It might be secreted from host cells using the signal peptide of human tissue plasminogen activator (PLAT) [42,43], and the secretory H C 50 might be presented to antigen-presenting cells (APCs) more efficiently after vaccination. In any case, the vaccine construct was more potent at inducing host immune responses than was an adenoviral vector encoding the native H C 50 sequence (data not shown).…”

Effect of aluminum hydroxide adjuvant and formaldehyde in the formulation of rPA anthrax vaccine

“…Various formulations have been tested in preparing anthrax vaccines based upon rPA for its ability to elicit optimal immunological responses. Recent examples include Toll-like receptor ligands CpG ODN and Resiquimod R-848 [35,36], pluronic F127, a non-ionic, hydrophilic polyoxyethylenepolyoxypropylene block copolymer [37], additional vaccine antigens such as capsule [38] or EF [39,40], DNA vaccines [41], and mucosal vaccine strategies [42,43]. That antibodies have been recognized as important in protection is demonstrated by the number of immunotherapeutic reagents that have been recently suggested [44][45][46][47][48][49].…”

Recombinant Vaccine Displaying the Loop-Neutralizing Determinant from Protective Antigen Completely Protects Rabbits from Experimental Inhalation Anthrax

“…Since 2001, when spores of B. anthracis sent through the U.S. mail resulted in infection in 22 individuals, including 5 fatal cases of inhalation anthrax, significant efforts have been directed toward reevaluating our preparedness for possible bioterrorist threats, including weaponized anthrax. This has included renewed efforts to more critically evaluate the anthrax vaccine currently approved in the United States, BioThrax, as well as continued development of new, alternative vaccines for anthrax (1)(2)(3)(4)(5)(6). We previously showed that immunization of rabbits with a multiple antigenic peptide (MAP), which display multiple copies of a target sequence extending from a branched lysine core, was capable of eliciting antibody specific for a linear determinant in the 2␤2-2␤3 loop, which mediated high-titer neutralization of lethal toxin (LeTx) in vitro (7,8) and protection of rabbits from a targeted aerosol challenge of 200 50% lethal doses (LD 50 ) of B. anthracis Ames strain in vivo (9).…”