The Major Neutralizing Antibody Responses to Recombinant Anthrax Lethal and Edema Factors Are Directed to Non-Cross-Reactive Epitopes

Nguyen, Melissa; Terzyan, Simon; Ballard, Jimmy D.; James, Judith A.; Farris, A. Darise

doi:10.1128/iai.00749-09

Cited by 18 publications

(18 citation statements)

References 40 publications

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“…This is in contrast to previous work from our group evaluating EF responses in mice that showed common sequential epitopes residing preferentially in the N-terminal and catalytic domains, with no binding in the C-terminal helical domain (32). Nevertheless, IgG from AVP samples bound to a recombinant N-terminal fragment (aa 1 to 290) of EF, indicating that these samples recognize a conformational epitope(s) in this domain (data not shown).…”

Section: Discussioncontrasting

confidence: 55%

“…Analysis of AVP serum samples by sequential humoral epitope mapping using solid-phase ELISAs provided results supporting this concept. Evaluation of sera from 11 AVP recipients with EF titers of at least 100 revealed nine common sequential epitopes of EF, only one of which had been described previously in EF-immunized mice (32). Careful evaluation of EF decapeptide binding patterns by sera from the four AVP subjects from whom ET neutralization activity of purified EF antibodies was determined showed that serum antibodies from an AVP recipient with EF antibodies with no or very low neutralizing activity recognized multiple epitopes in a region of EF (aa 249 to 354, including parts of the N-terminal and catalytic domains) that were largely unrecognized by three other samples with ET-neutralizing EF antibodies.…”

Section: Discussionmentioning

confidence: 99%

“…However, the potential contribution of EF antibodies to ET neutralization in AVP recipients remains unclear. Several animal studies have shown that EF-specific antibodies can neutralize ET and protect animals from ET challenge (30)(31)(32) as well as contribute to protection from spore challenge (33)(34)(35)(36). Turnbull et al showed that AVP recipients make antibodies to all three components of the tripartite anthrax toxin, although EF antibodies appeared later and were of lower titer than responses to PA and LF (37).…”

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confidence: 99%

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Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients

Dumas

Gross

Larabee

et al. 2017

Clin Vaccine Immunol

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Edema toxin (ET), composed of edema factor (EF) and protective antigen (PA), is a virulence factor of Bacillus anthracis that alters host immune cell function and contributes to anthrax disease. Anthrax vaccine precipitated (AVP) contains low but detectable levels of EF and can elicit EF-specific antibodies in human recipients of AVP. Active and passive vaccination of mice with EF can contribute to protection from challenge with Bacillus anthracis spores or ET. This study compared humoral responses to ET in recipients of AVP (n ϭ 33) versus anthrax vaccine adsorbed (AVA; n ϭ 66), matched for number of vaccinations and time postvaccination, and further determined whether EF antibodies elicited by AVP contribute to ET neutralization. AVP induced higher incidence (77.8%) and titer (229.8 Ϯ 58.6) of EF antibodies than AVA (4.2% and 7.8 Ϯ 8.3, respectively), reflecting the reported low but detectable presence of EF in AVP. In contrast, PA IgG levels and ET neutralization measured using a luciferase-based cyclic AMP reporter assay were robust and did not differ between the two vaccine groups. Multiple regression analysis failed to detect an independent contribution of EF antibodies to ET neutralization in AVP recipients; however, EF antibodies purified from AVP sera neutralized ET. Serum samples from at least half of EF IgG-positive AVP recipients bound to nine decapeptides located in EF domains II and III. Although PA antibodies are primarily responsible for ET neutralization in recipients of AVP, increased amounts of an EF component should be investigated for the capacity to enhance next-generation, PA-based vaccines.

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Section: Discussioncontrasting

confidence: 55%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients

Dumas

Gross

Larabee

et al. 2017

Clin Vaccine Immunol

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“…A tractable number of antibodies were selected for characterization through the two-tiered screening approach of ELISA followed by SPR. These antibodies bound to several different domains of EF (PA binding domain, catalytic C B domain, and helical domain), which further illustrates the previously described diverse response of the mouse immune system to EF (22).…”

Section: Discussionmentioning

confidence: 80%

Mouse Monoclonal Antibodies to Anthrax Edema Factor Protect against Infection

et al. 2011

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Bacillus anthracis is the causative agent of anthrax, and the tripartite anthrax toxin is an essential element of its pathogenesis. Edema factor (EF), a potent adenylyl cyclase, is one of the toxin components. In this work, anti-EF monoclonal antibodies (MAb) were produced following immunization of mice, and four of the antibodies were fully characterized. MAb 3F2 has an affinity of 388 pM, was most effective for EF detection, and appears to be the first antibody reported to neutralize EF by binding to the catalytic C B domain. MAb 7F10 shows potent neutralization of edema toxin activity in vitro and in vivo; it targets the N-terminal protective antigen binding domain. The four MAb react with three different domains of edema factor, and all were able to detect purified edema factor in Western blot analysis. None of the four MAb cross-reacted with the lethal factor toxin component. Three of the four MAb protected mice in both a systemic edema toxin challenge model and a subcutaneous spore-induced foreleg edema model. A combination of three of the MAb also significantly delayed the time to death in a third subcutaneous spore challenge model. This appears to be the first direct evidence that monoclonal antibody-mediated neutralization of EF alone is sufficient to delay anthrax disease progression.

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“…Further, while all the MAbs generated in this study reacted with LF, some of the MAbs also showed reactivity with PA and EF by ELISA, but not by Western analysis. This phenomenon is likely due to recognition of cross-reactive epitopes that are known to exist in anthrax toxin components (32). Interestingly, the MAb that did not show any cross-reactivity to other anthrax toxin components was 20C1, so perhaps this specificity contributed to its toxin neutralization capability.…”

Section: Discussionmentioning

confidence: 99%

Combinations of Monoclonal Antibodies to Anthrax Toxin Manifest New Properties in Neutralization Assays

et al. 2013

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Monoclonal antibodies (MAbs) are potential therapeutic agents against Bacillus anthracis toxins, since there is no current treatment to counteract the detrimental effects of toxemia. In hopes of isolating new protective MAbs to the toxin component lethal factor (LF), we used a strain of mice (C57BL/6) that had not been used in previous studies, generating MAbs to LF. Six LF-binding MAbs were obtained, representing 3 IgG isotypes and one IgM. One MAb (20C1) provided protection from lethal toxin (LeTx) in an in vitro mouse macrophage system but did not provide significant protection in vivo. However, the combination of two MAbs to LF (17F1 and 20C1) provided synergistic increases in protection both in vitro and in vivo. In addition, when these MAbs were mixed with MAbs to protective antigen (PA) previously generated in our laboratory, these MAb combinations produced synergistic toxin neutralization in vitro. But when 17F1 was combined with another MAb to LF, 19C9, the combination resulted in enhanced lethal toxicity. While no single MAb to LF provided significant toxin neutralization, LF-immunized mice were completely protected from infection with B. anthracis strain Sterne, which suggested that a polyclonal response is required for effective toxin neutralization. In total, these studies show that while a single MAb against LeTx may not be effective, combinations of multiple MAbs may provide the most effective form of passive immunotherapy, with the caveat that these may demonstrate emergent properties with regard to protective efficacy.

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The Major Neutralizing Antibody Responses to Recombinant Anthrax Lethal and Edema Factors Are Directed to Non-Cross-Reactive Epitopes

Abstract: Anthrax lethal and edema toxins (LeTx andEdTx

Cited by 18 publications

References 40 publications

Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients

Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients

Mouse Monoclonal Antibodies to Anthrax Edema Factor Protect against Infection

Combinations of Monoclonal Antibodies to Anthrax Toxin Manifest New Properties in Neutralization Assays

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