Biology subjects

Bar-David, E.

Publications and source records attributed to Bar-David, E..

7 recordsLinked to original sources

bioRxiv2025

Efficacy of Doxycycline as monotherapy or in combination with Levofloxacin in treating late-stage systemic anthrax in NHP

Bacillus anthracis spores pose a major biosecurity threat, in light of their use in several documented bio-terror attacks and the fact that it was weaponized. The absence of specific and accurate treatment instructions in the 2001 anthrax letter attacks and the poor prognosis of patient receiving noneffective treatment, emphasized the need for reliable guidelines for treating exposed(prophylaxis) or symptomatic populations. The recent 2024 CDC guidelines for treating systemic anthrax recommend a combined treatment of a tetracycline (Minocycline or Doxycycline) with Meropenem or a fluoroquinolone. These recommendations differ from the 2001 or 2015 updates, and in the absence of significant clinical data, rely on animal studies. Previously we demonstrated, based on a rabbit model, that these recommendations are efficient in treating various stages of anthrax, ranging from post exposure prophylaxis, through systemic to involvement of the CNS. Herein we confirm our rabbit results by demonstrating the efficacy of Doxycycline as a monotherapy or in combination with Levofloxacin in treating late-stage systemic anthrax in non-human primates (NHP), in a trigger to treat type of experiment. Our experiments show high efficacy of the mono or combined therapy. Altogether, these results support the CDC guidelines by demonstrating the efficacy of this treatment in a second highly relevant NHP model.

pharmacology and toxicology↗

bioRxiv2024

Closing the gaps: testing the efficacy of carbapenem and cephalosporins in treating late-stage anthrax

Anthrax is a fatal zoonotic disease caused by exposure to Bacillus anthracis spores. Treatment of systemic anthrax is usually efficient when using the right antibiotics as close as possible to exposure, preferably prior to symptoms onset as post exposure prophylaxis (PEP). The efficacy decreases as treatment is initiated later in disease progression. The CDC in its guidelines divides anthrax treatment to three different indications according to the progression of the disease: PEP, systemic and systemic with indications of CNS infection. While the prognosis of PEP or early treatment of systemic anthrax is very good, ingress of the bacteria into the CNS significantly decreases treatment efficacy, creating a substantial clinical challenge. Since anthrax in humans is rare, the CDC recommendations are mainly based on animal model experiments and data obtained from patients infected with other pathogens. Here we use rabbits to test the efficacy of the combined treatment of Meropenem and Doxycycline which is the first choice in the CDC recommendations for treating systemic patients with indication of CNS infection. In addition, we test the efficacy of the first-generation cephalosporin, cefazolin, in treating the different stages of the disease. We found that the combination of Doxycycline and Meropenem is highly effective in treating rabbits in our inhalation and CNS infection models. Cefazoline was efficient only as PEP or systemic stage treatment but not CNS infected animals. Our findings support the CDC recommendation of using a combination of Doxycycline and Meropenem for systemic patients with or without indications for CNS infection. We found that Cefazoline is a decent choice for PEP or early sage systemic disease but recommend considering using this antibiotic only if all other options are not available.

microbiology↗

bioRxiv2023

Doxycycline Levofloxacin or Moxifloxacin are superior to ciprofloxacin in treating anthrax meningitis in rabbits

Efficient treatment of anthrax related meningitis in patients poses a significant therapeutic challenge. Previously we demonstrated in our anthrax meningitis rabbit model that ciprofloxacin treatment in ineffective with most of the treated animals succumbing to the infection. Herein we tested the efficacy of Doxycycline in our rabbit model and found it highly effective. To test whether the low efficacy of Ciprofloxacin is an example of low efficacy of all fluoroquinolones or only this substance, we treated rabbits that were inoculated intra cisterna magna (ICM) with Levofloxacin or Moxifloxacin. We found that in contrast to Ciprofloxacin, Levofloxacin and Moxifloxacin were highly efficient in treating lethal anthrax related meningitis in rabbits. We demonstrated (in naive rabbits) that this deference probably results from variances in blood brain barrier (BBB) penetration of the different fluoroquinolones. The combined treatment of doxycycline and any one of the tested fluoroquinolones was highly effective in the rabbit CNS infection model. The combined treatment of doxycycline and levofloxacin was effective in inhalation rabbit model, as good as the doxycycline monotherapy. These findings imply that while Ciprofloxacin is highly effective as a post exposure prophylactic drug, using this drug to treat symptomatic patients should be reconsidered.

microbiology↗

bioRxiv2022

Alternate response of Bacillus anthracis atxA and acpA to serum, HCO3- and CO2

Bacillus anthracis overcomes host immune responses by producing capsule and secreting toxins. Production of these virulence factors in response to entering the host environment was shown to be regulated by atxA, the major virulence regulator, known to be activated by HCO3- and CO2. While toxin production is regulated directly by atxA, capsule production is independently mediated by two regulators; acpA and acpB. In addition, it was demonstrated that acpA has at least two promotors, one of them shared with atxA. We used a genetic approach to study capsule and toxin production under different conditions. Unlike previous works utilizing NBY-HCO3- medium under CO2 enriched conditions, we used a sDMEM-based medium. Thus, toxin and capsule production can be induced in ambient or CO2 enriched atmosphere. Using this system, we could differentiate between induction by 10% NRS, 10% CO2 or 0.75% HCO3-. In response to high CO2, capsule production is induced by acpA in an atxA-independent manner, with little to no toxin (protective antigen PA) production. atxA is activated in response to serum independently of CO2, inducing toxin and capsule production in an acpA or acpB dependent manner. HCO3- was also found to activate atxA, but in non-physiological concentrations. Our findings may help explain the first stages of inhalational infection, in which spores germinating in dendritic cells require protection (by encapsulation) without affecting cell migration to the draining lymph-node by toxin secretion.

microbiology↗

bioRxiv2021

Cap-independent translation and a precisely localized RNA sequence enable SARS-CoV-2 to control host translation and escape anti-viral response

Translation of SARS-CoV-2-encoded mRNAs by the host ribosomes is essential for its propagation. Following infection, the early expressed viral protein NSP1 binds the ribosome, represseses translation and induces mRNA degradation, while the host elicits anti-viral response. The mechanisms enabling viral mRNAs to escape this multifaceted repression remain obscure. Here we show that expression of NSP1 leads to destabilization of multi-exon cellular mRNAs, while intron-less transcripts, such as viral mRNAs and anti-viral interferon genes, remain relatively stable. We identified a conserved and precisely located cap-proximal RNA element devoid of guanosines that confers resistance to NSP1-meidated translation inhibition. Importantly, the primary sequence rather than the secondary structure is critical for protection. We further show that the genomic 5UTR of SARS-CoV-2 exhibits an IRES-like activity and promotes expression of NSP1 in an eIF4E-independent and Torin-1 resistant manner. Upon expression, NSP1 enhances cap-independent translation. However, the sub-genomic 5UTRs are highly sensitive to eIF4E availability, rendering viral propagation partially sensitive to Torin-1. The combined NSP1-mediated degradation of spliced mRNAs and translation inhibition of single-exon genes, along with the unique features present in the viral 5UTRs, ensure robust expression of viral mRNAs. These features can be exploited as potential therapeutic targets.

molecular biology↗

bioRxiv2021

Nonclinical Safety and Immunogenicity of an rVSV-ΔG-SARS-CoV-2-S vaccine in mice, hamsters, rabbits and pigs

rVSV-{Delta}G-SARS-CoV-2-S is a clinical stage (Phase 2) replication competent recombinant vaccine against SARS-CoV-2. Nonclinical safety, immunogenicity and efficacy studies were conducted in 4 animal species, using multiple dose levels (up to 108 PFU/animal) and various dosing regimens. There were no treatment related mortalities in any study, or any noticeable clinical signs. Compared to unvaccinated controls, hematology and biochemistry parameters were unremarkable and no adverse histopathological findings gave cause for safety concern in any of the studies. There was no viral shedding in urine, nor viral RNA detected in whole blood or serum samples 7 days post vaccination. The rVSV-{Delta}G-SARS-CoV-2-S vaccine immune response gave rise to neutralizing antibodies, cellular immune response, and increased lymphocytic cellularity in the spleen germinal centers and regional lymph node. No evidence for neurovirulence was found in C57BL/6 immune competent mice or in highly sensitive IFNAR KO mice. Vaccine virus replication and distribution in K18 hACE2 transgenic mice showed a gradual clearance from the vaccination site with no vaccine virus recovered from the lungs. The rVSV-{Delta}G-SARS-CoV-2-S vaccine was well tolerated locally and systemically and elicited an effective immunogenic response up to the highest dose tested, supporting further clinical development.

pharmacology and toxicology↗

bioRxiv2020

COVID Moonshot: Open Science Discovery of SARS-CoV-2 Main Protease Inhibitors by Combining Crowdsourcing, High-Throughput Experiments, Computational Simulations, and Machine Learning

We report the results of the COVID Moonshot, a fully open-science, crowd sourced, structure-enabled drug discovery campaign targeting the SARS-CoV-2 main protease. We discovered a non-covalent, non-peptidic inhibitor scaffold with lead-like properties that is differentiated from current main protease inhibitors. Our approach leveraged crowdsourcing, machine learning, exascale molecular simulations, and high-throughput structural biology and chemistry. We generated a detailed map of the structural plasticity of the SARS-CoV-2 main protease, extensive structure-activity relationships for multiple chemotypes, and a wealth of biochemical activity data. All compound designs (>18,000 designs), crystallographic data (>840 ligand-bound X-ray structures), assay data (>10,000 measurements), and synthesized molecules (>2,400 compounds) for this campaign were shared rapidly and openly, creating a rich open and IP-free knowledgebase for future anti-coronavirus drug discovery.

biochemistry↗