Establishment of a New Zealand White Rabbit Model for Lethal Toxin (LT) Challenge and Efficacy of Monoclonal Antibody 5E11 in the LT-Challenged Rabbit Model

Anthrax caused by Bacillus anthracis is a lethal infectious disease, especially when inhaled, and the mortality rate approaches 100% without treatment. The anthrax antitoxin monoclonal antibody (MAb) 5E11 is a humanized antibody that targets the anthrax protective antigen (PA). The efficacy of 5E11 needs proper animal models. However, anthrax spores are extremely dangerous, so experiments must be conducted under Biosafety Level 3 conditions. Considering the critical effects of lethal toxin (LT) on hosts during infection, we report the establishment of a LT-challenged rabbit model, which caused 100% mortality with a dose of 2 mg PA + 1 mg LF, while a 4 mg PA + 2 mg LF challenge could limit death to within three days. Then, we evaluated 5E11 efficacy against LT. A prophylactic study showed that the i.v. administration of 40 mg/kg 5E11 four days before lethal dose LT challenge could lead to 100% survival. In therapeutic studies, the i.v. administration of 40 mg/kg 5E11 10 min after lethal dose LT challenge could provide complete protection. Overall, we developed a new LT-challenged rabbit model, and our results indicate that 5E11 shows potential for the clinical application in anthrax treatment.

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Delayed treatment with W1-mAb, a chimpanzee-derived monoclonal antibody against protective antigen, reduces mortality from challenges with anthrax edema or lethal toxin in rats and with anthrax spores in mice

Critical Care Medicine ◽

10.1097/ccm.0b013e3182120691 ◽

2011 ◽

Vol 39 (6) ◽

pp. 1439-1447 ◽

Cited By ~ 8

Author(s):

Laith Altaweel ◽

Zhaochun Chen ◽

Mahtab Moayeri ◽

Xizhong Cui ◽

Yan Li ◽

...

Keyword(s):

Monoclonal Antibody ◽

Protective Antigen ◽

Lethal Toxin ◽

Delayed Treatment ◽

Anthrax Spores

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Efficacy of ETI-204 Monoclonal Antibody as an Adjunct Therapy in a New Zealand White Rabbit Partial Survival Model for Inhalational Anthrax

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04593-14 ◽

2015 ◽

Vol 59 (4) ◽

pp. 2206-2214 ◽

Cited By ~ 12

Author(s):

Bethany Biron ◽

Katie Beck ◽

David Dyer ◽

Marc Mattix ◽

Nancy Twenhafel ◽

...

Keyword(s):

Monoclonal Antibody ◽

New Zealand ◽

Protective Antigen ◽

Protective Efficacy ◽

Rabbit Model ◽

Zealand White Rabbit ◽

Adjunct Therapy ◽

Antibiotic Resistant ◽

Content Type ◽

Effective Therapeutic Strategy

ABSTRACTInhalational anthrax is characterized by extensive bacteremia and toxemia as well as nonspecific to mild flu-like symptoms, until the onset of hypotension, shock, and mortality. Without treatment, the mortality rate approaches 100%. Antibiotic treatment is not always effective, and alternative treatments are needed, such as monotherapy for antibiotic-resistant inhalational anthrax or as an adjunct therapy in combination with antibiotics. TheBacillus anthracisantitoxin monoclonal antibody (MAb) ETI-204 is a high-affinity chimeric deimmunized antibody which targets the anthrax toxin protective antigen (PA). In this study, a partial protection New Zealand White (NZW) rabbit model was used to evaluate the protective efficacy of the adjunct therapy with the MAb. Following detection of PA in the blood, NZW rabbits were administered either an antibiotic (doxycycline) alone or the antibiotic in conjunction with ETI-204. Survival was evaluated to compare the efficacy of the combination adjunct therapy with that of an antibiotic alone in treating inhalational anthrax. Overall, the results from this study indicate that a subtherapeutic regimen consisting of an antibiotic in combination with an anti-PA MAb results in increased survival compared to the antibiotic alone and would provide an effective therapeutic strategy against symptomatic anthrax in nonvaccinated individuals.

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A High-Affinity Monoclonal Antibody to Anthrax Protective Antigen Passively Protects Rabbits before and after Aerosolized Bacillus anthracis Spore Challenge

Infection and Immunity ◽

10.1128/iai.73.2.795-802.2005 ◽

2005 ◽

Vol 73 (2) ◽

pp. 795-802 ◽

Cited By ~ 90

Author(s):

Nehal Mohamed ◽

Michelle Clagett ◽

Juan Li ◽

Steven Jones ◽

Steven Pincus ◽

...

Keyword(s):

Monoclonal Antibody ◽

Bacillus Anthracis ◽

Protective Antigen ◽

Lethal Dose ◽

Cell Binding ◽

Anthrax Spore ◽

Before And After ◽

Anthrax Infection ◽

Anthrax Protective Antigen ◽

Binding Component

ABSTRACT We have developed a therapeutic for the treatment of anthrax using an affinity-enhanced monoclonal antibody (ETI-204) to protective antigen (PA), which is the central cell-binding component of the anthrax exotoxins. ETI-204 administered preexposure by a single intravenous injection of a dose of between 2.5 and 10 mg per animal significantly protected rabbits from a lethal aerosolized anthrax spore challenge (∼60 to 450 times the 50% lethal dose of Bacillus anthracis Ames). Against a similar challenge, ETI-204 administered intramuscularly at a 20-mg dose per animal completely protected rabbits from death (100% survival). In the postexposure setting, intravenous administration of ETI-204 provided protection 24 h (8 of 10) and 36 h (5 of 10) after spore challenge. Administration at 48 h postchallenge, when 3 of 10 animals had already succumbed to anthrax infection, resulted in the survival of 3 of 7 animals (43%) for the duration of the study (28 days). Importantly, surviving ETI-204-treated animals were free of bacteremia by day 10 and remained so until the end of the studies. Only 11 of 51 ETI-204-treated rabbits had positive lung cultures at the end of the studies. Also, rabbits that were protected from inhalational anthrax by administration of ETI-204 developed significant titers of PA-specific antibodies. Presently, the sole therapeutic regimen available to treat infection by inhalation of B. anthracis spores is a 60-day course of antibiotics that is effective only if administered prior to or shortly after exposure. Based upon results reported here, ETI-204 is an effective therapy for prevention and treatment of inhalational anthrax.

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Human Monoclonal Antibody AVP-21D9 to Protective Antigen Reduces Dissemination of the Bacillus anthracis Ames Strain from the Lungs in a Rabbit Model

Infection and Immunity ◽

10.1128/iai.00352-07 ◽

2007 ◽

Vol 75 (7) ◽

pp. 3414-3424 ◽

Cited By ~ 47

Author(s):

Johnny W. Peterson ◽

Jason E. Comer ◽

Wallace B. Baze ◽

David M. Noffsinger ◽

Autumn Wenglikowski ◽

...

Keyword(s):

Monoclonal Antibody ◽

Bacillus Anthracis ◽

Protective Antigen ◽

Human Monoclonal Antibody ◽

Rabbit Model ◽

Concomitant Treatment ◽

Dependent Manner ◽

Lethal Challenge ◽

Tissue Sections ◽

Inhalation Anthrax

ABSTRACT Dutch-belted and New Zealand White rabbits were passively immunized with AVP-21D9, a human monoclonal antibody to protective antigen (PA), at the time of Bacillus anthracis spore challenge using either nasal instillation or aerosol challenge techniques. AVP-21D9 (10 mg/kg) completely protected both rabbit strains against lethal infection with Bacillus anthracis Ames spores, regardless of the inoculation method. Further, all but one of the passively immunized animals (23/24) were completely resistant to rechallenge with spores by either respiratory challenge method at 5 weeks after primary challenge. Analysis of the sera at 5 weeks after primary challenge showed that residual human anti-PA levels decreased by 85 to 95%, but low titers of rabbit-specific anti-PA titers were also measured. Both sources of anti-PA could have contributed to protection from rechallenge. In a subsequent study, bacteriological and histopathology analyses revealed that B. anthracis disseminated to the bloodstream in some naïve animals as early as 24 h postchallenge and increased in frequency with time. AVP-21D9 significantly reduced the dissemination of the bacteria to the bloodstream and to various organs following infection. Examination of tissue sections from infected control animals, stained with hematoxylin-eosin and the Gram stain, showed edema and/or hemorrhage in the lungs and the presence of bacteria in mediastinal lymph nodes, with necrosis and inflammation. Tissue sections from infected rabbits dosed with AVP-21D9 appeared comparable to corresponding tissues from uninfected animals despite lethal challenge with B. anthracis Ames spores. Concomitant treatment with AVP-21D9 at the time of challenge conferred complete protection in the rabbit inhalation anthrax model. Early treatment increased the efficacy progressively and in a dose-dependent manner. Thus, AVP-21D9 could offer an adjunct or alternative clinical treatment regimen against inhalation anthrax.

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Mechanism of Lethal Toxin Neutralization by a Human Monoclonal Antibody Specific for the PA20 Region of Bacillus anthracis Protective Antigen

Toxins ◽

10.3390/toxins3080979 ◽

2011 ◽

Vol 3 (8) ◽

pp. 979-990 ◽

Cited By ~ 5

Author(s):

Donald Reason ◽

Justine Liberato ◽

Jinying Sun ◽

Jessica Camacho ◽

Jianhui Zhou

Keyword(s):

Monoclonal Antibody ◽

Bacillus Anthracis ◽

Protective Antigen ◽

Human Monoclonal Antibody ◽

Lethal Toxin

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Detection of anthrax protective antigen (PA) using europium labeled anti-PA monoclonal antibody and time-resolved fluorescence

Journal of Immunological Methods ◽

10.1016/j.jim.2014.05.008 ◽

2014 ◽

Vol 408 ◽

pp. 78-88 ◽

Cited By ~ 10

Author(s):

Robyn A. Stoddard ◽

Conrad P. Quinn ◽

Jarad M. Schiffer ◽

Anne E. Boyer ◽

Jason Goldstein ◽

...

Keyword(s):

Monoclonal Antibody ◽

Protective Antigen ◽

Time Resolved Fluorescence ◽

Time Resolved ◽

Anthrax Protective Antigen

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Correlation between Lethal Toxin-Neutralizing Antibody Titers and Protection from Intranasal Challenge with Bacillus anthracis Ames Strain Spores in Mice after Transcutaneous Immunization with Recombinant Anthrax Protective Antigen

Infection and Immunity ◽

10.1128/iai.74.1.794-797.2006 ◽

2006 ◽

Vol 74 (1) ◽

pp. 794-797 ◽

Cited By ~ 43

Author(s):

Kristina K. Peachman ◽

Mangala Rao ◽

Carl R. Alving ◽

Robert Burge ◽

Stephen H. Leppla ◽

...

Keyword(s):

Bacillus Anthracis ◽

Protective Antigen ◽

Neutralizing Antibody ◽

Lethal Toxin ◽

Vaccine Strategy ◽

Transcutaneous Immunization ◽

Antibody Titers ◽

Anthrax Protective Antigen ◽

Ames Strain ◽

Recombinant Protective Antigen

ABSTRACT Transcutaneous immunization of mice with recombinant protective antigen (rPA) of Bacillus anthracis resulted in significantly higher lethal toxin-neutralizing antibody titers than did intramuscular injection of alum-adsorbed rPA. Immunized mice were partially protected against intranasal challenge with 235,000 (10 50% lethal doses) Ames strain B. anthracis spores. A highly significant correlation was observed between toxin-neutralizing antibody titer and survival after challenge. Future experiments with rabbits and nonhuman primates should confirm the significance of protection by this vaccine strategy.

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Development of Protective Immunity in New Zealand White Rabbits Challenged with Bacillus anthracis Spores and Treated with Antibiotics and Obiltoxaximab, a Monoclonal Antibody against Protective Antigen

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01590-17 ◽

2017 ◽

Vol 62 (2) ◽

Cited By ~ 3

Author(s):

Lisa N. Henning ◽

Sarah Carpenter ◽

Gregory V. Stark ◽

Natalya V. Serbina

Keyword(s):

Monoclonal Antibody ◽

New Zealand ◽

Bacillus Anthracis ◽

Protective Immunity ◽

Protective Antigen ◽

Lethal Dose ◽

Survival Rates ◽

Anamnestic Response ◽

Content Type ◽

Treatment Regimens

ABSTRACT The recommended management of inhalational anthrax, a high-priority bioterrorist threat, includes antibiotics and antitoxins. Obiltoxaximab, a chimeric monoclonal antibody against anthrax protective antigen (PA), is licensed under the U.S. Food and Drug Administration's (FDA's) Animal Rule for the treatment of inhalational anthrax. Because of spore latency, disease reemergence after treatment cessation is a concern, and there is a need to understand the development of endogenous protective immune responses following antitoxin-containing anthrax treatment regimens. Here, acquired protective immunity was examined in New Zealand White (NZW) rabbits challenged with a targeted lethal dose of Bacillus anthracis spores and treated with antibiotics, obiltoxaximab, or a combination of both. Survivors of the primary challenge were rechallenged 9 months later and monitored for survival. Survival rates after primary and rechallenge for controls and animals treated with obiltoxaximab, levofloxacin, or a combination of both were 0, 65, 100, and 95%, and 0, 100, 95, and 89%, respectively. All surviving immune animals had circulating antibodies to PA and serum toxin-neutralizing titers prior to rechallenge. Following rechallenge, systemic bacteremia and toxemia were not detected in most animals, and the levels of circulating anti-PA IgG titers increased starting at 5 days postrechallenge. We conclude that treatment with obiltoxaximab, alone or combined with antibiotics, significantly improves the survival of rabbits that received a lethal inhalation B. anthracis spore challenge dose and does not interfere with the development of immunity. Survivors of primary challenge are protected against reexposure, have rare incidents of systemic bacteremia and toxemia, and have evidence of an anamnestic response.

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Development of an Inhalational Bacillus anthracis Exposure Therapeutic Model in Cynomolgus Macaques

Clinical and Vaccine Immunology ◽

10.1128/cvi.00288-12 ◽

2012 ◽

Vol 19 (11) ◽

pp. 1765-1775 ◽

Cited By ~ 20

Author(s):

Lisa N. Henning ◽

Jason E. Comer ◽

Gregory V. Stark ◽

Bryan D. Ray ◽

Kevin P. Tordoff ◽

...

Keyword(s):

Monoclonal Antibody ◽

Bacillus Anthracis ◽

Protective Antigen ◽

Lethal Dose ◽

Clinical Signs ◽

Cynomolgus Macaque ◽

Content Type ◽

Clinical Observations ◽

Medical Countermeasures ◽

Therapeutic Model

ABSTRACTAppropriate animal models are required to test medical countermeasures to bioterrorist threats. To that end, we characterized a nonhuman primate (NHP) inhalational anthrax therapeutic model for use in testing anthrax therapeutic medical countermeasures according to the U.S. Food and Drug Administration Animal Rule. A clinical profile was recorded for each NHP exposed to a lethal dose ofBacillus anthracisAmes spores. Specific diagnostic parameters were detected relatively early in disease progression, i.e., by blood culture (∼37 h postchallenge) and the presence of circulating protective antigen (PA) detected by electrochemiluminescence (ECL) ∼38 h postchallenge, whereas nonspecific clinical signs of disease, i.e., changes in body temperature, hematologic parameters (ca. 52 to 66 h), and clinical observations, were delayed. To determine whether the presentation of antigenemia (PA in the blood) was an appropriate trigger for therapeutic intervention, a monoclonal antibody specific for PA was administered to 12 additional animals after the circulating levels of PA were detected by ECL. Seventy-five percent of the monoclonal antibody-treated animals survived compared to 17% of the untreated controls, suggesting that intervention at the onset of antigenemia is an appropriate treatment trigger for this model. Moreover, the onset of antigenemia correlated with bacteremia, and NHPs were treated in a therapeutic manner. Interestingly, brain lesions were observed by histopathology in the treated nonsurviving animals, whereas this observation was absent from 90% of the nonsurviving untreated animals. Our results support the use of the cynomolgus macaque as an appropriate therapeutic animal model for assessing the efficacy of medical countermeasures developed against anthrax when administered after a confirmation of infection.

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