Paratope diversity in the human antibody response to Bacillus anthracis protective antigen

Zhou, Jian; Ullal, Anuska; Liberato, Justine; Sun, Jinying; Keitel, Wendy A.; Reason, Donald C.

doi:10.1016/j.molimm.2007.06.159

Cited by 8 publications

(14 citation statements)

References 38 publications

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“…Fab expression libraries were constructed from mononuclear cells enriched for PA-specific B cells in a manner similar to that previously described for PA-and polysaccharide-specific antibody expression libraries (16,17,21; J. Zhou and D. C. Reason, unpublished data). PA 83 was purchased from List Biological Laboratories, Campbell, CA.…”

Section: Methodsmentioning

confidence: 99%

“…PA elicits a polyclonal antibody response in vaccinated humans that utilizes a wide variety of immunoglobulin variable (V)-region genes. Preliminary studies have indicated that after vaccination, antibodies undergo the somatic hypermutation and class switch normally associated with affinity maturation (21). We have previously demonstrated the human antibody response to PA to be significantly biased toward epitopes associated with the amino-terminal domain of the PA protein (PA 20 ) and have postulated that these antibodies may be deficient in their ability to neutralize toxin (16).…”

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confidence: 99%

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Frequency and Domain Specificity of Toxin-Neutralizing Paratopes in the Human Antibody Response to Anthrax Vaccine Adsorbed

Reason¹,

Liberato²,

Sun³

et al. 2009

Infect Immun

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Protective antigen (PA) is the cell surface recognition unit of the binary anthrax toxin system and the primary immunogenic component in both the current and proposed "next-generation" anthrax vaccines. Several studies utilizing animal models have indicated that PA-specific antibodies, acquired by either active or passive immunization, are sufficient to protect against infection with Bacillus anthracis. To investigate the human antibody response to anthrax immunization, we have established a large panel of human PA-specific monoclonal antibodies derived from multiple individuals vaccinated with the currently approved anthrax vaccine BioThrax. We have determined that although these antibodies bind PA in standard binding assays such as enzyme-linked immunosorbent assay, Western blotting, capture assays, and dot blots, less than 25% are capable of neutralizing lethal toxin (LT) in vitro. Nonneutralizing antibodies also fail to neutralize toxin when present in combination with other nonneutralizing paratopes. Although neutralizing antibodies recognize determinants throughout the PA monomer, they are significantly less common among those paratopes that bind to the immunodominant amino-terminal portion of the molecule. These findings demonstrate that PA binding alone is not sufficient to neutralize LT and suggest that for an antibody to effectively block PA-mediated toxicity, it must bind to PA such that one of the requisite toxin functions is disrupted. A vaccine design strategy that directed a higher percentage of the antibody response toward neutralizing epitopes may result in a more efficacious vaccine for the prevention of anthrax infection.The Bacillus anthracis binary toxin system contributes directly to anthrax pathogenicity in the host (3,14). The cell surface recognition element of this toxin system is an 83-kDa protein known as protective antigen (PA 83 ). Antibodies that bind PA protect against infection (8, 12), and PA is the primary immunogenic component in the anthrax vaccine currently licensed for use in the United States (BioThrax, or anthrax vaccine adsorbed [AVA]; Emergent Biosystems). Ongoing attempts to develop a "next-generation" anthrax vaccine are relying on a recombinant form of PA as the sole immunogenic component. PA's role as an important vaccine target has driven a significant amount of research into both the biology of this protein toxin and the immunobiology of its interaction with the immune system of the vaccinated or infected host.PA 83 binds to the cell surface receptors tumor endothelial marker 8 and the capillary morphogenesis gene 2 product (4, 20). Bound PA is cleaved by cell surface-associated furin proteases to release the 20-kDa amino-terminal portion of the molecule (PA 20 ), which has no further role in intoxication. Following proteolytic cleavage, cell-bound PA 63 self-assembles to form a heptameric prepore structure that can bind several molecules of the catalytic toxin components lethal factor (LF) and/or edema factor (EF). Receptor-mediated endocytosis results in the int...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Frequency and Domain Specificity of Toxin-Neutralizing Paratopes in the Human Antibody Response to Anthrax Vaccine Adsorbed

Reason¹,

Liberato²,

Sun³

et al. 2009

Infect Immun

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“…Fab expression libraries were constructed from mononuclear cells (MNCs) enriched for PAspecific B cells in a manner similar to that previously described for PA and polysaccharidespecific antibody expression libraries [8,[12][13][14][15]. PA 83 , PA 20 , and PA 63 were purchased from List Biological Laboratories, Campbell, CA.…”

Section: Construction Of Fab Expression Librariesmentioning

confidence: 99%

“…As a large protein antigen, PA would be expected to elicit a polyclonal antibody response, and initial studies indicate this to be the case [8]. Most individual (monoclonal) PA-specific antibodies are not capable of neutralizing toxin function in vitro, suggesting that antibody binding alone is insufficient, and that a particular function of PA must be blocked for toxin neutralization to occur [9].…”

Section: Introductionmentioning

confidence: 99%

Domain specificity of the human antibody response to Bacillus anthracis protective antigen

Reason¹,

Ullal²,

Liberato³

et al. 2008

Vaccine

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Protective antigen (PA) is the cell surface recognition moiety of the Bacillus anthracis A-B toxin system, and the active immunogenic component in the currently licensed human anthrax vaccine (BioThrax™, or AVA). The serum antibody response to the PA protein is polyclonal and complex both in terms of the antibody combining sites utilized to bind PA and the PA-associated epitopes recognized. We have cloned, sequenced, and expressed a large panel of PA-specific human monoclonal antibodies from 7 AVA-immunized donors. Dot blots, Western blots, and radio-labeled antigen capture assays employing both proteolytic fragments of PA and engineered PA sub-domain fusion proteins were used to determine the region (domain) of the PA monomer to which each of the cloned human antibodies bound. The domain specificity of the isolated monoclonals was highly biased towards the amino-terminal 20kd fragment of PA (PA 20 ), with the majority (62%) of independently arising antibody clones reacting with determinants located on this PA fragment. A similar bias in domain specificity was also demonstrated in the serum response of AVA-vaccinated donors. Since PA 20 is cleaved from the remainder of the monomer rapidly following cell surface binding and has no known role in the intoxication process, the immunodominance of PA 20 -associated epitopes may directly affect the efficacy of PA-based anthrax vaccines.

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“…It has been shown that AVA primarily induces IgG1 antibodies 108 . Although the primary class of TMV-PA6 and TMV-PA12 induced antibodies was not determined, a study using TMV to display an influenza HA peptide showed that both IgG1 and IgG2…”

Section: Protective Efficacy Of Antibodies Induced By Tmv-pa Constructsmentioning

confidence: 99%

Design and Testing of Novel Anthrax Vaccines Utilizing a Tobacco Mosaic Virus Expression System

McComb¹

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Paratope diversity in the human antibody response to Bacillus anthracis protective antigen

Cited by 8 publications

References 38 publications

Frequency and Domain Specificity of Toxin-Neutralizing Paratopes in the Human Antibody Response to Anthrax Vaccine Adsorbed

Frequency and Domain Specificity of Toxin-Neutralizing Paratopes in the Human Antibody Response to Anthrax Vaccine Adsorbed

Domain specificity of the human antibody response to Bacillus anthracis protective antigen

Design and Testing of Novel Anthrax Vaccines Utilizing a Tobacco Mosaic Virus Expression System

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