Showing papers on "Anthrax vaccines published in 2007"

Mucosal Immunization with a Novel Nanoemulsion-Based Recombinant Anthrax Protective Antigen Vaccine Protects against Bacillus anthracis Spore Challenge

Abstract: The currently available commercial human anthrax vaccine requires multiple injections for efficacy and has side effects due to its alum adjuvant. These factors limit its utility when immunizing exposed populations in emergent situations. We evaluated a novel mucosal adjuvant that consists of a nontoxic, water-in-oil nanoemulsion (NE). This material does not contain a proinflammatory component but penetrates mucosal surfaces to load antigens into dendritic cells. Mice and guinea pigs were intranasally immunized with recombinant Bacillus anthracis protective antigen (rPA) mixed in NE as an adjuvant. rPA-NE immunization was effective in inducing both serum anti-PA immunoglobulin G (IgG) and bronchial anti-PA IgA and IgG antibodies after either one or two mucosal administrations. Serum anti-PA IgG2a and IgG2b antibodies and PA-specific cytokine induction after immunization indicate a Th1-polarized immune response. rPA-NE immunization also produced high titers of lethal-toxin-neutralizing serum antibodies in both mice and guinea pigs. Guinea pigs nasally immunized with rPA-NE vaccine were protected against an intradermal challenge with ∼1,000 times the 50% lethal dose (∼1,000× LD50) of B. anthracis Ames strain spores (1.38 × 103 spores), which killed control animals within 96 h. Nasal immunization also resulted in 70% and 40% survival rates against intranasal challenge with 10× LD50 and 100× LD50 (1.2 × 106 and 1.2 × 107) Ames strain spores. Our results indicate that NE can effectively adjuvant rPA for intranasal immunization. This potentially could lead to a needle-free anthrax vaccine requiring fewer doses and having fewer side effects than the currently available human vaccine.

Human Monoclonal Antibodies against Anthrax Lethal Factor and Protective Antigen Act Independently To Protect against Bacillus anthracis Infection and Enhance Endogenous Immunity to Anthrax

Abstract: The unpredictable nature of bioterrorism and the absence of real-time detection systems have highlighted the need for an efficient postexposure therapy for Bacillus anthracis infection. One approach is passive immunization through the administration of antibodies that mitigate the biological action of anthrax toxin. We isolated and characterized two protective fully human monoclonal antibodies with specificity for protective antigen (PA) and lethal factor (LF). These antibodies, designated IQNPA (anti-PA) and IQNLF (anti-LF), were developed as hybridomas from individuals immunized with licensed anthrax vaccine. The effective concentration of IQNPA that neutralized 50% of the toxin in anthrax toxin neutralization assays was 0.3 nM, while 0.1 nM IQNLF neutralized the same amount of toxin. When combined, the antibodies had additive neutralization efficacy. IQNPA binds to domain IV of PA containing the host cell receptor binding site, while IQNLF recognizes domain I containing the PA binding region in LF. A single 180-μg dose of either antibody given to A/J mice 2.5 h before challenge conferred 100% protection against a lethal intraperitoneal spore challenge with 24 50% lethal doses [LD50s] of B. anthracis Sterne and against rechallenge on day 20 with a more aggressive challenge dose of 41 LD50s. Mice treated with either antibody and infected with B. anthracis Sterne developed detectable murine anti-PA and anti-LF immunoglobulin G antibody responses by day 17 that were dependent on which antibody the mice had received. Based on these results, IQNPA and IQNLF act independently during prophylactic anthrax treatment and do not interfere with the establishment of endogenous immunity.

A viral nanoparticle with dual function as an anthrax antitoxin and vaccine.

Abstract: The recent use of Bacillus anthracis as a bioweapon has stimulated the search for novel antitoxins and vaccines that act rapidly and with minimal adverse effects. B. anthracis produces an AB-type toxin composed of the receptor-binding moiety protective antigen (PA) and the enzymatic moieties edema factor and lethal factor. PA is a key target for both antitoxin and vaccine development. We used the icosahedral insect virus Flock House virus as a platform to display 180 copies of the high affinity, PA-binding von Willebrand A domain of the ANTXR2 cellular receptor. The chimeric virus-like particles (VLPs) correctly displayed the receptor von Willebrand A domain on their surface and inhibited lethal toxin action in in vitro and in vivo models of anthrax intoxication. Moreover, VLPs complexed with PA elicited a potent toxin-neutralizing antibody response that protected rats from anthrax lethal toxin challenge after a single immunization without adjuvant. This recombinant VLP platform represents a novel and highly effective, dually-acting reagent for treatment and protection against anthrax.

Safety, reactogenicity and immunogenicity of a recombinant protective antigen anthrax vaccine given to healthy adults.

Abstract: 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 to 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 4 doses (5, 25, 50, or 75 μg). 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 4-fold increases by enzyme-linked immunosorbent and toxin neutralization assays, re...

Oral administration of a Salmonella enterica-based vaccine expressing Bacillus anthracis protective antigen confers protection against aerosolized B. anthracis

Abstract: Bacillus anthracis is the causative agent of anthrax, a disease that affects wildlife, livestock, and humans. Protection against anthrax is primarily afforded by immunity to the B. anthracis protective antigen (PA), particularly PA domains 4 and 1. To further the development of an orally delivered human vaccine for mass vaccination against anthrax, we produced Salmonella enterica serovar Typhimurium expressing full-length PA, PA domains 1 and 4, or PA domain 4 using codon-optimized PA DNA fused to the S. enterica serovar Typhi ClyA and under the control of the ompC promoter. Oral immunization of A/J mice with Salmonella expressing full-length PA protected five of six mice against a challenge with 10(5) CFU of aerosolized B. anthracis STI spores, whereas Salmonella expressing PA domains 1 and 4 provided only 25% protection (two of eight mice), and Salmonella expressing PA domain 4 or a Salmonella-only control afforded no measurable protection. However, a purified recombinant fusion protein of domains 1 and 4 provided 100% protection, and purified recombinant 4 provided protection in three of eight immunized mice. Thus, we demonstrate for the first time the efficacy of an oral S. enterica-based vaccine against aerosolized B. anthracis spores.

Recombinant Exosporium Protein BclA of Bacillus anthracis Is Effective as a Booster for Mice Primed with Suboptimal Amounts of Protective Antigen

Abstract: Bacillus collagen-like protein of anthracis (BclA) is an immunodominant glycoprotein located on the exosporium of Bacillus anthracis. We hypothesized that antibodies to this spore surface antigen are largely responsible for the augmented immunity to anthrax that has been reported for animals vaccinated with inactivated spores and protective antigen (PA) compared to vaccination with PA alone. To test this theory, we first evaluated the capacity of recombinant, histidine-tagged, nonglycosylated BclA (rBclA) given with adjuvant to protect A/J mice against 10 times the 50% lethal dose of Sterne strain spores introduced subcutaneously. Although the animals elicited anti-rBclA antibodies and showed a slight but statistically significant prolongation in the mean time to death (MTD), none of the mice survived. Similarly, rabbit anti-rBclA immunoglobulin G (IgG) administered intraperitoneally to mice before spore inoculation increased the MTD statistically significantly but afforded protection to only 1 of 10 animals. However, all mice that received suboptimal amounts of recombinant PA and that then received rBclA 2 weeks later survived spore challenge. Additionally, anti-rBclA IgG, compared to anti-PA IgG, promoted a sevenfold-greater uptake of opsonized spores by mouse macrophages and markedly decreased intramacrophage spore germination. Since BclA has some sequence similarity to human collagen, we also tested the extent of binding of anti-rBclA antibodies to human collagen types I, III, and V and found no discernible cross-reactivity. Taken together, these results support the concept of rBclA as being a safe and effective boost for a PA-primed individual against anthrax and further suggest that such rBclA-enhanced protection occurs by the induction of spore-opsonizing and germination-inhibiting antibodies.

Project BioShield : What It Is, Why It Is Needed, and Its Accomplishments So Far

Abstract: Project BioShield is a comprehensive effort involving the US Department of Health and Human Services (HHS), its component agencies, and other partner federal agencies to speed the research, development, acquisition, and availability of medical countermeasures to improve the government's preparedness for and ability to counter chemical, biological, radiological, and nuclear threat agents. The legislation authorizes use of the Special Reserve Fund, which makes available $5.6 billion over 10 years for the advanced development and purchase of medical countermeasures. This appropriation is intended to provide an economic incentive to the pharmaceutical industry to develop medical countermeasures for which the government is the only significant market. Acquisitions under Project BioShield are restricted to products in development that are potentially licensable within 8 years from the time of contract award. In exercising the procurement authorities under Project BioShield, HHS has launched acquisition programs to address each of the 4 threat agents, including Bacillus anthracis (anthrax), smallpox virus, botulinum toxins, and radiological/nuclear agents, originally deemed by the Department of Homeland Security to be threats to the US population sufficient to affect national security. At the time of writing, 7 contracts have been awarded: (1) recombinant protective antigen anthrax vaccine, the next-generation anthrax vaccine (contract terminated in December 2006 for default); (2) anthrax vaccine adsorbed, the currently licensed anthrax vaccine; (3) anthrax therapeutics (monoclonal); (4) anthrax therapeutics (human immune globulin); (5) the pediatric formulation of potassium iodide; (6) Ca- and Zn-diethylenetriaminepentaacetate (DTPA), chelating agents to treat ingestion of certain radiological particles; and (7) botulinum antitoxins. Additional acquisition contracts are expected to be awarded in 2007.

Intranasal administration of dry powder anthrax vaccine provides protection against lethal aerosol spore challenge.

Abstract: The use of an aerosolizable form of anthrax as a biological weapon is considered to be among the most serious bioterror threats. Intranasal (IN) delivery of a dry powder anthrax vaccine could provide an effective and non-invasive administration alternative to traditional intramuscular (IM) or subcutaneous (SC) injection. We evaluated a dry powder vaccine based on the recombinant Protective Antigen (rPA) of Bacillus anthracis for vaccination against anthrax via IN immunization in a rabbit model. rPA powders were formulated and administered IN using a prototype powder delivery device. We compared serum IgG and toxin neutralizing antibody (TNA) titers of rabbits immunized IN with 10 microg rPA of a powder formulation with those immunized with the same dose of liquid rPA vaccine, delivered either IN or by IM injection. In addition, each group was tested for survival after aerosol spore challenge. Our results showed that IN vaccination with rPA powders elicited serum PA-specific IgG and TNA titers that were equivalent to those raised by liquid rPA administered IN. Serum PA-specific IgG and TNA titers after IN delivery were lower than for IM injection, however, after aerosol spore challenge, rabbits immunized IN with powders displayed 100% protection versus 63% for the group immunized IN with the liquid vaccine and 86% for the group immunized by IM injection. The results suggest that an IN powder vaccine based on rPA is at least as protective as a liquid delivered by IM injection.

Anthrax vaccine and public health policy.

Abstract: The Centers for Disease Control and Prevention has classified Bacillus anthracis, the causative organism of anthrax, as a category A potential bioterrorism agent.There are critical shortcomings in the US anthrax vaccine program. Rather than depending on the private sector, the government must assume direct production of anthrax vaccine.The development of a capacity capable of preemptive immunization of the public against anthrax should be considered.

Antigen-Specific CD4+ T Cells Recognize Epitopes of Protective Antigen following Vaccination with an Anthrax Vaccine

Abstract: Detection of antigen-specific CD4+ T cells is facilitated by the use of fluorescently labeled soluble peptide-major histocompatibility complex (MHC) multimers which mirror the antigen specificity of T-cell receptor recognition. We have used soluble peptide-MHC class II tetramers containing peptides from the protective antigen (PA) of Bacillus anthracis to detect circulating T cells in peripheral blood of subjects vaccinated with an anthrax vaccine. PA-specific HLA class II-restricted T lymphocytes were isolated which displayed both TH1- and TH2-like characteristics, indicating heterogeneity of the lymphocyte lineage within the CD4+ response. Presentation of antigen to these T-cell clones by HLA-matched antigen-presenting cells exposed to the intact PA protein confirmed that the identified epitopes are indeed naturally processed by the human immune system. Specific tetramer-derived T-cell profiling may be useful for monitoring helper CD4+ T-cell responses to anthrax vaccination.

Public Health Response to An Anthrax Attack: An Evaluation of Vaccination Policy Options

Abstract: A discrete-time, deterministic, compartmental model was developed and analyzed to provide insight into how the use of anthrax vaccine before or after a large-scale attack can reduce casualties. The...

Short-term reactogenicity and gender effect of anthrax vaccine: analysis of a 1967-1972 study and review of the 1955-2005 medical literature.

Abstract: Purpose In the 1960s, the Centers for Disease Control and Prevention (CDC) held the investigational new drug (IND) application for the anthrax vaccine and collected short-term safety data from approximately 16 000 doses administered to almost 7000 individuals. While some recent anthrax vaccine safety studies have suggested that women experience more injection site reactions (ISRs), to our knowledge the IND safety data were not previously examined for a gender-specific difference. Methods We identified and analyzed a subset of the IND study data representing a total of 1749 persons who received 3592 doses from 1967 to 1972. Original data collection forms were located and information extracted, including: vaccine recipient's name, age at vaccination, gender, dose number, date of vaccination, lot number, grading of ISR, presence and type of systemic reactions. Overall and gender-specific rates for adverse reactions to anthrax vaccine were calculated and we performed a multivariable analysis. Results We found an ISR was associated with 28% of anthrax vaccine doses; however, 87% of these were considered mild. Systemic reactions were uncommon (<1%) and most (70%) accompanied an ISR. Our dose-specific analysis by gender found women had at least twice the risk of having a vaccine reaction compared to men. Our age-adjusted relative risk for ISR in women compared to men was 2.78 (95%CI: 2.29, 3.38). Conclusions Our results for both overall and gender-specific reactogenicity are consistent with other anthrax safety studies. To date, possible implications of these gender differences observed for anthrax and other vaccines are unknown and deserve further study. Copyright © 2007 John Wiley & Sons, Ltd.

Complement C3d conjugation to anthrax protective antigen promotes a rapid, sustained, and protective antibody response.

Abstract: B. anthracis is the causative agent of anthrax. Pathogenesis is primarily mediated through the exotoxins lethal factor and edema factor, which bind protective antigen (PA) to gain entry into the host cell. The current anthrax vaccine (AVA, Biothrax™) consists of aluminum-adsorbed cell-free filtrates of unencapsulated B. anthracis, wherein PA is thought to be the principle target of neutralization. In this study, we evaluated the efficacy of the natural adjuvant, C3d, versus alum in eliciting an anti-PA humoral response and found that C3d conjugation to PA and emulsion in incomplete Freund's adjuvant (IFA) imparted superior protection from anthrax challenge relative to PA in IFA or PA adsorbed to alum. Relative to alum-PA, immunization of mice with C3d-PA/IFA augmented both the onset and sustained production of PA-specific antibodies, including neutralizing antibodies to the receptor-binding portion (domain 4) of PA. C3d-PA/IFA was efficacious when administered either i.p. or s.c., and in adolescent mice lacking a fully mature B cell compartment. Induction of PA-specific antibodies by C3d-PA/IFA correlated with increased efficiency of germinal center formation and plasma cell generation. Importantly, C3d-PA immunization effectively protected mice from intranasal challenge with B. anthracis spores, and was approximately 10-fold more effective than alum-PA immunization or PA/IFA based on dose challenge. These data suggest that incorporation of C3d as an adjuvant may overcome shortcomings of the currently licensed aluminum-based vaccine, and may confer protection in the early days following acute anthrax exposure.

A study of the physiology of Bacillus anthracis Sterne during manufacture of the UK acellular anthrax vaccine

Abstract: Aim: To analyse the growth of Bacillus anthracis during simulations of the UK anthrax vaccine manufacturing process Methods and Results: Simulated vaccine production runs were performed using the toxigenic, acapsulate Sterne 34F2 strain of B anthracis in semi-defined medium After rising during the logarithmic growth phase, the pH of the culture starts to fall at about 18 h from pH 8·7 to reach <7·6 at 26 h, coincident with consumption of glucose and optimal production of protective antigen (PA; 7·89 g ml−1, SD 1·0) and lethal factor (LF; 1·85 g ml−1, SD 0·29) No increased breakdown of toxin antigens was seen over the 26–32 h period When glucose was exhausted, amino acids (principally serine) were utilized as an alternative carbon source Sporulation was not observed during the 32 h Conclusions: PA and LF, the principal constituents in the UK anthrax vaccine, undergo little degradation during vaccine fermentation The vaccine manufacturing process is robust and reproducible Significance and Impact of the Study: This is the first detailed analysis of the manufacturing process used for the UK acellular anthrax vaccine; insight gained into the process will support continued and safe vaccine manufacture

Assessment of anthrax vaccination data in the Defense Medical Surveillance System, 1998–2004

Abstract: Purpose Understanding the completeness and accuracy of U.S. military anthrax vaccination data is important to the design and interpretation of studies to assess the safety of anthrax vaccine. We estimated the agreement between electronically recorded anthrax vaccination data in the Defense Medical Surveillance System (DMSS) versus anthrax vaccination data abstracted from hardcopy medical charts in a representative sample of the U.S. military from 1998 to 2004. Methods Medical chart abstractions were conducted at 28 military treatment facilities for 4201 personnel. Abstracted anthrax vaccination data for 1817 personnel, representing 7400 anthrax vaccine doses, were compared with electronically captured data in the DMSS from 1998 to 2004. Sensitivity, positive predictive value (PPV), specificity and negative predictive value (NPV) were calculated using weighted analyses. Results Weighted person-level analysis revealed DMSS sensitivity = 93.8% (95%CI = 91.1, 95.8), specificity = 87.0% (79.0, 92.3), PPV = 85.6% (77.2, 91.3) and NPV = 94.5% (91.7, 96.4). Report of anthrax vaccination within a ±7 days window in both medical chart and DMSS electronic data had a sensitivity of 88.3% (85.4, 90.7) and a PPV of 86.6% (84.9, 88.2) in the vaccine dose-level analysis. Conclusions These results support that anthrax vaccination data captured by the DMSS are adequate for post-marketing surveillance investigations in the U.S. military and are of comparable quality to data captured by other vaccine safety databases. Copyright © 2007 John Wiley & Sons, Ltd.

Rapid generation of an anthrax immunotherapeutic from goats using a novel non-toxic muramyl dipeptide adjuvant

Abstract: Background There is a clear need for vaccines and therapeutics for potential biological weapons of mass destruction and emerging diseases. Anthrax, caused by the bacterium Bacillus anthracis, has been used as both a biological warfare agent and bioterrorist weapon previously. Although antibiotic therapy is effective in the early stages of anthrax infection, it does not have any effect once exposed individuals become symptomatic due to B. anthracis exotoxin accumulation. The bipartite exotoxins are the major contributing factors to the morbidity and mortality observed in acute anthrax infections.

Assessing the safety of anthrax immunization in US Army aircrew members via physical examination.

Abstract: Objective: Anthrax in weaponized form is the bioterrorism agent of most concern. Questions raised about the safety of the anthrax vaccine can be addressed by comparing immunized and unimmunized people in population-based studies. Methods: A retrospective evaluation of data from periodic physical examinations collected on anthrax-immunized and -unimmunized US Army aircrew members between 1998 and 2005 was performed to evaluate the safety of anthrax immunization. Mean changes in variables found on physical examination and laboratory analysis were compared by use oft tests. Multiple linear regression predicted change in outcome from baseline characteristics. Results: We compared 6820 immunized subjects and 4145 unimmunized controls based on US Army aircrew physical examination and screening laboratory tests. No association between anthrax immunization and a clinically relevant change in a tested physiologic parameter was detected. Conclusions: No attributable risk of anthrax immunization was observed in this group of Army aircrew members.

Development of a competitive enzyme linked immunosorbent assay to identify epitope specific antibodies in recipients of the U.S. licensed anthrax vaccine.

Abstract: Vaccination with anthrax vaccine adsorbed (AVA) results in the production of protective antigen (PA) specific antibodies, which play an important protective role against anthrax toxins. Analyzing the specificity of serum antibodies generated in response to AVA vaccination can provide insight into the mechanisms of protective immunity against this important pathogen. The goal of this study was to develop a competitive enzyme linked immunosorbent assay (cELISA) to test human immune serum for antibodies specific for a known lethal toxin neutralizing epitope in PA. PA‐specific antibodies in sera from individuals who received the six‐dose AVA vaccine series competed for binding to immobilized PA with monoclonal antibody F20G75, which binds to a linear epitope in domain 2 of PA and neutralizes lethal toxin activity in vitro. These results suggest that antibodies in human AVA vaccinee serum recognize the same epitope as F20G75, or one in close proximity to it, and may serve a protective role against ant...

Detection of anthrax pathogenicity factors

Abstract: One major problem in diagnosis methods presently available for anthrax is that these methods require several days to produce a result. The only existing treatment for anthrax requires administration soon after infection at a time when patients are exhibiting only mild flu- like symptoms. Thus, a patient may be days beyond the time when treatment would be effective by the time a diagnosis is made. The present invention reduces diagnosis time to as little as four hours providing same day identification of anthrax radically increasing the odds of delivering proper treatment and patient recovery. The rapid identification of anthrax lethal factor activity exhibited by the instant invention is also amenable to in vivo screening protocols for the discovery and development of anthrax vaccines and lethal factor inhibitors. The instant invention isolates and concentrates lethal factor and lethal toxin from nearly any biological sample. By capitalizing on the endopeptidase activity of lethal factor the present invention amplifies output signals producing reliable detection of picomolar concentrations of lethal factor. The instant invention involves novel purification and detection techniques and substrates for rapid, reproducible, and quantitative measurements of anthrax lethal factor in biological samples.