Comparative vaccine efficacy of different isoforms of recombinant protective antigen against Bacillus anthracis spore challenge in rabbits

Ribot, Wilson J.; Powell, Bradford S.; Ivins, Bruce E.; Little, Stephen F.; Johnson, Wendy M.; Hoover, Timothy A.; Norris, Sarah L.; Adamovicz, Jeffrey J.; Friedlander, Arthur M.; Andrews, Gerard P.

doi:10.1016/j.vaccine.2006.02.013

Cited by 25 publications

(40 citation statements)

References 37 publications

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“…This development began within the U.S. Department of Defense and has since expanded into the commercial arena. The recombinant PA (rPA) pilot lot vaccine tested in this trial underwent extensive laboratory and animal testing before clinical trials were begun, [11][12][13][14] and became the first rPA vaccine produced in the United States. Herein we describe our Phase I evaluation, in healthy young adults, of the safety, reactogenicity and immunogenicity of two intramuscular injections of four different dosages of rPA.…”

Section: Introductionmentioning

confidence: 99%

Safety, Reactogenicity, and Immunogenicity of a Recombinant Protective Antigen Anthrax Vaccine Given to Healthy Adults

Campbell¹,

Clement²,

Wasserman³

et al. 2007

Human Vaccines

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Background: Bacillus anthracis causes anthrax, a vaccine-preventable zoonotic disease that may follow intentional or unintentional exposure to its spores. Although an anthrax vaccine is currently licensed in the USA, better vaccines are desirable for both pre-and post-exposure prophylaxis.Methods: Healthy adults, aged 18-40 years, received anthrax immunization with either licensed Anthrax Vaccine Adsorbed (AVA, BioThrax™), or an experimental recombinant Protective Antigen vaccine (rPA) produced from an avirulent, non-spore-forming strain of B. anthracis at one of four doses (5, 25, 50 or 75 mg). Volunteers were followed for safety, reactogenicity, and immunogenicity.Results: rPA vaccine was well tolerated with a low rate of local or systemic reactions. Although antibody responses were poor following unadjuvanted rPA administration, 89 and 100% of volunteers who received Alhydrogel-adjuvanted rPA given intramuscularly had four-fold increases by enzyme-linked immunosorbent and toxin neutralization assays, respectively. Peak antibody responses to adjuvanted rPA given intramuscularly were equivalent to AVA, given either intramuscularly or subcutaneously, when measured by either assay.Conclusions: This recombinant Protective Antigen anthrax vaccine, when given with the adjuvant Alhydrogel to healthy adults in two intramuscular injections four weeks apart, is very well-tolerated and highly immunogenic.

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Section: Introductionmentioning

confidence: 99%

Safety, Reactogenicity, and Immunogenicity of a Recombinant Protective Antigen Anthrax Vaccine Given to Healthy Adults

Campbell¹,

Clement²,

Wasserman³

et al. 2007

Human Vaccines

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“…While deamidation of Asn residues in rPA has been demonstrated, little is known about the effect that deamidation might have on the immunogenicity of the protein. Previously, Ribot et al (19) examined the immunogenicity and protective efficacy of isoforms of rPA that differed in deamidation levels (18,19). The two isoforms compared in that study exhibited comparable immunogenicity and protective immunity; however, the difference in the extent of deamidation between the two isoforms used in that study was minimal, as judged by the incremental difference in charge between the two isoforms (18,19).…”

mentioning

confidence: 97%

“…Previously, Ribot et al (19) examined the immunogenicity and protective efficacy of isoforms of rPA that differed in deamidation levels (18,19). The two isoforms compared in that study exhibited comparable immunogenicity and protective immunity; however, the difference in the extent of deamidation between the two isoforms used in that study was minimal, as judged by the incremental difference in charge between the two isoforms (18,19). Thus, this difference in deamidation most likely did not adequately mimic the extent of deamidation that might be expected upon long-term vaccine storage.…”

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confidence: 99%

Use of Site-Directed Mutagenesis To Model the Effects of Spontaneous Deamidation on the Immunogenicity of Bacillus anthracis Protective Antigen

et al. 2013

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c Long-term stability is a desired characteristic of vaccines, especially anthrax vaccines, which must be stockpiled for large-scale use in an emergency situation; however, spontaneous deamidation of purified vaccine antigens has the potential to adversely affect vaccine immunogenicity over time. In order to explore whether spontaneous deamidation of recombinant protective antigen (rPA)-the major component of new-generation anthrax vaccines-affects vaccine immunogenicity, we created a "genetically deamidated" form of rPA using site-directed mutagenesis to replace six deamidation-prone asparagine residues, at positions 408, 466, 537, 601, 713, and 719, with either aspartate, glutamine, or alanine residues. We found that the structure of the six-Asp mutant rPA was not significantly altered relative to that of the wild-type protein as assessed by circular dichroism (CD) spectroscopy and biological activity. In contrast, immunogenicity of aluminum-adjuvanted six-Asp mutant rPA, as measured by induction of toxin-neutralizing antibodies, was significantly lower than that of the corresponding wild-type rPA vaccine formulation. The six-Gln and six-Ala mutants also exhibited lower immunogenicity than the wild type. While the wild-type rPA vaccine formulation exhibited a high level of immunogenicity initially, its immunogenicity declined significantly upon storage at 25°C for 4 weeks. In contrast, the immunogenicity of the six-Asp mutant rPA vaccine formulation was low initially but did not change significantly upon storage. Taken together, results from this study suggest that spontaneous deamidation of asparagine residues predicted to occur during storage of rPA vaccines would adversely affect vaccine immunogenicity and therefore the storage life of vaccines.

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“…Deamidation of Asn occurs in vivo on a time scale ranging from a few seconds to centuries, depending on the local environment (10). In theory, deamidation might adversely affect the interaction of rPA with the aluminum adjuvant of the vaccine, might alter the epitope structure of the antigen, and/or might affect the ability of the protein to elicit T-cell help for antibody production which, in turn, might affect the vaccine immunogenicity (11)(12)(13)(14)(15).Earlier studies have demonstrated that certain Asn residues of rPA deamidate during the purification process and upon storage (8,16,17). Previously, we generated a mutant form of rPA in which the six Asn residues that are the most prone to deamidation were changed to Asp residues (six-Asp mutant rPA).…”

mentioning

confidence: 99%

“…Earlier studies have demonstrated that certain Asn residues of rPA deamidate during the purification process and upon storage (8,16,17). Previously, we generated a mutant form of rPA in which the six Asn residues that are the most prone to deamidation were changed to Asp residues (six-Asp mutant rPA).…”

mentioning

confidence: 99%

Mechanistic Analysis of the Effect of Deamidation on the Immunogenicity of Anthrax Protective Antigen

Verma

Ngundi

Burns

2016

Clin Vaccine Immunol

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The spontaneous modification of proteins, such as deamidation of asparagine residues, can significantly affect the immunogenicity of protein-based vaccines. Using a "genetically deamidated" form of recombinant protective antigen (rPA), we have previously shown that deamidation can decrease the immunogenicity of rPA, the primary component of new-generation anthrax vaccines. In this study, we investigated the biochemical and immunological mechanisms by which deamidation of rPA might decrease the immunogenicity of the protein. We found that loss of the immunogenicity of rPA vaccine was independent of the presence of adjuvant. We assessed the effect of deamidation on the immunodominant neutralizing B-cell epitopes of rPA and found that these epitopes were not significantly affected by deamidation. In order to assess the effect of deamidation on T-cell help for antibody production elicited by rPA vaccine, we examined the ability of the wild-type and genetically deamidated forms of rPA to serve as hapten carriers. We found that when wild-type and genetically deamidated rPA were modified to similar extents with 2,4-dinitrophenyl hapten (DNP) and then used to immunize mice, higher levels of anti-DNP antibodies were elicited by wild-type DNP-rPA than those elicited by the genetically deamidated DNP-rPA, indicating that wild-type rPA elicits more T-cell help than the genetically deamidated form of the protein. These results suggest that a decrease in the ability of deamidated rPA to elicit T-cell help for antibody production is a possible contributor to its lower immunogenicity. Inhalation anthrax is a serious, often fatal, disease caused by Bacillus anthracis. Because of the fatal nature of the disease and the ease of dispersion of B. anthracis spores, B. anthracis is one of the most feared of all bioterror weapons. Due to the low incidence of natural anthrax disease in humans, anthrax vaccines are not given routinely. However, the potential for the use of B. anthracis as a bioterror agent has prompted stockpiling of anthrax vaccines by national governments. Long-term stability is a highly desired characteristic of a stockpiled vaccine since a long shelf life significantly decreases the cost of the stockpile.Many anthrax vaccines are based on protective antigen (PA), which is a nontoxic component of anthrax toxin. Anthrax toxin is a critical virulence factor of B. anthracis and is essential for disease symptomatology and progression (1, 2). The toxin is composed of PA, lethal factor (LF), and edema factor (EF). PA binds to cell receptors, heptamerizes, and then binds LF or EF to form lethal toxin (LT) and edema toxin (ET), respectively (3). Internalization of LT and ET leads to introduction of the enzymatically active effector proteins LF and EF into the cell cytosol where they exert their cytotoxicity (2). Vaccines based on PA or a recombinant form of PA (rPA) elicit antibodies, in particular functional toxinneutralizing antibodies (TNAs), that have been correlated with protection against the disease (4-6).Unfortunately...

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Comparative vaccine efficacy of different isoforms of recombinant protective antigen against Bacillus anthracis spore challenge in rabbits

Cited by 25 publications

References 37 publications

Safety, Reactogenicity, and Immunogenicity of a Recombinant Protective Antigen Anthrax Vaccine Given to Healthy Adults

Safety, Reactogenicity, and Immunogenicity of a Recombinant Protective Antigen Anthrax Vaccine Given to Healthy Adults

Use of Site-Directed Mutagenesis To Model the Effects of Spontaneous Deamidation on the Immunogenicity of Bacillus anthracis Protective Antigen

Mechanistic Analysis of the Effect of Deamidation on the Immunogenicity of Anthrax Protective Antigen

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