Model Of Anthrax Research Articles

P-1106. Sulopenem is Efficacious in a Rabbit Model of Inhalational Anthrax

Abstract Background Sulopenem (SUL) is a penem β-lactam antibiotic in development for the treatment of resistant bacterial infections. It is available as intravenous and oral prodrug formulations, and its activity aligns with the most urgent drug-resistant antimicrobial threats defined by the CDC. SUL possesses potent activity against Enterobacterales species that encode ESBLs or AmpC-type β-lactamases that confer resistance to 3rd generation cephalosporins. SUL has also demonstrated potent in vitro activity against numerous biothreat pathogens, including Bacillus anthracis at concentrations likely to be achieved after oral dosing in humans. B. anthracis is a CDC Tier 1 Select Agent, and remains of considerable concern for biodefense. The potential for mass casualties resulting from a biothreat incident combined with the risk of antibiotic resistance necessitates development of novel medical countermeasures (MCM) for B. anthracis. Orally administered SUL was previously shown to be protective in the murine model of inhalational anthrax and provided proof-of-concept to advance the drug into the well-established rabbit model. Methods Female New Zealand White rabbits were challenged with a lethal dose of B. anthracis Ames spores via the inhalational route. Post-exposure prophylaxis (PEP) was initiated at 24 ±1 h postchallenge with cohorts (N=6) of animals receiving vehicle (saline, SC), ciprofloxacin (CIP) 10 mg/kg, SC or SUL 10 mg/kg, SC. This dosing regimen was informed by pharmacokinetic models to establish a human-equivalent dose. Treatment was continued BID for 14 days. Clinical progression and survival were assessed up to 30 days postchallenge. Results The untreated saline control group demonstrated 100% lethality with a median time to death of 48 h. Both the SUL and CIP groups demonstrated 100% survival through study termination on day 30. Conclusion As a MCM for inhalational anthrax, SUL would provide considerable advantages as an addition to the slate of current standards of care. Combined with positive efficacy results in two preclinical models of inhalational anthrax and advantages offered by an orally available penem antibiotic, SUL remains a promising candidate for advanced development for treating B. anthracis. Disclosures Sailaja Puttagunta, MD, Iterum Therapeutics: Employee|Iterum Therapeutics: Employee|Iterum Therapeutics: Stocks/Bonds (Public Company)|Iterum Therapeutics: Stocks/Bonds (Public Company) Steven I. Aronin, MD, Iterum Therapeutics: Employee|Iterum Therapeutics: Employee|Iterum Therapeutics: Stocks/Bonds (Public Company)|Iterum Therapeutics: Stocks/Bonds (Public Company)

Efficacy of therapeutically administered gepotidacin in a rabbit model of inhalational anthrax.

Bacillus anthracis is a Gram-positive Centers for Disease Control and Prevention category "A" biothreat pathogen. Without early treatment, inhalation of anthrax spores with progression to inhalational anthrax disease is associated with high fatality rates. Gepotidacin is a novel first-in-class triazaacenaphthylene antibiotic that inhibits bacterial DNA replication by a distinct mechanism of action and is being evaluated for use against biothreat and conventional pathogens. Gepotidacin selectively inhibits bacterial DNA replication via a unique binding mode and has in vitro activity against a collection of B. anthracis isolates including antibacterial-resistant strains, with the MIC90 ranging from 0.5 to 1 µg/mL. In vivo activity of gepotidacin was also evaluated in the New Zealand White rabbit model of inhalational anthrax. The primary endpoint was survival, with survival duration and bacterial clearance as secondary endpoints. The trigger for treatment was the presence of anthrax protective antigen in serum. New Zealand White rabbits were dosed intravenously for 5 days with saline or gepotidacin at 114 mg/kg/d to simulate a dosing regimen of 1,000 mg intravenous (i.v.) three times a day (TID) in humans. Gepotidacin provided a survival benefit compared to saline control, with 91% survival (P-value: 0.0001). All control animals succumbed to anthrax and were found to be blood- and organ culture-positive for B. anthracis. The novel mode of action, in vitro microbiology, preclinical safety, and animal model efficacy data, which were generated in line with Food and Drug Administration Animal Rule, support gepotidacin as a potential treatment for anthrax in an emergency biothreat situation.

Analysis of a degenerate reaction–diffusion anthrax model with spatial heterogeneity

To investigate the impact of spatial heterogeneity on anthrax transmission, we develop a novel degenerate reaction–diffusion model for anthrax. Despite the lack of compactness of the solution map, the asymptotic smoothness is confirmed by examining its contractility. We establish two thresholds, s(J) obtained by an auxiliary system and R0 defined by next generation operator, corresponding to the extinction and persistence of anthrax, respectively. Additionally, we investigate the steady-state bifurcation at the disease-free equilibrium by bifurcation theory. Our numerical simulations reveal the effects of heterogeneity on the transmission of anthrax and discover a phenomenon of spatial synchronization, which maintains the invariance of the basic reproduction number. Notably, we demonstrate that synchronization is the underlying mechanism for this invariance. In summary, our findings provide valuable insights for advancing the understanding of infectious disease transmission dynamics.

Dynamics and density function for a stochastic anthrax epidemic model

<abstract><p>In response to the pressing need to understand anthrax biology, this paper focused on the dynamical behavior of the anthrax model under environmental influence. We defined the threshold parameter $ R^s $, when $ R^s > 1 $; the disease was almost certainly present and the model exists a unique ergodic stationary distribution. Subsequently, statistical features were employed to analyze the dynamic behavior of the disease. The exact representation of the probability density function in the vicinity of the quasi-equilibrium point was determined by the Fokker-Planck equation. Finally, some numerical simulations validated our theoretical results.</p></abstract>

Lung Damage Prevention of Ethanolic Extract of Propolis and Synbiotics in Inhalation Anthrax Model

<p class="AbstractNormal"><strong>Introduction:</strong><strong> </strong>Inflammatory response and oxidative stress can be found in inhalation anthrax characterized by the increased level of serum Tumor Necrosis Factor Alpha (TNF-α) and Malondialdehyde (MDA). Ethanolic Extract of Propolis (EEP) and synbiotics were known to have anti-inflammatory and antioxidant properties. This study aimed to determine the effects of EEP and synbiotics on the level of TNF-α and MDA in inhalation anthrax model.</p><p class="AbstractNormal"><strong>Methods:</strong><strong> </strong>This was an experimental study with post-test only control group design on 40 samples of <em>Rattus norvegicus</em> with inhalation anthrax. Samples were randomized into 5 groups: control (K), antibiotic and EEP (P1), antibiotic and synbiotic (P2), EEP (P3), and synbiotics(P4). The value of TNF-α and MDA were measured 7 days after the spore’s inhalation and 14<sup>th</sup> day since the given treatment. To compare the effects of EEP and synbiotics, we used the two-way ANOVA continued by the LSD post-hoc test (if the data normally distributed) or the Kruskal Wallis continued by the Mann Whitney test (if the data not normally distributed).</p><p class="AbstractNormal"><strong>Results: </strong>EEP and synbiotics significantly reduced the level of TNF-α and MDA compared to control group. P2 showed the highest changes on TNF-α and MDA, which TNF-α was decreasing from 14.2825 ± 0.41623 to 8.4363 ± 0.44938 pg/ml and MDA changed from 14.2825 ± 0.41623 to 2.9638 ± 0.39885 nmol/ml. Followed by P4, P1, and P3 groups.<strong> </strong></p><p class="AbstractNormal"><strong>Conclusion: </strong>EEP and synbiotics have significant impacts on reducing TNF-α and MDA in model of inhalational anthrax.</p>

Recombinant full-length Bacillus Anthracis protective antigen and its 63 kDa form elicits protective response in formulation with addavax.

Bacillus anthracis is the causative agent for the lethal disease anthrax, primarily affecting animals and humans in close contact with an infected host. The pathogenicity of B. anthracis is attributed to the secreted exotoxins and their outer capsule. The host cell-binding exotoxin component "protective antigen" (PA) is reported to be a potent vaccine candidate. The aim of our study is to produce several PA constructs and analyze their vaccine potential. We have designed the various subunit, PA-based recombinant proteins, i.e., full-length Protective antigen (PA-FL), C-terminal 63 kDa fragment (PA63), Protective antigen domain 1-domain 4 chimeras (PA-D1-4) and protective antigen domain 4 (PA-D4) and analyzed their vaccine potential with different human-compatible adjuvants in the mouse model. We have optimized the process and successfully expressed our recombinant antigens as soluble proteins, except full-length PA. All the recombinant antigen formulations with three different adjuvants i.e., Addavax, Alhydrogel, and Montanide ISA 720, were immunized in different mouse groups. The vaccine efficacy of the formulations was analyzed by mouse serum antigen-specific antibody titer, toxin neutralization assay, and survival analysis of mouse groups challenged with a lethal dose of B. anthracis virulent spores. We have demonstrated that the PA-FL addavax and PA63 addavax formulations were most effective in protecting spore-challenged mice and serum from the mice immunized with PAFL addavax, PA-FL alhydrogel, PA63 addavax, and PA63 alhydrogel formulations were equivalently efficient in neutralizing the anthrax lethal toxin. The higher levels of serum Th1, Th2, and Th17 cytokines in PA-FL addavax immunized mice correspond to the enhanced protection provided by the formulation in challenged mice. We have demonstrated that the PA-FL addavax and PA63 addavax formulations exhibit equivalent efficiency as vaccine formulation both in a mouse model of anthrax and mammalian cell lines. However, PA63 is a smaller antigen than PA-FL and more importantly, PA63 is expressed as a soluble protein in E. coli, which imparts a translational advantage to PA63-based formulation. Thus, the outcome of our study has significant implications for the development of protective antigen-based vaccine formulations for human use against the lethal disease anthrax.

Pre- and Postlicensure Animal Efficacy Studies Comparing Anthrax Antitoxins.

The deliberate use of Bacillus anthracis spores is believed by the US government to be a high bioweapons threat. The first line of defense following potential exposure to B. anthracis spores would be postexposure prophylaxis with antimicrobials that have activity against B. anthracis. Additional therapies to address the effects of toxins may be needed in systemically ill individuals. Over the last 2 decades, the United States government (USG) collaborated with the private sector to develop, test, and stockpile 3 antitoxins: anthrax immunoglobulin intravenous (AIGIV), raxibacumab, and obiltoxaximab. All 3 products target protective antigen, a protein factor common to the 2 exotoxins released by B. anthracis, and hamper or block the toxins' effects and prevent or reduce pathogenesis. These antitoxins were approved for licensure by the United States Food and Drug Administration based on animal efficacy studies compared to placebo. We describe USG-sponsored pre- and postlicensure studies that compared efficacy of 3 antitoxins in a New Zealand White rabbit model of inhalation anthrax; survival following a lethal aerosolized dose of B. anthracis spores was the key measure of effectiveness. To model therapeutic intervention, intravenous treatments were started following onset of antigenemia. In pre- and postlicensure studies, all 3 antitoxins were superior to placebo; in the postlicensure study, raxibacumab and obiltoxaximab were superior to AIGIV, but neither was superior to the other. These data illustrate the relative therapeutic benefit of the 3 antitoxins and provide a rationale to prioritize their deployment.

Determination of the Postexposure Prophylactic Benefit of Oral Azithromycin and Clarithromycin Against Inhalation Anthrax in Cynomolgus Macaques.

Sufficient and diverse medical countermeasures against severe pathogenic infections, such as inhalation anthrax, are a critical need. Azithromycin and clarithromycin are antimicrobials commonly used for both upper and lower respiratory infections. They inhibit protein synthesis by blocking the formation of the 50S ribosomal subunit. To expand the armamentarium, these 2 antibiotics were evaluated in a postexposure prophylactic model of inhalation anthrax in cynomolgus macaques. This prophylaxis study had 4 test arms: azithromycin, clarithromycin, a levofloxacin control, and a placebo. Beginning 24 hours after exposure to a target challenge dose of 200 lethal dose 50 (LD50) of Bacillus anthracis Ames spores, animals were treated orally until 30 days postchallenge and then observed until 75 days postchallenge. The test group that received clarithromycin had a survival rate of 67%. The test group that received azithromycin had a survival rate of 50%, but the peak azithromycin plasma levels achieved were <30 ng/mL-much lower than the expected 410 ng/mL. The levofloxacin positive control had a survival rate of 50%; all of the negative controls succumbed to infection. The efficacy of clarithromycin prophylaxis was statistically significant compared with placebo, while azithromycin prophylaxis was indistinguishable from placebo. Given the low plasma concentrations of azithromycin achieved in the study, it is not surprising that half the animals succumbed to anthrax during the dosing period; the animals that survived beyond the time during which placebo control animals succumbed survived to the end of the observation period.

MODEL FOR TRANSMISSION AND OPTIMAL CONTROL OF ANTHRAX INVOLVING HUMAN AND ANIMAL POPULATION

Anthrax is a disease caused by Bacillus anthracis, commonly affects animals as well as humans health. In this paper, a nonlinear deterministic anthrax model involving human and animal is proposed and analyzed. The reproduction number [Formula: see text] and equilibrium points are explored to study the dynamic behavior of the disease. The existence and stability of equilibrium points are discussed. For [Formula: see text], the disease-free equilibrium [Formula: see text] is globally stable. However, it is unstable when [Formula: see text] and a locally stable endemic equilibrium point [Formula: see text] exists. The model is then extended to optimal control model considering human vaccination, animal vaccination and proper removal of carcass. The vaccination class of human and animal population appears separately in a model. The existence and characterization of optimal control are discussed. The numerical simulations are carried out for the choice of parametric values and initial conditions. These illustrate scavengers in the suspected area which eat infected dead body of animals contributing to the effort of reducing the expansion of disease. In addition, numerical comparison analysis with four distinct control strategies is carried out. Our findings show that each control technique has its own influence on reducing the total number of infections in the human and animal populations. The cumulative impact of all control measures is found to be extremely effective in lowering the prevalence of the disease.

Rapid Capsular Antigen Immunoassay for Diagnosis of Inhalational Anthrax: Preclinical Studies and Evaluation in a Nonhuman Primate Model.

ABSTRACTInhalational anthrax is a fatal infectious disease. Rapid and effective treatment is critically dependent on early and accurate diagnosis. Blood culture followed by identification and confirmation may take days to provide clinically relevant information. In contrast, immunoassay for a shed antigen, the capsular polypeptide gamma-d-polyglutamate (γDPGA), can provide rapid results at the point of care. In this study, a lateral flow immunoassay for γDPGA was evaluated in a robust nonhuman primate model of inhalational anthrax. The results showed that the time to a positive result with the rapid test using either serum or blood as a clinical specimen was similar to the time after infection when a blood culture became positive. In vitro testing showed that the test was equally sensitive with cultures of the three major clades of Bacillus anthracis. Cultures from other Bacillus spp. that are known to produce γDPGA also produced positive results. The test was negative with human sera from 200 normal subjects and 45 subjects with culture-confirmed nonanthrax bacterial or fungal sepsis. Taken together, the results showed that immunoassay for γDPGA is an effective surrogate for blood culture in a relevant cynomolgus monkey model of inhalational anthrax. The test would be a valuable aid in early diagnosis of anthrax, which is critical for rapid intervention and a positive outcome. Use of the test could facilitate triage of patients with signs and symptoms of anthrax in a mass-exposure incident and in low-resource settings where laboratory resources are not readily available.

COMPARISON OF PROPOLIS EFFECTS ON TUMOR NECROSIS FACTOR ALPHA AND MALONDIALDEHYDE BETWEEN INHALATION AND CUTANEOUS ANTHRAX ANIMAL MODELS.

Background:Inflammatory response and oxidative stress can be found in anthrax characterized by increased level of serum Tumor Necrosis Factor Alpha (TNF-α) and Malondialdehyde (MDA). The use of antibiotics in anthrax has been known to cause some disturbing side-effects, such as allergic reaction, nausea, vomiting, and antibiotic resistance. Thus, ethanolic extract of propolis (EEP) might be the alternative regimen, due to its anti-inflammatory and antioxidant properties. This study aimed to compare the effects of ethanolic extract of propolis (EEP) on TNF-α and MDA between the inhalation and cutaneous anthrax animal model.Materials and Methods:This was an experimental study with a post-test-only control group design on 40 samples of Rattus norvegicus. Samples were randomized into 5 groups: control, inhalation anthrax model, inhalation anthrax model + EEP, cutaneous anthrax model, and cutaneous anthrax model + EEP. After 14 days, the level of TNF-α and MDA were measured. To compare the data, we used the ANOVA test continued by the post-hoc Turkey test.Results:The results obtained showed that the level of TNF-α and MDA between the inhalation and cutaneous anthrax animal models treated with EEP were statistically different (p < 0.05). The P5 group showed the lowest level of TNF-α (6.822 ± 0.383 pg/ml) and MDA (2.717 ± 0.383 nmol/ml).Conclusion:EEP has a better effect on reducing TNF-α and MDA in cutaneous anthrax animal models compared to the inhalation anthrax animal model.

Physiological Responses to Multiple Low-Doses of Bacillus anthracis Spores in the Rabbit Model of Inhalation Anthrax.

Bacillus anthracis spores that are re-aerosolized from surface deposits after initial contamination present significant health risks for personnel involved in decontamination. To model repeated exposure to low dose B. anthracis spores, three groups of seven rabbits were challenged with multiple low-doses of B. anthracis spores 5 days a week for 3 weeks. Mortality, body temperature, heart and respiration rates, hematology, C-reactive protein, bacteremia, and serum protective antigen were monitored for 21 days post-exposure after the last of multiple doses. All rabbits exposed to a mean daily dose of 2.91 × 102 colony forming units (CFU) survived and showed minimal physiological changes attributable to exposure. One of seven rabbits receiving a mean daily dose of 1.22 × 103 CFU died and four of seven receiving a mean daily dose of 1.17 × 104 CFU died. The LD50 was calculated to be 8.1 × 103 CFU of accumulated dose. Rabbits that succumbed to the higher dose exhibited bacteremia and increases above baseline in heart rate, respiration rate, and body temperature. Two rabbits in the mean daily dose group of 1.17 × 104 CFU exhibited clinical signs of inhalation anthrax yet survived. This study provides a description of lethality, pathophysiology, and pathology in a controlled multiple low-dose inhalation exposure study of B. anthracis in the rabbit model. The data suggest that the accumulated dose is important in survival outcome and that a subset of rabbits may show clinical signs of disease but fully recover without therapeutic intervention

Anthrax Edema and Lethal Toxins Differentially Target Human Lung and Blood Phagocytes

Bacillus anthracis, the causative agent of inhalation anthrax, is a serious concern as a bioterrorism weapon. The vegetative form produces two exotoxins: Lethal toxin (LT) and edema toxin (ET). We recently characterized and compared six human airway and alveolar-resident phagocyte (AARP) subsets at the transcriptional and functional levels. In this study, we examined the effects of LT and ET on these subsets and human leukocytes. AARPs and leukocytes do not express high levels of the toxin receptors, tumor endothelium marker-8 (TEM8) and capillary morphogenesis protein-2 (CMG2). Less than 20% expressed surface TEM8, while less than 15% expressed CMG2. All cell types bound or internalized protective antigen, the common component of the two toxins, in a dose-dependent manner. Most protective antigen was likely internalized via macropinocytosis. Cells were not sensitive to LT-induced apoptosis or necrosis at concentrations up to 1000 ng/mL. However, toxin exposure inhibited B. anthracis spore internalization. This inhibition was driven primarily by ET in AARPs and LT in leukocytes. These results support a model of inhalation anthrax in which spores germinate and produce toxins. ET inhibits pathogen phagocytosis by AARPs, allowing alveolar escape. In late-stage disease, LT inhibits phagocytosis by leukocytes, allowing bacterial replication in the bloodstream.

Physiological Responses to a Single Low-Dose of Bacillus anthracis Spores in the Rabbit Model of Inhalational Anthrax.

Credible dose–response relationships are needed to more accurately assess the risk posed by exposure to low-level Bacillus anthracis contamination during or following a release. To begin to fill this knowledge gap, New Zealand White rabbits were implanted with D70-PCT telemetry transmitters and subsequently aerosol challenged with average inhaled doses of 2.86 × 102 to 2.75 × 105 colony forming units (CFU) of B. anthracis spores. Rabbits exposed to a single inhaled dose at or above 2.54 × 104 CFU succumbed with dose-dependent time to death. Death was associated with increases above baseline in heart rate, respiration rate, and body temperature and all rabbits that died exhibited bacteremia at some point prior to death. Rabbits that inhaled doses of 2.06 × 103 CFU or lower survived to the end of the study and showed no or minimal adverse changes in the measured physiological responses in response to the challenge. Moreover, no bacteremia nor toxemia were observed in rabbits that survived to the end of the study. Overall, the data indicate that challenge doses of B. anthracis below the level sufficient to establish systemic infection do not produce observable physiological responses; however, doses that triggered a response resulted in death.

Development of a guinea pig inhalational anthrax model for evaluation of post-exposure prophylaxis efficacy of anthrax vaccines

A next-generation anthrax vaccine candidate, AV7909, is being developed for post-exposure prophylaxis (PEP) of inhalational anthrax in combination with the recommended course of antimicrobial therapy. Clinical efficacy studies of anthrax countermeasures in humans are not ethical or feasible, therefore, licensure of AV7909 for PEP is being pursued under the US Food and Drug Administration (FDA) Animal Rule, which requires that evidence of effectiveness be demonstrated in an animal model of anthrax, where results of studies in such a model can establish reasonable likelihood of AV7909 to produce clinical benefit in humans. Initial development of a PEP model for inhalational anthrax included evaluation of post-exposure ciprofloxacin pharmacokinetics (PK), tolerability and survival in guinea pigs treated with various ciprofloxacin dosing regimens. Three times per day (TID) intraperitoneal (IP) dosing with 7.5 mg/kg of ciprofloxacin initiated 1 day following inhalational anthrax challenge and continued for 14 days was identified as a well tolerated partially curative ciprofloxacin treatment regimen. The added benefit of AV7909 vaccination was evaluated in guinea pigs given the partially curative ciprofloxacin treatment regimen. Groups of ciprofloxacin-treated guinea pigs were vaccinated.1 and 8 days post-challenge with serial dilutions of AV7909, a 1:16 dilution of AVA, or normal saline. A group of untreated guinea pigs was included as a positive control to confirm lethal B. anthracis exposure. Post-exposure vaccination with the AV7909 anthrax vaccine candidate administered in combination with the partially curative ciprofloxacin treatment significantly increased survival of guinea pigs compared to ciprofloxacin treatment alone. These results suggest that the developed model can be useful in demonstrating added value of the vaccine for PEP.

Investigating the effects of intervention strategies in a spatio-temporal anthrax model

In this paper, we extend our previous work on optimal control applied in an anthrax outbreak in wild animals. We use a system of ordinary differential equation (ODE) and partial differential equations (PDEs) to track the change in susceptible, infected and vaccinated animals as well as the infected carcasses. In addition to the assumption that the infected animals and the infected carcasses are the main source of infection, we consider the animal movement by diffusion and see its effects in disease transmission. Two controls: vaccinating susceptible animals and disposing infected carcasses properly are applied in the model and these controls depend on both space and time. We formulate an optimal control problem to investigate the effect of intervention strategies in our spatio-temporal model in controlling the outbreak at minimum cost. Finally some numerical results for the optimal control problem are presented.

A discrete‐time anthrax model in human and herbivore populations

AbstractWe introduce a discrete‐time anthrax disease model in human and herbivore populations, where the herbivore recruitment function is the classic Beverton–Holt model while that of humans is a constant recruitment function. We use the next generation method to compute the basic reproduction numbers for the submodels consisting of only herbivores and only humans . In addition, we compute it for the full human–herbivore model . When or or , the number of anthrax infections decreases and the disease does not invade the corresponding population. Whereas, the number of anthrax infections increases and the disease invades the corresponding population when or or . Our simulations show that it is possible for the anthrax disease to invade a human–herbivore population where the disease does not invade either herbivores or humans in isolation. Recommendations for resource managers To help guide anthrax disease prevention and control strategies, we provide basic reproduction numbers for the herbivore only population , human‐only population and human–herbivore population . implies the number of anthrax infections deceases and anthrax does not invade the population, while implies the number of anthrax cases increases and anthrax invasion occurs. It is possible for anthrax to invade a population consisting of herbivores and humans where the disease does not invade either the herbivores or humans in isolation. Thus, more anthrax surveillance is required in mixed populations of herbivores and humans. Our human–herbivore model can be used to predict the number of anthrax‐infected humans and animals given the number of known anthrax infections in populations.

A Mathematical Model for Coinfection of Listeriosis and Anthrax Diseases

Listeriosis and Anthrax are fatal zoonotic diseases caused by Listeria monocytogene and Bacillus Anthracis, respectively. In this paper, we proposed and analysed a compartmental Listeriosis-Anthrax coinfection model describing the transmission dynamics of Listeriosis and Anthrax epidemic in human population using the stability theory of differential equations. Our model revealed that the disease-free equilibrium of the Anthrax model only is locally stable when the basic reproduction number is less than one. Sensitivity analysis was carried out on the model parameters in order to determine their impact on the disease dynamics. Numerical simulation of the coinfection model was carried out and the results are displayed graphically and discussed. We simulate the Listeriosis-Anthrax coinfection model by varying the human contact rate to see its effects on infected Anthrax population, infected Listeriosis population, and Listeriosis-Anthrax coinfected population.

Galactosylation of the Secondary Cell Wall Polysaccharide of Bacillus anthracis and Its Contribution to Anthrax Pathogenesis.

Bacillus anthracis, the causative agent of anthrax disease, elaborates a secondary cell wall polysaccharide (SCWP) that is essential for bacterial growth and cell division. B. anthracis SCWP is comprised of trisaccharide repeats with the structure, [→4)-β-ManNAc-(1→4)-β-GlcNAc(O3-α-Gal)-(1→6)-α-GlcNAc(O3-α-Gal, O4-β-Gal)-(1→]6-12 The genes whose products promote the galactosylation of B. anthracis SCWP are not yet known. We show here that the expression of galE1, encoding a UDP-glucose 4-epimerase necessary for the synthesis of UDP-galactose, is required for B. anthracis SCWP galactosylation. The galE1 mutant assembles surface (S) layer and S layer-associated proteins that associate with ketal-pyruvylated SCWP via their S layer homology domains similarly to wild-type B. anthracis, but the mutant displays a defect in γ-phage murein hydrolase binding to SCWP. Furthermore, deletion of galE1 diminishes the capsulation of B. anthracis with poly-d-γ-glutamic acid (PDGA) and causes a reduction in bacterial virulence. These data suggest that SCWP galactosylation is required for the physiologic assembly of the B. anthracis cell wall envelope and for the pathogenesis of anthrax disease.IMPORTANCE Unlike virulent Bacillus anthracis isolates, B. anthracis strain CDC684 synthesizes secondary cell wall polysaccharide (SCWP) trisaccharide repeats without galactosyl modification, exhibits diminished growth in vitro in broth cultures, and is severely attenuated in an animal model of anthrax. To examine whether SCWP galactosylation is a requirement for anthrax disease, we generated variants of B. anthracis strains Sterne 34F2 and Ames lacking UDP-glucose 4-epimerase by mutating the genes galE1 and galE2 We identified galE1 as necessary for SCWP galactosylation. Deletion of galE1 decreased the poly-d-γ-glutamic acid (PDGA) capsulation of the vegetative form of B. anthracis and increased the bacterial inoculum required to produce lethal disease in mice, indicating that SCWP galactosylation is indeed a determinant of anthrax disease.

Immune-modulating Activity of Hydrogel Microparticles Contributes to the Host Defense in a Murine Model of Cutaneous Anthrax.

We recently reported that the open-mesh (0.7 μ) polyacrylamide microparticles (MPs) with internally-coupled Cibacron affinity dye demonstrate protective effect in mice challenged into footpads with high doses (200 LD50) of anthrax (Sterne) spores. A single injection of MPs before spore challenge reduces inflammatory response, delays onset of mortality and promotes survival. In this study, we show that the effect of MPs was substantially increased at the lower spore dose (7 LD50). The inflammation of footpads was reduced to the background level, and 60% of animals survived for 16 days while all untreated infected animals died within 6 days with strong inflammation. The effects of MPs were promoted when the MPs were loaded with a combination of neutrophil-attracting chemokines IL-8 and MIP-1α which delayed the onset of mortality in comparison with untreated mice for additional 8 days. The MPs were not inherently cytotoxic against the bacteria or cultured murine Raw 264.7 cells, but stimulated these cells to release G-CSF, MCP-1, MIP-1α, and TNF-α. Consistent with this finding the injection of MPs induced neutrophil influx into footpads, stimulated production of TNF-α associated with migration of pERK1/2-positive cells with the Langerhans phenotype from epidermis to regional lymph nodes. Our data support the mechanism of protection in which the immune defense induced by MPs along with the exogenous chemokines counterbalances the suppressive effect caused by anthrax infection.