In Vivo Activity of Repurposed Amodiaquine as a Host-Targeting Therapy for the Treatment of Anthrax

Anthrax is caused by Bacillus anthracis and can result in nearly 100% mortality due in part to anthrax toxin. Antimalarial amodiaquine (AQ) acts as a host-oriented inhibitor of anthrax toxin endocytosis. Here, we determined the pharmacokinetics and safety of AQ in mice, rabbits, and humans as well as the efficacy in the fly, mouse, and rabbit models of anthrax infection. In the therapeutic-intervention studies, AQ nearly doubled the survival of mice infected subcutaneously with a B. anthracis dose lethal to 60% of the animals (LD₆₀). In rabbits challenged with 200 LD₅₀ of aerosolized B. anthracis, AQ as a monotherapy delayed death, doubled the survival rate of infected animals that received a suboptimal amount of antibacterial levofloxacin, and reduced bacteremia and toxemia in tissues. Surprisingly, the anthrax efficacy of AQ relies on an additional host macrophage-directed antibacterial mechanism, which was validated in the toxin-independent Drosophila model of Bacillus infection. Lastly, a systematic literature review of the safety and pharmacokinetics of AQ in humans from over 2 000 published articles revealed that AQ is likely safe when taken as prescribed, and its pharmacokinetics predicts anthrax efficacy in humans. Our results support the future examination of AQ as adjunctive therapy for the prophylactic anthrax treatment.

Catching and killing of airborne SARS-CoV-2 to control spread of COVID-19 by a heated air disinfection system

Airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via air-conditioning systems poses a significant threat for the continued escalation of the current coronavirus disease (COVID-19) pandemic. Considering that SARS-CoV-2 cannot tolerate temperatures above 70 °C, here we designed and fabricated efficient filters based on heated nickel (Ni) foam to catch and kill SARS-CoV-2. Virus test results revealed that 99.8% of the aerosolized SARS-CoV-2 was caught and killed by a single pass through a novel Ni-foam-based filter when heated up to 200 °C. In addition, the same filter was also used to catch and kill 99.9% of Bacillus anthracis, an airborne spore. This study paves the way for preventing transmission of SARS-CoV-2 and other highly infectious airborne agents in closed environments.

Catching and killing of airborne SARS-CoV-2 to control spread of COVID-19 by a heated air disinfection system

Airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) via air-conditioning systems poses a significant threat for the continued escalation of the current coronavirus disease (COVID-19) pandemic. Considering that SARS-CoV-2 cannot tolerate temperatures above 70 °C, here we designed and fabricated efficient filters based on heated nickel (Ni) foam to catch and kill SARS-CoV-2. Virus test results revealed that 99.8% of the aerosolized SARS-CoV-2 was caught and killed by a single pass through a novel Ni-foam-based filter when heated up to 200 °C. In addition, the same filter was also used to catch and kill 99.9% of Bacillus anthracis, an airborne spore. This study paves the way for preventing transmission of SARS-CoV-2 and other highly infectious airborne agents in closed environments.

Teixobactin Provides Protection against Inhalation Anthrax in the Rabbit Model

The use of antibiotics is a vital means of treating infections caused by the bacteria Bacillus (B.) anthracis. Importantly, with the potential future use of multidrug-resistant strains of B. anthracis as bioweapons, new antibiotics are needed as alternative therapeutics. In this blinded study, we assessed the protective efficacy of teixobactin, a recently discovered antibiotic, against inhalation anthrax infection in the adult rabbit model. New Zealand White rabbits were infected with a lethal dose of B. anthracis Ames spores via the inhalation route, and blood samples were collected at various times to assess antigenemia, bacteremia, tissue bacterial load, and antibody production. Treatments were administered upon detection of B. anthracis protective antigen in the animals’ sera. For comparison, a fully protective dose of levofloxacin was used as a positive control. Rabbits treated with teixobactin showed 100% survival following infection, and the bacteremia was completely resolved by 24–48 h post-treatment. In addition, the bacterial/spore loads in tissues of the animals treated with teixobactin were either zero or dramatically less relative to that of the negative control animals. Moreover, microscopic evaluation of the tissues revealed decreased pathology following treatment with teixobactin. Overall, these results show that teixobactin was protective against inhalation anthrax infection in the rabbit model, and they indicate the potential of teixobactin as a therapeutic for the disease.

Experimental Infection of Syrian Hamsters With Aerosolized Nipah Virus

Background

Nipah virus (NiV) is a paramyxovirus (genus Henipavirus) that can cause severe respiratory illness and encephalitis in humans. Transmission occurs through consumption of NiV-contaminated foods, and contact with NiV-infected animals or human body fluids. However, it is unclear whether aerosols derived from aforesaid sources or others also contribute to transmission, and current knowledge on NiV-induced pathogenicity after small-particle aerosol exposure is still limited.

Methods

Infectivity, pathogenicity, and real-time dissemination of aerosolized NiV in Syrian hamsters was evaluated using NiV-Malaysia (NiV-M) and/or its recombinant expressing firefly luciferase (rNiV-FlucNP).

Results

Both viruses had an equivalent pathogenicity in hamsters, which developed respiratory and neurological symptoms of disease, similar to using intranasal route, with no direct correlations to the dose. We showed that virus replication was predominantly initiated in the lower respiratory tract and, although delayed, also intensely in the oronasal cavity and possibly the brain, with gradual increase of signal in these regions until at least day 5-6 postinfection.

Conclusion

Hamsters infected with small-particle aerosolized NiV undergo similar clinical manifestations of the disease as previously described using liquid inoculum, and exhibit histopathological lesions consistent with NiV patient reports. NiV droplets could therefore play a role in transmission by close contact.

Phospholipase A2-activating protein is associated with a novel form of leukoencephalopathy

Leukoencephalopathies are a group of white matter disorders related to abnormal formation, maintenance, and turnover of myelin in the central nervous system. These disorders of the brain are categorized according to neuroradiological and pathophysiological criteria. Herein, we have identified a unique form of leukoencephalopathy in seven patients presenting at ages 2 to 4 months with progressive microcephaly, spastic quadriparesis, and global developmental delay. Clinical, metabolic, and imaging characterization of seven patients followed by homozygosity mapping and linkage analysis were performed. Next generation sequencing, bioinformatics, and segregation analyses followed, to determine a loss of function sequence variation in the phospholipase A₂-activating protein encoding gene (PLAA). Expression and functional studies of the encoded protein were performed and included measurement of prostaglandin E₂ and cytosolic phospholipase A₂ activity in membrane fractions of fibroblasts derived from patients and healthy controls. Plaa-null mice were generated and prostaglandin E₂ levels were measured in different tissues. The novel phenotype of our patients segregated with a homozygous loss-of-function sequence variant, causing the substitution of leucine at position 752 to phenylalanine, in PLAA, which causes disruption of the protein's ability to induce prostaglandin E₂ and cytosolic phospholipase A₂ synthesis in patients' fibroblasts. Plaa-null mice were perinatal lethal with reduced brain levels of prostaglandin E₂ The non-functional phospholipase A₂-activating protein and the associated neurological phenotype, reported herein for the first time, join other complex phospholipid defects that cause leukoencephalopathies in humans, emphasizing the importance of this axis in white matter development and maintenance.

A mutated cholera toxin without the ADP-ribosyltransferase activity induces cytokine production and inhibits apoptosis of splenocytes in mice possibly via toll-like receptor-4 signaling

Native cholera toxin (CT) and its mutated form (CT-2*) without ADP-ribosyltransferase activity differ in their immunomodulatory effects on host cells, and the mechanisms of these differences are poorly understood. In this study, we demonstrated that CT-2* induced higher levels of cytokine production and down-regulated ex-vivo apoptosis of splenocytes from C57BL/6 mice. After exposure of the splenocytes ex-vivo to CT or CT-2* (2μg/ml) for 48h, CT-2* stimulated expression of the toll-like receptor (TLR-4) gene was much higher and the cells produced increased levels of interleukin (IL)-12, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α, compared to splenocytes of mice exposed to native CT. We confirmed these findings by observing that CT-2*, induced much lower levels of IL-12, IFN-γ, and TNF-α in a TLR-4 knockout macrophage cell line derived from C57BL/6 mice. In addition, while CT is known to stimulate apoptosis in splenocytes, we observed that CT-2* significantly down-regulated apoptosis (4.2%), compared to splenocytes exposed to CT (18.7%) or PBS (negative control, 8.5%). On the contrary, we noted both native CT and CT-2* to exhibit similar levels of apoptosis in TLR-4(-/-) cell line. Overall, the evidence supports the conclusion that CT-2* modulated cytokine production and apoptosis in splenocytes of mice possibly through the TLR-4 signaling pathway.

Structure-based redesign of an edema toxin inhibitor

Edema factor (EF) toxin of Bacillus anthracis (NIAID category A), and several other toxins from NIAID category B Biodefense target bacteria are adenylyl cyclases or adenylyl cyclase agonists that catalyze the conversion of ATP to 3',5'-cyclic adenosine monophosphate (cAMP). We previously identified compound 1 (3-[(9-oxo-9H-fluorene-1-carbonyl)-amino]-benzoic acid), that inhibits EF activity in cultured mammalian cells, and reduces diarrhea caused by enterotoxigenic Escherichia coli (ETEC) at an oral dosage of 15μg/mouse. Here, molecular docking was used to predict improvements in potency and solubility of new derivatives of compound 1 in inhibiting edema toxin (ET)-catalyzed stimulation of cyclic AMP production in murine monocyte-macrophage cells (RAW 264.7). Structure-activity relationship (SAR) analysis of the bioassay results for 22 compounds indicated positions important for activity. Several derivatives demonstrated superior pharmacological properties compared to our initial lead compound, and are promising candidates to treat anthrax infections and diarrheal diseases induced by toxin-producing bacteria.

Telemetric left ventricular monitoring using wireless telemetry in the rabbit model

Background

Heart failure is a critical condition that affects many people and often results from left ventricular dysfunction. Numerous studies investigating this condition have been performed using various model systems. To do so, investigators must be able to accurately measure myocardial performance in order to determine the degree of left ventricular function. In this model development study, we employ a wireless telemetry system purchased from Data Sciences International to continuously assess left ventricular function in the rabbit model.

Findings

We surgically implanted pressure-sensitive catheters fitted to wireless radio-transmitters into the left ventricle of Dutch-belted rabbits. Following recovery of the animals, we continuously recorded indices of cardiac contractility and ventricular relaxation at baseline for a given time period. The telemetry system allowed us to continuously record baseline left ventricular parameters for the entire recording period. During this time, the animals were unrestrained and fully conscious. The values we recorded are similar to those obtained using other reported methods.

Conclusions

The wireless telemetry system can continuously measure left ventricular pressure, cardiac contractility, and cardiac relaxation in the rabbit model. These results, which were obtained just as baseline levels, substantiate the need for further validation in this model system of left ventricular assessment.

Hemodynamic effects of anthrax toxins in the rabbit model and the cardiac pathology induced by lethal toxin

Anthrax lethal toxin (LeTx) and edema toxin (EdTx) have been shown to alter hemodynamics in the rodent model, while LeTx primarily is reported to induce extensive tissue pathology. However, the rodent model has limitations when used for comparison to higher organisms such as humans. The rabbit model, on the other hand, has gained recognition as a useful model for studying anthrax infection and its pathophysiological effects. In this study, we assessed the hemodynamic effects of lethal toxin (LeTx) and edema toxin (EdTx) in the rabbit model using physiologically relevant amounts of the toxins. Moreover, we further examine the pathological effects of LeTx on cardiac tissue. We intravenously injected Dutch-belted rabbits with either low-dose and high-dose recombinant LeTx or a single dose of EdTx. The animals’ heart rate and mean arterial pressure were continuously monitored via telemetry until either 48 or 72 h post-challenge. Additional animals challenged with LeTx were used for cardiac troponin I (cTnI) quantitation, cardiac histopathology, and echocardiography. LeTx depressed heart rate at the lower dose and mean arterial pressure (MAP) at the higher dose. EdTx, on the other hand, temporarily intensified heart rate while lowering MAP. Both doses of LeTx caused cardiac pathology with the higher dose having a more profound effect. Lastly, left-ventricular dilation due to LeTx was not apparent at the given time-points. Our study demonstrates the hemodynamic effects of anthrax toxins, as well as the pathological effects of LeTx on the heart in the rabbit model, and it provides further evidence for the toxins’ direct impact on the heart.

Recombinant anthrax toxin receptor-Fc fusion proteins produced in plants protect rabbits against inhalational anthrax

Inhalational anthrax, a zoonotic disease caused by the inhalation of Bacillus anthracis spores, has a ∼50% fatality rate even when treated with antibiotics. Pathogenesis is dependent on the activity of two toxic noncovalent complexes: edema toxin (EdTx) and lethal toxin (LeTx). Protective antigen (PA), an essential component of both complexes, binds with high affinity to the major receptor mediating the lethality of anthrax toxin in vivo, capillary morphogenesis protein 2 (CMG2). Certain antibodies against PA have been shown to protect against anthrax in vivo. As an alternative to anti-PA antibodies, we produced a fusion of the extracellular domain of human CMG2 and human IgG Fc, using both transient and stable tobacco plant expression systems. Optimized expression led to the CMG2-Fc fusion protein being produced at high levels: 730 mg/kg fresh leaf weight in Nicotiana benthamiana and 65 mg/kg in N. tabacum. CMG2-Fc, purified from tobacco plants, fully protected rabbits against a lethal challenge with B. anthracis spores at a dose of 2 mg/kg body weight administered at the time of challenge. Treatment with CMG2-Fc did not interfere with the development of the animals' own immunity to anthrax, as treated animals that survived an initial challenge also survived a rechallenge 30 days later. The glycosylation of the Fc (or lack thereof) had no significant effect on the protective potency of CMG2-Fc in rabbits or on its serum half-life, which was about 5 days. Significantly, CMG2-Fc effectively neutralized, in vitro, LeTx-containing mutant forms of PA that were not neutralized by anti-PA monoclonal antibodies.

Emergence of anthrax edema toxin as a master manipulator of macrophage and B cell functions

Anthrax edema toxin (ET), a powerful adenylyl cyclase, is an important virulence factor of Bacillus anthracis. Until recently, only a modest amount of research was performed to understand the role this toxin plays in the organism's immune evasion strategy. A new wave of studies have begun to elucidate the effects this toxin has on a variety of host cells. While efforts have been made to illuminate the effect ET has on cells of the adaptive immune system, such as T cells, the greatest focus has been on cells of the innate immune system, particularly the macrophage. Here we discuss the immunoevasive activities that ET exerts on macrophages, as well as new research on the effects of this toxin on B cells.

In vitro detection of antibody to cholera enterotoxin in cholera patients and laboratory animals

Two new in vitro microtests for anticholeragen (cholera exo-enterotoxin) antibodies are described and compared. In both tests, choleragen and choleragenoid, antigenically identical purified moieties which differ in size, charge, and toxicity, may be used as sensitizing antigens with apparently equal facility. The passive hemagglutination (PHA) test in which sensitized tanned chicken erythrocytes are used was found to be more sensitive than the sensitized bentonite flocculation test. Tests with sera from cholera patients almost invariably demonstrated a rise in titer on convalescence. Results with the PHA test were directly correlated with results derived from in vivo toxin neutralization assays involving inhibition of skin reactivity and the ileal loop reaction. These observations strengthen the hypothesis that choleragen is involved in the pathogenesis of cholera in man and support the unitarian concept that skin reactivity and choleragenesis are manifestations of the same toxin acting in different tissues. Both of the tests described have been modified and used as inhibition tests in the detection and assay of choleragen antigen.

Protection Afforded by Fluoroquinolones in Animal Models of Respiratory Infections with Bacillus anthracis, Yersinia pestis, and Francisella tularensis

Successful treatment of inhalation anthrax, pneumonic plague and tularemia can be achieved with fluoroquinolone antibiotics, such as ciprofloxacin and levofloxacin, and initiation of treatment is most effective when administered as soon as possible following exposure. Bacillus anthracis Ames, Yersinia pestis CO92, and Francisella tularensis SCHU S4 have equivalent susceptibility in vitro to ciprofloxacin and levofloxacin (minimal inhibitory concentration is 0.03 μg/ml); however, limited information is available regarding in vivo susceptibility of these infectious agents to the fluoroquinolone antibiotics in small animal models. Mice, guinea pig, and rabbit models have been developed to evaluate the protective efficacy of antibiotic therapy against these life-threatening infections. Our results indicated that doses of ciprofloxacin and levofloxacin required to protect mice against inhalation anthrax were approximately 18-fold higher than the doses of levofloxacin required to protect against pneumonic plague and tularemia. Further, the critical period following aerosol exposure of mice to either B. anthracis spores or Y. pestis was 24 h, while mice challenged with F. tularensis could be effectively protected when treatment was delayed for as long as 72 h postchallenge. In addition, it was apparent that prolonged antibiotic treatment was important in the effective treatment of inhalation anthrax in mice, but short-term treatment of mice with pneumonic plague or tularemia infections were usually successful. These results provide effective antibiotic dosages in mice, guinea pigs, and rabbits and lay the foundation for the development and evaluation of combinational treatment modalities.

Analysis of the sporicidal activity of chlorine dioxide disinfectant against Bacillus anthracis (Sterne strain)

Routine surface decontamination is an essential hospital and laboratory procedure, but the list of effective, noncorrosive disinfectants that kill spores is limited. We investigated the sporicidal potential of an aqueous chlorine dioxide solution and encountered some unanticipated problems. Quantitative bacteriological culture methods were used to determine the log(10) reduction of Bacillus anthracis (Sterne strain) spores following 3min exposure to various concentrations of aqueous chlorine dioxide solutions at room temperature in sealed tubes, as well as spraying onto plastic and stainless steel surfaces in a biological safety cabinet. Serial 10-fold dilutions of the treated spores were then plated on 5% sheep blood agar plates, and the survivor colonies were enumerated. Disinfection of spore suspensions with aqueous chlorine dioxide solution in sealed microfuge tubes was highly effective, reducing the viable spore counts by 8log(10) in only 3min. By contrast, the process of spraying or spreading the disinfectant onto surfaces resulted in only a 1log(10) kill because the chlorine dioxide gas was rapidly vaporised from the solutions. Full potency of the sprayed aqueous chlorine dioxide solution was restored by preparing the chlorine dioxide solution in 5% bleach (0.3% sodium hypochlorite). The volatility of chlorine dioxide can cause treatment failures that constitute a serious hazard for unsuspecting users. Supplementation of the chlorine dioxide solution with 5% bleach (0.3% sodium hypochlorite) restored full potency and increased stability for one week.

ATP Depletion Via Mitochondrial F1F0 Complex by Lethal Factor is an Early Event in B. Anthracis-Induced Sudden Cell Death

Bacillus anthracis’ primary virulence factor is a tripartite anthrax toxin consisting of edema factor (EF), lethal factor (LF) and protective antigen (PA). In complex with PA, EF and LF are internalized via receptor-mediated endocytosis. EF is a calmodulin-dependent adenylate cyclase that induces tissue edema. LF is a zinc-metalloprotease that cleaves members of mitogen-activated protein kinase kinases. Lethal toxin (LT: PA plus LF)-induced death of macrophages is primarily attributed to expression of the sensitive Nalp1b allele, inflammasome formation and activation of caspase-1, but early events that initiate these processes are unknown. Here we provide evidence that an early essential event in pyroptosis of alveolar macrophages is LF-mediated depletion of cellular ATP. The underlying mechanism involves interaction of LF with F₁F₀-complex gamma and beta subunits leading to increased ATPase activity in mitochondria. In support, mitochondrial DNA-depleted MH-S cells have decreased F₁F₀ ATPase activity due to the lack of F₀6 and F₀8 polypeptides and show increased resistance to LT. We conclude that ATP depletion is an important early event in LT-induced sudden cell death and its prevention increases survival of toxin-sensitive cells.

Anthrax LFn-PA Hybrid Antigens: Biochemistry, Immunogenicity, and Protection Against Lethal Ames Spore Challenge in Rabbits

We describe a novel hybrid anthrax toxin approach that incorporates multiple components into a single vaccine product. The key domains of protective antigen (PA) and lethal factor (LF) that may be critical for inducing protective immunity are combined into one recombinant molecule. Two LF N-terminal domain-PA hybrids, one with wild-type PA and another with furin cleavage-minus PA, were expressed in E. coli and purified in a native form. Both the hybrids bind to the extracellular domain of the host receptor, CMG2; the wild-type hybrid can be cleaved by furin exposing the LF interacting domain, allowing it to oligomerize into lethal toxin as well as translocation pore-like complexes. The hybrid antigens are immunogenic in Dutch-belted rabbits, eliciting strong PA-specific and LF-specific antibodies. However, the lethal toxin neutralizing antibody titers are 3-7 times lower than those elicited by PA-alum. The hybrid antigens conferred 100% (6/6) protection in rabbits challenged intranasally with a 100 LD(50) dose of Bacillus anthracis Ames strain spores.

Comparative antimicrobial activity of granulysin against bacterial biothreat agents

Granulysin is a cationic protein produced by human T cells and natural killer cells that can kill bacterial pathogens through disruption of microbial membrane integrity. Herein we demonstrate antimicrobial activity of the granulysin peptide derived from the active site against Bacillus anthracis, Yersinia pestis, Francisella tularensis, and Burkholderia mallei, and show pathogen-specific differences in granulysin peptide effects. The susceptibility of Y. pestis to granulysin is temperature dependent, being less susceptible when grown at the flea arthropod vector temperature (26°C) than when grown at human body temperature. These studies suggest that augmentation of granulysin expression by cytotoxic lymphocytes, or therapeutic application of granulysin peptides, could constitute important strategies for protection against select agent bacterial pathogens. Investigations of the microbial surface molecules that determine susceptibility to granulysin may identify important mechanisms that contribute to pathogenesis.

The physiologic responses of Dutch belted rabbits infected with inhalational anthrax

Bacillus anthracis, the causative agent of anthrax, is a category A priority pathogen that causes extensive damage in humans. For this reason, B. anthracis has been the focus of numerous studies using various animal models. In this study, we explored physiologic parameters in Dutch belted rabbits with inhalation anthrax to characterize the disease progression in this model. To this end, we infected Dutch belted rabbits with 100 LD(50) B. anthracis Ames spores by nasal instillation and continuously recorded various physiologic parameters by using telemetry. In addition, samples were collected at selected times for serum chemistry, hematology, and blood gas analysis. The animals exhibited hemodynamic and respiratory changes that coincided with those reported in human cases of inhalational anthrax infection, including hypotension, altered heart rate, and respiratory distress. Likewise, hematology, serum chemistry, and blood gas analysis revealed trends comparable to human anthrax-related pathophysiology. The Dutch belted rabbit model of inhalational anthrax exhibited most of the physiologic, hematologic, and biochemical sequelae noted in human cases. Therefore, this rabbit model fulfills several of the criteria of a useful animal model for studying disease pathogenesis and evaluating therapeutics during inhalational anthrax.

Interferon protects mice against inhalation anthrax

Interferons (IFNs) play a role in innate immunity during many viral, bacterial, and protozoal infections. With the increasing threat of bioterrorist attacks with Bacillus anthracis, its high lethality, and the limited effectiveness of antibiotics, alternative treatments are being studied. Antibodies to protective antigen (PA) are promising, as is IFN. During many bacterial infections, production of and protection by IFNs has been reported, including B. anthracis in vitro. In vivo, we find that (1) the type I IFN inducer, Poly-ICLC, strongly and rapidly protects mice; (2) the protection is IFN-mediated since recombinant murine IFN-beta can protect, and protection by Poly-ICLC is abrogated in IFN type I receptor knockout mice. The greatest protection by Poly-ICLC was conferred by intranasal treatment. A delay in death was observed with the intramuscular route alone, but was not significant. Together, the results suggest the IFN defense could protect mice, up to 60%, against lethal inhalational anthrax, and thus have important medical implications for therapy of human anthrax.

Stimulated innate resistance of lung epithelium protects mice broadly against bacteria and fungi

Pneumonia is a serious problem worldwide. We recently demonstrated that innate defense mechanisms of the lung are highly inducible against pneumococcal pneumonia. To determine the breadth of protection conferred by stimulation of lung mucosal innate immunity, and to identify cells and signaling pathways activated by this treatment, mice were treated with an aerosolized bacterial lysate, then challenged with lethal doses of bacterial and fungal pathogens. Mice were highly protected against a broad array of Gram-positive, Gram-negative, and class A bioterror bacterial pathogens, and the fungal pathogen, Aspergillus fumigatus. Protection was associated with rapid pathogen killing within the lungs, and this effect was recapitulated in vitro using a respiratory epithelial cell line. Gene expression analysis of lung tissue showed marked activation of NF-kappaB, type I and II IFN, and antifungal Card9-Bcl10-Malt1 pathways. Cytokines were the most strongly induced genes, but the inflammatory cytokines TNF and IL-6 were not required for protection. Lung-expressed antimicrobial peptides were also highly up-regulated. Taken together, stimulated innate resistance appears to occur through the activation of multiple host defense signaling pathways in lung epithelial cells, inducing rapid pathogen killing, and conferring broad protection against virulent bacterial and fungal pathogens. Augmentation of innate antimicrobial defenses of the lungs might have therapeutic value for protection of patients with neutropenia or impaired adaptive immunity against opportunistic pneumonia, and for defense of immunocompetent subjects against a bioterror threat or epidemic respiratory infection.

Characterization of the rat pneumonic plague model: infection kinetics following aerosolization of Yersinia pestis CO92

Yersinia pestis, the causative agent of human bubonic and pneumonic plague, is spread during natural infection by the fleas of rodents. Historically associated with infected rat fleas, studies on the kinetics of infection in rats are surprisingly few, and these reports have focused mainly on bubonic plague. Although the natural route of primary infection results in bubonic plague in humans, it is commonly thought that aerosolized Y. pestis will be utilized during a biowarfare attack. Accordingly, based on our previous characterization of the mouse model of pneumonic plague, we sought to examine the progression of infection in rats exposed in a whole-body Madison chamber to aerosolized Y. pestis CO92. Following an 8.6 LD(50) dose of Y. pestis, injury was apparent in the rat tissues based on histopathology, and chemokines and cytokines rose above control levels (1h post infection [p.i.]) in the sera and organ homogenates over a 72-h infection period. Bacteria disseminated from the lungs to peripheral organs, with the largest increases in the spleen, followed by the liver and blood at 72h p.i. compared to the 1h controls. Importantly, rats were as sensitive to pneumonic plague as mice, having a similar LD(50) dose by the intranasal and aerosolized routes. Further, we showed direct transmission of plague bacteria from infected to uninfected rats. Taken together, the data allowed us to characterize for the first time a rat pneumonic plague model following aerosolization of Y. pestis.

Characterization of a mouse model of plague after aerosolization of Yersinia pestis CO92

Yersinia pestis is a Gram-negative bacterium, and the causative agent of bubonic plague and pneumonic plague. Because of its potential use as a biological warfare weapon, the plague bacterium has been placed on the list of category A select agents. The dynamics of pneumonic infection following aerosolization of the highly virulent Y. pestis CO92 strain have been poorly studied; therefore, the purpose of this study was to determine the LD(50) dose, bacterial dissemination, cytokine/chemokine production and tissue damage in Swiss-Webster mice over a 72 h course of infection. We exposed mice in a whole-body Madison chamber to various doses of Y. pestis CO92 aerosolized by a Collison nebulizer, and determined that the LD(50) presented dose (Dp) of the bacterium in the lungs was 2.1 x 10(3) c.f.u. In a subsequent study, we infected mice at a Dp of 1.3 x 10(4) c.f.u., and harvested organs and blood at 1, 24, 48 and 72 h post-infection. Histopathological examination, in addition to measurement of bacterial dissemination and cytokine/chemokine analysis, indicated progressive tissue injury, and an increased number of animals succumbing to infection over the course of the experiment. Using these data, we were able to characterize the mouse plague model following aerosolization of Y. pestis CO92.

Novel inhibitors of anthrax edema factor

Several pathogenic bacteria produce adenylyl cyclase toxins, such as the edema factor (EF) of Bacillus anthracis. These disturb cellular metabolism by catalyzing production of excessive amounts of the regulatory molecule cAMP. Here, a structure-based method, where a 3D-pharmacophore that fit the active site of EF was constructed from fragments, was used to identify non-nucleotide inhibitors of EF. A library of small molecule fragments was docked to the EF-active site in existing crystal structures, and those with the highest HINT scores were assembled into a 3D-pharmacophore. About 10,000 compounds, from over 2.7 million compounds in the ZINC database, had a similar molecular framework. These were ranked according to their docking scores, using methodology that was shown to achieve maximum accuracy (i.e., how well the docked position matched the experimentally determined site for ATP analogues in crystal structures of the complex). Finally, 19 diverse compounds with the best AutoDock binding/docking scores were assayed in a cell-based assay for their ability to reduce cAMP secretion induced by EF. Four of the test compounds, from different structural groups, inhibited in the low micromolar range. One of these has a core structure common to phosphatase inhibitors previously identified by high-throughput assays of a diversity library. Thus, the fragment-based pharmacophore identified a small number of diverse compounds for assay, and greatly enhanced the selection process of advanced lead compounds for combinatorial design.

Synthesis and screening of small molecule inhibitors of anthrax edema factor

The synthesis and development of a novel class of molecules that inhibit anthrax edema factor, an adenylyl cyclase, is reported. These molecules are derived from the initial discovery that histidine and imidazole adducts of the prostaglandin PGE(2) reduce the net secretory response of cholera toxin-challenged mice and act directly on the action of anthrax edema factor, a calmodulin-dependent adenylyl cyclase. The simple enones examined in this letter were prepared by palladium-catalyzed Suzuki reaction.

Alteration in the activation state of new inflammation-associated targets by phospholipase A2-activating protein (PLAA)

Phospholipase A(2) (PLA(2))-activating protein (PLAA) is a novel signaling molecule that regulates the production of prostaglandins (PGE(2)) and tumor necrosis factor (TNF)-alpha. To characterize the function of native PLAA in situ, we generated HeLa (Tet-off) cells overexpressing plaa (plaa(high)) and control (plaa(low)) cells, with the plaa gene in opposite orientation in the latter construct. The plaa(high) cells produced significantly more PGE(2) and interleukin (IL)-6 compared to plaa(low) cells in response to TNF-alpha. There was an increased activation and/or expression of cytosolic PLA(2), cyclooxgenase-2, and NF-kappaB after induction of plaa(high) cells with TNF-alpha compared to the respective plaa(low) cells. Microarray analysis of plaa(high) cells followed by functional assays revealed increased production of proinflammatory cytokine IL-32 and a decrease in the production of annexin A4 and clusterin compared to plaa(low) cells. We demonstrated the role of annexin A4 as an inhibitor of PLA(2) and showed that addition of exogeneous clusterin limited the production of PGE(2) from plaa(high) cells. To understand regulation of plaa gene expression, we used a luciferase reporter system in HeLa cells and identified one stimulatory element, with Sp1 binding sites, and one inhibitory element, in exon 1 of the plaa gene. By using decoy DNA oligonucleotides to Sp1 and competitive binding assays, we showed that Sp1 maintains basal expression of the plaa gene and binds to the above-mentioned stimulatory element. We demonstrated for the first time that the induction of native PLAA by TNF-alpha can perpetuate inflammation by enhancing activation of PLA(2) and NF-kappaB.

Transcriptional profiling of murine organ genes in response to infection with Bacillus anthracis Ames spores

Bacillus anthracis is the Gram-positive, spore-forming etiological agent of anthrax, an affliction studied because of its importance as a potential bioweapon. Although in vitro transcriptional responses of macrophages to either spore or anthrax toxins have been previously reported, little is known regarding the impact of infection on gene expression in host tissues. We infected Swiss-Webster mice intranasally with 5 LD(50) of B. anthracis-virulent Ames spores and observed the global transcriptional profiles of various tissues over a 48 h time period. RNA was extracted from spleen, lung, and heart tissues of infected and control mice and examined by Affymetrix GeneChip analysis. Approximately 580 host genes were significantly over or under expressed among the lung, spleen, and heart tissues at 8 and 48 h time points. Expression of genes encoding for surfactant and major histocompatibility complex (MHC) presentation was diminished during the early phase of infection in lungs. By 48 h, a significant number of genes were modulated in the heart, including up-regulation of calcium-binding-related gene expression, and down-regulation of multiple genes related to cell adhesion, formation of the extracellular matrix, and the cell cytoskeleton. Interestingly, the spleen 8h post-infection showed striking increases in the expression of genes that encode hydrolytic enzymes, and these levels remained elevated throughout infection. Further, genes involving antigen presentation and interferon responses were down-regulated in the spleen at 8 h. In late stages of infection, splenic genes related to the inflammatory response were up-regulated. This study is the first to describe the in vivo global transcriptional response of multiple organs during inhalational anthrax. Although numerous genes related to the host immunological response and certain protection mechanisms were up-regulated in these organs, a vast list of genes important for fully developing and maintaining this response were decreased. Additionally, the lung, spleen, and heart showed differential responses to the infection, further validating the demand for a better understanding of anthrax pathogenesis in order to design therapies against novel targets.

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

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.

METHODS

Using recombinant B. anthracis protective antigen (PA83), covalently coupled to a novel non-toxic muramyl dipeptide (NT-MDP) derivative we hyper-immunized goats three times over the course of 14 weeks. Goats were plasmapheresed and the IgG fraction (not affinity purified) and F(ab')2 derivatives were characterized in vitro and in vivo for protection against lethal toxin mediated intoxication.

RESULTS

Anti-PA83 IgG conferred 100% protection at 7.5 mug in a cell toxin neutralization assay. Mice exposed to 5 LD50 of Bacillus anthracis Ames spores by intranares inoculation demonstrated 60% survival 14 d post-infection when administered a single bolus dose (32 mg/kg body weight) of anti-PA83 IgG at 24 h post spore challenge. Anti-PA83 F(ab')2 fragments retained similar neutralization and protection levels both in vitro and in vivo.

CONCLUSION

The protection afforded by these GMP-grade caprine immunotherapeutics post-exposure in the pilot murine model suggests they could be used effectively to treat post-exposure, symptomatic human anthrax patients following a bioterrorism event. These results also indicate that recombinant PA83 coupled to NT-MDP is a potent inducer of neutralizing antibodies and suggest it would be a promising vaccine candidate for anthrax. The ease of production, ease of covalent attachment, and immunostimulatory activity of the NT-MDP indicate it would be a superior adjuvant to alum or other traditional adjuvants in vaccine formulations.

Accounting for ligand-bound metal ions in docking small molecules on adenylyl cyclase toxins

The adenylyl cyclase toxins produced by bacteria (such as the edema factor (EF) of Bacillus anthracis and CyaA of Bordetella pertussis) are important virulence factors in anthrax and whooping cough. Co-crystal structures of these proteins differ in the number and positioning of metal ions in the active site. Metal ions bound only to the ligands in the crystal structures are not included during the docking. To determine what effect these "missing" metals have on docking results, the AutoDock, LigandFit/Cerius2, and FlexX programs were compared for their ability to correctly place substrate analogues and inhibitors into the active sites of the crystal structures of EF, CyaA, and mammalian adenylate cyclase. Protonating the phosphates of substrate analogues improved the accuracy of docking into the active site of CyaA, where the grid did not account for one of the three Mg2+ ions in the crystal structure. The AutoDock ranking (based on docking energies) of a test group of compounds was relatively unaffected by protonation of carboxyl groups. However, the ranking by FlexX-ChemScore varied significantly, especially for docking to CyaA, suggesting that alternate protonation states should be tested when screening compound libraries with this program. When the charges on the bound metal were set correctly, AutoDock was the most reliable program of the three tested with respect to positioning substrate analogues and ranking compounds according to their experimentally determined ability to inhibit EF.

Mucosal immunization with a novel nanoemulsion-based recombinant anthrax protective antigen vaccine protects against Bacillus anthracis spore challenge

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 approximately 1,000 times the 50% lethal dose ( approximately 1,000x LD(50)) of B. anthracis Ames strain spores (1.38 x 10(3) spores), which killed control animals within 96 h. Nasal immunization also resulted in 70% and 40% survival rates against intranasal challenge with 10x LD(50) and 100x LD(50) (1.2 x 10(6) and 1.2 x 10(7)) 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 antibody AVP-21D9 to protective antigen reduces dissemination of the Bacillus anthracis Ames strain from the lungs in a rabbit model

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.

Proteomic analyses of murine macrophages treated with Bacillus anthracis lethal toxin

Bacillus anthracis is the etiological agent of anthrax and the bacterium produces a tripartite anthrax toxin composed of protective antigen (PA), lethal factor (LF) and edema factor (EF). PA represents the binding domain of the toxin and acts in concert with either LF, a metalloprotease, or EF, an adenylate cyclase, to form lethal toxin (LeTx) or edema toxin (EdTx), respectively. We analyzed the proteomics response of two murine macrophage cell lines (J774.1A and RAW264.7) following B. anthracis LeTx treatment to detect unique host proteins involved in anthrax infection using difference in-gel electrophoresis (DIGE) followed by nanoLC-MS for identification of the proteins. The comparative proteomics approach identified a set of proteins in each cell line that was consistently upregulated when the two macrophage cell lines were treated with LeTx. The upregulated proteins include those involved in energy metabolism, cytoskeleton structure and stress response. A subset of five proteins (ATP synthase beta subunit, beta-actin, Hsp70, vimentin, and Hsp60 homolog) was identified that were commonly upregulated in both cell lines. The proteomic data suggest the involvement of reactive oxygen species (ROS) in cell lysis as seen by the upregulation of proteins that lead to the production of ROS in both the cell lines used in our study. However, proteins that afford protection against ROS may play an important role in the survival of the macrophage to LeTx infection as shown by the differences in proteomic responses of the two cell lines to the action of LeTx. These identified proteins may have the potential to be used as biomarkers for diagnostics and therapeutics.

Localization of superoxide anion production to mitochondrial electron transport chain in 3-NPA-treated cells

3-Nitropropionic acid (3-NPA), an inhibitor of succinate dehydrogenase (SDH) at complex II of the mitochondrial electron transport chain induces cellular energy deficit and oxidative stress-related neurotoxicity. In the present study, we identified the site of reactive oxygen species production in mitochondria. 3-NPA increased O2- generation in mitochondria respiring on the complex I substrates pyruvate+malate, an effect fully inhibited by rotenone. Antimycin A increased O2- production in the presence of complex I and/or II substrates. Addition of 3-NPA markedly increased antimycin A-induced O2- production by mitochondria incubated with complex I substrates, but 3-NPA inhibited O2- formation driven with the complex II substrate succinate. At 0.6 microM, myxothiazol inhibits complex III, but only partially decreases complex I activity, and allowed 3-NPA-induced O2- formation; however, at 40 microM myxothiazol (which completely inhibits both complexes I and III) eliminated O2- production from mitochondria respiring via complex I substrates. These results indicate that in the presence of 3-NPA, mitochondria generate O2- from a site between the ubiquinol pool and the 3-NPA block in the respiratory complex II.

Murine macrophage transcriptional and functional responses to Bacillus anthracis edema toxin

Edema toxin (EdTx), which is a combination of edema factor and a binding moiety (protective antigen), is produced by Bacillus anthracis, the etiological agent of anthrax. EdTx is an adenylyl cyclase enzyme that converts adenosine triphosphate to adenosine-3',5'-monophosphate, resulting in interstitial edema seen in anthrax patients. We used GeneChip analysis to examine global transcriptional profiles of EdTx-treated RAW 264.7 murine macrophage-like cells and identified 71 and 259 genes whose expression was significantly altered by the toxin at 3 and 6h, respectively. Alteration in the expression levels of selected genes was confirmed by real time-reverse transcriptase polymerase chain reaction. The genes with up-regulated expression in macrophages in response to EdTx-treatment were known to be involved in inflammatory responses, regulation of apoptosis, adhesion, immune cell activation, and transcription regulation. Additionally, GeneChip analysis results implied that EdTx-induced activation of activator protein-1 (AP-1) and CAAAT/enhancer-binding protein-beta (C/EBP-beta). Gel shift assays were therefore performed, and an increase in the activities of both of these transcription factors was observed within 30 min. EdTx also inhibited tumor necrosis factor alpha production and crippled the phagocytic ability of the macrophages. This is the first report detailing the host cell global transcriptional responses to EdTx.

Evaluation of the protective effects of quinacrine against Bacillus anthracis Ames

Bacillus anthracis has gained notoriety as a dangerous biological weapon because of its virulence and ability to produce highly resistant spores. In addition, the ability of this organism to produce plasmid-encoded edema toxin (EdTx) and lethal toxin (LeTx) plays a pivotal role in the pathogenesis of anthrax. In this study, the efficacy of quinacrine was evaluated against the effects of anthrax toxins in vitro and its ability to provide protection against challenge with B. anthracis Ames strain spores in an intranasal mouse and guinea pig model. Quinacrine protected murine macrophages in vitro against cytotoxicity and cAMP production induced by LeTx and EdTx, respectively, at concentrations of 40-80 microM, most likely by preventing acidification of the endosomes. However, animals dosed with human equivalent doses of quinacrine were not protected against respiratory spore challenge. The failure of quinacrine to provide protection against inhalation anthrax was attributed to our inability to attain inhibitory concentrations of the drug in the serum or tissues. After daily administration of 43.3 mg quinacrine to guinea pigs (300 g), serum levels after 96 h were only 9.9 microM, a concentration not sufficient to protect macrophages in vitro. Administration of high doses of quinacrine (86.6 mg/kg) was toxic to the animals. These results illustrate some of the difficulties in developing protective therapeutic strategies against inhalation anthrax even when antitoxic drugs appear effective in vitro.

Human monoclonal anti-protective antigen antibody completely protects rabbits and is synergistic with ciprofloxacin in protecting mice and guinea pigs against inhalation anthrax

Prevention of inhalation anthrax requires early and extended antibiotic therapy, and therefore, alternative treatment strategies are needed. We investigated whether a human monoclonal antibody (AVP-21D9) to protective antigen (PA) would protect mice, guinea pigs, and rabbits against anthrax. Control animals challenged with Bacillus anthracis Ames spores by the intranasal route died within 3 to 7 days. AVP-21D9 alone provided minimal protection against anthrax in the murine model, but its efficacy was notably better in guinea pigs. When Swiss-Webster mice, challenged with five 50% lethal doses (LD50s) of anthrax spores, were given a single 16.7-mg/kg of body weight AVP-21D9 antibody dose combined with ciprofloxacin (30 mg/kg/day for 6 days) 24 h after challenge, 100% of the mice were protected for more than 30 days, while ciprofloxacin or AVP-21D9 alone showed minimal protection. Similarly, when AVP-21D9 antibody (10 to 50 mg/kg) was combined with a low, nonprotective dose of ciprofloxacin (3.7 mg/kg/day) and administered to guinea pigs for 6 days, synergistic protection against anthrax was observed. In contrast, a single dose of AVP-21D9 antibody (1, 5, 10, or 20 mg/kg) but not 0.2 mg/kg alone completely protected rabbits against challenge with 100 LD50s of B. anthracis Ames spores, and 100% of the rabbits survived rechallenge. Further, administration of AVP-21D9 (10 mg/kg) to rabbits at 0, 6, and 12 h after challenge with anthrax spores resulted in 100% survival; however, delay of antibody treatment by 24 and 48 h reduced survival to 80% and 60%, respectively. Serological analysis of sera from various surviving animals 30 days postprimary infection showed development of a species-specific PA enzyme-linked immunosorbent assay antibody titer that correlated with protection against reinfection. Taken together, the effectiveness of human anti-PA antibody alone or in combination with low ciprofloxacin levels may provide the basis for an improved strategy for prophylaxis or treatment following inhalation anthrax infection.

Direct inhibition of T-lymphocyte activation by anthrax toxins in vivo

The causative agent of anthrax, Bacillus anthracis, produces two toxins that contribute in part to its virulence. Lethal toxin is a metalloprotease that cleaves upstream mitogen-activated protein kinase kinases. Edema toxin is a calmodulin-dependent adenylate cyclase. Previous studies demonstrated that the anthrax toxins are important immunomodulators that promote immune evasion of the bacterium by suppressing activation of macrophages and dendritic cells. Here we showed that injection of sublethal doses of either lethal or edema toxin into mice directly inhibited the subsequent activation of T lymphocytes by T-cell receptor-mediated stimulation. Lymphocytes were isolated from toxin-injected mice after 1 or 4 days and stimulated with antibodies against CD3 and CD28. Treatment with either toxin inhibited the proliferation of T cells. Injection of lethal toxin also potently inhibited cytokine secretion by stimulated T cells. The effects of edema toxin on cytokine secretion were more complex and were dependent on the length of time between the injection of edema toxin and the isolation of lymphocytes. Treatment with lethal toxin blocked multiple kinase signaling pathways important for T-cell receptor-mediated activation of T cells. Phosphorylation of the extracellular signal-regulated kinase and the stress-activated kinase p38 was significantly decreased. In addition, phosphorylation of the serine/threonine kinase AKT and of glycogen synthase kinase 3 was inhibited in T cells from lethal toxin-injected mice. Thus, anthrax toxins directly act on T lymphocytes in a mouse model. These findings are important for future anthrax vaccine development and treatment.

A two-codon mutant of cholera toxin lacking ADP-ribosylating activity functions as an effective adjuvant for eliciting mucosal and systemic cellular immune responses to peptide antigens

Vaccination with peptide antigens is an effective strategy against mucosal viral infections. We tested a two-codon mutant of cholera toxin (CT-2*) lacking ADP-ribosylating activity and toxicity as a mucosal adjuvant for T cell epitope peptides for intranasal immunization of mice. Efficient induction of helper and cytotoxic T lymphocyte responses associated with TH1 cytokine production were observed in the systemic and mucosal compartments including nasal, gut, and vaginal associated lymphoid tissues. Single or multiple dosing with the peptide antigen and CT-2* induced strong memory immunity without tolerance. These results demonstrate CT-2* as a suitable mucosal adjuvant for priming antigen-specific cellular immune responses.

GeneChip analyses of global transcriptional responses of murine macrophages to the lethal toxin of Bacillus anthracis

We performed GeneChip analyses on RNA from Bacillus anthracis lethal toxin (LeTx)-treated RAW 264.7 murine macrophages to investigate global effects of anthrax toxin on host cell gene expression. Stringent analysis of data revealed that the expression of several mitogen-activated protein kinase kinase-regulatory genes was affected within 1.5 h post-exposure to LeTx. By 3.0 h, the expression of 103 genes was altered, including those involved in intracellular signaling, energy production, and protein metabolism.

Antidiarrheal effects of L-histidine-supplemented rice-based oral rehydration solution in the treatment of male adults with severe cholera in Bangladesh: a double-blind, randomized trial

BACKGROUND

Because of the antisecretory potential of L-histidine in the intestinal tract, its antidiarrheal effects were determined in cholera.

METHODS

In a double-blind trial of 126 adult male patients with cholera, L-histidine (2.5 g/L) was mixed with a rice-based oral rehydration solution (ORS) and administered to 62 patients; 64 patients received the same ORS without L-histidine. All patients received ciprofloxacin at a dosage of 500 mg every 12 h for 72 h. Fluid output (of stool, urine, and vomit) and intake (of ORS, water, and intravenous fluid) were determined every 8 h for 72 h.

RESULTS

Administration of ORS with L-histidine significantly (P<.05) reduced the frequency of stool output during 32-64 h after initiation of ORS treatment, compared with that in patients given ORS without L-histidine ([all data are means+/-SD] 32-48 h, 11.5+/-6.9 mL/kg vs. 18.8+/-16.0 mL/kg; 40-48 h, 6.7+/-4.4 mL/kg vs. 11.5+/-9.7 mL/kg; and 56-64 h, 6.3+/-5.8 mL/kg vs. 7.8+/-4.1 mL/kg). An overall reduction of 22% in the volume of stool was observed in patients given ORS without L-histidine. The amount of required unscheduled intravenous fluid was lower in patients given ORS with L-histidine, compared with that in patients given ORS without L-histidine (0-24 h, 82.5+/-44.4 mL/kg vs. 158.6+/-72.2 mL/kg [P<.01]; and 24-48 h, 41.6+/-40.4 mL/kg vs. 52.5+/-22.1 mL/kg [P>.05]). Administration of ORS with L-histidine also significantly reduced (P<.05) the intake of ORS and the duration of illness. No adverse effects were observed in these patients.

CONCLUSIONS

L-histidine reduces the weight of stool and the frequency of stool output in cholera and could be a useful and safe adjunct treatment that will increase the success rate of ORS and antibiotic therapy in cholera.

Molecular characterization of a glucose-inhibited division gene, gidA, that regulates cytotoxic enterotoxin of Aeromonas hydrophila

By using a mini-transposon, we obtained two mutated strains of a diarrheal isolate, SSU, of Aeromonas hydrophila that exhibited a 50 to 53% reduction in the hemolytic activity and 83 to 87% less cytotoxic activity associated with the cytotoxic enterotoxin (Act). Act is a potent virulence factor of A. hydrophila and has been shown to contribute significantly to the development of both diarrhea and septicemia in animal models. Subsequent cloning and DNA sequence analysis revealed that transposon insertion occurred at different locations in these two mutants within the same 1,890-bp open reading frame for the glucose-inhibited division gene (gidA). A similar reduction in hemolytic (46%) and cytotoxic (81%) activity of Act was noted in the gidA isogenic mutant of A. hydrophila that was generated by marker exchange mutagenesis. Northern blot analysis revealed that the transcription of the cytotoxic enterotoxin gene (act) was not altered in the gidA transposon and isogenic mutants. However, by generating a chromosomal act::alkaline phosphatase gene (phoA) reporter construct, we demonstrated significantly reduced phosphatase activity in these mutants, indicating the effect of glucose-inhibited division (GidA) protein in modulating act gene expression at the translational level. The biological effects of Act in the gidA mutants were restored by complementation. The virulence of the gidA mutants in mice was dramatically reduced compared to the those of the wild-type (WT) and complemented strains of A. hydrophila. The histopathological examination of lungs, in particular, indicated severe congestion, alveolar hemorrhage, and acute inflammatory infiltrate in the interstitial compartment and the alveolar spaces when mice were infected with the WT and complemented strains. Minimal-to-mild changes were noted in the lungs with the gidA mutants. Taken together, our data indicate for the first time that GidA regulates the most-potent virulence factor of A. hydrophila, Act.

Role of cyclooxygenase enzymes in a murine model of experimental cholera

Nonsteroidal anti-inflammatory drugs (e.g., indomethacin) inhibit and reduce the fluid secretion responses elicited by cholera toxin (CT), but it has not been conclusively determined which cyclooxygenase (COX) isoform is involved in CT's action. This study evaluated the role of the COX enzymes and their arachidonic acid metabolites in experimental cholera. Swiss-Webster mice were dosed with celecoxib and rofecoxib and challenged with CT in ligated small intestinal loops, and intestinal segments from mice deficient in COX-1 and COX-2 were challenged with CT. The effects of CT on fluid accumulation, prostaglandin E(2) production, mucosal tissue injury, and markers of oxidative stress were measured. Celecoxib and rofecoxib given at 160 micro g per mouse inhibited CT-induced fluid accumulation by 48% and 31%, respectively, but there was no significant difference among cox-1(-/-) and cox-2(-/-) mice in response to CT compared to wild-type controls. CT elevated tissue levels of oxidized glutathione and lipid peroxides and elicited small intestinal tissue injury in two of five cox-1(-/-) and four of five cox-2(-/-) mice. A role for COX-2 in CT's mechanism of action has previously been suggested by the effectiveness of COX-2 inhibitors in reducing CT-induced fluid secretion, but CT challenge of COX-1 and COX-2 knockout mice did not corroborate the pharmacological data. The results of this study show that CT induced oxidative stress in COX-deficient mice and suggest a tissue-protective role for arachidonic acid metabolites in the small intestine against oxidative stress.

The cox-2-specific inhibitor celecoxib inhibits adenylyl cyclase

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well-known causes of acute renal insufficiency and gastropathy in patients with chronic inflammatory diseases. This action is presumed to result from nonselective inhibition of both constitutive and inducible forms of prostaglandin H synthases, also known as the cyclooxygenase enzymes (i.e., COX-1 amd COX-2). Celecoxib (Celebrex) is a COX-2 enzyme inhibitor and has emerged as a preferred therapeutic agent for the treatment of rheumatoid arthritis as compared to other NSAIDs. Celecoxib has recently been the subject of criticism for its side effects, mainly arterial thrombosis and renal hemorrhage, although it is considered a superior drug in protecting the gastrointestinal tract. In the present study, we report that celecoxib not only inhibited COX-2, but also exhibited the property of inhibiting adenylyl cyclase, an important enzyme forming the intracellular second messenger 3',5'-adenosine monophosphate (cAMP) from adenosine triphosphate (ATP). Celecoxib also inhibited cholera toxin-stimulated cAMP formation, which indicated its ability to permeate cell membranes in order to reach intracellular adenylyl cyclase. It inhibited in vitro adenylyl cyclase activity in both human colonic epithelial cells and purified adenylyl cyclase from Bordetella pertussis. The IC50 of celecoxib for B. pertussis adenylyl cyclase was calculated to be 0.375 mM. Lineweaver-Burk analysis showed that the type of enzyme inhibition was competitive. The apparent Km and Vm of adenylyl cyclase was calculated as 25.0 nM and 7.14 nmol/min/mg, respectively. Celecoxib changed the Km value to 66.6 nM without affecting the Vmax. The current study suggests that apart from inflammation, celecoxib therapy could be further extended to diseases involving cAMP upregulation either by endogenous reactions or exogenous agents. These new data showing inhibition of adenylyl cyclase should be considered in light of the drug's pathological effects or in patients specifically excluded from treatment (e.g., asthmatics).

Role of melittin-like region within phospholipase A(2)-activating protein in biological function

Phospholipase A(2)-activating protein (PLAA) has been implicated in the production of prostaglandins (e.g. PGE(2)) via activation of phospholipases in various stimulated cell types. Human PLAA, with 738 amino acid (aa) residues, contains a region of 38% homology (aa 503-538) with the 26-aa long melittin peptide, a major component of bee venom and a reported regulator of phospholipase A(2) and phospholipase D activity. To learn more about the role of PLAA in the production of eicosanoids and other inflammatory mediators, we synthesized a murine PLAA peptide (36-aa long) having homology to melittin, as well as to human and rat PLAA. The PLAA peptide and melittin increased the expression of genes encoding the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha) and cyclooxygenase-2 (COX-2), which is involved in PGE(2) production. We determined that the C-terminal region of the PLAA peptide (aa 515-538) was essential, since truncation of the C-terminal end of the PLAA peptide significantly reduced expression of genes encoding TNFalpha and COX-2 in macrophages. We concluded that PLAA could be important in the regulation of the inflammatory response because of its stimulatory effects on eicosanoid and cytokine synthesis. Consequently, control of plaa gene expression could be a target for the development of new drugs to control the inflammatory response.

Early cell signaling by the cytotoxic enterotoxin of Aeromonas hydrophila in macrophages

A cytotoxic enterotoxin (Act) of Aeromonas hydrophila is an important virulence factor with hemolytic, cytotoxic and enterotoxic activities. In this report, we demonstrated Act rapidly mobilized calcium from intracellular stores and evoked influx of calcium from the extracellular milieu in macrophages. A direct role of calcium in Act-induced prostaglandin (e.g. PGE(2)) and tumor necrosis factor alpha (TNF alpha) production was demonstrated in macrophages using a cell-permeable calcium chelator BAPTA-AM, which also down-regulated activation of transcription factor NF-kappa B. We showed that Act's capacity to increase PGE(2) and TNF alpha production could be blocked by inhibitors of tyrosine kinases and protein kinase A. In addition, Act caused up-regulation of the DNA repair enzyme redox factor-1 (Ref-1), which potentially could promote DNA binding of the transcription factors allowing modulation of various genes involved in the inflammatory response. Taken together, a link between Act-induced calcium release, regulation of downstream kinase cascades and Ref-1, and activation of NF-kappa B leading to PGE(2) and TNF alpha production was established. Since Act also caused extensive tissue damage, we showed that Act increased reactive oxygen species, and the antioxidant N-acetyl cysteine, blocked Act-induced PGE(2) and TNF alpha production, as well as NF-kappa B nuclear translocation in macrophages. We have demonstrated for the first time early cell signaling initiated in eukaryotic cells by Act, which leads to various biological effects associated with this toxin.

Phospholipase A2-activating protein--an important regulatory molecule in modulating cyclooxygenase-2 and tumor necrosis factor production during inflammation

Inflammation is a complex multifactorial process and a hallmark of many inflammatory diseases. Most of the tissue destruction that occurs in these diseases is the result of an aberrant or often uncontrolled immune response. Factors that play an important role in such diseases include pro-inflammatory cytokines, complement, and eicosanoids. This review focuses on eicosanoids and their regulation via phospholipase A2-activating protein, which could be targeted as a new therapeutic tool to control inflammatory diseases.

Transected neurites, apoptotic neurons, and reduced inflammation in cortical multiple sclerosis lesions

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system that causes motor, sensory, and cognitive deficits. The present study characterized demyelinated lesions in the cerebral cortex of MS patients. One hundred twelve cortical lesions were identified in 110 tissue blocks from 50 MS patients. Three patterns of cortical demyelination were identified: Type I lesions were contiguous with subcortical white matter lesions; Type II lesions were small, confined to the cortex, and often perivascular; Type III lesions extended from the pial surface to cortical layer 3 or 4. Inflammation and neuronal pathology were studied in tissue from 8 and 7 patients, respectively. Compared to white matter lesions, cortical lesions contained 13 times fewer CD3-positive lymphocytes (195 vs 2,596/mm3 of tissue) and 6 times fewer CD68-positive microglia/macrophages (11,948 vs 67,956/mm3 of tissue). Transected neurites (both axons and dendrites) occurred at a density of 4,119/mm3 in active cortical lesions, 1,107/mm3 in chronic active cortical lesions, 25/mm3 in chronic inactive cortical lesions, 8/mm3 in myelinated MS cortex, and 1/mm3 in control cortex. In active and chronic active cortical lesions, activated microglia closely apposed and ensheathed apical dendrites, neurites, and neuronal perikarya. In addition, apoptotic neurons were increased significantly in demyelinated cortex compared to myelinated cortex. These data support the hypothesis that demyelination, axonal transection, dendritic transection, and apoptotic loss of neurons in the cerebral cortex contribute to neurological dysfunction in MS patients.